Merge pull request #40 from szisti/fixedNetwork

Support for configuration based fixed network

.github/workflows/pr-testing.yml

@@ -0,0 +1,33 @@
+name: PR testing
+
+on:
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  mavenTesting:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - name: Cache local Maven repository
+      uses: actions/cache@v2
+      with:
+        path: ~/.m2/repository
+        key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}
+        restore-keys: |
+          ${{ runner.os }}-maven-
+    - name: Set up the Java JDK
+      uses: actions/setup-java@v2
+      with:
+        java-version: '11'
+        distribution: 'adopt'
+
+    - name: Run all tests
+      run: |
+        mvn -B clean test -DskipTests=false --file pom.xml
+        if [ -f "target/site/jacoco/index.html" ]; then echo "Total coverage: $(cat target/site/jacoco/index.html | grep -o 'Total[^%]*%' | grep -o '[0-9]*%')"; fi
+
+    - name: Log coverage percentage
+      run: |
+        if [ ! -f "target/site/jacoco/index.html" ]; then echo "No coverage information available"; fi
+        if [ -f "target/site/jacoco/index.html" ]; then echo "Total coverage: $(cat target/site/jacoco/index.html | grep -o 'Total[^%]*%' | grep -o '[0-9]*%')"; fi

.gitignore

@@ -16,3 +16,11 @@
 /settings*.json
 /testchain.json
 /run-testnet.sh
+/.idea
+/qortal.iml
+.DS_Store
+/src/main/resources/resources
+/src/main/resources/log*.properties
+/*.jar
+/run.pid
+/run.log

AutoUpdates.md

@@ -1,5 +1,20 @@
 # Auto Updates
 
+## TL;DR: how-to
+
+* Prepare new release version (see way below for details)
+* Assuming you are in git 'master' branch, at HEAD
+* Shutdown local node if running
+* Build auto-update download: `tools/build-auto-update.sh` - uploads auto-update file into new git branch
+* Restart local node
+* Publish auto-update transaction using *private key* for **non-admin** member of "dev" group:
+	`tools/publish-auto-update.sh non-admin-dev-member-private-key-in-base58`
+* Wait for auto-update `ARBITRARY` transaction to be confirmed into a block
+* Have "dev" group admins 'approve' auto-update using `tools/approve-auto-update.sh`
+	This tool will prompt for *private key* of **admin** of "dev" group
+* A minimum number of admins are required for approval, and a minimum number of blocks must pass also.
+* Nodes will start to download, and apply, the update over the next 20 minutes or so (see CHECK_INTERVAL in AutoUpdate.java)
+
 ## Theory
 * Using a specific git commit (e.g. abcdef123) we produce a determinstic JAR with consistent hash.
 * To avoid issues with over-eager anti-virus / firewalls we obfuscate JAR using very simplistic XOR-based method.
@@ -25,8 +40,8 @@ The same method is used to obfuscate and de-obfuscate:
 
 ## Typical download locations
 The git SHA1 commit hash is used to replace `%s` in various download locations, e.g.:
-* https://github.com/QORT/qortal/raw/%s/qortal.update
-* https://raw.githubusercontent.com@151.101.16.133/QORT/qortal/%s/qortal.update
+* https://github.com/Qortal/qortal/raw/%s/qortal.update
+* https://raw.githubusercontent.com@151.101.16.133/Qortal/qortal/%s/qortal.update
 
 These locations are part of the org.qortal.settings.Settings class and can be overriden in settings.json like:
 ```
@@ -45,4 +60,12 @@ $ java -cp qortal.jar org.qortal.XorUpdate
 usage: XorUpdate <input-file> <output-file>
 $ java -cp qortal.jar org.qortal.XorUpdate qortal.jar qortal.update
 $
-```
+```
+
+## Preparing new release version
+
+* Shutdown local node
+* Modify `pom.xml` and increase version inside `<version>` tag
+* Commit new `pom.xml` and push to github, e.g. `git commit -m 'Bumped to v1.4.2' -- pom.xml; git push`
+* Tag this new commit with same version: `git tag v1.4.2`
+* Push tag up to github: `git push origin v1.4.2`

DATABASE.md

@@ -4,10 +4,10 @@ You can examine your node's database using [HSQLDB's "sqltool"](http://www.hsqld
 It's a good idea to install "rlwrap" (ReadLine wrapper) too as sqltool doesn't support command history/editing.
 
 Typical command line for sqltool would be:
-`rlwrap java -cp ${HSQLDB_JAR}:${SQLTOOL_JAR} org.hsqldb.cmdline.SqlTool --rcFile=${SQLTOOL_RC} qora`
+`rlwrap java -cp ${HSQLDB_JAR}:${SQLTOOL_JAR} org.hsqldb.cmdline.SqlTool --rcFile=${SQLTOOL_RC} qortal`
 
 `${HSQLDB_JAR}` should be set with pathname where Maven downloaded hsqldb, 
-typically `${HOME}/.m2/repository/org/hsqldb/hsqldb/2.5.0/hsqldb-2.5.0.jar`
+typically `${HOME}/.m2/repository/org/hsqldb/hsqldb/2.5.1/hsqldb-2.5.1.jar`
 
 `${SQLTOOL_JAR}` should be set with pathname where Maven downloaded sqltool,
 typically  `${HOME}/.m2/repository/org/hsqldb/sqltool/2.5.0/sqltool-2.5.0.jar`
@@ -25,10 +25,16 @@ Above `url` component `file:db/blockchain` assumes you will call `sqltool` from
 
 Another idea is to assign a shell alias in your `.bashrc` like:
 ```
-export HSQLDB_JAR=${HOME}/.m2/repository/org/hsqldb/hsqldb/2.5.0/hsqldb-2.5.0.jar
+export HSQLDB_JAR=${HOME}/.m2/repository/org/hsqldb/hsqldb/2.5.1/hsqldb-2.5.1.jar
 export SQLTOOL_JAR=${HOME}/.m2/repository/org/hsqldb/sqltool/2.5.0/sqltool-2.5.0.jar
 alias sqltool='rlwrap java -cp ${HSQLDB_JAR}:${SQLTOOL_JAR} org.hsqldb.cmdline.SqlTool --rcFile=${SQLTOOL_RC}'
 ```
 So you can simply type: `sqltool qortal`
 
 Don't forget to use `SHUTDOWN;` before exiting sqltool so that database files are closed cleanly.
+
+## Quick and dirty version
+
+With `sqltool-2.5.0.jar` and `qortal.jar` in current directory, and database in `db/`
+
+`java -cp qortal.jar:sqltool-2.5.0.jar org.hsqldb.cmdline.SqlTool --inlineRc=url=jdbc:hsqldb:file:db/blockchain`

README.md

@@ -9,4 +9,4 @@
 - Create basic *settings.json* file: `echo '{}' > settings.json`
 - Run JAR in same working directory as *settings.json*: `java -jar target/qortal-1.0.jar`
 - Wrap in shell script, add JVM flags, redirection, backgrounding, etc. as necessary.
-- Or use supplied example shell script: *run.sh*
+- Or use supplied example shell script: *start.sh*

TestNets.md

@@ -0,0 +1,69 @@
+# How to build a testnet
+
+## Create testnet blockchain config
+
+- You can begin by copying the mainnet blockchain config `src/main/resources/blockchain.json`
+- Insert `"isTestChain": true,` after the opening `{`
+- Modify testnet genesis block
+
+### Testnet genesis block
+
+- Set `timestamp` to a nearby future value, e.g. 15 mins from 'now'
+	This is to give yourself enough time to set up other testnet nodes
+- Retain the initial `ISSUE_ASSET` transactions!
+- Add `ACCOUNT_FLAGS` transactions with `"andMask": -1, "orMask": 1, "xorMask": 0` to create founders
+- Add at least one `REWARD_SHARE` transaction otherwise no-one can mint initial blocks!
+	You will need to calculate `rewardSharePublicKey` (and private key),
+	or make a new account on mainnet and use self-share key values
+- Add `ACCOUNT_LEVEL` transactions to set initial level of accounts as needed
+- Add `GENESIS` transactions to add QORT/LEGACY_QORA funds to accounts as needed
+
+## Testnet `settings.json`
+
+- Create a new `settings-test.json`
+- Make sure to add `"isTestNet": true,`
+- Make sure to reference testnet blockchain config file: `"blockchainConfig": "testchain.json",`
+- It is a good idea to use a separate database: `"repositoryPath": "db-testnet",`
+- You might also need to add `"bitcoinNet": "TEST3",` and `"litecoinNet": "TEST3",`
+
+## Other nodes
+
+- Copy `testchain.json` and `settings-test.json` to other nodes
+- Alternatively, you can run multiple nodes on the same machine by:
+	* Copying `settings-test.json` to `settings-test-1.json`
+	* Configure different `repositoryPath`
+	* Configure use of different ports:
+		+ `"apiPort": 22391,`
+		+ `"listenPort": 22392,`
+
+## Starting-up
+
+- Start up at least as many nodes as `minBlockchainPeers` (or adjust this value instead)
+- Probably best to perform API call `DELETE /peers/known`
+- Add other nodes via API call `POST /peers <peer-hostname-or-IP>`
+- Add minting private key to node(s) via API call `POST /admin/mintingaccounts <minting-private-key>`
+	This key must have corresponding `REWARD_SHARE` transaction in testnet genesis block
+- Wait for genesis block timestamp to pass
+- A node should mint block 2 approximately 60 seconds after genesis block timestamp
+- Other testnet nodes will sync *as long as there is at least `minBlockchainPeers` peers with an "up-to-date" chain`
+- You can also use API call `POST /admin/forcesync <connected-peer-IP-and-port>` on stuck nodes
+
+## Dealing with stuck chain
+
+Maybe your nodes have been offline and no-one has minted a recent testnet block.
+Your options are:
+
+- Start a new testnet from scratch
+- Fire up your testnet node(s)
+- Force one of your nodes to mint by:
+	+ Set a debugger breakpoint on Settings.getMinBlockchainPeers()
+	+ When breakpoint is hit, change `this.minBlockchainPeers` to zero, then continue
+- Once one of your nodes has minted blocks up to 'now', you can use "forcesync" on the other nodes
+
+## Tools
+
+- `qort` tool, but use `-t` option for default testnet API port (62391)
+- `qort` tool, but first set shell variable: `export BASE_URL=some-node-hostname-or-ip:port`
+- `qort` tool, but prepend with one-time shell variable: `BASE_URL=some-node-hostname-or-ip:port qort ......`
+- `peer-heights`, but use `-t` option, or `BASE_URL` shell variable as above
+

WindowsInstaller/dictionary.ail

@@ -3,95 +3,115 @@
   <!-- Control table -->
   <ENTRY id="Control.Text.CustomizeDataPathDlg#Description">
     <STRING lang="en" value="Do you want to store the blockchain, and other data, in a specific folder?"/>
+	<STRING lang="ru" value="Вы можете выбрать место хранения блокчейна и других данных."/>
     <STRING lang="zh" value="你想把区块链数据存放在一个特定的文件夹吗？"/>
     <STRING lang="zh_TW" value="你想把区块链数据存放在一个特定的文件夹吗？"/>
   </ENTRY>
   <ENTRY id="Control.Text.CustomizeDataPathDlg#Text">
     <STRING lang="en" value="Select one of the options below, then click &quot;Next&quot;."/>
+	<STRING lang="ru" value="Выберите один из вариантов ниже, затем нажмите Далее"/>
     <STRING lang="zh" value="请选择，然后“下一步”"/>
     <STRING lang="zh_TW" value="请选择，然后“下一步”"/>
   </ENTRY>
   <ENTRY id="Control.Text.CustomizeDataPathDlg#Title">
     <STRING lang="en" value="Choose Custom Data Storage Folder?"/>
+	<STRING lang="ru" value="Выберите место хранения данных."/>
     <STRING lang="zh" value="选择数据保存的文件夹?"/>
     <STRING lang="zh_TW" value="选择数据保存的文件夹?"/>
   </ENTRY>
   <ENTRY id="Control.Text.CustomizeDbDlg#Description">
     <STRING lang="en" value="Do you want to store the blockchain, and other data, in a specific folder?"/>
+	<STRING lang="ru" value="Вы можете выбрать место хранения блокчейна и других данных."/>
     <STRING lang="zh" value="Do you want to store the blockchain, and other data, in a specific folder?"/>
     <STRING lang="zh_TW" value="Do you want to store the blockchain, and other data, in a specific folder?"/>
   </ENTRY>
   <ENTRY id="Control.Text.CustomizeDbDlg#Title">
     <STRING lang="en" value="Choose Custom Data Storage Folder?"/>
+	<STRING lang="ru" value="Выберите место хранения данных."/>
     <STRING lang="zh" value="Choose Custom Data Storage Folder?"/>
     <STRING lang="zh_TW" value="Choose Custom Data Storage Folder?"/>
   </ENTRY>
   <ENTRY id="Control.Text.DataFolderDlg#Description">
     <STRING lang="en" value="This is the folder where the blockchain, and other data, will be stored."/>
+	<STRING lang="ru" value="Это папка, в которой будет храниться блокчейн и другие данные."/>
     <STRING lang="zh" value="这里是区块链及其它数据存放的文件夹"/>
     <STRING lang="zh_TW" value="这里是区块链及其它数据存放的文件夹"/>
   </ENTRY>
   <ENTRY id="Control.Text.DataFolderDlg#Text">
     <STRING lang="en" value="To store data in this folder, click &quot;[Text_Next]&quot;. To store data in a different folder, enter it below or click &quot;Browse&quot;."/>
+	<STRING lang="ru" value="Чтобы сохранить данные в этой папке, нажмите &quot;[Text_Next]&quot;. Чтобы сохранить данные в другой папке, введите ее ниже или нажмите &quot;Обзор&quot;."/>
     <STRING lang="zh" value="如果存放在这个文件夹，点 “下一步”。如果存放在其它位置，请选择“浏览”。"/>
     <STRING lang="zh_TW" value="如果存放在这个文件夹，点 “下一步”。如果存放在其它位置，请选择“浏览”。"/>
   </ENTRY>
   <ENTRY id="Control.Text.DataFolderDlg#Title">
     <STRING lang="en" value="Select Data Storage Folder"/>
+	<STRING lang="ru" value="Выберите папку для хранения данных"/>
     <STRING lang="zh" value="请选择文件存储地方"/>
     <STRING lang="zh_TW" value="请选择文件存储地方"/>
   </ENTRY>
   <ENTRY id="Control.Text.DbFolderDlg#Description">
     <STRING lang="en" value="This is the folder where the blockchain, and other data, will be stored."/>
+	<STRING lang="ru" value="Это папка, в которой будет храниться блокчейн и другие данные."/>
     <STRING lang="zh" value="This is the folder where the blockchain, and other data, will be stored."/>
     <STRING lang="zh_TW" value="This is the folder where the blockchain, and other data, will be stored."/>
   </ENTRY>
   <ENTRY id="Control.Text.DbFolderDlg#Title">
     <STRING lang="en" value="Select Data Storage Folder"/>
+	<STRING lang="ru" value="Выберите папку для хранения данных"/>
     <STRING lang="zh" value="请选择文件存储地方"/>
     <STRING lang="zh_TW" value="请选择文件存储地方"/>
   </ENTRY>
   <ENTRY id="Control.Text.NTPDialog#Description">
     <STRING lang="en" value="Reconfigure Windows for more accurate time?"/>
+	<STRING lang="ru" value="Настроить синхронизацию времени системы Windows?"/>
     <STRING lang="zh" value="重新配置Windows以获得更准确的时间？"/>
   </ENTRY>
   <ENTRY id="Control.Text.NTPDialog#Text_1">
     <STRING lang="en" value="An accurate Windows clock is required to connect to the [ProductName] network and make transactions."/>
+	<STRING lang="ru" value="Для подключения к сети Qortal и совершения транзакций требуется точная настройка времени Windows"/>
     <STRING lang="zh" value="需要准确的Windows时钟才能连接到[ProductName]网络并进行交易。"/>
   </ENTRY>
   <ENTRY id="Control.Text.NTPDialog#Text_2">
     <STRING lang="en" value="Select one of the options below, then click &quot;Next&quot;."/>
+	<STRING lang="ru" value="Выберите один из вариантов ниже, затем нажмите"/>
     <STRING lang="zh" value="请选择，然后“下一步”"/>
   </ENTRY>
   <ENTRY id="Control.Text.NTPDialog#Text_3">
     <STRING lang="en" value="Your computer&apos;s clock needs to be accurate to within 0.5 seconds."/>
+	<STRING lang="ru" value="Точность времени вашего компьютера должна составлять 0.5 секунд."/>
     <STRING lang="zh" value="您的计算机时钟需要准确到0.5秒内。"/>
   </ENTRY>
   <ENTRY id="Control.Text.NTPDialog#Title">
     <STRING lang="en" value="Windows clock accuracy"/>
+	<STRING lang="ru" value="Настройка времени системы Windows"/>
     <STRING lang="zh" value="Windows 时钟精度"/>
   </ENTRY>
   <ENTRY id="Control.Text.VerifyRemoveDlg#RemoveBlockchainCheckbox">
     <STRING lang="en" value="Remove downloaded blockchain and other data"/>
+	<STRING lang="ru" value="Удалить загруженный блокчейн и другие данные"/>
     <STRING lang="zh" value="删除您下载的区块链"/>
   </ENTRY>
   <!-- RadioButton table -->
   <ENTRY id="RadioButton.Text.CUSTOM_DB_BOOL#choose">
     <STRING lang="en" value="Choose custom data storage folder..."/>
+	<STRING lang="ru" value="Выбрать папку для хранения данных..."/>
     <STRING lang="zh" value="选择特定的文件夹存储"/>
     <STRING lang="zh_TW" value="选择特定的文件夹存储"/>
   </ENTRY>
   <ENTRY id="RadioButton.Text.CUSTOM_DB_BOOL#default">
     <STRING lang="en" value="Use default location "/>
+	<STRING lang="ru" value="Использовать папку по умолчанию"/>
     <STRING lang="zh" value="使用默认存储地点"/>
     <STRING lang="zh_TW" value="使用默认存储地点"/>
   </ENTRY>
   <ENTRY id="RadioButton.Text.RECONFIG_NTP#1">
     <STRING lang="en" value="Yes, configure Windows to use internet time servers (Recommended)"/>
+	<STRING lang="ru" value="Да, настроить синхронизацию времени Windows (Рекомендуется)"/>
     <STRING lang="zh" value="是，将Windows配置为使用多个Internet时间服务器 (推荐的)"/>
   </ENTRY>
   <ENTRY id="RadioButton.Text.RECONFIG_NTP#2">
     <STRING lang="en" value="No, I will manage clock accuracy myself"/>
+	<STRING lang="ru" value="Нет, я сам буду управлять настройками часов"/>
     <STRING lang="zh" value="不，我会自己管理时钟精度。"/>
   </ENTRY>
 </DICTIONARY>

lib/org/ciyam/AT/1.3.7/AT-1.3.7.pom

@@ -4,6 +4,6 @@
   <modelVersion>4.0.0</modelVersion>
   <groupId>org.ciyam</groupId>
   <artifactId>AT</artifactId>
-  <version>1.3.5</version>
+  <version>1.3.7</version>
   <description>POM was created from install:install-file</description>
 </project>

lib/org/ciyam/AT/1.3.8/AT-1.3.8.pom

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+  <modelVersion>4.0.0</modelVersion>
+  <groupId>org.ciyam</groupId>
+  <artifactId>AT</artifactId>
+  <version>1.3.8</version>
+  <description>POM was created from install:install-file</description>
+</project>

lib/org/ciyam/AT/maven-metadata-local.xml

@@ -3,11 +3,14 @@
   <groupId>org.ciyam</groupId>
   <artifactId>AT</artifactId>
   <versioning>
-    <release>1.3.5</release>
+    <release>1.3.8</release>
     <versions>
       <version>1.3.4</version>
       <version>1.3.5</version>
+      <version>1.3.6</version>
+      <version>1.3.7</version>
+      <version>1.3.8</version>
     </versions>
-    <lastUpdated>20200717104214</lastUpdated>
+    <lastUpdated>20200925114415</lastUpdated>
   </versioning>
 </metadata>

pom.xml

@@ -3,19 +3,20 @@
 	<modelVersion>4.0.0</modelVersion>
 	<groupId>org.qortal</groupId>
 	<artifactId>qortal</artifactId>
-	<version>1.3.0</version>
+	<version>1.5.2</version>
 	<packaging>jar</packaging>
 	<properties>
-		<bitcoinj.version>0.15.5</bitcoinj.version>
+		<skipTests>true</skipTests>
+		<altcoinj.version>bf9fb80</altcoinj.version>
+		<bitcoinj.version>0.15.10</bitcoinj.version>
 		<bouncycastle.version>1.64</bouncycastle.version>
 		<build.timestamp>${maven.build.timestamp}</build.timestamp>
-		<ciyam-at.version>1.3.5</ciyam-at.version>
+		<ciyam-at.version>1.3.8</ciyam-at.version>
 		<commons-net.version>3.6</commons-net.version>
 		<commons-text.version>1.8</commons-text.version>
 		<dagger.version>1.2.2</dagger.version>
 		<guava.version>28.1-jre</guava.version>
-		<hsqldb.version>2.5.0-fixed</hsqldb.version>
-		<hsqldb-sqltool.version>2.5.0</hsqldb-sqltool.version>
+		<hsqldb.version>2.5.1</hsqldb.version>
 		<jersey.version>2.29.1</jersey.version>
 		<jetty.version>9.4.29.v20200521</jetty.version>
 		<log4j.version>2.12.1</log4j.version>
@@ -199,6 +200,10 @@
 							<pattern>org.qortal.api.model**</pattern>
 							<template>${project.build.sourceDirectory}/org/qortal/data/package-info.java</template>
 						</package>
+						<package>
+							<pattern>org.qortal.api.model.**</pattern>
+							<template>${project.build.sourceDirectory}/org/qortal/data/package-info.java</template>
+						</package>
 					</packages>
 					<outputDirectory>${project.build.directory}/generated-sources/package-info</outputDirectory>
 				</configuration>
@@ -313,6 +318,14 @@
 					</execution>
 				</executions>
 			</plugin>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-surefire-plugin</artifactId>
+				<version>2.22.2</version>
+				<configuration>
+					<skipTests>${skipTests}</skipTests>
+				</configuration>
+			</plugin>
 		</plugins>
 		<pluginManagement>
 			<plugins>
@@ -375,6 +388,11 @@
 			<name>project</name>
 			<url>file:${project.basedir}/lib</url>
 		</repository>
+		<!-- jitpack for build-on-demand of altcoinj -->
+		<repository>
+			<id>jitpack.io</id>
+			<url>https://jitpack.io</url>
+		</repository>
 	</repositories>
 	<dependencies>
 		<!-- https://mvnrepository.com/artifact/org.codehaus.mojo/build-helper-maven-plugin -->
@@ -397,12 +415,6 @@
 			<artifactId>hsqldb</artifactId>
 			<version>${hsqldb.version}</version>
 		</dependency>
-		<dependency>
-			<groupId>org.hsqldb</groupId>
-			<artifactId>sqltool</artifactId>
-			<version>${hsqldb-sqltool.version}</version>
-			<scope>test</scope>
-		</dependency>
 		<!-- CIYAM AT (automated transactions) -->
 		<dependency>
 			<groupId>org.ciyam</groupId>
@@ -415,12 +427,23 @@
 			<artifactId>bitcoinj-core</artifactId>
 			<version>${bitcoinj.version}</version>
 		</dependency>
+		<!-- For Litecoin, etc. support, requires bitcoinj -->
+		<dependency>
+			<groupId>com.github.jjos2372</groupId>
+			<artifactId>altcoinj</artifactId>
+			<version>${altcoinj.version}</version>
+		</dependency>
 		<!-- Utilities -->
 		<dependency>
 			<groupId>com.googlecode.json-simple</groupId>
 			<artifactId>json-simple</artifactId>
 			<version>1.1.1</version>
 		</dependency>
+		<dependency>
+			<groupId>org.json</groupId>
+			<artifactId>json</artifactId>
+			<version>20210307</version>
+		</dependency>
 		<dependency>
 			<groupId>org.apache.commons</groupId>
 			<artifactId>commons-text</artifactId>

run.sh

@@ -1,51 +0,0 @@
-#!/bin/sh
-
-# There's no need to run as root, so don't allow it, for security reasons
-if [ "$USER" = "root" ]; then
-	echo "Please su to non-root user before running"
-	exit
-fi
-
-# Validate Java is installed and the minimum version is available
-MIN_JAVA_VER='11'
-
-if command -v java > /dev/null 2>&1; then
-    version=$(java -version 2>&1 | awk -F '"' '/version/ {print $2}')
-    version=$(echo $version | cut -d'.' -f1,2)
-    if [ `echo "${version}>=${MIN_JAVA_VER}" | bc` -eq 1 ]; then
-        echo 'Passed Java version check'
-    else
-        echo 'Please upgrade your Java to version 11 or greater'
-        exit 1
-    fi
-else
-  echo 'Java is not available, please install Java 11 or greater'
-  exit 1
-fi
-
-# No qortal.jar but we have a Maven built one?
-# Be helpful and copy across to correct location
-if [ ! -e qortal.jar -a -f target/qortal*.jar ]; then
-	echo "Copying Maven-built Qortal JAR to correct pathname"
-	cp target/qortal*.jar qortal.jar
-fi
-
-# Limits Java JVM stack size and maximum heap usage.
-# Comment out for bigger systems, e.g. non-routers
-# or when API documentation is enabled
-# JVM_MEMORY_ARGS="-Xss256k -Xmx128m"
-
-# Although java.net.preferIPv4Stack is supposed to be false
-# by default in Java 11, on some platforms (e.g. FreeBSD 12),
-# it is overriden to be true by default. Hence we explicitly
-# set it to true to obtain desired behaviour.
-nohup nice -n 20 java \
-	-Djava.net.preferIPv4Stack=false \
-	-XX:NativeMemoryTracking=summary \
-	${JVM_MEMORY_ARGS} \
-	-jar qortal.jar \
-	1>run.log 2>&1 &
-
-# Save backgrounded process's PID
-echo $! > run.pid
-echo qortal running as pid $!

run.sh

@@ -0,0 +1 @@
+start.sh

src/main/java/org/hsqldb/jdbc/HSQLDBPool.java

@@ -21,18 +21,28 @@ public class HSQLDBPool extends JDBCPool {
 	public Connection tryConnection() throws SQLException {
 		for (int i = 0; i < states.length(); i++) {
 			if (states.compareAndSet(i, RefState.available, RefState.allocated)) {
-				return connections[i].getConnection();
+				JDBCPooledConnection pooledConnection = connections[i];
+
+				if (pooledConnection == null)
+					// Probably shutdown situation
+					return null;
+
+				return pooledConnection.getConnection();
 			}
 
 			if (states.compareAndSet(i, RefState.empty, RefState.allocated)) {
 				try {
-					JDBCPooledConnection connection = (JDBCPooledConnection) source.getPooledConnection();
+					JDBCPooledConnection pooledConnection = (JDBCPooledConnection) source.getPooledConnection();
 
-					connection.addConnectionEventListener(this);
-					connection.addStatementEventListener(this);
-					connections[i] = connection;
+					if (pooledConnection == null)
+						// Probably shutdown situation
+						return null;
 
-					return connections[i].getConnection();
+					pooledConnection.addConnectionEventListener(this);
+					pooledConnection.addStatementEventListener(this);
+					connections[i] = pooledConnection;
+
+					return pooledConnection.getConnection();
 				} catch (SQLException e) {
 					states.set(i, RefState.empty);
 				}

src/main/java/org/qortal/ApplyUpdate.java

@@ -35,6 +35,8 @@ public class ApplyUpdate {
 	private static final String JAR_FILENAME = AutoUpdate.JAR_FILENAME;
 	private static final String NEW_JAR_FILENAME = AutoUpdate.NEW_JAR_FILENAME;
 	private static final String WINDOWS_EXE_LAUNCHER = "qortal.exe";
+	private static final String JAVA_TOOL_OPTIONS_NAME = "JAVA_TOOL_OPTIONS";
+	private static final String JAVA_TOOL_OPTIONS_VALUE = "-XX:MaxRAMFraction=4";
 
 	private static final long CHECK_INTERVAL = 10 * 1000L; // ms
 	private static final int MAX_ATTEMPTS = 12;
@@ -65,17 +67,19 @@ public class ApplyUpdate {
 	}
 
 	private static boolean shutdownNode() {
-		String BASE_URI = "http://localhost:" + Settings.getInstance().getApiPort() + "/";
-		LOGGER.info(String.format("Shutting down node using API via %s", BASE_URI));
+		String baseUri = "http://localhost:" + Settings.getInstance().getApiPort() + "/";
+		LOGGER.info(() -> String.format("Shutting down node using API via %s", baseUri));
 
 		int attempt;
 		for (attempt = 0; attempt < MAX_ATTEMPTS; ++attempt) {
-			LOGGER.info(String.format("Attempt #%d out of %d to shutdown node", attempt + 1, MAX_ATTEMPTS));
-			String response = ApiRequest.perform(BASE_URI + "admin/stop", null);
+			final int attemptForLogging = attempt;
+			LOGGER.info(() -> String.format("Attempt #%d out of %d to shutdown node", attemptForLogging + 1, MAX_ATTEMPTS));
+			String response = ApiRequest.perform(baseUri + "admin/stop", null);
 			if (response == null)
-				break;
+				// No response - consider node shut down
+				return true;
 
-			LOGGER.info(String.format("Response from API: %s", response));
+			LOGGER.info(() -> String.format("Response from API: %s", response));
 
 			try {
 				Thread.sleep(CHECK_INTERVAL);
@@ -99,19 +103,20 @@ public class ApplyUpdate {
 		Path newJar = Paths.get(NEW_JAR_FILENAME);
 
 		if (!Files.exists(newJar)) {
-			LOGGER.warn(String.format("Replacement JAR '%s' not found?", newJar));
+			LOGGER.warn(() -> String.format("Replacement JAR '%s' not found?", newJar));
 			return;
 		}
 
 		int attempt;
 		for (attempt = 0; attempt < MAX_ATTEMPTS; ++attempt) {
-			LOGGER.info(String.format("Attempt #%d out of %d to replace JAR", attempt + 1, MAX_ATTEMPTS));
+			final int attemptForLogging = attempt;
+			LOGGER.info(() -> String.format("Attempt #%d out of %d to replace JAR", attemptForLogging + 1, MAX_ATTEMPTS));
 
 			try {
 				Files.copy(newJar, realJar, StandardCopyOption.REPLACE_EXISTING);
 				break;
 			} catch (IOException e) {
-				LOGGER.info(String.format("Unable to replace JAR: %s", e.getMessage()));
+				LOGGER.info(() -> String.format("Unable to replace JAR: %s", e.getMessage()));
 
 				// Try again
 			}
@@ -119,6 +124,7 @@ public class ApplyUpdate {
 			try {
 				Thread.sleep(CHECK_INTERVAL);
 			} catch (InterruptedException e) {
+				LOGGER.warn("Ignoring interrupt...");
 				// Doggedly retry
 			}
 		}
@@ -129,13 +135,13 @@ public class ApplyUpdate {
 
 	private static void restartNode(String[] args) {
 		String javaHome = System.getProperty("java.home");
-		LOGGER.info(String.format("Java home: %s", javaHome));
+		LOGGER.info(() -> String.format("Java home: %s", javaHome));
 
 		Path javaBinary = Paths.get(javaHome, "bin", "java");
-		LOGGER.info(String.format("Java binary: %s", javaBinary));
+		LOGGER.info(() -> String.format("Java binary: %s", javaBinary));
 
 		Path exeLauncher = Paths.get(WINDOWS_EXE_LAUNCHER);
-		LOGGER.info(String.format("Windows EXE launcher: %s", exeLauncher));
+		LOGGER.info(() -> String.format("Windows EXE launcher: %s", exeLauncher));
 
 		List<String> javaCmd;
 		if (Files.exists(exeLauncher)) {
@@ -156,9 +162,16 @@ public class ApplyUpdate {
 		}
 
 		try {
-			LOGGER.info(String.format("Restarting node with: %s", String.join(" ", javaCmd)));
+			LOGGER.info(() -> String.format("Restarting node with: %s", String.join(" ", javaCmd)));
 
-			new ProcessBuilder(javaCmd).start();
+			ProcessBuilder processBuilder = new ProcessBuilder(javaCmd);
+
+			if (Files.exists(exeLauncher)) {
+				LOGGER.info(() -> String.format("Setting env %s to %s", JAVA_TOOL_OPTIONS_NAME, JAVA_TOOL_OPTIONS_VALUE));
+				processBuilder.environment().put(JAVA_TOOL_OPTIONS_NAME, JAVA_TOOL_OPTIONS_VALUE);
+			}
+
+			processBuilder.start();
 		} catch (IOException e) {
 			LOGGER.error(String.format("Failed to restart node (BAD): %s", e.getMessage()));
 		}

src/main/java/org/qortal/RepositoryMaintenance.java

@@ -0,0 +1,75 @@
+package org.qortal;
+
+import java.security.Security;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.bouncycastle.jce.provider.BouncyCastleProvider;
+import org.bouncycastle.jsse.provider.BouncyCastleJsseProvider;
+import org.qortal.controller.Controller;
+import org.qortal.repository.DataException;
+import org.qortal.repository.Repository;
+import org.qortal.repository.RepositoryFactory;
+import org.qortal.repository.RepositoryManager;
+import org.qortal.repository.hsqldb.HSQLDBRepositoryFactory;
+import org.qortal.settings.Settings;
+
+public class RepositoryMaintenance {
+
+	static {
+		// This must go before any calls to LogManager/Logger
+		System.setProperty("java.util.logging.manager", "org.apache.logging.log4j.jul.LogManager");
+	}
+
+	private static final Logger LOGGER = LogManager.getLogger(RepositoryMaintenance.class);
+
+	public static void main(String[] args) {
+		LOGGER.info("Repository maintenance starting up...");
+
+		Security.insertProviderAt(new BouncyCastleProvider(), 0);
+		Security.insertProviderAt(new BouncyCastleJsseProvider(), 1);
+
+		// Load/check settings, which potentially sets up blockchain config, etc.
+		try {
+			if (args.length > 0)
+				Settings.fileInstance(args[0]);
+			else
+				Settings.getInstance();
+		} catch (Throwable t) {
+			LOGGER.error("Settings file error: " + t.getMessage());
+			System.exit(2);
+		}
+
+		LOGGER.info("Opening repository");
+		try {
+			RepositoryFactory repositoryFactory = new HSQLDBRepositoryFactory(Controller.getRepositoryUrl());
+			RepositoryManager.setRepositoryFactory(repositoryFactory);
+		} catch (DataException e) {
+			// If exception has no cause then repository is in use by some other process.
+			if (e.getCause() == null) {
+				LOGGER.info("Repository in use by another process?");
+			} else {
+				LOGGER.error("Unable to start repository", e);
+			}
+
+			System.exit(1);
+		}
+
+		LOGGER.info("Starting repository periodic maintenance. This can take a while...");
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			repository.performPeriodicMaintenance();
+
+			LOGGER.info("Repository periodic maintenance completed");
+		} catch (DataException e) {
+			LOGGER.error("Repository periodic maintenance failed", e);
+		}
+
+		try {
+			LOGGER.info("Shutting down repository");
+			RepositoryManager.closeRepositoryFactory();
+		} catch (DataException e) {
+			LOGGER.error("Error occurred while shutting down repository", e);
+		}
+	}
+
+}

src/main/java/org/qortal/api/ApiError.java

@@ -15,7 +15,7 @@ public enum ApiError {
 	// COMMON
 	// UNKNOWN(0, 500),
 	JSON(1, 400),
-	// NO_BALANCE(2, 422),
+	INSUFFICIENT_BALANCE(2, 402),
 	// NOT_YET_RELEASED(3, 422),
 	UNAUTHORIZED(4, 403),
 	REPOSITORY_ISSUE(5, 500),
@@ -126,10 +126,10 @@ public enum ApiError {
 	// Groups
 	GROUP_UNKNOWN(1101, 404),
 
-	// Bitcoin
-	BTC_NETWORK_ISSUE(1201, 500),
-	BTC_BALANCE_ISSUE(1202, 402),
-	BTC_TOO_SOON(1203, 408);
+	// Foreign blockchain
+	FOREIGN_BLOCKCHAIN_NETWORK_ISSUE(1201, 500),
+	FOREIGN_BLOCKCHAIN_BALANCE_ISSUE(1202, 402),
+	FOREIGN_BLOCKCHAIN_TOO_SOON(1203, 408);
 
 	private static final Map<Integer, ApiError> map = stream(ApiError.values()).collect(toMap(apiError -> apiError.code, apiError -> apiError));
 

src/main/java/org/qortal/api/ApiService.java

@@ -43,6 +43,7 @@ import org.qortal.api.websocket.ActiveChatsWebSocket;
 import org.qortal.api.websocket.AdminStatusWebSocket;
 import org.qortal.api.websocket.BlocksWebSocket;
 import org.qortal.api.websocket.ChatMessagesWebSocket;
+import org.qortal.api.websocket.PresenceWebSocket;
 import org.qortal.api.websocket.TradeBotWebSocket;
 import org.qortal.api.websocket.TradeOffersWebSocket;
 import org.qortal.settings.Settings;
@@ -200,6 +201,7 @@ public class ApiService {
 			context.addServlet(ChatMessagesWebSocket.class, "/websockets/chat/messages");
 			context.addServlet(TradeOffersWebSocket.class, "/websockets/crosschain/tradeoffers");
 			context.addServlet(TradeBotWebSocket.class, "/websockets/crosschain/tradebot");
+			context.addServlet(PresenceWebSocket.class, "/websockets/presence");
 
 			// Start server
 			this.server.start();

src/main/java/org/qortal/api/Base58TypeAdapter.java

@@ -2,7 +2,7 @@ package org.qortal.api;
 
 import javax.xml.bind.annotation.adapters.XmlAdapter;
 
-import org.bitcoinj.core.Base58;
+import org.qortal.utils.Base58;
 
 public class Base58TypeAdapter extends XmlAdapter<String, byte[]> {
 

src/main/java/org/qortal/api/Security.java

@@ -5,10 +5,20 @@ import java.net.UnknownHostException;
 
 import javax.servlet.http.HttpServletRequest;
 
-public class Security {
+import org.qortal.settings.Settings;
+
+public abstract class Security {
+
+	public static final String API_KEY_HEADER = "X-API-KEY";
 
-	// TODO: replace with proper authentication
 	public static void checkApiCallAllowed(HttpServletRequest request) {
+		String expectedApiKey = Settings.getInstance().getApiKey();
+		String passedApiKey = request.getHeader(API_KEY_HEADER);
+
+		if ((expectedApiKey != null && !expectedApiKey.equals(passedApiKey)) ||
+				(passedApiKey != null && !passedApiKey.equals(expectedApiKey)))
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.UNAUTHORIZED);
+
 		InetAddress remoteAddr;
 		try {
 			remoteAddr = InetAddress.getByName(request.getRemoteAddr());
@@ -19,4 +29,5 @@ public class Security {
 		if (!remoteAddr.isLoopbackAddress())
 			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.UNAUTHORIZED);
 	}
+
 }

src/main/java/org/qortal/api/model/ActivitySummary.java

@@ -1,5 +1,6 @@
 package org.qortal.api.model;
 
+import java.util.Collections;
 import java.util.EnumMap;
 import java.util.Map;
 
@@ -13,17 +14,61 @@ import org.qortal.transaction.Transaction.TransactionType;
 @XmlAccessorType(XmlAccessType.FIELD)
 public class ActivitySummary {
 
-	public int blockCount;
-	public int transactionCount;
-	public int assetsIssued;
-	public int namesRegistered;
+	private int blockCount;
+	private int assetsIssued;
+	private int namesRegistered;
 
 	// Assuming TransactionType values are contiguous so 'length' equals count
 	@XmlJavaTypeAdapter(TransactionCountMapXmlAdapter.class)
-	public Map<TransactionType, Integer> transactionCountByType = new EnumMap<>(TransactionType.class);
+	private Map<TransactionType, Integer> transactionCountByType = new EnumMap<>(TransactionType.class);
+	private int totalTransactionCount = 0;
 
 	public ActivitySummary() {
 		// Needed for JAXB
 	}
 
+	public int getBlockCount() {
+		return this.blockCount;
+	}
+
+	public void setBlockCount(int blockCount) {
+		this.blockCount = blockCount;
+	}
+
+	public int getTotalTransactionCount() {
+		return this.totalTransactionCount;
+	}
+
+	public int getAssetsIssued() {
+		return this.assetsIssued;
+	}
+
+	public void setAssetsIssued(int assetsIssued) {
+		this.assetsIssued = assetsIssued;
+	}
+
+	public int getNamesRegistered() {
+		return this.namesRegistered;
+	}
+
+	public void setNamesRegistered(int namesRegistered) {
+		this.namesRegistered = namesRegistered;
+	}
+
+	public Map<TransactionType, Integer> getTransactionCountByType() {
+		return Collections.unmodifiableMap(this.transactionCountByType);
+	}
+
+	public void setTransactionCountByType(TransactionType transactionType, int transactionCount) {
+		this.transactionCountByType.put(transactionType, transactionCount);
+
+		this.totalTransactionCount = this.transactionCountByType.values().stream().mapToInt(Integer::intValue).sum();
+	}
+
+	public void setTransactionCountByType(Map<TransactionType, Integer> transactionCountByType) {
+		this.transactionCountByType = new EnumMap<>(transactionCountByType);
+
+		this.totalTransactionCount = this.transactionCountByType.values().stream().mapToInt(Integer::intValue).sum();
+	}
+
 }

src/main/java/org/qortal/api/model/BlockInfo.java

@@ -1,71 +0,0 @@
-package org.qortal.api.model;
-
-import javax.xml.bind.annotation.XmlAccessType;
-import javax.xml.bind.annotation.XmlAccessorType;
-
-import org.qortal.data.account.RewardShareData;
-import org.qortal.data.block.BlockData;
-import org.qortal.repository.DataException;
-import org.qortal.repository.Repository;
-import org.qortal.repository.RepositoryManager;
-
-@XmlAccessorType(XmlAccessType.FIELD)
-public class BlockInfo {
-
-	private byte[] signature;
-	private int height;
-	private long timestamp;
-	private int transactionCount;
-	private String minterAddress;
-
-	protected BlockInfo() {
-		/* For JAXB */
-	}
-
-	public BlockInfo(byte[] signature, int height, long timestamp, int transactionCount, String minterAddress) {
-		this.signature = signature;
-		this.height = height;
-		this.timestamp = timestamp;
-		this.transactionCount = transactionCount;
-		this.minterAddress = minterAddress;
-	}
-
-	public BlockInfo(BlockData blockData) {
-		// Convert BlockData to BlockInfo, using additional data
-		this.minterAddress = "unknown?";
-
-		try (final Repository repository = RepositoryManager.getRepository()) {
-			RewardShareData rewardShareData = repository.getAccountRepository().getRewardShare(blockData.getMinterPublicKey());
-			if (rewardShareData != null)
-				this.minterAddress = rewardShareData.getMintingAccount();
-		} catch (DataException e) {
-			// We'll carry on with placeholder minterAddress then...
-		}
-
-		this.signature = blockData.getSignature();
-		this.height = blockData.getHeight();
-		this.timestamp = blockData.getTimestamp();
-		this.transactionCount = blockData.getTransactionCount();
-	}
-
-	public byte[] getSignature() {
-		return this.signature;
-	}
-
-	public int getHeight() {
-		return this.height;
-	}
-
-	public long getTimestamp() {
-		return this.timestamp;
-	}
-
-	public int getTransactionCount() {
-		return this.transactionCount;
-	}
-
-	public String getMinterAddress() {
-		return this.minterAddress;
-	}
-
-}

src/main/java/org/qortal/api/model/BlockMintingInfo.java

@@ -0,0 +1,23 @@
+package org.qortal.api.model;
+
+import javax.xml.bind.annotation.XmlAccessType;
+import javax.xml.bind.annotation.XmlAccessorType;
+import java.math.BigDecimal;
+import java.math.BigInteger;
+
+@XmlAccessorType(XmlAccessType.FIELD)
+public class BlockMintingInfo {
+
+	public byte[] minterPublicKey;
+	public int minterLevel;
+	public int onlineAccountsCount;
+	public BigDecimal maxDistance;
+	public BigInteger keyDistance;
+	public double keyDistanceRatio;
+	public long timestamp;
+	public long timeDelta;
+
+	public BlockMintingInfo() {
+	}
+
+}

src/main/java/org/qortal/api/model/ConnectedPeer.java

@@ -1,61 +1,74 @@
 package org.qortal.api.model;
 
-import javax.xml.bind.annotation.XmlAccessType;
-import javax.xml.bind.annotation.XmlAccessorType;
-
+import io.swagger.v3.oas.annotations.media.Schema;
 import org.qortal.data.network.PeerChainTipData;
 import org.qortal.data.network.PeerData;
 import org.qortal.network.Handshake;
 import org.qortal.network.Peer;
 
-import io.swagger.v3.oas.annotations.media.Schema;
+import javax.xml.bind.annotation.XmlAccessType;
+import javax.xml.bind.annotation.XmlAccessorType;
+import java.util.UUID;
+import java.util.concurrent.TimeUnit;
 
 @XmlAccessorType(XmlAccessType.FIELD)
 public class ConnectedPeer {
 
-	public enum Direction {
-		INBOUND,
-		OUTBOUND;
-	}
-	public Direction direction;
-	public Handshake handshakeStatus;
-	public Long lastPing;
-	public Long connectedWhen;
-	public Long peersConnectedWhen;
+    public enum Direction {
+        INBOUND,
+        OUTBOUND;
+    }
 
-	public String address;
-	public String version;
+    public Direction direction;
+    public Handshake handshakeStatus;
+    public Long lastPing;
+    public Long connectedWhen;
+    public Long peersConnectedWhen;
 
-	public String nodeId;
+    public String address;
+    public String version;
 
-	public Integer lastHeight;
-	@Schema(example = "base58")
-	public byte[] lastBlockSignature;
-	public Long lastBlockTimestamp;
+    public String nodeId;
 
-	protected ConnectedPeer() {
-	}
+    public Integer lastHeight;
+    @Schema(example = "base58")
+    public byte[] lastBlockSignature;
+    public Long lastBlockTimestamp;
+    public UUID connectionId;
+    public String age;
 
-	public ConnectedPeer(Peer peer) {
-		this.direction = peer.isOutbound() ? Direction.OUTBOUND : Direction.INBOUND;
-		this.handshakeStatus = peer.getHandshakeStatus();
-		this.lastPing = peer.getLastPing();
+    protected ConnectedPeer() {
+    }
 
-		PeerData peerData = peer.getPeerData();
-		this.connectedWhen = peer.getConnectionTimestamp();
-		this.peersConnectedWhen = peer.getPeersConnectionTimestamp();
+    public ConnectedPeer(Peer peer) {
+        this.direction = peer.isOutbound() ? Direction.OUTBOUND : Direction.INBOUND;
+        this.handshakeStatus = peer.getHandshakeStatus();
+        this.lastPing = peer.getLastPing();
 
-		this.address = peerData.getAddress().toString();
+        PeerData peerData = peer.getPeerData();
+        this.connectedWhen = peer.getConnectionTimestamp();
+        this.peersConnectedWhen = peer.getPeersConnectionTimestamp();
 
-		this.version = peer.getPeersVersionString();
-		this.nodeId = peer.getPeersNodeId();
+        this.address = peerData.getAddress().toString();
 
-		PeerChainTipData peerChainTipData = peer.getChainTipData();
-		if (peerChainTipData != null) {
-			this.lastHeight = peerChainTipData.getLastHeight();
-			this.lastBlockSignature = peerChainTipData.getLastBlockSignature();
-			this.lastBlockTimestamp = peerChainTipData.getLastBlockTimestamp();
-		}
-	}
+        this.version = peer.getPeersVersionString();
+        this.nodeId = peer.getPeersNodeId();
+        this.connectionId = peer.getPeerConnectionId();
+        if (peer.getConnectionEstablishedTime() > 0) {
+            long age = (System.currentTimeMillis() - peer.getConnectionEstablishedTime());
+            long minutes = TimeUnit.MILLISECONDS.toMinutes(age);
+            long seconds = TimeUnit.MILLISECONDS.toSeconds(age) - TimeUnit.MINUTES.toSeconds(minutes);
+            this.age = String.format("%dm %ds", minutes, seconds);
+        } else {
+            this.age = "connecting...";
+        }
+
+        PeerChainTipData peerChainTipData = peer.getChainTipData();
+        if (peerChainTipData != null) {
+            this.lastHeight = peerChainTipData.getLastHeight();
+            this.lastBlockSignature = peerChainTipData.getLastBlockSignature();
+            this.lastBlockTimestamp = peerChainTipData.getLastBlockTimestamp();
+        }
+    }
 
 }

src/main/java/org/qortal/api/model/CrossChainBitcoinP2SHStatus.java

@@ -1,31 +0,0 @@
-package org.qortal.api.model;
-
-import java.math.BigDecimal;
-
-import javax.xml.bind.annotation.XmlAccessType;
-import javax.xml.bind.annotation.XmlAccessorType;
-
-import io.swagger.v3.oas.annotations.media.Schema;
-
-@XmlAccessorType(XmlAccessType.FIELD)
-public class CrossChainBitcoinP2SHStatus {
-
-	@Schema(description = "Bitcoin P2SH address", example = "3CdH27kTpV8dcFHVRYjQ8EEV5FJg9X8pSJ (mainnet), 2fMiRRXVsxhZeyfum9ifybZvaMHbQTmwdZw (testnet)")
-	public String bitcoinP2shAddress;
-
-	@Schema(description = "Bitcoin P2SH balance")
-	public BigDecimal bitcoinP2shBalance;
-
-	@Schema(description = "Can P2SH redeem yet?")
-	public boolean canRedeem;
-
-	@Schema(description = "Can P2SH refund yet?")
-	public boolean canRefund;
-
-	@Schema(description = "Secret extracted by P2SH redeemer")
-	public byte[] secret;
-
-	public CrossChainBitcoinP2SHStatus() {
-	}
-
-}

src/main/java/org/qortal/api/model/CrossChainBitcoinRefundRequest.java

@@ -22,6 +22,9 @@ public class CrossChainBitcoinRefundRequest {
 	@Schema(description = "Bitcoin miner fee", example = "0.00001000")
 	public BigDecimal bitcoinMinerFee;
 
+	@Schema(description = "Bitcoin HASH160(public key) for receiving funds, or omit to derive from private key", example = "u17kBVKkKSp12oUzaxFwNnq1JZf")
+	public byte[] receivingAccountInfo;
+
 	public CrossChainBitcoinRefundRequest() {
 	}
 

src/main/java/org/qortal/api/model/CrossChainBitcoinyHTLCStatus.java

@@ -0,0 +1,31 @@
+package org.qortal.api.model;
+
+import java.math.BigDecimal;
+
+import javax.xml.bind.annotation.XmlAccessType;
+import javax.xml.bind.annotation.XmlAccessorType;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+
+@XmlAccessorType(XmlAccessType.FIELD)
+public class CrossChainBitcoinyHTLCStatus {
+
+	@Schema(description = "P2SH address", example = "3CdH27kTpV8dcFHVRYjQ8EEV5FJg9X8pSJ (mainnet), 2fMiRRXVsxhZeyfum9ifybZvaMHbQTmwdZw (testnet)")
+	public String bitcoinP2shAddress;
+
+	@Schema(description = "P2SH balance")
+	public BigDecimal bitcoinP2shBalance;
+
+	@Schema(description = "Can HTLC redeem yet?")
+	public boolean canRedeem;
+
+	@Schema(description = "Can HTLC refund yet?")
+	public boolean canRefund;
+
+	@Schema(description = "Secret used by HTLC redeemer")
+	public byte[] secret;
+
+	public CrossChainBitcoinyHTLCStatus() {
+	}
+
+}

src/main/java/org/qortal/api/model/CrossChainDualSecretRequest.java

@@ -0,0 +1,29 @@
+package org.qortal.api.model;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+
+import javax.xml.bind.annotation.XmlAccessType;
+import javax.xml.bind.annotation.XmlAccessorType;
+
+@XmlAccessorType(XmlAccessType.FIELD)
+public class CrossChainDualSecretRequest {
+
+	@Schema(description = "Public key to match AT's trade 'partner'", example = "C6wuddsBV3HzRrXUtezE7P5MoRXp5m3mEDokRDGZB6ry")
+	public byte[] partnerPublicKey;
+
+	@Schema(description = "Qortal AT address")
+	public String atAddress;
+
+	@Schema(description = "secret-A (32 bytes)", example = "FHMzten4he9jZ4HGb4297Utj6F5g2w7serjq2EnAg2s1")
+	public byte[] secretA;
+
+	@Schema(description = "secret-B (32 bytes)", example = "EN2Bgx3BcEMtxFCewmCVSMkfZjVKYhx3KEXC5A21KBGx")
+	public byte[] secretB;
+
+	@Schema(description = "Qortal address for receiving QORT from AT")
+	public String receivingAddress;
+
+	public CrossChainDualSecretRequest() {
+	}
+
+}

src/main/java/org/qortal/api/model/CrossChainOfferSummary.java

@@ -4,7 +4,7 @@ import javax.xml.bind.annotation.XmlAccessType;
 import javax.xml.bind.annotation.XmlAccessorType;
 import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
 
-import org.qortal.crosschain.BTCACCT;
+import org.qortal.crosschain.AcctMode;
 import org.qortal.data.crosschain.CrossChainTradeData;
 
 import io.swagger.v3.oas.annotations.media.Schema;
@@ -16,26 +16,41 @@ public class CrossChainOfferSummary {
 	// Properties
 
 	@Schema(description = "AT's Qortal address")
-	public String qortalAtAddress;
+	private String qortalAtAddress;
 
 	@Schema(description = "AT creator's Qortal address")
-	public String qortalCreator;
+	private String qortalCreator;
+
+	@Schema(description = "AT creator's ephemeral trading key-pair represented as Qortal address")
+	private String qortalCreatorTradeAddress;
 
 	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
 	private long qortAmount;
 
+	@Schema(description = "Bitcoin amount - DEPRECATED: use foreignAmount")
 	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
+	@Deprecated
 	private long btcAmount;
 
+	@Schema(description = "Foreign blockchain amount")
+	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
+	private long foreignAmount;
+
 	@Schema(description = "Suggested trade timeout (minutes)", example = "10080")
 	private int tradeTimeout;
 
-	private BTCACCT.Mode mode;
+	@Schema(description = "Current AT execution mode")
+	private AcctMode mode;
 
 	private long timestamp;
 
+	@Schema(description = "Trade partner's Qortal receiving address")
 	private String partnerQortalReceivingAddress;
 
+	private String foreignBlockchain;
+
+	private String acctName;
+
 	protected CrossChainOfferSummary() {
 		/* For JAXB */
 	}
@@ -43,12 +58,16 @@ public class CrossChainOfferSummary {
 	public CrossChainOfferSummary(CrossChainTradeData crossChainTradeData, long timestamp) {
 		this.qortalAtAddress = crossChainTradeData.qortalAtAddress;
 		this.qortalCreator = crossChainTradeData.qortalCreator;
+		this.qortalCreatorTradeAddress = crossChainTradeData.qortalCreatorTradeAddress;
 		this.qortAmount = crossChainTradeData.qortAmount;
-		this.btcAmount = crossChainTradeData.expectedBitcoin;
+		this.foreignAmount = crossChainTradeData.expectedForeignAmount;
+		this.btcAmount = this.foreignAmount; // Duplicate for deprecated field
 		this.tradeTimeout = crossChainTradeData.tradeTimeout;
 		this.mode = crossChainTradeData.mode;
 		this.timestamp = timestamp;
 		this.partnerQortalReceivingAddress = crossChainTradeData.qortalPartnerReceivingAddress;
+		this.foreignBlockchain = crossChainTradeData.foreignBlockchain;
+		this.acctName = crossChainTradeData.acctName;
 	}
 
 	public String getQortalAtAddress() {
@@ -59,6 +78,10 @@ public class CrossChainOfferSummary {
 		return this.qortalCreator;
 	}
 
+	public String getQortalCreatorTradeAddress() {
+		return this.qortalCreatorTradeAddress;
+	}
+
 	public long getQortAmount() {
 		return this.qortAmount;
 	}
@@ -67,11 +90,15 @@ public class CrossChainOfferSummary {
 		return this.btcAmount;
 	}
 
+	public long getForeignAmount() {
+		return this.foreignAmount;
+	}
+
 	public int getTradeTimeout() {
 		return this.tradeTimeout;
 	}
 
-	public BTCACCT.Mode getMode() {
+	public AcctMode getMode() {
 		return this.mode;
 	}
 
@@ -83,4 +110,18 @@ public class CrossChainOfferSummary {
 		return this.partnerQortalReceivingAddress;
 	}
 
+	public String getForeignBlockchain() {
+		return this.foreignBlockchain;
+	}
+
+	public String getAcctName() {
+		return this.acctName;
+	}
+
+	// For debugging mostly
+
+	public String toString() {
+		return String.format("%s: %s", this.qortalAtAddress, this.mode);
+	}
+
 }

src/main/java/org/qortal/api/model/CrossChainSecretRequest.java

@@ -8,17 +8,14 @@ import io.swagger.v3.oas.annotations.media.Schema;
 @XmlAccessorType(XmlAccessType.FIELD)
 public class CrossChainSecretRequest {
 
-	@Schema(description = "Public key to match AT's trade 'partner'", example = "C6wuddsBV3HzRrXUtezE7P5MoRXp5m3mEDokRDGZB6ry")
-	public byte[] partnerPublicKey;
+	@Schema(description = "Private key to match AT's trade 'partner'", example = "C6wuddsBV3HzRrXUtezE7P5MoRXp5m3mEDokRDGZB6ry")
+	public byte[] partnerPrivateKey;
 
 	@Schema(description = "Qortal AT address")
 	public String atAddress;
 
-	@Schema(description = "secret-A (32 bytes)", example = "FHMzten4he9jZ4HGb4297Utj6F5g2w7serjq2EnAg2s1")
-	public byte[] secretA;
-
-	@Schema(description = "secret-B (32 bytes)", example = "EN2Bgx3BcEMtxFCewmCVSMkfZjVKYhx3KEXC5A21KBGx")
-	public byte[] secretB;
+	@Schema(description = "Secret (32 bytes)", example = "FHMzten4he9jZ4HGb4297Utj6F5g2w7serjq2EnAg2s1")
+	public byte[] secret;
 
 	@Schema(description = "Qortal address for receiving QORT from AT")
 	public String receivingAddress;

src/main/java/org/qortal/api/model/CrossChainTradeSummary.java

@@ -6,6 +6,8 @@ import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
 
 import org.qortal.data.crosschain.CrossChainTradeData;
 
+import io.swagger.v3.oas.annotations.media.Schema;
+
 // All properties to be converted to JSON via JAXB
 @XmlAccessorType(XmlAccessType.FIELD)
 public class CrossChainTradeSummary {
@@ -15,9 +17,14 @@ public class CrossChainTradeSummary {
 	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
 	private long qortAmount;
 
+	@Deprecated
+	@Schema(description = "DEPRECATED: use foreignAmount instead")
 	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
 	private long btcAmount;
 
+	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
+	private long foreignAmount;
+
 	protected CrossChainTradeSummary() {
 		/* For JAXB */
 	}
@@ -25,7 +32,8 @@ public class CrossChainTradeSummary {
 	public CrossChainTradeSummary(CrossChainTradeData crossChainTradeData, long timestamp) {
 		this.tradeTimestamp = timestamp;
 		this.qortAmount = crossChainTradeData.qortAmount;
-		this.btcAmount = crossChainTradeData.expectedBitcoin;
+		this.foreignAmount = crossChainTradeData.expectedForeignAmount;
+		this.btcAmount = this.foreignAmount;
 	}
 
 	public long getTradeTimestamp() {
@@ -40,4 +48,7 @@ public class CrossChainTradeSummary {
 		return this.btcAmount;
 	}
 
+	public long getForeignAmount() {
+		return this.foreignAmount;
+	}
 }

src/main/java/org/qortal/api/model/NodeInfo.java

@@ -11,6 +11,7 @@ public class NodeInfo {
 	public String buildVersion;
 	public long buildTimestamp;
 	public String nodeId;
+	public boolean isTestNet;
 
 	public NodeInfo() {
 	}

src/main/java/org/qortal/api/model/NodeStatus.java

@@ -20,17 +20,14 @@ public class NodeStatus {
 	public final int height;
 
 	public NodeStatus() {
-		isMintingPossible = Controller.getInstance().isMintingPossible();
-		isSynchronizing = Controller.getInstance().isSynchronizing();
+		this.isMintingPossible = Controller.getInstance().isMintingPossible();
 
-		if (isSynchronizing)
-			syncPercent = Controller.getInstance().getSyncPercent();
-		else
-			syncPercent = null;
+		this.syncPercent = Controller.getInstance().getSyncPercent();
+		this.isSynchronizing = this.syncPercent != null;
 
-		numberOfConnections = Network.getInstance().getHandshakedPeers().size();
+		this.numberOfConnections = Network.getInstance().getHandshakedPeers().size();
 
-		height = Controller.getInstance().getChainHeight();
+		this.height = Controller.getInstance().getChainHeight();
 	}
 
 }

src/main/java/org/qortal/api/model/SimpleForeignTransaction.java

@@ -0,0 +1,157 @@
+package org.qortal.api.model;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Objects;
+
+import javax.xml.bind.annotation.XmlAccessType;
+import javax.xml.bind.annotation.XmlAccessorType;
+
+@XmlAccessorType(XmlAccessType.FIELD)
+public class SimpleForeignTransaction {
+
+	public static class AddressAmount {
+		public final String address;
+		public final long amount;
+
+		protected AddressAmount() {
+			/* For JAXB */
+			this.address = null;
+			this.amount = 0;
+		}
+
+		public AddressAmount(String address, long amount) {
+			this.address = address;
+			this.amount = amount;
+		}
+	}
+
+	private String txHash;
+	private long timestamp;
+
+	private List<AddressAmount> inputs;
+
+	public static class Output {
+		public final List<String> addresses;
+		public final long amount;
+
+		protected Output() {
+			/* For JAXB */
+			this.addresses = null;
+			this.amount = 0;
+		}
+
+		public Output(List<String> addresses, long amount) {
+			this.addresses = addresses;
+			this.amount = amount;
+		}
+	}
+	private List<Output> outputs;
+
+	private long totalAmount;
+	private long fees;
+
+	private Boolean isSentNotReceived;
+
+	protected SimpleForeignTransaction() {
+		/* For JAXB */
+	}
+
+	private SimpleForeignTransaction(Builder builder) {
+		this.txHash = builder.txHash;
+		this.timestamp = builder.timestamp;
+		this.inputs = Collections.unmodifiableList(builder.inputs);
+		this.outputs = Collections.unmodifiableList(builder.outputs);
+
+		Objects.requireNonNull(this.txHash);
+		if (timestamp <= 0)
+			throw new IllegalArgumentException("timestamp must be positive");
+
+		long totalGrossAmount = this.inputs.stream().map(addressAmount -> addressAmount.amount).reduce(0L, Long::sum);
+		this.totalAmount = this.outputs.stream().map(addressAmount -> addressAmount.amount).reduce(0L, Long::sum);
+
+		this.fees = totalGrossAmount - this.totalAmount;
+
+		this.isSentNotReceived = builder.isSentNotReceived;
+	}
+
+	public String getTxHash() {
+		return this.txHash;
+	}
+
+	public long getTimestamp() {
+		return this.timestamp;
+	}
+
+	public List<AddressAmount> getInputs() {
+		return this.inputs;
+	}
+
+	public List<Output> getOutputs() {
+		return this.outputs;
+	}
+
+	public long getTotalAmount() {
+		return this.totalAmount;
+	}
+
+	public long getFees() {
+		return this.fees;
+	}
+
+	public Boolean isSentNotReceived() {
+		return this.isSentNotReceived;
+	}
+
+	public static class Builder {
+		private String txHash;
+		private long timestamp;
+		private List<AddressAmount> inputs = new ArrayList<>();
+		private List<Output> outputs = new ArrayList<>();
+		private Boolean isSentNotReceived;
+
+		public Builder txHash(String txHash) {
+			this.txHash = Objects.requireNonNull(txHash);
+			return this;
+		}
+
+		public Builder timestamp(long timestamp) {
+			if (timestamp <= 0)
+				throw new IllegalArgumentException("timestamp must be positive");
+
+			this.timestamp = timestamp;
+			return this;
+		}
+
+		public Builder input(String address, long amount) {
+			Objects.requireNonNull(address);
+			if (amount < 0)
+				throw new IllegalArgumentException("amount must be zero or positive");
+
+			AddressAmount input = new AddressAmount(address, amount);
+			inputs.add(input);
+			return this;
+		}
+
+		public Builder output(List<String> addresses, long amount) {
+			Objects.requireNonNull(addresses);
+			if (amount < 0)
+				throw new IllegalArgumentException("amount must be zero or positive");
+
+			Output output = new Output(addresses, amount);
+			outputs.add(output);
+			return this;
+		}
+
+		public Builder isSentNotReceived(Boolean isSentNotReceived) {
+			this.isSentNotReceived = isSentNotReceived;
+			return this;
+		}
+
+		public SimpleForeignTransaction build() {
+			return new SimpleForeignTransaction(this);
+		}
+	}
+
+}

src/main/java/org/qortal/api/model/TradeBotRespondRequest.java

@@ -1,23 +0,0 @@
-package org.qortal.api.model;
-
-import javax.xml.bind.annotation.XmlAccessType;
-import javax.xml.bind.annotation.XmlAccessorType;
-
-import io.swagger.v3.oas.annotations.media.Schema;
-
-@XmlAccessorType(XmlAccessType.FIELD)
-public class TradeBotRespondRequest {
-
-	@Schema(description = "Qortal AT address", example = "AH3e3jHEsGHPVQPDiJx4pYqgVi72auxgVy")
-	public String atAddress;
-
-	@Schema(description = "Bitcoin BIP32 extended private key", example = "tprv8ZgxMBicQKsPdahhFSrCdvC1bsWyzHHZfTneTVqUXN6s1wEtZLwAkZXzFP6TbTVGajEB55L1HYLg2aQMecZLXLre5YJcawpdFG66STVAWPJ")
-	public String xprv58;
-
-	@Schema(description = "Qortal address for receiving QORT from AT")
-	public String receivingAddress;
-
-	public TradeBotRespondRequest() {
-	}
-
-}

src/main/java/org/qortal/api/model/crosschain/BitcoinSendRequest.java

@@ -1,4 +1,4 @@
-package org.qortal.api.model;
+package org.qortal.api.model.crosschain;
 
 import javax.xml.bind.annotation.XmlAccessType;
 import javax.xml.bind.annotation.XmlAccessorType;
@@ -9,16 +9,20 @@ import io.swagger.v3.oas.annotations.media.Schema;
 @XmlAccessorType(XmlAccessType.FIELD)
 public class BitcoinSendRequest {
 
-	@Schema(description = "Bitcoin BIP32 extended private key", example = "tprv8ZgxMBicQKsPdahhFSrCdvC1bsWyzHHZfTneTVqUXN6s1wEtZLwAkZXzFP6TbTVGajEB55L1HYLg2aQMecZLXLre5YJcawpdFG66STVAWPJ")
+	@Schema(description = "Bitcoin BIP32 extended private key", example = "tprv___________________________________________________________________________________________________________")
 	public String xprv58;
 
 	@Schema(description = "Recipient's Bitcoin address ('legacy' P2PKH only)", example = "1BitcoinEaterAddressDontSendf59kuE")
 	public String receivingAddress;
 
-	@Schema(description = "Amount of BTC to send")
+	@Schema(description = "Amount of BTC to send", type = "number")
 	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
 	public long bitcoinAmount;
 
+	@Schema(description = "Transaction fee per byte (optional). Default is 0.00000100 BTC (100 sats) per byte", example = "0.00000100", type = "number")
+	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
+	public Long feePerByte;
+
 	public BitcoinSendRequest() {
 	}
 

src/main/java/org/qortal/api/model/crosschain/LitecoinSendRequest.java

@@ -0,0 +1,29 @@
+package org.qortal.api.model.crosschain;
+
+import javax.xml.bind.annotation.XmlAccessType;
+import javax.xml.bind.annotation.XmlAccessorType;
+import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+
+@XmlAccessorType(XmlAccessType.FIELD)
+public class LitecoinSendRequest {
+
+	@Schema(description = "Litecoin BIP32 extended private key", example = "tprv___________________________________________________________________________________________________________")
+	public String xprv58;
+
+	@Schema(description = "Recipient's Litecoin address ('legacy' P2PKH only)", example = "LiTecoinEaterAddressDontSendhLfzKD")
+	public String receivingAddress;
+
+	@Schema(description = "Amount of LTC to send", type = "number")
+	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
+	public long litecoinAmount;
+
+	@Schema(description = "Transaction fee per byte (optional). Default is 0.00000100 LTC (100 sats) per byte", example = "0.00000100", type = "number")
+	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
+	public Long feePerByte;
+
+	public LitecoinSendRequest() {
+	}
+
+}

src/main/java/org/qortal/api/model/crosschain/TradeBotCreateRequest.java

@@ -1,9 +1,11 @@
-package org.qortal.api.model;
+package org.qortal.api.model.crosschain;
 
 import javax.xml.bind.annotation.XmlAccessType;
 import javax.xml.bind.annotation.XmlAccessorType;
 import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
 
+import org.qortal.crosschain.SupportedBlockchain;
+
 import io.swagger.v3.oas.annotations.media.Schema;
 
 @XmlAccessorType(XmlAccessType.FIELD)
@@ -12,22 +14,30 @@ public class TradeBotCreateRequest {
 	@Schema(description = "Trade creator's public key", example = "2zR1WFsbM7akHghqSCYKBPk6LDP8aKiQSRS1FrwoLvoB")
 	public byte[] creatorPublicKey;
 
-	@Schema(description = "QORT amount paid out on successful trade", example = "80.40200000")
+	@Schema(description = "QORT amount paid out on successful trade", example = "80.40000000", type = "number")
 	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
 	public long qortAmount;
 
-	@Schema(description = "QORT amount funding AT, including covering AT execution fees", example = "81")
+	@Schema(description = "QORT amount funding AT, including covering AT execution fees", example = "80.50000000", type = "number")
 	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
 	public long fundingQortAmount;
 
-	@Schema(description = "Bitcoin amount wanted in return", example = "0.00864200")
+	@Deprecated
+	@Schema(description = "Bitcoin amount wanted in return. DEPRECATED: use foreignAmount instead", example = "0.00864200", type = "number", hidden = true)
 	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
-	public long bitcoinAmount;
+	public Long bitcoinAmount;
+
+	@Schema(description = "Foreign blockchain. Note: default (BITCOIN) to be removed in the future", example = "BITCOIN", implementation = SupportedBlockchain.class)
+	public SupportedBlockchain foreignBlockchain;
+
+	@Schema(description = "Foreign blockchain amount wanted in return", example = "0.00864200", type = "number")
+	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
+	public Long foreignAmount;
 
 	@Schema(description = "Suggested trade timeout (minutes)", example = "10080")
 	public int tradeTimeout;
 
-	@Schema(description = "Bitcoin address for receiving", example = "1BitcoinEaterAddressDontSendf59kuE")
+	@Schema(description = "Foreign blockchain address for receiving", example = "1BitcoinEaterAddressDontSendf59kuE")
 	public String receivingAddress;
 
 	public TradeBotCreateRequest() {

src/main/java/org/qortal/api/model/crosschain/TradeBotRespondRequest.java

@@ -0,0 +1,29 @@
+package org.qortal.api.model.crosschain;
+
+import javax.xml.bind.annotation.XmlAccessType;
+import javax.xml.bind.annotation.XmlAccessorType;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+
+@XmlAccessorType(XmlAccessType.FIELD)
+public class TradeBotRespondRequest {
+
+	@Schema(description = "Qortal AT address", example = "Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa")
+	public String atAddress;
+
+	@Deprecated
+	@Schema(description = "Bitcoin BIP32 extended private key. DEPRECATED: use foreignKey instead", hidden = true,
+			example = "xprv___________________________________________________________________________________________________________")
+	public String xprv58;
+
+	@Schema(description = "Foreign blockchain private key, e.g. BIP32 'm' key for Bitcoin/Litecoin starting with 'xprv'",
+			example = "xprv___________________________________________________________________________________________________________")
+	public String foreignKey;
+
+	@Schema(description = "Qortal address for receiving QORT from AT", example = "Qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqq")
+	public String receivingAddress;
+
+	public TradeBotRespondRequest() {
+	}
+
+}

src/main/java/org/qortal/api/resource/AddressesResource.java

@@ -7,6 +7,7 @@ import io.swagger.v3.oas.annotations.media.Content;
 import io.swagger.v3.oas.annotations.media.Schema;
 import io.swagger.v3.oas.annotations.parameters.RequestBody;
 import io.swagger.v3.oas.annotations.responses.ApiResponse;
+import io.swagger.v3.oas.annotations.security.SecurityRequirement;
 import io.swagger.v3.oas.annotations.tags.Tag;
 
 import java.math.BigDecimal;
@@ -473,6 +474,7 @@ public class AddressesResource {
 		}
 	)
 	@ApiErrors({ApiError.TRANSACTION_INVALID, ApiError.INVALID_DATA, ApiError.TRANSFORMATION_ERROR, ApiError.REPOSITORY_ISSUE})
+	@SecurityRequirement(name = "apiKey")
 	public String computePublicize(String rawBytes58) {
 		Security.checkApiCallAllowed(request);
 

src/main/java/org/qortal/api/resource/AdminResource.java

@@ -8,6 +8,7 @@ import io.swagger.v3.oas.annotations.media.Content;
 import io.swagger.v3.oas.annotations.media.Schema;
 import io.swagger.v3.oas.annotations.parameters.RequestBody;
 import io.swagger.v3.oas.annotations.responses.ApiResponse;
+import io.swagger.v3.oas.annotations.security.SecurityRequirement;
 import io.swagger.v3.oas.annotations.tags.Tag;
 
 import java.io.IOException;
@@ -40,7 +41,6 @@ import org.qortal.account.Account;
 import org.qortal.account.PrivateKeyAccount;
 import org.qortal.api.ApiError;
 import org.qortal.api.ApiErrors;
-import org.qortal.api.ApiException;
 import org.qortal.api.ApiExceptionFactory;
 import org.qortal.api.Security;
 import org.qortal.api.model.ActivitySummary;
@@ -57,6 +57,7 @@ import org.qortal.network.PeerAddress;
 import org.qortal.repository.DataException;
 import org.qortal.repository.Repository;
 import org.qortal.repository.RepositoryManager;
+import org.qortal.settings.Settings;
 import org.qortal.utils.Base58;
 import org.qortal.utils.NTP;
 
@@ -118,6 +119,7 @@ public class AdminResource {
 		nodeInfo.buildVersion = Controller.getInstance().getVersionString();
 		nodeInfo.buildTimestamp = Controller.getInstance().getBuildTimestamp();
 		nodeInfo.nodeId = Network.getInstance().getOurNodeId();
+		nodeInfo.isTestNet = Settings.getInstance().isTestNet();
 
 		return nodeInfo;
 	}
@@ -132,6 +134,7 @@ public class AdminResource {
 			)
 		}
 	)
+	@SecurityRequirement(name = "apiKey")
 	public NodeStatus status() {
 		Security.checkApiCallAllowed(request);
 
@@ -152,6 +155,7 @@ public class AdminResource {
 			)
 		}
 	)
+	@SecurityRequirement(name = "apiKey")
 	public String shutdown() {
 		Security.checkApiCallAllowed(request);
 
@@ -180,7 +184,10 @@ public class AdminResource {
 		}
 	)
 	@ApiErrors({ApiError.REPOSITORY_ISSUE})
+	@SecurityRequirement(name = "apiKey")
 	public ActivitySummary summary() {
+		Security.checkApiCallAllowed(request);
+
 		ActivitySummary summary = new ActivitySummary();
 
 		LocalDate date = LocalDate.now();
@@ -192,16 +199,13 @@ public class AdminResource {
 			int startHeight = repository.getBlockRepository().getHeightFromTimestamp(start);
 			int endHeight = repository.getBlockRepository().getBlockchainHeight();
 
-			summary.blockCount = endHeight - startHeight;
+			summary.setBlockCount(endHeight - startHeight);
 
-			summary.transactionCountByType = repository.getTransactionRepository().getTransactionSummary(startHeight + 1, endHeight);
+			summary.setTransactionCountByType(repository.getTransactionRepository().getTransactionSummary(startHeight + 1, endHeight));
 
-			for (Integer count : summary.transactionCountByType.values())
-				summary.transactionCount += count;
+			summary.setAssetsIssued(repository.getAssetRepository().getRecentAssetIds(start).size());
 
-			summary.assetsIssued = repository.getAssetRepository().getRecentAssetIds(start).size();
-
-			summary.namesRegistered = repository.getNameRepository().getRecentNames(start).size();
+			summary.setNamesRegistered (repository.getNameRepository().getRecentNames(start).size());
 
 			return summary;
 		} catch (DataException e) {
@@ -209,6 +213,30 @@ public class AdminResource {
 		}
 	}
 
+	@GET
+	@Path("/enginestats")
+	@Operation(
+		summary = "Fetch statistics snapshot for core engine",
+		responses = {
+			@ApiResponse(
+				content = @Content(
+					mediaType = MediaType.APPLICATION_JSON,
+					array = @ArraySchema(
+						schema = @Schema(
+							implementation = Controller.StatsSnapshot.class
+						)
+					)
+				)
+			)
+		}
+	)
+	@SecurityRequirement(name = "apiKey")
+	public Controller.StatsSnapshot getEngineStats() {
+		Security.checkApiCallAllowed(request);
+
+		return Controller.getInstance().getStatsSnapshot();
+	}
+
 	@GET
 	@Path("/mintingaccounts")
 	@Operation(
@@ -221,6 +249,7 @@ public class AdminResource {
 		}
 	)
 	@ApiErrors({ApiError.REPOSITORY_ISSUE})
+	@SecurityRequirement(name = "apiKey")
 	public List<MintingAccountData> getMintingAccounts() {
 		Security.checkApiCallAllowed(request);
 
@@ -267,6 +296,7 @@ public class AdminResource {
 		}
 	)
 	@ApiErrors({ApiError.INVALID_PRIVATE_KEY, ApiError.REPOSITORY_ISSUE, ApiError.CANNOT_MINT})
+	@SecurityRequirement(name = "apiKey")
 	public String addMintingAccount(String seed58) {
 		Security.checkApiCallAllowed(request);
 
@@ -319,6 +349,7 @@ public class AdminResource {
 		}
 	)
 	@ApiErrors({ApiError.INVALID_PRIVATE_KEY, ApiError.REPOSITORY_ISSUE})
+	@SecurityRequirement(name = "apiKey")
 	public String deleteMintingAccount(String key58) {
 		Security.checkApiCallAllowed(request);
 
@@ -418,6 +449,7 @@ public class AdminResource {
 		}
 	)
 	@ApiErrors({ApiError.INVALID_HEIGHT, ApiError.REPOSITORY_ISSUE})
+	@SecurityRequirement(name = "apiKey")
 	public String orphan(String targetHeightString) {
 		Security.checkApiCallAllowed(request);
 
@@ -435,8 +467,6 @@ public class AdminResource {
 			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.REPOSITORY_ISSUE, e);
 		} catch (NumberFormatException e) {
 			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_HEIGHT);
-		} catch (ApiException e) {
-			throw e;
 		}
 	}
 
@@ -461,6 +491,7 @@ public class AdminResource {
 		}
 	)
 	@ApiErrors({ApiError.INVALID_DATA, ApiError.REPOSITORY_ISSUE})
+	@SecurityRequirement(name = "apiKey")
 	public String forceSync(String targetPeerAddress) {
 		Security.checkApiCallAllowed(request);
 
@@ -492,8 +523,6 @@ public class AdminResource {
 			return syncResult.name();
 		} catch (IllegalArgumentException e) {
 			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_DATA);
-		} catch (ApiException e) {
-			throw e;
 		} catch (UnknownHostException e) {
 			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_DATA);
 		} catch (InterruptedException e) {
@@ -501,4 +530,161 @@ public class AdminResource {
 		}
 	}
 
+	@GET
+	@Path("/repository/data")
+	@Operation(
+		summary = "Export sensitive/node-local data from repository.",
+		description = "Exports data to .script files on local machine"
+	)
+	@ApiErrors({ApiError.INVALID_DATA, ApiError.REPOSITORY_ISSUE})
+	@SecurityRequirement(name = "apiKey")
+	public String exportRepository() {
+		Security.checkApiCallAllowed(request);
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			repository.exportNodeLocalData();
+			return "true";
+		} catch (DataException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.REPOSITORY_ISSUE, e);
+		}
+	}
+
+	@POST
+	@Path("/repository/data")
+	@Operation(
+		summary = "Import data into repository.",
+		description = "Imports data from file on local machine. Filename is forced to 'import.json' if apiKey is not set.",
+		requestBody = @RequestBody(
+			required = true,
+			content = @Content(
+				mediaType = MediaType.TEXT_PLAIN,
+				schema = @Schema(
+					type = "string", example = "MintingAccounts.script"
+				)
+			)
+		),
+		responses = {
+			@ApiResponse(
+				description = "\"true\"",
+				content = @Content(mediaType = MediaType.TEXT_PLAIN, schema = @Schema(type = "string"))
+			)
+		}
+	)
+	@ApiErrors({ApiError.REPOSITORY_ISSUE})
+	@SecurityRequirement(name = "apiKey")
+	public String importRepository(String filename) {
+		Security.checkApiCallAllowed(request);
+
+		// Hard-coded because it's too dangerous to allow user-supplied filenames in weaker security contexts
+		if (Settings.getInstance().getApiKey() == null)
+			filename = "import.json";
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			ReentrantLock blockchainLock = Controller.getInstance().getBlockchainLock();
+
+			blockchainLock.lockInterruptibly();
+
+			try {
+				repository.importDataFromFile(filename);
+				repository.saveChanges();
+
+				return "true";
+			} finally {
+				blockchainLock.unlock();
+			}
+		} catch (InterruptedException e) {
+			// We couldn't lock blockchain to perform import
+			return "false";
+		} catch (DataException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.REPOSITORY_ISSUE, e);
+		}
+	}
+
+	@POST
+	@Path("/repository/checkpoint")
+	@Operation(
+		summary = "Checkpoint data in repository.",
+		description = "Forces repository to checkpoint uncommitted writes.",
+		responses = {
+			@ApiResponse(
+				description = "\"true\"",
+				content = @Content(mediaType = MediaType.TEXT_PLAIN, schema = @Schema(type = "string"))
+			)
+		}
+	)
+	@ApiErrors({ApiError.REPOSITORY_ISSUE})
+	@SecurityRequirement(name = "apiKey")
+	public String checkpointRepository() {
+		Security.checkApiCallAllowed(request);
+
+		RepositoryManager.setRequestedCheckpoint(Boolean.TRUE);
+
+		return "true";
+	}
+
+	@POST
+	@Path("/repository/backup")
+	@Operation(
+		summary = "Perform online backup of repository.",
+		responses = {
+			@ApiResponse(
+				description = "\"true\"",
+				content = @Content(mediaType = MediaType.TEXT_PLAIN, schema = @Schema(type = "string"))
+			)
+		}
+	)
+	@ApiErrors({ApiError.REPOSITORY_ISSUE})
+	@SecurityRequirement(name = "apiKey")
+	public String backupRepository() {
+		Security.checkApiCallAllowed(request);
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			ReentrantLock blockchainLock = Controller.getInstance().getBlockchainLock();
+
+			blockchainLock.lockInterruptibly();
+
+			try {
+				repository.backup(true);
+				repository.saveChanges();
+
+				return "true";
+			} finally {
+				blockchainLock.unlock();
+			}
+		} catch (InterruptedException e) {
+			// We couldn't lock blockchain to perform backup
+			return "false";
+		} catch (DataException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.REPOSITORY_ISSUE, e);
+		}
+	}
+
+	@DELETE
+	@Path("/repository")
+	@Operation(
+		summary = "Perform maintenance on repository.",
+		description = "Requires enough free space to rebuild repository. This will pause your node for a while."
+	)
+	@ApiErrors({ApiError.REPOSITORY_ISSUE})
+	@SecurityRequirement(name = "apiKey")
+	public void performRepositoryMaintenance() {
+		Security.checkApiCallAllowed(request);
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			ReentrantLock blockchainLock = Controller.getInstance().getBlockchainLock();
+
+			blockchainLock.lockInterruptibly();
+
+			try {
+				repository.performPeriodicMaintenance();
+			} finally {
+				blockchainLock.unlock();
+			}
+		} catch (InterruptedException e) {
+			// No big deal
+		} catch (DataException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.REPOSITORY_ISSUE, e);
+		}
+	}
+
 }

src/main/java/org/qortal/api/resource/ApiDefinition.java

@@ -1,11 +1,17 @@
 package org.qortal.api.resource;
 
 import io.swagger.v3.oas.annotations.OpenAPIDefinition;
+import io.swagger.v3.oas.annotations.enums.SecuritySchemeIn;
+import io.swagger.v3.oas.annotations.enums.SecuritySchemeType;
 import io.swagger.v3.oas.annotations.extensions.Extension;
 import io.swagger.v3.oas.annotations.extensions.ExtensionProperty;
 import io.swagger.v3.oas.annotations.info.Info;
+import io.swagger.v3.oas.annotations.security.SecurityScheme;
+import io.swagger.v3.oas.annotations.security.SecuritySchemes;
 import io.swagger.v3.oas.annotations.tags.Tag;
 
+import org.qortal.api.Security;
+
 @OpenAPIDefinition(
 		info = @Info( title = "Qortal API", description = "NOTE: byte-arrays are encoded in Base58" ),
 		tags = {
@@ -30,5 +36,9 @@ import io.swagger.v3.oas.annotations.tags.Tag;
 			})
 		}
 )
+@SecuritySchemes({
+	@SecurityScheme(name = "basicAuth", type = SecuritySchemeType.HTTP, scheme = "basic"),
+	@SecurityScheme(name = "apiKey", type = SecuritySchemeType.APIKEY, in = SecuritySchemeIn.HEADER, paramName = Security.API_KEY_HEADER)
+})
 public class ApiDefinition {
 }

src/main/java/org/qortal/api/resource/AtResource.java

@@ -25,7 +25,6 @@ import org.qortal.api.ApiError;
 import org.qortal.api.ApiErrors;
 import org.qortal.api.ApiException;
 import org.qortal.api.ApiExceptionFactory;
-import org.qortal.at.QortalAtLoggerFactory;
 import org.qortal.data.at.ATData;
 import org.qortal.data.at.ATStateData;
 import org.qortal.data.transaction.DeployAtTransactionData;
@@ -147,8 +146,7 @@ public class AtResource {
 			ATStateData atStateData = repository.getATRepository().getLatestATState(atAddress);
 			byte[] stateData = atStateData.getStateData();
 
-			QortalAtLoggerFactory loggerFactory = QortalAtLoggerFactory.getInstance();
-			byte[] dataBytes = MachineState.extractDataBytes(loggerFactory, stateData);
+			byte[] dataBytes = MachineState.extractDataBytes(stateData);
 
 			return dataBytes;
 		} catch (ApiException e) {

src/main/java/org/qortal/api/resource/BlocksResource.java

@@ -1,5 +1,6 @@
 package org.qortal.api.resource;
 
+import com.google.common.primitives.Ints;
 import io.swagger.v3.oas.annotations.Operation;
 import io.swagger.v3.oas.annotations.Parameter;
 import io.swagger.v3.oas.annotations.media.ArraySchema;
@@ -8,6 +9,11 @@ import io.swagger.v3.oas.annotations.media.Schema;
 import io.swagger.v3.oas.annotations.responses.ApiResponse;
 import io.swagger.v3.oas.annotations.tags.Tag;
 
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.math.BigDecimal;
+import java.math.BigInteger;
+import java.math.RoundingMode;
 import java.util.ArrayList;
 import java.util.List;
 
@@ -20,11 +26,13 @@ import javax.ws.rs.QueryParam;
 import javax.ws.rs.core.Context;
 import javax.ws.rs.core.MediaType;
 
+import org.qortal.account.Account;
 import org.qortal.api.ApiError;
 import org.qortal.api.ApiErrors;
 import org.qortal.api.ApiExceptionFactory;
-import org.qortal.api.model.BlockInfo;
+import org.qortal.api.model.BlockMintingInfo;
 import org.qortal.api.model.BlockSignerSummary;
+import org.qortal.block.Block;
 import org.qortal.crypto.Crypto;
 import org.qortal.data.account.AccountData;
 import org.qortal.data.block.BlockData;
@@ -33,6 +41,8 @@ import org.qortal.data.transaction.TransactionData;
 import org.qortal.repository.DataException;
 import org.qortal.repository.Repository;
 import org.qortal.repository.RepositoryManager;
+import org.qortal.transform.TransformationException;
+import org.qortal.transform.block.BlockTransformer;
 import org.qortal.utils.Base58;
 
 @Path("/blocks")
@@ -81,6 +91,48 @@ public class BlocksResource {
 		}
 	}
 
+	@GET
+	@Path("/signature/{signature}/data")
+	@Operation(
+			summary = "Fetch serialized, base58 encoded block data using base58 signature",
+			description = "Returns serialized data for the block that matches the given signature",
+			responses = {
+					@ApiResponse(
+							description = "the block data",
+							content = @Content(mediaType = MediaType.TEXT_PLAIN, schema = @Schema(type = "string"))
+					)
+			}
+	)
+	@ApiErrors({
+			ApiError.INVALID_SIGNATURE, ApiError.BLOCK_UNKNOWN, ApiError.INVALID_DATA, ApiError.REPOSITORY_ISSUE
+	})
+	public String getSerializedBlockData(@PathParam("signature") String signature58) {
+		// Decode signature
+		byte[] signature;
+		try {
+			signature = Base58.decode(signature58);
+		} catch (NumberFormatException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_SIGNATURE, e);
+		}
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			BlockData blockData = repository.getBlockRepository().fromSignature(signature);
+			if (blockData == null)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.BLOCK_UNKNOWN);
+
+			Block block = new Block(repository, blockData);
+			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+			bytes.write(Ints.toByteArray(block.getBlockData().getHeight()));
+			bytes.write(BlockTransformer.toBytes(block));
+			return Base58.encode(bytes.toByteArray());
+
+		} catch (TransformationException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_DATA, e);
+		} catch (DataException | IOException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.REPOSITORY_ISSUE, e);
+		}
+	}
+
 	@GET
 	@Path("/signature/{signature}/transactions")
 	@Operation(
@@ -329,6 +381,59 @@ public class BlocksResource {
 		}
 	}
 
+	@GET
+	@Path("/byheight/{height}/mintinginfo")
+	@Operation(
+			summary = "Fetch block minter info using block height",
+			description = "Returns the minter info for the block with given height",
+			responses = {
+					@ApiResponse(
+							description = "the block",
+							content = @Content(
+									schema = @Schema(
+											implementation = BlockData.class
+									)
+							)
+					)
+			}
+	)
+	@ApiErrors({
+			ApiError.BLOCK_UNKNOWN, ApiError.REPOSITORY_ISSUE
+	})
+	public BlockMintingInfo getBlockMintingInfoByHeight(@PathParam("height") int height) {
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			BlockData blockData = repository.getBlockRepository().fromHeight(height);
+			if (blockData == null)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.BLOCK_UNKNOWN);
+
+			Block block = new Block(repository, blockData);
+			BlockData parentBlockData = repository.getBlockRepository().fromSignature(blockData.getReference());
+			int minterLevel = Account.getRewardShareEffectiveMintingLevel(repository, blockData.getMinterPublicKey());
+			if (minterLevel == 0)
+				// This may be unavailable when requesting a trimmed block
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_DATA);
+
+			BigInteger distance = block.calcKeyDistance(parentBlockData.getHeight(), parentBlockData.getSignature(), blockData.getMinterPublicKey(), minterLevel);
+			double ratio = new BigDecimal(distance).divide(new BigDecimal(block.MAX_DISTANCE), 40, RoundingMode.DOWN).doubleValue();
+			long timestamp = block.calcTimestamp(parentBlockData, blockData.getMinterPublicKey(), minterLevel);
+			long timeDelta = timestamp - parentBlockData.getTimestamp();
+
+			BlockMintingInfo blockMintingInfo = new BlockMintingInfo();
+			blockMintingInfo.minterPublicKey = blockData.getMinterPublicKey();
+			blockMintingInfo.minterLevel = minterLevel;
+			blockMintingInfo.onlineAccountsCount = blockData.getOnlineAccountsCount();
+			blockMintingInfo.maxDistance = new BigDecimal(block.MAX_DISTANCE);
+			blockMintingInfo.keyDistance = distance;
+			blockMintingInfo.keyDistanceRatio = ratio;
+			blockMintingInfo.timestamp = timestamp;
+			blockMintingInfo.timeDelta = timeDelta;
+
+			return blockMintingInfo;
+		} catch (DataException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.REPOSITORY_ISSUE, e);
+		}
+	}
+
 	@GET
 	@Path("/timestamp/{timestamp}")
 	@Operation(
@@ -492,7 +597,7 @@ public class BlocksResource {
 				content = @Content(
 					array = @ArraySchema(
 						schema = @Schema(
-							implementation = BlockInfo.class
+							implementation = BlockSummaryData.class
 						)
 					)
 				)
@@ -502,7 +607,7 @@ public class BlocksResource {
 	@ApiErrors({
 		ApiError.REPOSITORY_ISSUE
 	})
-	public List<BlockInfo> getBlockRange(
+	public List<BlockSummaryData> getBlockSummaries(
 			@QueryParam("start") Integer startHeight,
 			@QueryParam("end") Integer endHeight,
 			@Parameter(ref = "count") @QueryParam("count") Integer count) {
@@ -515,7 +620,7 @@ public class BlocksResource {
 			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
 
 		try (final Repository repository = RepositoryManager.getRepository()) {
-			return repository.getBlockRepository().getBlockInfos(startHeight, endHeight, count);
+			return repository.getBlockRepository().getBlockSummaries(startHeight, endHeight, count);
 		} catch (DataException e) {
 			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.REPOSITORY_ISSUE, e);
 		}

src/main/java/org/qortal/api/resource/ChatResource.java

@@ -7,6 +7,7 @@ import io.swagger.v3.oas.annotations.media.Content;
 import io.swagger.v3.oas.annotations.media.Schema;
 import io.swagger.v3.oas.annotations.parameters.RequestBody;
 import io.swagger.v3.oas.annotations.responses.ApiResponse;
+import io.swagger.v3.oas.annotations.security.SecurityRequirement;
 import io.swagger.v3.oas.annotations.tags.Tag;
 
 import java.util.List;
@@ -156,6 +157,7 @@ public class ChatResource {
 		}
 	)
 	@ApiErrors({ApiError.TRANSACTION_INVALID, ApiError.TRANSFORMATION_ERROR, ApiError.REPOSITORY_ISSUE})
+	@SecurityRequirement(name = "apiKey")
 	public String buildChat(ChatTransactionData transactionData) {
 		Security.checkApiCallAllowed(request);
 
@@ -203,6 +205,7 @@ public class ChatResource {
 		}
 	)
 	@ApiErrors({ApiError.TRANSACTION_INVALID, ApiError.INVALID_DATA, ApiError.TRANSFORMATION_ERROR, ApiError.REPOSITORY_ISSUE})
+	@SecurityRequirement(name = "apiKey")
 	public String buildChat(String rawBytes58) {
 		Security.checkApiCallAllowed(request);
 

src/main/java/org/qortal/api/resource/CrossChainBitcoinACCTv1Resource.java

@@ -0,0 +1,363 @@
+package org.qortal.api.resource;
+
+import io.swagger.v3.oas.annotations.Operation;
+import io.swagger.v3.oas.annotations.media.Content;
+import io.swagger.v3.oas.annotations.media.Schema;
+import io.swagger.v3.oas.annotations.parameters.RequestBody;
+import io.swagger.v3.oas.annotations.responses.ApiResponse;
+import io.swagger.v3.oas.annotations.tags.Tag;
+
+import java.util.Arrays;
+import java.util.Random;
+
+import javax.servlet.http.HttpServletRequest;
+import javax.ws.rs.POST;
+import javax.ws.rs.Path;
+import javax.ws.rs.core.Context;
+import javax.ws.rs.core.MediaType;
+
+import org.qortal.account.PublicKeyAccount;
+import org.qortal.api.ApiError;
+import org.qortal.api.ApiErrors;
+import org.qortal.api.ApiExceptionFactory;
+import org.qortal.api.Security;
+import org.qortal.api.model.CrossChainBuildRequest;
+import org.qortal.api.model.CrossChainDualSecretRequest;
+import org.qortal.api.model.CrossChainTradeRequest;
+import org.qortal.asset.Asset;
+import org.qortal.crosschain.BitcoinACCTv1;
+import org.qortal.crosschain.Bitcoiny;
+import org.qortal.crosschain.AcctMode;
+import org.qortal.crypto.Crypto;
+import org.qortal.data.at.ATData;
+import org.qortal.data.crosschain.CrossChainTradeData;
+import org.qortal.data.transaction.BaseTransactionData;
+import org.qortal.data.transaction.DeployAtTransactionData;
+import org.qortal.data.transaction.MessageTransactionData;
+import org.qortal.data.transaction.TransactionData;
+import org.qortal.group.Group;
+import org.qortal.repository.DataException;
+import org.qortal.repository.Repository;
+import org.qortal.repository.RepositoryManager;
+import org.qortal.transaction.DeployAtTransaction;
+import org.qortal.transaction.MessageTransaction;
+import org.qortal.transaction.Transaction;
+import org.qortal.transaction.Transaction.TransactionType;
+import org.qortal.transaction.Transaction.ValidationResult;
+import org.qortal.transform.TransformationException;
+import org.qortal.transform.Transformer;
+import org.qortal.transform.transaction.DeployAtTransactionTransformer;
+import org.qortal.transform.transaction.MessageTransactionTransformer;
+import org.qortal.utils.Base58;
+import org.qortal.utils.NTP;
+
+@Path("/crosschain/BitcoinACCTv1")
+@Tag(name = "Cross-Chain (BitcoinACCTv1)")
+public class CrossChainBitcoinACCTv1Resource {
+
+	@Context
+	HttpServletRequest request;
+
+	@POST
+	@Path("/build")
+	@Operation(
+		summary = "Build Bitcoin cross-chain trading AT",
+		description = "Returns raw, unsigned DEPLOY_AT transaction",
+		requestBody = @RequestBody(
+			required = true,
+			content = @Content(
+				mediaType = MediaType.APPLICATION_JSON,
+				schema = @Schema(
+					implementation = CrossChainBuildRequest.class
+				)
+			)
+		),
+		responses = {
+			@ApiResponse(
+				content = @Content(mediaType = MediaType.TEXT_PLAIN, schema = @Schema(type = "string"))
+			)
+		}
+	)
+	@ApiErrors({ApiError.INVALID_PUBLIC_KEY, ApiError.INVALID_DATA, ApiError.INVALID_REFERENCE, ApiError.TRANSFORMATION_ERROR, ApiError.REPOSITORY_ISSUE})
+	public String buildTrade(CrossChainBuildRequest tradeRequest) {
+		Security.checkApiCallAllowed(request);
+
+		byte[] creatorPublicKey = tradeRequest.creatorPublicKey;
+
+		if (creatorPublicKey == null || creatorPublicKey.length != Transformer.PUBLIC_KEY_LENGTH)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_PUBLIC_KEY);
+
+		if (tradeRequest.hashOfSecretB == null || tradeRequest.hashOfSecretB.length != Bitcoiny.HASH160_LENGTH)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_DATA);
+
+		if (tradeRequest.tradeTimeout == null)
+			tradeRequest.tradeTimeout = 7 * 24 * 60; // 7 days
+		else
+			if (tradeRequest.tradeTimeout < 10 || tradeRequest.tradeTimeout > 50000)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_DATA);
+
+		if (tradeRequest.qortAmount <= 0)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_DATA);
+
+		if (tradeRequest.fundingQortAmount <= 0)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_DATA);
+
+		// funding amount must exceed initial + final
+		if (tradeRequest.fundingQortAmount <= tradeRequest.qortAmount)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_DATA);
+
+		if (tradeRequest.bitcoinAmount <= 0)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_DATA);
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			PublicKeyAccount creatorAccount = new PublicKeyAccount(repository, creatorPublicKey);
+
+			byte[] creationBytes = BitcoinACCTv1.buildQortalAT(creatorAccount.getAddress(), tradeRequest.bitcoinPublicKeyHash, tradeRequest.hashOfSecretB,
+					tradeRequest.qortAmount, tradeRequest.bitcoinAmount, tradeRequest.tradeTimeout);
+
+			long txTimestamp = NTP.getTime();
+			byte[] lastReference = creatorAccount.getLastReference();
+			if (lastReference == null)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_REFERENCE);
+
+			long fee = 0;
+			String name = "QORT-BTC cross-chain trade";
+			String description = "Qortal-Bitcoin cross-chain trade";
+			String atType = "ACCT";
+			String tags = "QORT-BTC ACCT";
+
+			BaseTransactionData baseTransactionData = new BaseTransactionData(txTimestamp, Group.NO_GROUP, lastReference, creatorAccount.getPublicKey(), fee, null);
+			TransactionData deployAtTransactionData = new DeployAtTransactionData(baseTransactionData, name, description, atType, tags, creationBytes, tradeRequest.fundingQortAmount, Asset.QORT);
+
+			Transaction deployAtTransaction = new DeployAtTransaction(repository, deployAtTransactionData);
+
+			fee = deployAtTransaction.calcRecommendedFee();
+			deployAtTransactionData.setFee(fee);
+
+			ValidationResult result = deployAtTransaction.isValidUnconfirmed();
+			if (result != ValidationResult.OK)
+				throw TransactionsResource.createTransactionInvalidException(request, result);
+
+			byte[] bytes = DeployAtTransactionTransformer.toBytes(deployAtTransactionData);
+			return Base58.encode(bytes);
+		} catch (TransformationException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.TRANSFORMATION_ERROR, e);
+		} catch (DataException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.REPOSITORY_ISSUE, e);
+		}
+	}
+
+	@POST
+	@Path("/trademessage")
+	@Operation(
+		summary = "Builds raw, unsigned 'trade' MESSAGE transaction that sends cross-chain trade recipient address, triggering 'trade' mode",
+		description = "Specify address of cross-chain AT that needs to be messaged, and signature of 'offer' MESSAGE from trade partner.<br>"
+			+ "AT needs to be in 'offer' mode. Messages sent to an AT in any other mode will be ignored, but still cost fees to send!<br>"
+			+ "You need to sign output with trade private key otherwise the MESSAGE transaction will be invalid.",
+		requestBody = @RequestBody(
+			required = true,
+			content = @Content(
+				mediaType = MediaType.APPLICATION_JSON,
+				schema = @Schema(
+					implementation = CrossChainTradeRequest.class
+				)
+			)
+		),
+		responses = {
+			@ApiResponse(
+				content = @Content(
+					schema = @Schema(
+						type = "string"
+					)
+				)
+			)
+		}
+	)
+	@ApiErrors({ApiError.INVALID_PUBLIC_KEY, ApiError.INVALID_ADDRESS, ApiError.INVALID_CRITERIA, ApiError.REPOSITORY_ISSUE})
+	public String buildTradeMessage(CrossChainTradeRequest tradeRequest) {
+		Security.checkApiCallAllowed(request);
+
+		byte[] tradePublicKey = tradeRequest.tradePublicKey;
+
+		if (tradePublicKey == null || tradePublicKey.length != Transformer.PUBLIC_KEY_LENGTH)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_PUBLIC_KEY);
+
+		if (tradeRequest.atAddress == null || !Crypto.isValidAtAddress(tradeRequest.atAddress))
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_ADDRESS);
+
+		if (tradeRequest.messageTransactionSignature == null || !Crypto.isValidAddress(tradeRequest.messageTransactionSignature))
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_ADDRESS);
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			ATData atData = fetchAtDataWithChecking(repository, tradeRequest.atAddress);
+			CrossChainTradeData crossChainTradeData = BitcoinACCTv1.getInstance().populateTradeData(repository, atData);
+
+			if (crossChainTradeData.mode != AcctMode.OFFERING)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+			// Does supplied public key match trade public key?
+			if (!Crypto.toAddress(tradePublicKey).equals(crossChainTradeData.qortalCreatorTradeAddress))
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_PUBLIC_KEY);
+
+			TransactionData transactionData = repository.getTransactionRepository().fromSignature(tradeRequest.messageTransactionSignature);
+			if (transactionData == null)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.TRANSACTION_UNKNOWN);
+
+			if (transactionData.getType() != TransactionType.MESSAGE)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.TRANSACTION_INVALID);
+
+			MessageTransactionData messageTransactionData = (MessageTransactionData) transactionData;
+			byte[] messageData = messageTransactionData.getData();
+			BitcoinACCTv1.OfferMessageData offerMessageData = BitcoinACCTv1.extractOfferMessageData(messageData);
+			if (offerMessageData == null)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.TRANSACTION_INVALID);
+
+			// Good to make MESSAGE
+
+			byte[] aliceForeignPublicKeyHash = offerMessageData.partnerBitcoinPKH;
+			byte[] hashOfSecretA = offerMessageData.hashOfSecretA;
+			int lockTimeA = (int) offerMessageData.lockTimeA;
+
+			String aliceNativeAddress = Crypto.toAddress(messageTransactionData.getCreatorPublicKey());
+			int lockTimeB = BitcoinACCTv1.calcLockTimeB(messageTransactionData.getTimestamp(), lockTimeA);
+
+			byte[] outgoingMessageData = BitcoinACCTv1.buildTradeMessage(aliceNativeAddress, aliceForeignPublicKeyHash, hashOfSecretA, lockTimeA, lockTimeB);
+			byte[] messageTransactionBytes = buildAtMessage(repository, tradePublicKey, tradeRequest.atAddress, outgoingMessageData);
+
+			return Base58.encode(messageTransactionBytes);
+		} catch (DataException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.REPOSITORY_ISSUE, e);
+		}
+	}
+
+	@POST
+	@Path("/redeemmessage")
+	@Operation(
+		summary = "Builds raw, unsigned 'redeem' MESSAGE transaction that sends secrets to AT, releasing funds to partner",
+		description = "Specify address of cross-chain AT that needs to be messaged, both 32-byte secrets and an address for receiving QORT from AT.<br>"
+			+ "AT needs to be in 'trade' mode. Messages sent to an AT in any other mode will be ignored, but still cost fees to send!<br>"
+			+ "You need to sign output with account the AT considers the trade 'partner' otherwise the MESSAGE transaction will be invalid.",
+		requestBody = @RequestBody(
+			required = true,
+			content = @Content(
+				mediaType = MediaType.APPLICATION_JSON,
+				schema = @Schema(
+					implementation = CrossChainDualSecretRequest.class
+				)
+			)
+		),
+		responses = {
+			@ApiResponse(
+				content = @Content(
+					schema = @Schema(
+						type = "string"
+					)
+				)
+			)
+		}
+	)
+	@ApiErrors({ApiError.INVALID_PUBLIC_KEY, ApiError.INVALID_ADDRESS, ApiError.INVALID_DATA, ApiError.INVALID_CRITERIA, ApiError.REPOSITORY_ISSUE})
+	public String buildRedeemMessage(CrossChainDualSecretRequest secretRequest) {
+		Security.checkApiCallAllowed(request);
+
+		byte[] partnerPublicKey = secretRequest.partnerPublicKey;
+
+		if (partnerPublicKey == null || partnerPublicKey.length != Transformer.PUBLIC_KEY_LENGTH)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_PUBLIC_KEY);
+
+		if (secretRequest.atAddress == null || !Crypto.isValidAtAddress(secretRequest.atAddress))
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_ADDRESS);
+
+		if (secretRequest.secretA == null || secretRequest.secretA.length != BitcoinACCTv1.SECRET_LENGTH)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_DATA);
+
+		if (secretRequest.secretB == null || secretRequest.secretB.length != BitcoinACCTv1.SECRET_LENGTH)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_DATA);
+
+		if (secretRequest.receivingAddress == null || !Crypto.isValidAddress(secretRequest.receivingAddress))
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_ADDRESS);
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			ATData atData = fetchAtDataWithChecking(repository, secretRequest.atAddress);
+			CrossChainTradeData crossChainTradeData = BitcoinACCTv1.getInstance().populateTradeData(repository, atData);
+
+			if (crossChainTradeData.mode != AcctMode.TRADING)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+			String partnerAddress = Crypto.toAddress(partnerPublicKey);
+
+			// MESSAGE must come from address that AT considers trade partner
+			if (!crossChainTradeData.qortalPartnerAddress.equals(partnerAddress))
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_ADDRESS);
+
+			// Good to make MESSAGE
+
+			byte[] messageData = BitcoinACCTv1.buildRedeemMessage(secretRequest.secretA, secretRequest.secretB, secretRequest.receivingAddress);
+			byte[] messageTransactionBytes = buildAtMessage(repository, partnerPublicKey, secretRequest.atAddress, messageData);
+
+			return Base58.encode(messageTransactionBytes);
+		} catch (DataException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.REPOSITORY_ISSUE, e);
+		}
+	}
+
+	private ATData fetchAtDataWithChecking(Repository repository, String atAddress) throws DataException {
+		ATData atData = repository.getATRepository().fromATAddress(atAddress);
+		if (atData == null)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.ADDRESS_UNKNOWN);
+
+		// Must be correct AT - check functionality using code hash
+		if (!Arrays.equals(atData.getCodeHash(), BitcoinACCTv1.CODE_BYTES_HASH))
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+		// No point sending message to AT that's finished
+		if (atData.getIsFinished())
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+		return atData;
+	}
+
+	private byte[] buildAtMessage(Repository repository, byte[] senderPublicKey, String atAddress, byte[] messageData) throws DataException {
+		long txTimestamp = NTP.getTime();
+
+		// senderPublicKey could be ephemeral trade public key where there is no corresponding account and hence no reference
+		String senderAddress = Crypto.toAddress(senderPublicKey);
+		byte[] lastReference = repository.getAccountRepository().getLastReference(senderAddress);
+		final boolean requiresPoW = lastReference == null;
+
+		if (requiresPoW) {
+			Random random = new Random();
+			lastReference = new byte[Transformer.SIGNATURE_LENGTH];
+			random.nextBytes(lastReference);
+		}
+
+		int version = 4;
+		int nonce = 0;
+		long amount = 0L;
+		Long assetId = null; // no assetId as amount is zero
+		Long fee = 0L;
+
+		BaseTransactionData baseTransactionData = new BaseTransactionData(txTimestamp, Group.NO_GROUP, lastReference, senderPublicKey, fee, null);
+		TransactionData messageTransactionData = new MessageTransactionData(baseTransactionData, version, nonce, atAddress, amount, assetId, messageData, false, false);
+
+		MessageTransaction messageTransaction = new MessageTransaction(repository, messageTransactionData);
+
+		if (requiresPoW) {
+			messageTransaction.computeNonce();
+		} else {
+			fee = messageTransaction.calcRecommendedFee();
+			messageTransactionData.setFee(fee);
+		}
+
+		ValidationResult result = messageTransaction.isValidUnconfirmed();
+		if (result != ValidationResult.OK)
+			throw TransactionsResource.createTransactionInvalidException(request, result);
+
+		try {
+			return MessageTransactionTransformer.toBytes(messageTransactionData);
+		} catch (TransformationException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.TRANSFORMATION_ERROR, e);
+		}
+	}
+
+}

src/main/java/org/qortal/api/resource/CrossChainBitcoinResource.java

@@ -0,0 +1,167 @@
+package org.qortal.api.resource;
+
+import io.swagger.v3.oas.annotations.Operation;
+import io.swagger.v3.oas.annotations.media.ArraySchema;
+import io.swagger.v3.oas.annotations.media.Content;
+import io.swagger.v3.oas.annotations.media.Schema;
+import io.swagger.v3.oas.annotations.parameters.RequestBody;
+import io.swagger.v3.oas.annotations.responses.ApiResponse;
+import io.swagger.v3.oas.annotations.tags.Tag;
+
+import java.util.List;
+
+import javax.servlet.http.HttpServletRequest;
+import javax.ws.rs.POST;
+import javax.ws.rs.Path;
+import javax.ws.rs.core.Context;
+import javax.ws.rs.core.MediaType;
+
+import org.bitcoinj.core.Transaction;
+import org.qortal.api.ApiError;
+import org.qortal.api.ApiErrors;
+import org.qortal.api.ApiExceptionFactory;
+import org.qortal.api.Security;
+import org.qortal.api.model.crosschain.BitcoinSendRequest;
+import org.qortal.crosschain.Bitcoin;
+import org.qortal.crosschain.ForeignBlockchainException;
+import org.qortal.crosschain.SimpleTransaction;
+
+@Path("/crosschain/btc")
+@Tag(name = "Cross-Chain (Bitcoin)")
+public class CrossChainBitcoinResource {
+
+	@Context
+	HttpServletRequest request;
+
+	@POST
+	@Path("/walletbalance")
+	@Operation(
+		summary = "Returns BTC balance for hierarchical, deterministic BIP32 wallet",
+		description = "Supply BIP32 'm' private/public key in base58, starting with 'xprv'/'xpub' for mainnet, 'tprv'/'tpub' for testnet",
+		requestBody = @RequestBody(
+			required = true,
+			content = @Content(
+				mediaType = MediaType.TEXT_PLAIN,
+				schema = @Schema(
+					type = "string",
+					description = "BIP32 'm' private/public key in base58",
+					example = "tpubD6NzVbkrYhZ4XTPc4btCZ6SMgn8CxmWkj6VBVZ1tfcJfMq4UwAjZbG8U74gGSypL9XBYk2R2BLbDBe8pcEyBKM1edsGQEPKXNbEskZozeZc"
+				)
+			)
+		),
+		responses = {
+			@ApiResponse(
+				content = @Content(mediaType = MediaType.TEXT_PLAIN, schema = @Schema(type = "string", description = "balance (satoshis)"))
+			)
+		}
+	)
+	@ApiErrors({ApiError.INVALID_PRIVATE_KEY, ApiError.FOREIGN_BLOCKCHAIN_NETWORK_ISSUE})
+	public String getBitcoinWalletBalance(String key58) {
+		Security.checkApiCallAllowed(request);
+
+		Bitcoin bitcoin = Bitcoin.getInstance();
+
+		if (!bitcoin.isValidDeterministicKey(key58))
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_PRIVATE_KEY);
+
+		Long balance = bitcoin.getWalletBalance(key58);
+		if (balance == null)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.FOREIGN_BLOCKCHAIN_NETWORK_ISSUE);
+
+		return balance.toString();
+	}
+
+	@POST
+	@Path("/wallettransactions")
+	@Operation(
+		summary = "Returns transactions for hierarchical, deterministic BIP32 wallet",
+		description = "Supply BIP32 'm' private/public key in base58, starting with 'xprv'/'xpub' for mainnet, 'tprv'/'tpub' for testnet",
+		requestBody = @RequestBody(
+			required = true,
+			content = @Content(
+				mediaType = MediaType.TEXT_PLAIN,
+				schema = @Schema(
+					type = "string",
+					description = "BIP32 'm' private/public key in base58",
+					example = "tpubD6NzVbkrYhZ4XTPc4btCZ6SMgn8CxmWkj6VBVZ1tfcJfMq4UwAjZbG8U74gGSypL9XBYk2R2BLbDBe8pcEyBKM1edsGQEPKXNbEskZozeZc"
+				)
+			)
+		),
+		responses = {
+			@ApiResponse(
+				content = @Content(array = @ArraySchema( schema = @Schema( implementation = SimpleTransaction.class ) ) )
+			)
+		}
+	)
+	@ApiErrors({ApiError.INVALID_PRIVATE_KEY, ApiError.FOREIGN_BLOCKCHAIN_NETWORK_ISSUE})
+	public List<SimpleTransaction> getBitcoinWalletTransactions(String key58) {
+		Security.checkApiCallAllowed(request);
+
+		Bitcoin bitcoin = Bitcoin.getInstance();
+
+		if (!bitcoin.isValidDeterministicKey(key58))
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_PRIVATE_KEY);
+
+		try {
+			return bitcoin.getWalletTransactions(key58);
+		} catch (ForeignBlockchainException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.FOREIGN_BLOCKCHAIN_NETWORK_ISSUE);
+		}
+	}
+
+	@POST
+	@Path("/send")
+	@Operation(
+		summary = "Sends BTC from hierarchical, deterministic BIP32 wallet to specific address",
+		description = "Currently only supports 'legacy' P2PKH Bitcoin addresses. Supply BIP32 'm' private key in base58, starting with 'xprv' for mainnet, 'tprv' for testnet",
+		requestBody = @RequestBody(
+			required = true,
+			content = @Content(
+				mediaType = MediaType.APPLICATION_JSON,
+				schema = @Schema(
+					implementation = BitcoinSendRequest.class
+				)
+			)
+		),
+		responses = {
+			@ApiResponse(
+				content = @Content(mediaType = MediaType.TEXT_PLAIN, schema = @Schema(type = "string", description = "transaction hash"))
+			)
+		}
+	)
+	@ApiErrors({ApiError.INVALID_PRIVATE_KEY, ApiError.INVALID_CRITERIA, ApiError.INVALID_ADDRESS, ApiError.FOREIGN_BLOCKCHAIN_BALANCE_ISSUE, ApiError.FOREIGN_BLOCKCHAIN_NETWORK_ISSUE})
+	public String sendBitcoin(BitcoinSendRequest bitcoinSendRequest) {
+		Security.checkApiCallAllowed(request);
+
+		if (bitcoinSendRequest.bitcoinAmount <= 0)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+		if (bitcoinSendRequest.feePerByte != null && bitcoinSendRequest.feePerByte <= 0)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+		Bitcoin bitcoin = Bitcoin.getInstance();
+
+		if (!bitcoin.isValidAddress(bitcoinSendRequest.receivingAddress))
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_ADDRESS);
+
+		if (!bitcoin.isValidDeterministicKey(bitcoinSendRequest.xprv58))
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_PRIVATE_KEY);
+
+		Transaction spendTransaction = bitcoin.buildSpend(bitcoinSendRequest.xprv58,
+				bitcoinSendRequest.receivingAddress,
+				bitcoinSendRequest.bitcoinAmount,
+				bitcoinSendRequest.feePerByte);
+
+		if (spendTransaction == null)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.FOREIGN_BLOCKCHAIN_BALANCE_ISSUE);
+
+		try {
+			bitcoin.broadcastTransaction(spendTransaction);
+		} catch (ForeignBlockchainException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.FOREIGN_BLOCKCHAIN_NETWORK_ISSUE);
+		}
+
+		return spendTransaction.getTxId().toString();
+	}
+
+}

src/main/java/org/qortal/api/resource/CrossChainHtlcResource.java

@@ -0,0 +1,515 @@
+package org.qortal.api.resource;
+
+import io.swagger.v3.oas.annotations.Operation;
+import io.swagger.v3.oas.annotations.media.Content;
+import io.swagger.v3.oas.annotations.media.Schema;
+import io.swagger.v3.oas.annotations.responses.ApiResponse;
+import io.swagger.v3.oas.annotations.tags.Tag;
+
+import java.math.BigDecimal;
+import java.util.List;
+
+import javax.servlet.http.HttpServletRequest;
+import javax.ws.rs.GET;
+import javax.ws.rs.Path;
+import javax.ws.rs.PathParam;
+import javax.ws.rs.core.Context;
+import javax.ws.rs.core.MediaType;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.bitcoinj.core.*;
+import org.bitcoinj.script.Script;
+import org.qortal.api.ApiError;
+import org.qortal.api.ApiErrors;
+import org.qortal.api.ApiExceptionFactory;
+import org.qortal.api.Security;
+import org.qortal.api.model.CrossChainBitcoinyHTLCStatus;
+import org.qortal.crosschain.*;
+import org.qortal.crypto.Crypto;
+import org.qortal.data.at.ATData;
+import org.qortal.data.crosschain.CrossChainTradeData;
+import org.qortal.data.crosschain.TradeBotData;
+import org.qortal.repository.DataException;
+import org.qortal.repository.Repository;
+import org.qortal.repository.RepositoryManager;
+import org.qortal.utils.Base58;
+import org.qortal.utils.NTP;
+
+@Path("/crosschain/htlc")
+@Tag(name = "Cross-Chain (Hash time-locked contracts)")
+public class CrossChainHtlcResource {
+
+	private static final Logger LOGGER = LogManager.getLogger(CrossChainHtlcResource.class);
+
+	@Context
+	HttpServletRequest request;
+
+	@GET
+	@Path("/address/{blockchain}/{refundPKH}/{locktime}/{redeemPKH}/{hashOfSecret}")
+	@Operation(
+		summary = "Returns HTLC address based on trade info",
+		description = "Blockchain can be BITCOIN or LITECOIN. Public key hashes (PKH) and hash of secret should be 20 bytes (base58 encoded). Locktime is seconds since epoch.",
+		responses = {
+			@ApiResponse(
+				content = @Content(mediaType = MediaType.TEXT_PLAIN, schema = @Schema(type = "string"))
+			)
+		}
+	)
+	@ApiErrors({ApiError.INVALID_PUBLIC_KEY, ApiError.INVALID_CRITERIA})
+	public String deriveHtlcAddress(@PathParam("blockchain") String blockchainName,
+			@PathParam("refundPKH") String refundPKH,
+			@PathParam("locktime") int lockTime,
+			@PathParam("redeemPKH") String redeemPKH,
+			@PathParam("hashOfSecret") String hashOfSecret) {
+		SupportedBlockchain blockchain = SupportedBlockchain.valueOf(blockchainName);
+		if (blockchain == null)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+		byte[] refunderPubKeyHash;
+		byte[] redeemerPubKeyHash;
+		byte[] decodedHashOfSecret;
+
+		try {
+			refunderPubKeyHash = Base58.decode(refundPKH);
+			redeemerPubKeyHash = Base58.decode(redeemPKH);
+
+			if (refunderPubKeyHash.length != 20 || redeemerPubKeyHash.length != 20)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_PUBLIC_KEY);
+		} catch (IllegalArgumentException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_PUBLIC_KEY);
+		}
+
+		try {
+			decodedHashOfSecret = Base58.decode(hashOfSecret);
+			if (decodedHashOfSecret.length != 20)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+		} catch (IllegalArgumentException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+		}
+
+		byte[] redeemScript = BitcoinyHTLC.buildScript(refunderPubKeyHash, lockTime, redeemerPubKeyHash, decodedHashOfSecret);
+
+		Bitcoiny bitcoiny = (Bitcoiny) blockchain.getInstance();
+
+		return bitcoiny.deriveP2shAddress(redeemScript);
+	}
+
+	@GET
+	@Path("/status/{blockchain}/{refundPKH}/{locktime}/{redeemPKH}/{hashOfSecret}")
+	@Operation(
+		summary = "Checks HTLC status",
+		description = "Blockchain can be BITCOIN or LITECOIN. Public key hashes (PKH) and hash of secret should be 20 bytes (base58 encoded). Locktime is seconds since epoch.",
+		responses = {
+			@ApiResponse(
+				content = @Content(mediaType = MediaType.APPLICATION_JSON, schema = @Schema(implementation = CrossChainBitcoinyHTLCStatus.class))
+			)
+		}
+	)
+	@ApiErrors({ApiError.INVALID_CRITERIA, ApiError.INVALID_ADDRESS, ApiError.ADDRESS_UNKNOWN})
+	public CrossChainBitcoinyHTLCStatus checkHtlcStatus(@PathParam("blockchain") String blockchainName,
+			@PathParam("refundPKH") String refundPKH,
+			@PathParam("locktime") int lockTime,
+			@PathParam("redeemPKH") String redeemPKH,
+			@PathParam("hashOfSecret") String hashOfSecret) {
+		Security.checkApiCallAllowed(request);
+
+		SupportedBlockchain blockchain = SupportedBlockchain.valueOf(blockchainName);
+		if (blockchain == null)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+		byte[] refunderPubKeyHash;
+		byte[] redeemerPubKeyHash;
+		byte[] decodedHashOfSecret;
+
+		try {
+			refunderPubKeyHash = Base58.decode(refundPKH);
+			redeemerPubKeyHash = Base58.decode(redeemPKH);
+
+			if (refunderPubKeyHash.length != 20 || redeemerPubKeyHash.length != 20)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_PUBLIC_KEY);
+		} catch (IllegalArgumentException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_PUBLIC_KEY);
+		}
+
+		try {
+			decodedHashOfSecret = Base58.decode(hashOfSecret);
+			if (decodedHashOfSecret.length != 20)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+		} catch (IllegalArgumentException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+		}
+
+		byte[] redeemScript = BitcoinyHTLC.buildScript(refunderPubKeyHash, lockTime, redeemerPubKeyHash, decodedHashOfSecret);
+
+		Bitcoiny bitcoiny = (Bitcoiny) blockchain.getInstance();
+
+		String p2shAddress = bitcoiny.deriveP2shAddress(redeemScript);
+
+		long now = NTP.getTime();
+
+		try {
+			int medianBlockTime = bitcoiny.getMedianBlockTime();
+
+			// Check P2SH is funded
+			long p2shBalance = bitcoiny.getConfirmedBalance(p2shAddress.toString());
+
+			CrossChainBitcoinyHTLCStatus htlcStatus = new CrossChainBitcoinyHTLCStatus();
+			htlcStatus.bitcoinP2shAddress = p2shAddress;
+			htlcStatus.bitcoinP2shBalance = BigDecimal.valueOf(p2shBalance, 8);
+
+			List<TransactionOutput> fundingOutputs = bitcoiny.getUnspentOutputs(p2shAddress.toString());
+
+			if (p2shBalance > 0L && !fundingOutputs.isEmpty()) {
+				htlcStatus.canRedeem = now >= medianBlockTime * 1000L;
+				htlcStatus.canRefund = now >= lockTime * 1000L;
+			}
+
+			if (now >= medianBlockTime * 1000L) {
+				// See if we can extract secret
+				htlcStatus.secret = BitcoinyHTLC.findHtlcSecret(bitcoiny, htlcStatus.bitcoinP2shAddress);
+			}
+
+			return htlcStatus;
+		} catch (ForeignBlockchainException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.FOREIGN_BLOCKCHAIN_NETWORK_ISSUE);
+		}
+	}
+
+	@GET
+	@Path("/redeem/LITECOIN/{ataddress}/{tradePrivateKey}/{secret}/{receivingAddress}")
+	@Operation(
+			summary = "Redeems HTLC associated with supplied AT, using private key, secret, and receiving address",
+			description = "Secret and private key should be 32 bytes (base58 encoded). Receiving address must be a valid LTC P2PKH address.<br>" +
+					"The secret can be found in Alice's trade bot data or in the message to Bob's AT.<br>" +
+					"The trade private key and receiving address can be found in Bob's trade bot data.",
+			responses = {
+					@ApiResponse(
+							content = @Content(mediaType = MediaType.TEXT_PLAIN, schema = @Schema(type = "boolean"))
+					)
+			}
+	)
+	@ApiErrors({ApiError.INVALID_CRITERIA, ApiError.INVALID_ADDRESS, ApiError.ADDRESS_UNKNOWN})
+	public boolean redeemHtlc(@PathParam("ataddress") String atAddress,
+							  @PathParam("tradePrivateKey") String tradePrivateKey,
+							  @PathParam("secret") String secret,
+							  @PathParam("receivingAddress") String receivingAddress) {
+		Security.checkApiCallAllowed(request);
+
+		// base58 decode the trade private key
+		byte[] decodedTradePrivateKey = null;
+		if (tradePrivateKey != null)
+			decodedTradePrivateKey = Base58.decode(tradePrivateKey);
+
+		// base58 decode the secret
+		byte[] decodedSecret = null;
+		if (secret != null)
+			decodedSecret = Base58.decode(secret);
+
+		// Convert supplied Litecoin receiving address into public key hash (we only support P2PKH at this time)
+		Address litecoinReceivingAddress;
+		try {
+			litecoinReceivingAddress = Address.fromString(Litecoin.getInstance().getNetworkParameters(), receivingAddress);
+		} catch (AddressFormatException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+		}
+		if (litecoinReceivingAddress.getOutputScriptType() != Script.ScriptType.P2PKH)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+		byte[] litecoinReceivingAccountInfo = litecoinReceivingAddress.getHash();
+
+		return this.doRedeemHtlc(atAddress, decodedTradePrivateKey, decodedSecret, litecoinReceivingAccountInfo);
+	}
+
+	@GET
+	@Path("/redeem/LITECOIN/{ataddress}")
+	@Operation(
+			summary = "Redeems HTLC associated with supplied AT",
+			description = "To be used by a QORT seller (Bob) who needs to redeem LTC proceeds that are stuck in a P2SH.<br>" +
+					"This requires Bob's trade bot data to be present in the database for this AT.<br>" +
+					"It will fail if the buyer has yet to redeem the QORT held in the AT.",
+			responses = {
+					@ApiResponse(
+							content = @Content(mediaType = MediaType.TEXT_PLAIN, schema = @Schema(type = "boolean"))
+					)
+			}
+	)
+	@ApiErrors({ApiError.INVALID_CRITERIA, ApiError.INVALID_ADDRESS, ApiError.ADDRESS_UNKNOWN})
+	public boolean redeemHtlc(@PathParam("ataddress") String atAddress) {
+		Security.checkApiCallAllowed(request);
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			ATData atData = repository.getATRepository().fromATAddress(atAddress);
+			if (atData == null)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.ADDRESS_UNKNOWN);
+
+			ACCT acct = SupportedBlockchain.getAcctByCodeHash(atData.getCodeHash());
+			if (acct == null)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+			CrossChainTradeData crossChainTradeData = acct.populateTradeData(repository, atData);
+			if (crossChainTradeData == null)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+			// Attempt to find secret from the buyer's message to AT
+			byte[] decodedSecret = LitecoinACCTv1.findSecretA(repository, crossChainTradeData);
+			if (decodedSecret == null) {
+				LOGGER.info(() -> String.format("Unable to find secret-A from redeem message to AT %s", atAddress));
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+			}
+
+			List<TradeBotData> allTradeBotData = repository.getCrossChainRepository().getAllTradeBotData();
+			TradeBotData tradeBotData = allTradeBotData.stream().filter(tradeBotDataItem -> tradeBotDataItem.getAtAddress().equals(atAddress)).findFirst().orElse(null);
+
+			// Search for the tradePrivateKey in the tradebot data
+			byte[] decodedPrivateKey = null;
+			if (tradeBotData != null)
+				decodedPrivateKey = tradeBotData.getTradePrivateKey();
+
+			// Search for the litecoin receiving address in the tradebot data
+			byte[] litecoinReceivingAccountInfo = null;
+			if (tradeBotData != null)
+				// Use receiving address PKH from tradebot data
+				litecoinReceivingAccountInfo = tradeBotData.getReceivingAccountInfo();
+
+			return this.doRedeemHtlc(atAddress, decodedPrivateKey, decodedSecret, litecoinReceivingAccountInfo);
+
+		} catch (DataException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.REPOSITORY_ISSUE, e);
+		}
+	}
+
+	private boolean doRedeemHtlc(String atAddress, byte[] decodedTradePrivateKey, byte[] decodedSecret, byte[] litecoinReceivingAccountInfo) {
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			ATData atData = repository.getATRepository().fromATAddress(atAddress);
+			if (atData == null)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.ADDRESS_UNKNOWN);
+
+			ACCT acct = SupportedBlockchain.getAcctByCodeHash(atData.getCodeHash());
+			if (acct == null)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+			CrossChainTradeData crossChainTradeData = acct.populateTradeData(repository, atData);
+			if (crossChainTradeData == null)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+			// Validate trade private key
+			if (decodedTradePrivateKey == null || decodedTradePrivateKey.length != 32)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+			// Validate secret
+			if (decodedSecret == null || decodedSecret.length != 32)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+			// Validate receiving address
+			if (litecoinReceivingAccountInfo == null || litecoinReceivingAccountInfo.length != 20)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+			// Make sure the receiving address isn't a QORT address, given that we can share the same field for both QORT and LTC
+			if (Crypto.isValidAddress(litecoinReceivingAccountInfo))
+				if (Base58.encode(litecoinReceivingAccountInfo).startsWith("Q"))
+					// This is likely a QORT address, not an LTC
+					throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+
+			// Use secret-A to redeem P2SH-A
+
+			Litecoin litecoin = Litecoin.getInstance();
+
+			int lockTime = crossChainTradeData.lockTimeA;
+			byte[] redeemScriptA = BitcoinyHTLC.buildScript(crossChainTradeData.partnerForeignPKH, lockTime, crossChainTradeData.creatorForeignPKH, crossChainTradeData.hashOfSecretA);
+			String p2shAddressA = litecoin.deriveP2shAddress(redeemScriptA);
+			LOGGER.info(String.format("Redeeming P2SH address: %s", p2shAddressA));
+
+			// Fee for redeem/refund is subtracted from P2SH-A balance.
+			long feeTimestamp = calcFeeTimestamp(lockTime, crossChainTradeData.tradeTimeout);
+			long p2shFee = Litecoin.getInstance().getP2shFee(feeTimestamp);
+			long minimumAmountA = crossChainTradeData.expectedForeignAmount + p2shFee;
+			BitcoinyHTLC.Status htlcStatusA = BitcoinyHTLC.determineHtlcStatus(litecoin.getBlockchainProvider(), p2shAddressA, minimumAmountA);
+
+			switch (htlcStatusA) {
+				case UNFUNDED:
+				case FUNDING_IN_PROGRESS:
+					// P2SH-A suddenly not funded? Our best bet at this point is to hope for AT auto-refund
+					return false;
+
+				case REDEEM_IN_PROGRESS:
+				case REDEEMED:
+					// Double-check that we have redeemed P2SH-A...
+					return false;
+
+				case REFUND_IN_PROGRESS:
+				case REFUNDED:
+					// Wait for AT to auto-refund
+					return false;
+
+				case FUNDED: {
+					Coin redeemAmount = Coin.valueOf(crossChainTradeData.expectedForeignAmount);
+					ECKey redeemKey = ECKey.fromPrivate(decodedTradePrivateKey);
+					List<TransactionOutput> fundingOutputs = litecoin.getUnspentOutputs(p2shAddressA);
+
+					Transaction p2shRedeemTransaction = BitcoinyHTLC.buildRedeemTransaction(litecoin.getNetworkParameters(), redeemAmount, redeemKey,
+							fundingOutputs, redeemScriptA, decodedSecret, litecoinReceivingAccountInfo);
+
+					litecoin.broadcastTransaction(p2shRedeemTransaction);
+					return true; // TODO: validate?
+				}
+			}
+
+		} catch (DataException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.REPOSITORY_ISSUE, e);
+		} catch (ForeignBlockchainException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.FOREIGN_BLOCKCHAIN_BALANCE_ISSUE, e);
+		}
+
+		return false;
+	}
+
+	@GET
+	@Path("/refund/LITECOIN/{ataddress}")
+	@Operation(
+			summary = "Refunds HTLC associated with supplied AT",
+			description = "To be used by a QORT buyer (Alice) who needs to refund their LTC that is stuck in a P2SH.<br>" +
+					"This requires Alice's trade bot data to be present in the database for this AT.<br>" +
+					"It will fail if it's already redeemed by the seller, or if the lockTime (60 minutes) hasn't passed yet.",
+			responses = {
+					@ApiResponse(
+							content = @Content(mediaType = MediaType.TEXT_PLAIN, schema = @Schema(type = "boolean"))
+					)
+			}
+	)
+	@ApiErrors({ApiError.INVALID_CRITERIA, ApiError.INVALID_ADDRESS, ApiError.ADDRESS_UNKNOWN})
+	public boolean refundHtlc(@PathParam("ataddress") String atAddress) {
+		Security.checkApiCallAllowed(request);
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			List<TradeBotData> allTradeBotData = repository.getCrossChainRepository().getAllTradeBotData();
+			TradeBotData tradeBotData = allTradeBotData.stream().filter(tradeBotDataItem -> tradeBotDataItem.getAtAddress().equals(atAddress)).findFirst().orElse(null);
+			if (tradeBotData == null)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+			if (tradeBotData.getForeignKey() == null)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+			// Determine LTC receive address for refund
+			Litecoin litecoin = Litecoin.getInstance();
+			String receiveAddress = litecoin.getUnusedReceiveAddress(tradeBotData.getForeignKey());
+
+			return this.doRefundHtlc(atAddress, receiveAddress);
+
+		} catch (DataException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.REPOSITORY_ISSUE, e);
+		} catch (ForeignBlockchainException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.FOREIGN_BLOCKCHAIN_BALANCE_ISSUE, e);
+		}
+	}
+
+	@GET
+	@Path("/refund/LITECOIN/{ataddress}/{receivingAddress}")
+	@Operation(
+			summary = "Refunds HTLC associated with supplied AT, to the specified LTC receiving address",
+			description = "To be used by a QORT buyer (Alice) who needs to refund their LTC that is stuck in a P2SH.<br>" +
+					"This requires Alice's trade bot data to be present in the database for this AT.<br>" +
+					"It will fail if it's already redeemed by the seller, or if the lockTime (60 minutes) hasn't passed yet.",
+			responses = {
+					@ApiResponse(
+							content = @Content(mediaType = MediaType.TEXT_PLAIN, schema = @Schema(type = "boolean"))
+					)
+			}
+	)
+	@ApiErrors({ApiError.INVALID_CRITERIA, ApiError.INVALID_ADDRESS, ApiError.ADDRESS_UNKNOWN})
+	public boolean refundHtlc(@PathParam("ataddress") String atAddress,
+							  @PathParam("receivingAddress") String receivingAddress) {
+		Security.checkApiCallAllowed(request);
+		return this.doRefundHtlc(atAddress, receivingAddress);
+	}
+
+
+	private boolean doRefundHtlc(String atAddress, String receiveAddress) {
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			ATData atData = repository.getATRepository().fromATAddress(atAddress);
+			if (atData == null)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.ADDRESS_UNKNOWN);
+
+			ACCT acct = SupportedBlockchain.getAcctByCodeHash(atData.getCodeHash());
+			if (acct == null)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+			CrossChainTradeData crossChainTradeData = acct.populateTradeData(repository, atData);
+			if (crossChainTradeData == null)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+			List<TradeBotData> allTradeBotData = repository.getCrossChainRepository().getAllTradeBotData();
+			TradeBotData tradeBotData = allTradeBotData.stream().filter(tradeBotDataItem -> tradeBotDataItem.getAtAddress().equals(atAddress)).findFirst().orElse(null);
+			if (tradeBotData == null)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+
+			int lockTime = tradeBotData.getLockTimeA();
+
+			// We can't refund P2SH-A until lockTime-A has passed
+			if (NTP.getTime() <= lockTime * 1000L)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.FOREIGN_BLOCKCHAIN_TOO_SOON);
+
+			Litecoin litecoin = Litecoin.getInstance();
+
+			// We can't refund P2SH-A until median block time has passed lockTime-A (see BIP113)
+			int medianBlockTime = litecoin.getMedianBlockTime();
+			if (medianBlockTime <= lockTime)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.FOREIGN_BLOCKCHAIN_TOO_SOON);
+
+			byte[] redeemScriptA = BitcoinyHTLC.buildScript(tradeBotData.getTradeForeignPublicKeyHash(), lockTime, crossChainTradeData.creatorForeignPKH, tradeBotData.getHashOfSecret());
+			String p2shAddressA = litecoin.deriveP2shAddress(redeemScriptA);
+			LOGGER.info(String.format("Refunding P2SH address: %s", p2shAddressA));
+
+			// Fee for redeem/refund is subtracted from P2SH-A balance.
+			long feeTimestamp = calcFeeTimestamp(lockTime, crossChainTradeData.tradeTimeout);
+			long p2shFee = Litecoin.getInstance().getP2shFee(feeTimestamp);
+			long minimumAmountA = crossChainTradeData.expectedForeignAmount + p2shFee;
+			BitcoinyHTLC.Status htlcStatusA = BitcoinyHTLC.determineHtlcStatus(litecoin.getBlockchainProvider(), p2shAddressA, minimumAmountA);
+
+			switch (htlcStatusA) {
+				case UNFUNDED:
+				case FUNDING_IN_PROGRESS:
+					// Still waiting for P2SH-A to be funded...
+					throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.FOREIGN_BLOCKCHAIN_TOO_SOON);
+
+				case REDEEM_IN_PROGRESS:
+				case REDEEMED:
+				case REFUND_IN_PROGRESS:
+				case REFUNDED:
+					// Too late!
+					return false;
+
+				case FUNDED:{
+					Coin refundAmount = Coin.valueOf(crossChainTradeData.expectedForeignAmount);
+					ECKey refundKey = ECKey.fromPrivate(tradeBotData.getTradePrivateKey());
+					List<TransactionOutput> fundingOutputs = litecoin.getUnspentOutputs(p2shAddressA);
+
+					// Validate the destination LTC address
+					Address receiving = Address.fromString(litecoin.getNetworkParameters(), receiveAddress);
+					if (receiving.getOutputScriptType() != Script.ScriptType.P2PKH)
+						throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+					Transaction p2shRefundTransaction = BitcoinyHTLC.buildRefundTransaction(litecoin.getNetworkParameters(), refundAmount, refundKey,
+							fundingOutputs, redeemScriptA, lockTime, receiving.getHash());
+
+					litecoin.broadcastTransaction(p2shRefundTransaction);
+					return true; // TODO: validate?
+				}
+			}
+
+		} catch (DataException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.REPOSITORY_ISSUE, e);
+		} catch (ForeignBlockchainException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.FOREIGN_BLOCKCHAIN_BALANCE_ISSUE, e);
+		}
+
+		return false;
+	}
+
+	private long calcFeeTimestamp(int lockTimeA, int tradeTimeout) {
+		return (lockTimeA - tradeTimeout * 60) * 1000L;
+	}
+
+}

src/main/java/org/qortal/api/resource/CrossChainLitecoinACCTv1Resource.java

@@ -0,0 +1,145 @@
+package org.qortal.api.resource;
+
+import io.swagger.v3.oas.annotations.Operation;
+import io.swagger.v3.oas.annotations.media.Content;
+import io.swagger.v3.oas.annotations.media.Schema;
+import io.swagger.v3.oas.annotations.parameters.RequestBody;
+import io.swagger.v3.oas.annotations.responses.ApiResponse;
+import io.swagger.v3.oas.annotations.tags.Tag;
+import org.qortal.account.PrivateKeyAccount;
+import org.qortal.api.ApiError;
+import org.qortal.api.ApiErrors;
+import org.qortal.api.ApiExceptionFactory;
+import org.qortal.api.Security;
+import org.qortal.api.model.CrossChainSecretRequest;
+import org.qortal.crosschain.AcctMode;
+import org.qortal.crosschain.LitecoinACCTv1;
+import org.qortal.crypto.Crypto;
+import org.qortal.data.at.ATData;
+import org.qortal.data.crosschain.CrossChainTradeData;
+import org.qortal.group.Group;
+import org.qortal.repository.DataException;
+import org.qortal.repository.Repository;
+import org.qortal.repository.RepositoryManager;
+import org.qortal.transaction.MessageTransaction;
+import org.qortal.transaction.Transaction.ValidationResult;
+import org.qortal.transform.TransformationException;
+import org.qortal.transform.Transformer;
+import org.qortal.transform.transaction.MessageTransactionTransformer;
+import org.qortal.utils.Base58;
+import org.qortal.utils.NTP;
+
+import javax.servlet.http.HttpServletRequest;
+import javax.ws.rs.POST;
+import javax.ws.rs.Path;
+import javax.ws.rs.core.Context;
+import javax.ws.rs.core.MediaType;
+import java.util.Arrays;
+import java.util.Random;
+
+@Path("/crosschain/LitecoinACCTv1")
+@Tag(name = "Cross-Chain (LitecoinACCTv1)")
+public class CrossChainLitecoinACCTv1Resource {
+
+	@Context
+	HttpServletRequest request;
+
+	@POST
+	@Path("/redeemmessage")
+	@Operation(
+		summary = "Signs and broadcasts a 'redeem' MESSAGE transaction that sends secrets to AT, releasing funds to partner",
+		description = "Specify address of cross-chain AT that needs to be messaged, Alice's trade private key, the 32-byte secret,<br>"
+			+ "and an address for receiving QORT from AT. All of these can be found in Alice's trade bot data.<br>"
+			+ "AT needs to be in 'trade' mode. Messages sent to an AT in any other mode will be ignored, but still cost fees to send!<br>"
+			+ "You need to use the private key that the AT considers the trade 'partner' otherwise the MESSAGE transaction will be invalid.",
+		requestBody = @RequestBody(
+			required = true,
+			content = @Content(
+				mediaType = MediaType.APPLICATION_JSON,
+				schema = @Schema(
+					implementation = CrossChainSecretRequest.class
+				)
+			)
+		),
+		responses = {
+			@ApiResponse(
+				content = @Content(
+					schema = @Schema(
+						type = "string"
+					)
+				)
+			)
+		}
+	)
+	@ApiErrors({ApiError.INVALID_PUBLIC_KEY, ApiError.INVALID_ADDRESS, ApiError.INVALID_DATA, ApiError.INVALID_CRITERIA, ApiError.REPOSITORY_ISSUE})
+	public boolean buildRedeemMessage(CrossChainSecretRequest secretRequest) {
+		Security.checkApiCallAllowed(request);
+
+		byte[] partnerPrivateKey = secretRequest.partnerPrivateKey;
+
+		if (partnerPrivateKey == null || partnerPrivateKey.length != Transformer.PRIVATE_KEY_LENGTH)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_PRIVATE_KEY);
+
+		if (secretRequest.atAddress == null || !Crypto.isValidAtAddress(secretRequest.atAddress))
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_ADDRESS);
+
+		if (secretRequest.secret == null || secretRequest.secret.length != LitecoinACCTv1.SECRET_LENGTH)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_DATA);
+
+		if (secretRequest.receivingAddress == null || !Crypto.isValidAddress(secretRequest.receivingAddress))
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_ADDRESS);
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			ATData atData = fetchAtDataWithChecking(repository, secretRequest.atAddress);
+			CrossChainTradeData crossChainTradeData = LitecoinACCTv1.getInstance().populateTradeData(repository, atData);
+
+			if (crossChainTradeData.mode != AcctMode.TRADING)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+			byte[] partnerPublicKey = new PrivateKeyAccount(null, partnerPrivateKey).getPublicKey();
+			String partnerAddress = Crypto.toAddress(partnerPublicKey);
+
+			// MESSAGE must come from address that AT considers trade partner
+			if (!crossChainTradeData.qortalPartnerAddress.equals(partnerAddress))
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_ADDRESS);
+
+			// Good to make MESSAGE
+
+			byte[] messageData = LitecoinACCTv1.buildRedeemMessage(secretRequest.secret, secretRequest.receivingAddress);
+
+			PrivateKeyAccount sender = new PrivateKeyAccount(repository, partnerPrivateKey);
+			MessageTransaction messageTransaction = MessageTransaction.build(repository, sender, Group.NO_GROUP, secretRequest.atAddress, messageData, false, false);
+
+			messageTransaction.computeNonce();
+			messageTransaction.sign(sender);
+
+			// reset repository state to prevent deadlock
+			repository.discardChanges();
+			ValidationResult result = messageTransaction.importAsUnconfirmed();
+
+			if (result != ValidationResult.OK)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.TRANSACTION_INVALID);
+
+			return true;
+		} catch (DataException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.REPOSITORY_ISSUE, e);
+		}
+	}
+
+	private ATData fetchAtDataWithChecking(Repository repository, String atAddress) throws DataException {
+		ATData atData = repository.getATRepository().fromATAddress(atAddress);
+		if (atData == null)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.ADDRESS_UNKNOWN);
+
+		// Must be correct AT - check functionality using code hash
+		if (!Arrays.equals(atData.getCodeHash(), LitecoinACCTv1.CODE_BYTES_HASH))
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+		// No point sending message to AT that's finished
+		if (atData.getIsFinished())
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+		return atData;
+	}
+
+}

src/main/java/org/qortal/api/resource/CrossChainLitecoinResource.java

@@ -0,0 +1,167 @@
+package org.qortal.api.resource;
+
+import io.swagger.v3.oas.annotations.Operation;
+import io.swagger.v3.oas.annotations.media.ArraySchema;
+import io.swagger.v3.oas.annotations.media.Content;
+import io.swagger.v3.oas.annotations.media.Schema;
+import io.swagger.v3.oas.annotations.parameters.RequestBody;
+import io.swagger.v3.oas.annotations.responses.ApiResponse;
+import io.swagger.v3.oas.annotations.tags.Tag;
+
+import java.util.List;
+
+import javax.servlet.http.HttpServletRequest;
+import javax.ws.rs.POST;
+import javax.ws.rs.Path;
+import javax.ws.rs.core.Context;
+import javax.ws.rs.core.MediaType;
+
+import org.bitcoinj.core.Transaction;
+import org.qortal.api.ApiError;
+import org.qortal.api.ApiErrors;
+import org.qortal.api.ApiExceptionFactory;
+import org.qortal.api.Security;
+import org.qortal.api.model.crosschain.LitecoinSendRequest;
+import org.qortal.crosschain.ForeignBlockchainException;
+import org.qortal.crosschain.Litecoin;
+import org.qortal.crosschain.SimpleTransaction;
+
+@Path("/crosschain/ltc")
+@Tag(name = "Cross-Chain (Litecoin)")
+public class CrossChainLitecoinResource {
+
+	@Context
+	HttpServletRequest request;
+
+	@POST
+	@Path("/walletbalance")
+	@Operation(
+		summary = "Returns LTC balance for hierarchical, deterministic BIP32 wallet",
+		description = "Supply BIP32 'm' private/public key in base58, starting with 'xprv'/'xpub' for mainnet, 'tprv'/'tpub' for testnet",
+		requestBody = @RequestBody(
+			required = true,
+			content = @Content(
+				mediaType = MediaType.TEXT_PLAIN,
+				schema = @Schema(
+					type = "string",
+					description = "BIP32 'm' private/public key in base58",
+					example = "tpubD6NzVbkrYhZ4XTPc4btCZ6SMgn8CxmWkj6VBVZ1tfcJfMq4UwAjZbG8U74gGSypL9XBYk2R2BLbDBe8pcEyBKM1edsGQEPKXNbEskZozeZc"
+				)
+			)
+		),
+		responses = {
+			@ApiResponse(
+				content = @Content(mediaType = MediaType.TEXT_PLAIN, schema = @Schema(type = "string", description = "balance (satoshis)"))
+			)
+		}
+	)
+	@ApiErrors({ApiError.INVALID_PRIVATE_KEY, ApiError.FOREIGN_BLOCKCHAIN_NETWORK_ISSUE})
+	public String getLitecoinWalletBalance(String key58) {
+		Security.checkApiCallAllowed(request);
+
+		Litecoin litecoin = Litecoin.getInstance();
+
+		if (!litecoin.isValidDeterministicKey(key58))
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_PRIVATE_KEY);
+
+		Long balance = litecoin.getWalletBalance(key58);
+		if (balance == null)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.FOREIGN_BLOCKCHAIN_NETWORK_ISSUE);
+
+		return balance.toString();
+	}
+
+	@POST
+	@Path("/wallettransactions")
+	@Operation(
+		summary = "Returns transactions for hierarchical, deterministic BIP32 wallet",
+		description = "Supply BIP32 'm' private/public key in base58, starting with 'xprv'/'xpub' for mainnet, 'tprv'/'tpub' for testnet",
+		requestBody = @RequestBody(
+			required = true,
+			content = @Content(
+				mediaType = MediaType.TEXT_PLAIN,
+				schema = @Schema(
+					type = "string",
+					description = "BIP32 'm' private/public key in base58",
+					example = "tpubD6NzVbkrYhZ4XTPc4btCZ6SMgn8CxmWkj6VBVZ1tfcJfMq4UwAjZbG8U74gGSypL9XBYk2R2BLbDBe8pcEyBKM1edsGQEPKXNbEskZozeZc"
+				)
+			)
+		),
+		responses = {
+			@ApiResponse(
+				content = @Content(array = @ArraySchema( schema = @Schema( implementation = SimpleTransaction.class ) ) )
+			)
+		}
+	)
+	@ApiErrors({ApiError.INVALID_PRIVATE_KEY, ApiError.FOREIGN_BLOCKCHAIN_NETWORK_ISSUE})
+	public List<SimpleTransaction> getLitecoinWalletTransactions(String key58) {
+		Security.checkApiCallAllowed(request);
+
+		Litecoin litecoin = Litecoin.getInstance();
+
+		if (!litecoin.isValidDeterministicKey(key58))
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_PRIVATE_KEY);
+
+		try {
+			return litecoin.getWalletTransactions(key58);
+		} catch (ForeignBlockchainException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.FOREIGN_BLOCKCHAIN_NETWORK_ISSUE);
+		}
+	}
+
+	@POST
+	@Path("/send")
+	@Operation(
+		summary = "Sends LTC from hierarchical, deterministic BIP32 wallet to specific address",
+		description = "Currently only supports 'legacy' P2PKH Litecoin addresses. Supply BIP32 'm' private key in base58, starting with 'xprv' for mainnet, 'tprv' for testnet",
+		requestBody = @RequestBody(
+			required = true,
+			content = @Content(
+				mediaType = MediaType.APPLICATION_JSON,
+				schema = @Schema(
+					implementation = LitecoinSendRequest.class
+				)
+			)
+		),
+		responses = {
+			@ApiResponse(
+				content = @Content(mediaType = MediaType.TEXT_PLAIN, schema = @Schema(type = "string", description = "transaction hash"))
+			)
+		}
+	)
+	@ApiErrors({ApiError.INVALID_PRIVATE_KEY, ApiError.INVALID_CRITERIA, ApiError.INVALID_ADDRESS, ApiError.FOREIGN_BLOCKCHAIN_BALANCE_ISSUE, ApiError.FOREIGN_BLOCKCHAIN_NETWORK_ISSUE})
+	public String sendBitcoin(LitecoinSendRequest litecoinSendRequest) {
+		Security.checkApiCallAllowed(request);
+
+		if (litecoinSendRequest.litecoinAmount <= 0)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+		if (litecoinSendRequest.feePerByte != null && litecoinSendRequest.feePerByte <= 0)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+		Litecoin litecoin = Litecoin.getInstance();
+
+		if (!litecoin.isValidAddress(litecoinSendRequest.receivingAddress))
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_ADDRESS);
+
+		if (!litecoin.isValidDeterministicKey(litecoinSendRequest.xprv58))
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_PRIVATE_KEY);
+
+		Transaction spendTransaction = litecoin.buildSpend(litecoinSendRequest.xprv58,
+				litecoinSendRequest.receivingAddress,
+				litecoinSendRequest.litecoinAmount,
+				litecoinSendRequest.feePerByte);
+
+		if (spendTransaction == null)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.FOREIGN_BLOCKCHAIN_BALANCE_ISSUE);
+
+		try {
+			litecoin.broadcastTransaction(spendTransaction);
+		} catch (ForeignBlockchainException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.FOREIGN_BLOCKCHAIN_NETWORK_ISSUE);
+		}
+
+		return spendTransaction.getTxId().toString();
+	}
+
+}

src/main/java/org/qortal/api/resource/CrossChainTradeBotResource.java

@@ -0,0 +1,286 @@
+package org.qortal.api.resource;
+
+import io.swagger.v3.oas.annotations.Operation;
+import io.swagger.v3.oas.annotations.Parameter;
+import io.swagger.v3.oas.annotations.media.ArraySchema;
+import io.swagger.v3.oas.annotations.media.Content;
+import io.swagger.v3.oas.annotations.media.Schema;
+import io.swagger.v3.oas.annotations.parameters.RequestBody;
+import io.swagger.v3.oas.annotations.responses.ApiResponse;
+import io.swagger.v3.oas.annotations.tags.Tag;
+
+import java.util.List;
+import java.util.stream.Collectors;
+
+import javax.servlet.http.HttpServletRequest;
+import javax.ws.rs.DELETE;
+import javax.ws.rs.GET;
+import javax.ws.rs.POST;
+import javax.ws.rs.Path;
+import javax.ws.rs.QueryParam;
+import javax.ws.rs.core.Context;
+import javax.ws.rs.core.MediaType;
+
+import org.qortal.account.Account;
+import org.qortal.account.PublicKeyAccount;
+import org.qortal.api.ApiError;
+import org.qortal.api.ApiErrors;
+import org.qortal.api.ApiExceptionFactory;
+import org.qortal.api.Security;
+import org.qortal.api.model.crosschain.TradeBotCreateRequest;
+import org.qortal.api.model.crosschain.TradeBotRespondRequest;
+import org.qortal.asset.Asset;
+import org.qortal.controller.tradebot.AcctTradeBot;
+import org.qortal.controller.tradebot.TradeBot;
+import org.qortal.crosschain.ForeignBlockchain;
+import org.qortal.crosschain.SupportedBlockchain;
+import org.qortal.crosschain.ACCT;
+import org.qortal.crosschain.AcctMode;
+import org.qortal.crypto.Crypto;
+import org.qortal.data.at.ATData;
+import org.qortal.data.crosschain.CrossChainTradeData;
+import org.qortal.data.crosschain.TradeBotData;
+import org.qortal.repository.DataException;
+import org.qortal.repository.Repository;
+import org.qortal.repository.RepositoryManager;
+import org.qortal.utils.Base58;
+
+@Path("/crosschain/tradebot")
+@Tag(name = "Cross-Chain (Trade-Bot)")
+public class CrossChainTradeBotResource {
+
+	@Context
+	HttpServletRequest request;
+
+	@GET
+	@Operation(
+		summary = "List current trade-bot states",
+		responses = {
+			@ApiResponse(
+				content = @Content(
+					array = @ArraySchema(
+						schema = @Schema(
+							implementation = TradeBotData.class
+						)
+					)
+				)
+			)
+		}
+	)
+	@ApiErrors({ApiError.REPOSITORY_ISSUE})
+	public List<TradeBotData> getTradeBotStates(
+			@Parameter(
+					description = "Limit to specific blockchain",
+					example = "LITECOIN",
+					schema = @Schema(implementation = SupportedBlockchain.class)
+				) @QueryParam("foreignBlockchain") SupportedBlockchain foreignBlockchain) {
+		Security.checkApiCallAllowed(request);
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			List<TradeBotData> allTradeBotData = repository.getCrossChainRepository().getAllTradeBotData();
+
+			if (foreignBlockchain == null)
+				return allTradeBotData;
+
+			return allTradeBotData.stream().filter(tradeBotData -> tradeBotData.getForeignBlockchain().equals(foreignBlockchain.name())).collect(Collectors.toList());
+		} catch (DataException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.REPOSITORY_ISSUE, e);
+		}
+	}
+
+	@POST
+	@Path("/create")
+	@Operation(
+		summary = "Create a trade offer (trade-bot entry)",
+		requestBody = @RequestBody(
+			required = true,
+			content = @Content(
+				mediaType = MediaType.APPLICATION_JSON,
+				schema = @Schema(
+					implementation = TradeBotCreateRequest.class
+				)
+			)
+		),
+		responses = {
+			@ApiResponse(
+				content = @Content(mediaType = MediaType.TEXT_PLAIN, schema = @Schema(type = "string"))
+			)
+		}
+	)
+	@ApiErrors({ApiError.INVALID_PUBLIC_KEY, ApiError.INVALID_ADDRESS, ApiError.INVALID_CRITERIA, ApiError.INSUFFICIENT_BALANCE, ApiError.REPOSITORY_ISSUE})
+	@SuppressWarnings("deprecation")
+	public String tradeBotCreator(TradeBotCreateRequest tradeBotCreateRequest) {
+		Security.checkApiCallAllowed(request);
+
+		if (tradeBotCreateRequest.foreignBlockchain == null)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+		ForeignBlockchain foreignBlockchain = tradeBotCreateRequest.foreignBlockchain.getInstance();
+
+		// We prefer foreignAmount to deprecated bitcoinAmount
+		if (tradeBotCreateRequest.foreignAmount == null)
+			tradeBotCreateRequest.foreignAmount = tradeBotCreateRequest.bitcoinAmount;
+
+		if (!foreignBlockchain.isValidAddress(tradeBotCreateRequest.receivingAddress))
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_ADDRESS);
+
+		if (tradeBotCreateRequest.tradeTimeout < 60)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+		if (tradeBotCreateRequest.foreignAmount == null || tradeBotCreateRequest.foreignAmount <= 0)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+		if (tradeBotCreateRequest.qortAmount <= 0 || tradeBotCreateRequest.fundingQortAmount <= 0)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			// Do some simple checking first
+			Account creator = new PublicKeyAccount(repository, tradeBotCreateRequest.creatorPublicKey);
+
+			if (creator.getConfirmedBalance(Asset.QORT) < tradeBotCreateRequest.fundingQortAmount)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INSUFFICIENT_BALANCE);
+
+			byte[] unsignedBytes = TradeBot.getInstance().createTrade(repository, tradeBotCreateRequest);
+			if (unsignedBytes == null)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+			return Base58.encode(unsignedBytes);
+		} catch (DataException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.REPOSITORY_ISSUE, e);
+		}
+	}
+
+	@POST
+	@Path("/respond")
+	@Operation(
+		summary = "Respond to a trade offer. NOTE: WILL SPEND FUNDS!)",
+		description = "Start a new trade-bot entry to respond to chosen trade offer.",
+		requestBody = @RequestBody(
+			required = true,
+			content = @Content(
+				mediaType = MediaType.APPLICATION_JSON,
+				schema = @Schema(
+					implementation = TradeBotRespondRequest.class
+				)
+			)
+		),
+		responses = {
+			@ApiResponse(
+				content = @Content(mediaType = MediaType.TEXT_PLAIN, schema = @Schema(type = "string"))
+			)
+		}
+	)
+	@ApiErrors({ApiError.INVALID_PRIVATE_KEY, ApiError.INVALID_ADDRESS, ApiError.INVALID_CRITERIA, ApiError.FOREIGN_BLOCKCHAIN_BALANCE_ISSUE, ApiError.FOREIGN_BLOCKCHAIN_NETWORK_ISSUE, ApiError.REPOSITORY_ISSUE})
+	@SuppressWarnings("deprecation")
+	public String tradeBotResponder(TradeBotRespondRequest tradeBotRespondRequest) {
+		Security.checkApiCallAllowed(request);
+
+		final String atAddress = tradeBotRespondRequest.atAddress;
+
+		// We prefer foreignKey to deprecated xprv58
+		if (tradeBotRespondRequest.foreignKey == null)
+			tradeBotRespondRequest.foreignKey = tradeBotRespondRequest.xprv58;
+
+		if (tradeBotRespondRequest.foreignKey == null)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_PRIVATE_KEY);
+
+		if (atAddress == null || !Crypto.isValidAtAddress(atAddress))
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_ADDRESS);
+
+		if (tradeBotRespondRequest.receivingAddress == null || !Crypto.isValidAddress(tradeBotRespondRequest.receivingAddress))
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_ADDRESS);
+
+		// Extract data from cross-chain trading AT
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			ATData atData = fetchAtDataWithChecking(repository, atAddress);
+
+			// TradeBot uses AT's code hash to map to ACCT
+			ACCT acct = TradeBot.getInstance().getAcctUsingAtData(atData);
+			if (acct == null)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_ADDRESS);
+
+			if (!acct.getBlockchain().isValidWalletKey(tradeBotRespondRequest.foreignKey))
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_PRIVATE_KEY);
+
+			CrossChainTradeData crossChainTradeData = acct.populateTradeData(repository, atData);
+			if (crossChainTradeData == null)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_ADDRESS);
+
+			if (crossChainTradeData.mode != AcctMode.OFFERING)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+			AcctTradeBot.ResponseResult result = TradeBot.getInstance().startResponse(repository, atData, acct, crossChainTradeData,
+					tradeBotRespondRequest.foreignKey, tradeBotRespondRequest.receivingAddress);
+
+			switch (result) {
+				case OK:
+					return "true";
+
+				case BALANCE_ISSUE:
+					throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.FOREIGN_BLOCKCHAIN_BALANCE_ISSUE);
+
+				case NETWORK_ISSUE:
+					throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.FOREIGN_BLOCKCHAIN_NETWORK_ISSUE);
+
+				default:
+					return "false";
+			}
+		} catch (DataException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.REPOSITORY_ISSUE, e);
+		}
+	}
+
+	@DELETE
+	@Operation(
+		summary = "Delete completed trade",
+		requestBody = @RequestBody(
+			required = true,
+			content = @Content(
+				mediaType = MediaType.TEXT_PLAIN,
+				schema = @Schema(
+					type = "string",
+					example = "93MB2qRDNVLxbmmPuYpLdAqn3u2x9ZhaVZK5wELHueP8"
+				)
+			)
+		),
+		responses = {
+			@ApiResponse(
+				content = @Content(mediaType = MediaType.TEXT_PLAIN, schema = @Schema(type = "string"))
+			)
+		}
+	)
+	@ApiErrors({ApiError.INVALID_ADDRESS, ApiError.REPOSITORY_ISSUE})
+	public String tradeBotDelete(String tradePrivateKey58) {
+		Security.checkApiCallAllowed(request);
+
+		final byte[] tradePrivateKey;
+		try {
+			tradePrivateKey = Base58.decode(tradePrivateKey58);
+
+			if (tradePrivateKey.length != 32)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_PRIVATE_KEY);
+		} catch (NumberFormatException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_PRIVATE_KEY);
+		}
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			// Handed off to TradeBot
+			return TradeBot.getInstance().deleteEntry(repository, tradePrivateKey) ? "true" : "false";
+		} catch (DataException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.REPOSITORY_ISSUE, e);
+		}
+	}
+
+	private ATData fetchAtDataWithChecking(Repository repository, String atAddress) throws DataException {
+		ATData atData = repository.getATRepository().fromATAddress(atAddress);
+		if (atData == null)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.ADDRESS_UNKNOWN);
+
+		// No point sending message to AT that's finished
+		if (atData.getIsFinished())
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+		return atData;
+	}
+
+}

src/main/java/org/qortal/api/resource/PeersResource.java

@@ -6,8 +6,11 @@ import io.swagger.v3.oas.annotations.media.Content;
 import io.swagger.v3.oas.annotations.media.Schema;
 import io.swagger.v3.oas.annotations.parameters.RequestBody;
 import io.swagger.v3.oas.annotations.responses.ApiResponse;
+import io.swagger.v3.oas.annotations.security.SecurityRequirement;
 import io.swagger.v3.oas.annotations.tags.Tag;
 
+import java.net.InetSocketAddress;
+import java.net.UnknownHostException;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.stream.Collectors;
@@ -26,10 +29,17 @@ import org.qortal.api.ApiException;
 import org.qortal.api.ApiExceptionFactory;
 import org.qortal.api.Security;
 import org.qortal.api.model.ConnectedPeer;
+import org.qortal.controller.Controller;
+import org.qortal.controller.Synchronizer;
+import org.qortal.controller.Synchronizer.SynchronizationResult;
+import org.qortal.data.block.BlockSummaryData;
 import org.qortal.data.network.PeerData;
 import org.qortal.network.Network;
+import org.qortal.network.Peer;
 import org.qortal.network.PeerAddress;
 import org.qortal.repository.DataException;
+import org.qortal.repository.Repository;
+import org.qortal.repository.RepositoryManager;
 import org.qortal.utils.ExecuteProduceConsume;
 import org.qortal.utils.NTP;
 
@@ -122,6 +132,7 @@ public class PeersResource {
 			)
 		}
 	)
+	@SecurityRequirement(name = "apiKey")
 	public ExecuteProduceConsume.StatsSnapshot getEngineStats() {
 		Security.checkApiCallAllowed(request);
 
@@ -159,6 +170,7 @@ public class PeersResource {
 	@ApiErrors({
 		ApiError.INVALID_NETWORK_ADDRESS, ApiError.REPOSITORY_ISSUE
 	})
+	@SecurityRequirement(name = "apiKey")
 	public String addPeer(String address) {
 		Security.checkApiCallAllowed(request);
 
@@ -213,6 +225,7 @@ public class PeersResource {
 	@ApiErrors({
 		ApiError.INVALID_NETWORK_ADDRESS, ApiError.REPOSITORY_ISSUE
 	})
+	@SecurityRequirement(name = "apiKey")
 	public String removePeer(String address) {
 		Security.checkApiCallAllowed(request);
 
@@ -248,6 +261,7 @@ public class PeersResource {
 	@ApiErrors({
 		ApiError.REPOSITORY_ISSUE
 	})
+	@SecurityRequirement(name = "apiKey")
 	public String removeKnownPeers(String address) {
 		Security.checkApiCallAllowed(request);
 
@@ -260,4 +274,68 @@ public class PeersResource {
 		}
 	}
 
+	@POST
+	@Path("/commonblock")
+	@Operation(
+		summary = "Report common block with given peer.",
+		requestBody = @RequestBody(
+			required = true,
+			content = @Content(
+				mediaType = MediaType.TEXT_PLAIN,
+				schema = @Schema(
+					type = "string", example = "node2.qortal.org"
+				)
+			)
+		),
+		responses = {
+			@ApiResponse(
+				description = "the block",
+				content = @Content(
+					array = @ArraySchema(
+						schema = @Schema(
+							implementation = BlockSummaryData.class
+						)
+					)
+				)
+			)
+		}
+	)
+	@ApiErrors({ApiError.INVALID_DATA, ApiError.REPOSITORY_ISSUE})
+	@SecurityRequirement(name = "apiKey")
+	public List<BlockSummaryData> commonBlock(String targetPeerAddress) {
+		Security.checkApiCallAllowed(request);
+
+		try {
+			// Try to resolve passed address to make things easier
+			PeerAddress peerAddress = PeerAddress.fromString(targetPeerAddress);
+			InetSocketAddress resolvedAddress = peerAddress.toSocketAddress();
+
+			List<Peer> peers = Network.getInstance().getHandshakedPeers();
+			Peer targetPeer = peers.stream().filter(peer -> peer.getResolvedAddress().equals(resolvedAddress)).findFirst().orElse(null);
+
+			if (targetPeer == null)
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_DATA);
+
+			try (final Repository repository = RepositoryManager.getRepository()) {
+				int ourInitialHeight = Controller.getInstance().getChainHeight();
+				boolean force = true;
+				List<BlockSummaryData> peerBlockSummaries = new ArrayList<>();
+
+				SynchronizationResult findCommonBlockResult = Synchronizer.getInstance().fetchSummariesFromCommonBlock(repository, targetPeer, ourInitialHeight, force, peerBlockSummaries, true);
+				if (findCommonBlockResult != SynchronizationResult.OK)
+					return null;
+
+				return peerBlockSummaries;
+			}
+		} catch (IllegalArgumentException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_DATA);
+		} catch (UnknownHostException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_DATA);
+		} catch (DataException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.REPOSITORY_ISSUE, e);
+		} catch (InterruptedException e) {
+			return null;
+		}
+	}
+
 }

src/main/java/org/qortal/api/resource/TransactionsResource.java

@@ -510,14 +510,19 @@ public class TransactionsResource {
 		if (!Controller.getInstance().isUpToDate())
 			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.BLOCKCHAIN_NEEDS_SYNC);
 
+		byte[] rawBytes = Base58.decode(rawBytes58);
+
+		TransactionData transactionData;
+		try {
+			transactionData = TransactionTransformer.fromBytes(rawBytes);
+		} catch (TransformationException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.TRANSFORMATION_ERROR, e);
+		}
+
+		if (transactionData == null)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_DATA);
+
 		try (final Repository repository = RepositoryManager.getRepository()) {
-			byte[] rawBytes = Base58.decode(rawBytes58);
-
-			TransactionData transactionData = TransactionTransformer.fromBytes(rawBytes);
-
-			if (transactionData == null)
-				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_DATA);
-
 			Transaction transaction = Transaction.fromData(repository, transactionData);
 
 			if (!transaction.isSignatureValid())
@@ -535,16 +540,9 @@ public class TransactionsResource {
 				blockchainLock.unlock();
 			}
 
-			// Notify controller of new transaction
-			Controller.getInstance().onNewTransaction(transactionData, null);
-
 			return "true";
 		} catch (NumberFormatException e) {
 			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_DATA, e);
-		} catch (TransformationException e) {
-			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.TRANSFORMATION_ERROR, e);
-		} catch (ApiException e) {
-			throw e;
 		} catch (DataException e) {
 			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.REPOSITORY_ISSUE, e);
 		} catch (InterruptedException e) {

src/main/java/org/qortal/api/websocket/ActiveChatsWebSocket.java

@@ -31,6 +31,7 @@ public class ActiveChatsWebSocket extends ApiWebSocket {
 	}
 
 	@OnWebSocketConnect
+	@Override
 	public void onWebSocketConnect(Session session) {
 		Map<String, String> pathParams = getPathParams(session, "/{address}");
 
@@ -49,16 +50,19 @@ public class ActiveChatsWebSocket extends ApiWebSocket {
 	}
 
 	@OnWebSocketClose
+	@Override
 	public void onWebSocketClose(Session session, int statusCode, String reason) {
 		ChatNotifier.getInstance().deregister(session);
 	}
 
 	@OnWebSocketError
 	public void onWebSocketError(Session session, Throwable throwable) {
+		/* ignored */
 	}
 
 	@OnWebSocketMessage
 	public void onWebSocketMessage(Session session, String message) {
+		/* ignored */
 	}
 
 	private void onNotify(Session session, ChatTransactionData chatTransactionData, String ourAddress, AtomicReference<String> previousOutput) {

src/main/java/org/qortal/api/websocket/AdminStatusWebSocket.java

@@ -13,59 +13,87 @@ import org.eclipse.jetty.websocket.api.annotations.OnWebSocketMessage;
 import org.eclipse.jetty.websocket.api.annotations.WebSocket;
 import org.eclipse.jetty.websocket.servlet.WebSocketServletFactory;
 import org.qortal.api.model.NodeStatus;
-import org.qortal.controller.StatusNotifier;
-import org.qortal.repository.DataException;
-import org.qortal.repository.Repository;
-import org.qortal.repository.RepositoryManager;
+import org.qortal.controller.Controller;
+import org.qortal.event.Event;
+import org.qortal.event.EventBus;
+import org.qortal.event.Listener;
 
 @WebSocket
 @SuppressWarnings("serial")
-public class AdminStatusWebSocket extends ApiWebSocket {
+public class AdminStatusWebSocket extends ApiWebSocket implements Listener {
+
+	private static final AtomicReference<String> previousOutput = new AtomicReference<>(null);
 
 	@Override
 	public void configure(WebSocketServletFactory factory) {
 		factory.register(AdminStatusWebSocket.class);
+
+		try {
+			previousOutput.set(buildStatusString());
+		} catch (IOException e) {
+			// How to fail properly?
+			return;
+		}
+
+		EventBus.INSTANCE.addListener(this::listen);
+	}
+
+	@Override
+	public void listen(Event event) {
+		if (!(event instanceof Controller.StatusChangeEvent))
+			return;
+
+		String newOutput;
+		try {
+			newOutput = buildStatusString();
+		} catch (IOException e) {
+			// Ignore this time?
+			return;
+		}
+
+		if (previousOutput.getAndUpdate(currentValue -> newOutput).equals(newOutput))
+			// Output hasn't changed, so don't send anything
+			return;
+
+		for (Session session : getSessions())
+			this.sendStatus(session, newOutput);
 	}
 
 	@OnWebSocketConnect
+	@Override
 	public void onWebSocketConnect(Session session) {
-		AtomicReference<String> previousOutput = new AtomicReference<>(null);
+		this.sendStatus(session, previousOutput.get());
 
-		StatusNotifier.Listener listener = timestamp -> onNotify(session, previousOutput);
-		StatusNotifier.getInstance().register(session, listener);
-
-		this.onNotify(session, previousOutput);
+		super.onWebSocketConnect(session);
 	}
 
 	@OnWebSocketClose
+	@Override
 	public void onWebSocketClose(Session session, int statusCode, String reason) {
-		StatusNotifier.getInstance().deregister(session);
+		super.onWebSocketClose(session, statusCode, reason);
 	}
 
 	@OnWebSocketError
 	public void onWebSocketError(Session session, Throwable throwable) {
+		/* We ignore errors for now, but method here to silence log spam */
 	}
 
 	@OnWebSocketMessage
 	public void onWebSocketMessage(Session session, String message) {
+		/* ignored */
 	}
 
-	private void onNotify(Session session,AtomicReference<String> previousOutput) {
-		try (final Repository repository = RepositoryManager.getRepository()) {
-			NodeStatus nodeStatus = new NodeStatus();
+	private static String buildStatusString() throws IOException {
+		NodeStatus nodeStatus = new NodeStatus();
+		StringWriter stringWriter = new StringWriter();
+		marshall(stringWriter, nodeStatus);
+		return stringWriter.toString();
+	}
 
-			StringWriter stringWriter = new StringWriter();
-
-			marshall(stringWriter, nodeStatus);
-
-			// Only output if something has changed
-			String output = stringWriter.toString();
-			if (output.equals(previousOutput.get()))
-				return;
-
-			previousOutput.set(output);
-			session.getRemote().sendStringByFuture(output);
-		} catch (DataException | IOException | WebSocketException e) {
+	private void sendStatus(Session session, String status) {
+		try {
+			session.getRemote().sendStringByFuture(status);
+		} catch (WebSocketException e) {
 			// No output this time?
 		}
 	}

src/main/java/org/qortal/api/websocket/ApiWebSocket.java

@@ -107,7 +107,9 @@ abstract class ApiWebSocket extends WebSocketServlet {
 
 	public void onWebSocketClose(Session session, int statusCode, String reason) {
 		synchronized (SESSIONS_BY_CLASS) {
-			SESSIONS_BY_CLASS.get(this.getClass()).remove(session);
+			List<Session> sessions = SESSIONS_BY_CLASS.get(this.getClass());
+			if (sessions != null)
+				sessions.remove(session);
 		}
 	}
 

src/main/java/org/qortal/api/websocket/BlocksWebSocket.java

@@ -13,8 +13,12 @@ import org.eclipse.jetty.websocket.api.annotations.OnWebSocketMessage;
 import org.eclipse.jetty.websocket.api.annotations.WebSocket;
 import org.eclipse.jetty.websocket.servlet.WebSocketServletFactory;
 import org.qortal.api.ApiError;
-import org.qortal.api.model.BlockInfo;
-import org.qortal.controller.BlockNotifier;
+import org.qortal.controller.Controller;
+import org.qortal.data.block.BlockData;
+import org.qortal.data.block.BlockSummaryData;
+import org.qortal.event.Event;
+import org.qortal.event.EventBus;
+import org.qortal.event.Listener;
 import org.qortal.repository.DataException;
 import org.qortal.repository.Repository;
 import org.qortal.repository.RepositoryManager;
@@ -22,26 +26,42 @@ import org.qortal.utils.Base58;
 
 @WebSocket
 @SuppressWarnings("serial")
-public class BlocksWebSocket extends ApiWebSocket {
+public class BlocksWebSocket extends ApiWebSocket implements Listener {
 
 	@Override
 	public void configure(WebSocketServletFactory factory) {
 		factory.register(BlocksWebSocket.class);
+
+		EventBus.INSTANCE.addListener(this::listen);
+	}
+
+	@Override
+	public void listen(Event event) {
+		if (!(event instanceof Controller.NewBlockEvent))
+			return;
+
+		BlockData blockData = ((Controller.NewBlockEvent) event).getBlockData();
+		BlockSummaryData blockSummary = new BlockSummaryData(blockData);
+
+		for (Session session : getSessions())
+			sendBlockSummary(session, blockSummary);
 	}
 
 	@OnWebSocketConnect
+	@Override
 	public void onWebSocketConnect(Session session) {
-		BlockNotifier.Listener listener = blockInfo -> onNotify(session, blockInfo);
-		BlockNotifier.getInstance().register(session, listener);
+		super.onWebSocketConnect(session);
 	}
 
 	@OnWebSocketClose
+	@Override
 	public void onWebSocketClose(Session session, int statusCode, String reason) {
-		BlockNotifier.getInstance().deregister(session);
+		super.onWebSocketClose(session, statusCode, reason);
 	}
 
 	@OnWebSocketError
 	public void onWebSocketError(Session session, Throwable throwable) {
+		/* We ignore errors for now, but method here to silence log spam */
 	}
 
 	@OnWebSocketMessage
@@ -65,13 +85,13 @@ public class BlocksWebSocket extends ApiWebSocket {
 					return;
 				}
 
-				List<BlockInfo> blockInfos = repository.getBlockRepository().getBlockInfos(height, null, 1);
-				if (blockInfos == null || blockInfos.isEmpty()) {
+				List<BlockSummaryData> blockSummaries = repository.getBlockRepository().getBlockSummaries(height, height);
+				if (blockSummaries == null || blockSummaries.isEmpty()) {
 					sendError(session, ApiError.BLOCK_UNKNOWN);
 					return;
 				}
 
-				onNotify(session, blockInfos.get(0));
+				sendBlockSummary(session, blockSummaries.get(0));
 			} catch (DataException e) {
 				sendError(session, ApiError.REPOSITORY_ISSUE);
 			}
@@ -94,23 +114,23 @@ public class BlocksWebSocket extends ApiWebSocket {
 		}
 
 		try (final Repository repository = RepositoryManager.getRepository()) {
-			List<BlockInfo> blockInfos = repository.getBlockRepository().getBlockInfos(height, null, 1);
-			if (blockInfos == null || blockInfos.isEmpty()) {
+			List<BlockSummaryData> blockSummaries = repository.getBlockRepository().getBlockSummaries(height, height);
+			if (blockSummaries == null || blockSummaries.isEmpty()) {
 				sendError(session, ApiError.BLOCK_UNKNOWN);
 				return;
 			}
 
-			onNotify(session, blockInfos.get(0));
+			sendBlockSummary(session, blockSummaries.get(0));
 		} catch (DataException e) {
 			sendError(session, ApiError.REPOSITORY_ISSUE);
 		}
 	}
 
-	private void onNotify(Session session, BlockInfo blockInfo) {
+	private void sendBlockSummary(Session session, BlockSummaryData blockSummary) {
 		StringWriter stringWriter = new StringWriter();
 
 		try {
-			marshall(stringWriter, blockInfo);
+			marshall(stringWriter, blockSummary);
 
 			session.getRemote().sendStringByFuture(stringWriter.toString());
 		} catch (IOException | WebSocketException e) {

src/main/java/org/qortal/api/websocket/ChatMessagesWebSocket.java

@@ -32,6 +32,7 @@ public class ChatMessagesWebSocket extends ApiWebSocket {
 	}
 
 	@OnWebSocketConnect
+	@Override
 	public void onWebSocketConnect(Session session) {
 		Map<String, List<String>> queryParams = session.getUpgradeRequest().getParameterMap();
 
@@ -86,16 +87,19 @@ public class ChatMessagesWebSocket extends ApiWebSocket {
 	}
 
 	@OnWebSocketClose
+	@Override
 	public void onWebSocketClose(Session session, int statusCode, String reason) {
 		ChatNotifier.getInstance().deregister(session);
 	}
 
 	@OnWebSocketError
 	public void onWebSocketError(Session session, Throwable throwable) {
+		/* ignored */
 	}
 
 	@OnWebSocketMessage
 	public void onWebSocketMessage(Session session, String message) {
+		/* ignored */
 	}
 
 	private void onNotify(Session session, ChatTransactionData chatTransactionData, int txGroupId) {

src/main/java/org/qortal/api/websocket/PresenceWebSocket.java

@@ -0,0 +1,244 @@
+package org.qortal.api.websocket;
+
+import java.io.IOException;
+import java.io.StringWriter;
+import java.util.Collections;
+import java.util.EnumMap;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+import javax.xml.bind.annotation.XmlAccessType;
+import javax.xml.bind.annotation.XmlAccessorType;
+
+import org.eclipse.jetty.websocket.api.Session;
+import org.eclipse.jetty.websocket.api.annotations.OnWebSocketClose;
+import org.eclipse.jetty.websocket.api.annotations.OnWebSocketConnect;
+import org.eclipse.jetty.websocket.api.annotations.OnWebSocketError;
+import org.eclipse.jetty.websocket.api.annotations.OnWebSocketMessage;
+import org.eclipse.jetty.websocket.api.annotations.WebSocket;
+import org.eclipse.jetty.websocket.servlet.WebSocketServletFactory;
+import org.qortal.controller.Controller;
+import org.qortal.crypto.Crypto;
+import org.qortal.data.transaction.PresenceTransactionData;
+import org.qortal.data.transaction.TransactionData;
+import org.qortal.event.Event;
+import org.qortal.event.EventBus;
+import org.qortal.event.Listener;
+import org.qortal.repository.DataException;
+import org.qortal.repository.Repository;
+import org.qortal.repository.RepositoryManager;
+import org.qortal.transaction.PresenceTransaction.PresenceType;
+import org.qortal.transaction.Transaction.TransactionType;
+import org.qortal.utils.Base58;
+import org.qortal.utils.NTP;
+
+@WebSocket
+@SuppressWarnings("serial")
+public class PresenceWebSocket extends ApiWebSocket implements Listener {
+
+	@XmlAccessorType(XmlAccessType.FIELD)
+	@SuppressWarnings("unused")
+	private static class PresenceInfo {
+		private final PresenceType presenceType;
+		private final String publicKey;
+		private final long timestamp;
+		private final String address;
+
+		protected PresenceInfo() {
+			this.presenceType = null;
+			this.publicKey = null;
+			this.timestamp = 0L;
+			this.address = null;
+		}
+
+		public PresenceInfo(PresenceType presenceType, String pubKey58, long timestamp) {
+			this.presenceType = presenceType;
+			this.publicKey = pubKey58;
+			this.timestamp = timestamp;
+			this.address = Crypto.toAddress(Base58.decode(this.publicKey));
+		}
+
+		public PresenceType getPresenceType() {
+			return this.presenceType;
+		}
+
+		public String getPublicKey() {
+			return this.publicKey;
+		}
+
+		public long getTimestamp() {
+			return this.timestamp;
+		}
+
+		public String getAddress() {
+			return this.address;
+		}
+	}
+
+	/** Outer map key is PresenceType (enum), inner map key is public key in base58, inner map value is timestamp */
+	private static final Map<PresenceType, Map<String, Long>> currentEntries = Collections.synchronizedMap(new EnumMap<>(PresenceType.class));
+
+	/** (Optional) PresenceType used for filtering by that Session. */
+	private static final Map<Session, PresenceType> sessionPresenceTypes = Collections.synchronizedMap(new HashMap<>());
+
+	@Override
+	public void configure(WebSocketServletFactory factory) {
+		factory.register(PresenceWebSocket.class);
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			populateCurrentInfo(repository);
+		} catch (DataException e) {
+			// How to fail properly?
+			return;
+		}
+
+		EventBus.INSTANCE.addListener(this::listen);
+	}
+
+	@Override
+	public void listen(Event event) {
+		// We use NewBlockEvent as a proxy for 1-minute timer
+		if (!(event instanceof Controller.NewTransactionEvent) && !(event instanceof Controller.NewBlockEvent))
+			return;
+
+		removeOldEntries();
+
+		if (event instanceof Controller.NewBlockEvent)
+			// We only wanted a chance to cull old entries
+			return;
+
+		TransactionData transactionData = ((Controller.NewTransactionEvent) event).getTransactionData();
+
+		if (transactionData.getType() != TransactionType.PRESENCE)
+			return;
+
+		PresenceTransactionData presenceData = (PresenceTransactionData) transactionData;
+		PresenceType presenceType = presenceData.getPresenceType();
+
+		// Put/replace for this publickey making sure we keep newest timestamp
+		String pubKey58 = Base58.encode(presenceData.getCreatorPublicKey());
+		long ourTimestamp = presenceData.getTimestamp();
+		long computedTimestamp = mergePresence(presenceType, pubKey58, ourTimestamp);
+
+		if (computedTimestamp != ourTimestamp)
+			// nothing changed
+			return;
+
+		List<PresenceInfo> presenceInfo = Collections.singletonList(new PresenceInfo(presenceType, pubKey58, computedTimestamp));
+
+		// Notify sessions
+		for (Session session : getSessions()) {
+			PresenceType sessionPresenceType = sessionPresenceTypes.get(session);
+
+			if (sessionPresenceType == null || sessionPresenceType == presenceType)
+				sendPresenceInfo(session, presenceInfo);
+		}
+	}
+
+	@OnWebSocketConnect
+	@Override
+	public void onWebSocketConnect(Session session) {
+		Map<String, List<String>> queryParams = session.getUpgradeRequest().getParameterMap();
+		List<String> presenceTypes = queryParams.get("presenceType");
+
+		// We only support ONE presenceType
+		String presenceTypeName = presenceTypes == null || presenceTypes.isEmpty() ? null : presenceTypes.get(0);
+
+		PresenceType presenceType = presenceTypeName == null ? null : PresenceType.fromString(presenceTypeName);
+
+		// Make sure that if caller does give a presenceType, that it is a valid/known one.
+		if (presenceTypeName != null && presenceType == null) {
+			session.close(4003, "unknown presenceType: " + presenceTypeName);
+			return;
+		}
+
+		// Save session's requested PresenceType, if given
+		if (presenceType != null)
+			sessionPresenceTypes.put(session, presenceType);
+
+		List<PresenceInfo> presenceInfo;
+
+		synchronized (currentEntries) {
+			presenceInfo = currentEntries.entrySet().stream()
+					.filter(entry -> presenceType == null ? true : entry.getKey() == presenceType)
+					.flatMap(entry -> entry.getValue().entrySet().stream().map(innerEntry -> new PresenceInfo(entry.getKey(), innerEntry.getKey(), innerEntry.getValue())))
+					.collect(Collectors.toList());
+		}
+
+		if (!sendPresenceInfo(session, presenceInfo)) {
+			session.close(4002, "websocket issue");
+			return;
+		}
+
+		super.onWebSocketConnect(session);
+	}
+
+	@OnWebSocketClose
+	@Override
+	public void onWebSocketClose(Session session, int statusCode, String reason) {
+		// clean up
+		sessionPresenceTypes.remove(session);
+
+		super.onWebSocketClose(session, statusCode, reason);
+	}
+
+	@OnWebSocketError
+	public void onWebSocketError(Session session, Throwable throwable) {
+		/* ignored */
+	}
+
+	@OnWebSocketMessage
+	public void onWebSocketMessage(Session session, String message) {
+		/* ignored */
+	}
+
+	private boolean sendPresenceInfo(Session session, List<PresenceInfo> presenceInfo) {
+		try {
+			StringWriter stringWriter = new StringWriter();
+			marshall(stringWriter, presenceInfo);
+
+			String output = stringWriter.toString();
+			session.getRemote().sendStringByFuture(output);
+		} catch (IOException e) {
+			// No output this time?
+			return false;
+		}
+
+		return true;
+	}
+
+	private static void populateCurrentInfo(Repository repository) throws DataException {
+		// We want ALL PRESENCE transactions
+
+		List<TransactionData> presenceTransactionsData = repository.getTransactionRepository().getUnconfirmedTransactions(TransactionType.PRESENCE, null);
+
+		for (TransactionData transactionData : presenceTransactionsData) {
+			PresenceTransactionData presenceData = (PresenceTransactionData) transactionData;
+
+			PresenceType presenceType = presenceData.getPresenceType();
+
+			// Put/replace for this publickey making sure we keep newest timestamp
+			String pubKey58 = Base58.encode(presenceData.getCreatorPublicKey());
+			long ourTimestamp = presenceData.getTimestamp();
+
+			mergePresence(presenceType, pubKey58, ourTimestamp);
+		}
+	}
+
+	private static long mergePresence(PresenceType presenceType, String pubKey58, long ourTimestamp) {
+		Map<String, Long> typedPubkeyTimestamps = currentEntries.computeIfAbsent(presenceType, someType -> Collections.synchronizedMap(new HashMap<>()));
+		return typedPubkeyTimestamps.compute(pubKey58, (somePubKey58, currentTimestamp) -> (currentTimestamp == null || currentTimestamp < ourTimestamp) ? ourTimestamp : currentTimestamp);
+	}
+
+	private static void removeOldEntries() {
+		long now = NTP.getTime();
+
+		currentEntries.entrySet().forEach(entry -> {
+			long expiryThreshold = now - entry.getKey().getLifetime();
+			entry.getValue().entrySet().removeIf(pubkeyTimestamp -> pubkeyTimestamp.getValue() < expiryThreshold);
+		});
+	}
+
+}

src/main/java/org/qortal/api/websocket/TradeBotWebSocket.java

@@ -11,10 +11,12 @@ import java.util.stream.Collectors;
 import org.eclipse.jetty.websocket.api.Session;
 import org.eclipse.jetty.websocket.api.annotations.OnWebSocketClose;
 import org.eclipse.jetty.websocket.api.annotations.OnWebSocketConnect;
+import org.eclipse.jetty.websocket.api.annotations.OnWebSocketError;
 import org.eclipse.jetty.websocket.api.annotations.OnWebSocketMessage;
 import org.eclipse.jetty.websocket.api.annotations.WebSocket;
 import org.eclipse.jetty.websocket.servlet.WebSocketServletFactory;
-import org.qortal.controller.TradeBot;
+import org.qortal.controller.tradebot.TradeBot;
+import org.qortal.crosschain.SupportedBlockchain;
 import org.qortal.data.crosschain.TradeBotData;
 import org.qortal.event.Event;
 import org.qortal.event.EventBus;
@@ -29,7 +31,9 @@ import org.qortal.utils.Base58;
 public class TradeBotWebSocket extends ApiWebSocket implements Listener {
 
 	/** Cache of trade-bot entry states, keyed by trade-bot entry's "trade private key" (base58) */
-	private static final Map<String, TradeBotData.State> PREVIOUS_STATES = new HashMap<>();
+	private static final Map<String, Integer> PREVIOUS_STATES = new HashMap<>();
+
+	private static final Map<Session, String> sessionBlockchain = Collections.synchronizedMap(new HashMap<>());
 
 	@Override
 	public void configure(WebSocketServletFactory factory) {
@@ -41,7 +45,7 @@ public class TradeBotWebSocket extends ApiWebSocket implements Listener {
 				// How do we properly fail here?
 				return;
 
-			PREVIOUS_STATES.putAll(tradeBotEntries.stream().collect(Collectors.toMap(entry -> Base58.encode(entry.getTradePrivateKey()), TradeBotData::getState)));
+			PREVIOUS_STATES.putAll(tradeBotEntries.stream().collect(Collectors.toMap(entry -> Base58.encode(entry.getTradePrivateKey()), TradeBotData::getStateValue)));
 		} catch (DataException e) {
 			// No output this time
 		}
@@ -58,44 +62,78 @@ public class TradeBotWebSocket extends ApiWebSocket implements Listener {
 		String tradePrivateKey58 = Base58.encode(tradeBotData.getTradePrivateKey());
 
 		synchronized (PREVIOUS_STATES) {
-			if (PREVIOUS_STATES.get(tradePrivateKey58) == tradeBotData.getState())
+			Integer previousStateValue = PREVIOUS_STATES.get(tradePrivateKey58);
+			if (previousStateValue != null && previousStateValue == tradeBotData.getStateValue())
 				// Not changed
 				return;
 
-			PREVIOUS_STATES.put(tradePrivateKey58, tradeBotData.getState());
+			PREVIOUS_STATES.put(tradePrivateKey58, tradeBotData.getStateValue());
 		}
 
 		List<TradeBotData> tradeBotEntries = Collections.singletonList(tradeBotData);
-		for (Session session : getSessions())
-			sendEntries(session, tradeBotEntries);
+
+		for (Session session : getSessions()) {
+			// Only send if this session has this/no preferred blockchain
+			String preferredBlockchain = sessionBlockchain.get(session);
+
+			if (preferredBlockchain == null || preferredBlockchain.equals(tradeBotData.getForeignBlockchain()))
+				sendEntries(session, tradeBotEntries);
+		}
 	}
 
 	@OnWebSocketConnect
+	@Override
 	public void onWebSocketConnect(Session session) {
+		Map<String, List<String>> queryParams = session.getUpgradeRequest().getParameterMap();
+
+		List<String> foreignBlockchains = queryParams.get("foreignBlockchain");
+		final String foreignBlockchain = foreignBlockchains == null ? null : foreignBlockchains.get(0);
+
+		// Make sure blockchain (if any) is valid
+		if (foreignBlockchain != null && SupportedBlockchain.fromString(foreignBlockchain) == null) {
+			session.close(4003, "unknown blockchain: " + foreignBlockchain);
+			return;
+		}
+
+		// save session's preferred blockchain (if any)
+		sessionBlockchain.put(session, foreignBlockchain);
+
 		// Send all known trade-bot entries
 		try (final Repository repository = RepositoryManager.getRepository()) {
 			List<TradeBotData> tradeBotEntries = repository.getCrossChainRepository().getAllTradeBotData();
-			if (tradeBotEntries == null) {
-				session.close(4001, "repository issue fetching trade-bot entries");
-				return;
-			}
+
+			// Optional filtering
+			if (foreignBlockchain != null)
+				tradeBotEntries = tradeBotEntries.stream()
+						.filter(tradeBotData -> tradeBotData.getForeignBlockchain().equals(foreignBlockchain))
+						.collect(Collectors.toList());
 
 			if (!sendEntries(session, tradeBotEntries)) {
 				session.close(4002, "websocket issue");
 				return;
 			}
 		} catch (DataException e) {
-			// No output this time
+			session.close(4001, "repository issue fetching trade-bot entries");
+			return;
 		}
 
 		super.onWebSocketConnect(session);
 	}
 
 	@OnWebSocketClose
+	@Override
 	public void onWebSocketClose(Session session, int statusCode, String reason) {
+		// clean up
+		sessionBlockchain.remove(session);
+
 		super.onWebSocketClose(session, statusCode, reason);
 	}
 
+	@OnWebSocketError
+	public void onWebSocketError(Session session, Throwable throwable) {
+		/* ignored */
+	}
+
 	@OnWebSocketMessage
 	public void onWebSocketMessage(Session session, String message) {
 		/* ignored */

src/main/java/org/qortal/api/websocket/TradeOffersWebSocket.java

@@ -3,128 +3,228 @@ package org.qortal.api.websocket;
 import java.io.IOException;
 import java.io.StringWriter;
 import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.function.Predicate;
+import java.util.function.Supplier;
 import java.util.stream.Collectors;
 
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
 import org.eclipse.jetty.websocket.api.Session;
 import org.eclipse.jetty.websocket.api.annotations.OnWebSocketClose;
 import org.eclipse.jetty.websocket.api.annotations.OnWebSocketConnect;
+import org.eclipse.jetty.websocket.api.annotations.OnWebSocketError;
 import org.eclipse.jetty.websocket.api.annotations.OnWebSocketMessage;
 import org.eclipse.jetty.websocket.api.annotations.WebSocket;
 import org.eclipse.jetty.websocket.servlet.WebSocketServletFactory;
-import org.qortal.api.model.BlockInfo;
 import org.qortal.api.model.CrossChainOfferSummary;
-import org.qortal.controller.BlockNotifier;
-import org.qortal.crosschain.BTCACCT;
+import org.qortal.controller.Controller;
+import org.qortal.crosschain.SupportedBlockchain;
+import org.qortal.crosschain.ACCT;
+import org.qortal.crosschain.AcctMode;
 import org.qortal.data.at.ATStateData;
+import org.qortal.data.block.BlockData;
 import org.qortal.data.crosschain.CrossChainTradeData;
+import org.qortal.event.Event;
+import org.qortal.event.EventBus;
+import org.qortal.event.Listener;
 import org.qortal.repository.DataException;
 import org.qortal.repository.Repository;
 import org.qortal.repository.RepositoryManager;
+import org.qortal.utils.ByteArray;
 import org.qortal.utils.NTP;
 
 @WebSocket
 @SuppressWarnings("serial")
-public class TradeOffersWebSocket extends ApiWebSocket {
+public class TradeOffersWebSocket extends ApiWebSocket implements Listener {
+
+	private static final Logger LOGGER = LogManager.getLogger(TradeOffersWebSocket.class);
+
+	private static class CachedOfferInfo {
+		public final Map<String, AcctMode> previousAtModes = new HashMap<>();
+
+		// OFFERING
+		public final Map<String, CrossChainOfferSummary> currentSummaries = new HashMap<>();
+		// REDEEMED/REFUNDED/CANCELLED
+		public final Map<String, CrossChainOfferSummary> historicSummaries = new HashMap<>();
+	}
+	// Manual synchronization
+	private static final Map<String, CachedOfferInfo> cachedInfoByBlockchain = new HashMap<>();
+
+	private static final Predicate<CrossChainOfferSummary> isHistoric = offerSummary
+			-> offerSummary.getMode() == AcctMode.REDEEMED
+			|| offerSummary.getMode() == AcctMode.REFUNDED
+			|| offerSummary.getMode() == AcctMode.CANCELLED;
+
+	private static final Map<Session, String> sessionBlockchain = Collections.synchronizedMap(new HashMap<>());
 
 	@Override
 	public void configure(WebSocketServletFactory factory) {
 		factory.register(TradeOffersWebSocket.class);
-	}
-
-	@OnWebSocketConnect
-	public void onWebSocketConnect(Session session) {
-		Map<String, List<String>> queryParams = session.getUpgradeRequest().getParameterMap();
-
-		final boolean includeHistoric = queryParams.get("includeHistoric") != null;
-		final Map<String, BTCACCT.Mode> previousAtModes = new HashMap<>();
-		List<CrossChainOfferSummary> crossChainOfferSummaries;
 
 		try (final Repository repository = RepositoryManager.getRepository()) {
-			List<ATStateData> initialAtStates;
+			populateCurrentSummaries(repository);
 
-			// We want ALL OFFERING trades
-			Boolean isFinished = Boolean.FALSE;
-			Integer dataByteOffset = BTCACCT.MODE_BYTE_OFFSET;
-			Long expectedValue = (long) BTCACCT.Mode.OFFERING.value;
-			Integer minimumFinalHeight = null;
+			populateHistoricSummaries(repository);
+		} catch (DataException e) {
+			// How to fail properly?
+			return;
+		}
 
-			initialAtStates = repository.getATRepository().getMatchingFinalATStates(BTCACCT.CODE_BYTES_HASH,
-					isFinished, dataByteOffset, expectedValue, minimumFinalHeight,
-					null, null, null);
+		EventBus.INSTANCE.addListener(this::listen);
+	}
 
-			if (initialAtStates == null) {
-				session.close(4001, "repository issue fetching OFFERING trades");
-				return;
-			}
+	@Override
+	public void listen(Event event) {
+		if (!(event instanceof Controller.NewBlockEvent))
+			return;
 
-			// Save initial AT modes
-			previousAtModes.putAll(initialAtStates.stream().collect(Collectors.toMap(ATStateData::getATAddress, atState -> BTCACCT.Mode.OFFERING)));
+		BlockData blockData = ((Controller.NewBlockEvent) event).getBlockData();
 
-			// Convert to offer summaries
-			crossChainOfferSummaries = produceSummaries(repository, initialAtStates, null);
+		// Process any new info
 
-			if (includeHistoric) {
-				// We also want REDEEMED/REFUNDED/CANCELLED trades over the last 24 hours
-				long timestamp = NTP.getTime() - 24 * 60 * 60 * 1000L;
-				minimumFinalHeight = repository.getBlockRepository().getHeightFromTimestamp(timestamp);
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			// Find any new/changed trade ATs since this block
+			final Boolean isFinished = null;
+			final Integer dataByteOffset = null;
+			final Long expectedValue = null;
+			final Integer minimumFinalHeight = blockData.getHeight();
 
-				if (minimumFinalHeight != 0) {
-					isFinished = Boolean.TRUE;
-					dataByteOffset = null;
-					expectedValue = null;
-					++minimumFinalHeight; // because height is just *before* timestamp
+			for (SupportedBlockchain blockchain : SupportedBlockchain.values()) {
+				Map<ByteArray, Supplier<ACCT>> acctsByCodeHash = SupportedBlockchain.getFilteredAcctMap(blockchain);
 
-					List<ATStateData> historicAtStates = repository.getATRepository().getMatchingFinalATStates(BTCACCT.CODE_BYTES_HASH,
-							isFinished, dataByteOffset, expectedValue, minimumFinalHeight,
-							null, null, null);
+				List<CrossChainOfferSummary> crossChainOfferSummaries = new ArrayList<>();
 
-					if (historicAtStates == null) {
-						session.close(4002, "repository issue fetching historic trades");
-						return;
+				synchronized (cachedInfoByBlockchain) {
+					CachedOfferInfo cachedInfo = cachedInfoByBlockchain.computeIfAbsent(blockchain.name(), k -> new CachedOfferInfo());
+
+					for (Map.Entry<ByteArray, Supplier<ACCT>> acctInfo : acctsByCodeHash.entrySet()) {
+						byte[] codeHash = acctInfo.getKey().value;
+						ACCT acct = acctInfo.getValue().get();
+
+						List<ATStateData> atStates = repository.getATRepository().getMatchingFinalATStates(codeHash,
+								isFinished, dataByteOffset, expectedValue, minimumFinalHeight,
+								null, null, null);
+
+						crossChainOfferSummaries.addAll(produceSummaries(repository, acct, atStates, blockData.getTimestamp()));
 					}
 
-					for (ATStateData historicAtState : historicAtStates) {
-						CrossChainOfferSummary historicOfferSummary = produceSummary(repository, historicAtState, null);
+					// Remove any entries unchanged from last time
+					crossChainOfferSummaries.removeIf(offerSummary -> cachedInfo.previousAtModes.get(offerSummary.getQortalAtAddress()) == offerSummary.getMode());
+
+					// Skip to next blockchain if nothing has changed (for this blockchain)
+					if (crossChainOfferSummaries.isEmpty())
+						continue;
+
+					// Update
+					for (CrossChainOfferSummary offerSummary : crossChainOfferSummaries) {
+						String offerAtAddress = offerSummary.getQortalAtAddress();
+
+						cachedInfo.previousAtModes.put(offerAtAddress, offerSummary.getMode());
+						LOGGER.trace(() -> String.format("Block height: %d, AT: %s, mode: %s", blockData.getHeight(), offerAtAddress, offerSummary.getMode().name()));
+
+						switch (offerSummary.getMode()) {
+							case OFFERING:
+								cachedInfo.currentSummaries.put(offerAtAddress, offerSummary);
+								cachedInfo.historicSummaries.remove(offerAtAddress);
+								break;
 
-						switch (historicOfferSummary.getMode()) {
 							case REDEEMED:
 							case REFUNDED:
 							case CANCELLED:
+								cachedInfo.currentSummaries.remove(offerAtAddress);
+								cachedInfo.historicSummaries.put(offerAtAddress, offerSummary);
 								break;
 
-							default:
-								continue;
+							case TRADING:
+								cachedInfo.currentSummaries.remove(offerAtAddress);
+								cachedInfo.historicSummaries.remove(offerAtAddress);
+								break;
 						}
-
-						// Add summary to initial burst
-						crossChainOfferSummaries.add(historicOfferSummary);
-
-						// Save initial AT mode
-						previousAtModes.put(historicAtState.getATAddress(), historicOfferSummary.getMode());
 					}
-				}
-			}
 
+					// Remove any historic offers that are over 24 hours old
+					final long tooOldTimestamp = NTP.getTime() - 24 * 60 * 60 * 1000L;
+					cachedInfo.historicSummaries.values().removeIf(historicSummary -> historicSummary.getTimestamp() < tooOldTimestamp);
+				}
+
+				// Notify sessions
+				for (Session session : getSessions()) {
+					// Only send if this session has this/no preferred blockchain
+					String preferredBlockchain = sessionBlockchain.get(session);
+
+					if (preferredBlockchain == null || preferredBlockchain.equals(blockchain.name()))
+						sendOfferSummaries(session, crossChainOfferSummaries);
+				}
+
+			}
 		} catch (DataException e) {
-			session.close(4003, "generic repository issue");
+			// No output this time
+		}
+	}
+
+	@OnWebSocketConnect
+	@Override
+	public void onWebSocketConnect(Session session) {
+		Map<String, List<String>> queryParams = session.getUpgradeRequest().getParameterMap();
+		final boolean includeHistoric = queryParams.get("includeHistoric") != null;
+
+		List<String> foreignBlockchains = queryParams.get("foreignBlockchain");
+		final String foreignBlockchain = foreignBlockchains == null ? null : foreignBlockchains.get(0);
+
+		// Make sure blockchain (if any) is valid
+		if (foreignBlockchain != null && SupportedBlockchain.fromString(foreignBlockchain) == null) {
+			session.close(4003, "unknown blockchain: " + foreignBlockchain);
 			return;
 		}
 
+		// Save session's preferred blockchain, if given
+		if (foreignBlockchain != null)
+			sessionBlockchain.put(session, foreignBlockchain);
+
+		List<CrossChainOfferSummary> crossChainOfferSummaries = new ArrayList<>();
+
+		synchronized (cachedInfoByBlockchain) {
+			Collection<CachedOfferInfo> cachedInfos;
+
+			if (foreignBlockchain == null)
+				// No preferred blockchain, so iterate through all of them
+				cachedInfos = cachedInfoByBlockchain.values();
+			else
+				cachedInfos = Collections.singleton(cachedInfoByBlockchain.computeIfAbsent(foreignBlockchain, k -> new CachedOfferInfo()));
+
+			for (CachedOfferInfo cachedInfo : cachedInfos) {
+				crossChainOfferSummaries.addAll(cachedInfo.currentSummaries.values());
+
+				if (includeHistoric)
+					crossChainOfferSummaries.addAll(cachedInfo.historicSummaries.values());
+			}
+		}
+
 		if (!sendOfferSummaries(session, crossChainOfferSummaries)) {
-			session.close(4004, "websocket issue");
+			session.close(4002, "websocket issue");
 			return;
 		}
 
-		BlockNotifier.Listener listener = blockInfo -> onNotify(session, blockInfo, previousAtModes);
-		BlockNotifier.getInstance().register(session, listener);
+		super.onWebSocketConnect(session);
 	}
 
 	@OnWebSocketClose
+	@Override
 	public void onWebSocketClose(Session session, int statusCode, String reason) {
-		BlockNotifier.getInstance().deregister(session);
+		// clean up
+		sessionBlockchain.remove(session);
+
+		super.onWebSocketClose(session, statusCode, reason);
+	}
+
+	@OnWebSocketError
+	public void onWebSocketError(Session session, Throwable throwable) {
+		/* ignored */
 	}
 
 	@OnWebSocketMessage
@@ -132,45 +232,6 @@ public class TradeOffersWebSocket extends ApiWebSocket {
 		/* ignored */
 	}
 
-	private void onNotify(Session session, BlockInfo blockInfo, final Map<String, BTCACCT.Mode> previousAtModes) {
-		List<CrossChainOfferSummary> crossChainOfferSummaries = null;
-
-		try (final Repository repository = RepositoryManager.getRepository()) {
-			// Find any new trade ATs since this block
-			final Boolean isFinished = null;
-			final Integer dataByteOffset = null;
-			final Long expectedValue = null;
-			final Integer minimumFinalHeight = blockInfo.getHeight();
-
-			List<ATStateData> atStates = repository.getATRepository().getMatchingFinalATStates(BTCACCT.CODE_BYTES_HASH,
-					isFinished, dataByteOffset, expectedValue, minimumFinalHeight,
-					null, null, null);
-
-			if (atStates == null)
-				return;
-
-			crossChainOfferSummaries = produceSummaries(repository, atStates, blockInfo.getTimestamp());
-		} catch (DataException e) {
-			// No output this time
-		}
-
-		synchronized (previousAtModes) { //NOSONAR squid:S2445 suppressed because previousAtModes is final and curried in lambda
-			// Remove any entries unchanged from last time
-			crossChainOfferSummaries.removeIf(offerSummary -> previousAtModes.get(offerSummary.getQortalAtAddress()) == offerSummary.getMode());
-
-			// Don't send anything if no results
-			if (crossChainOfferSummaries.isEmpty())
-				return;
-
-			final boolean wasSent = sendOfferSummaries(session, crossChainOfferSummaries);
-
-			if (!wasSent)
-				return;
-
-			previousAtModes.putAll(crossChainOfferSummaries.stream().collect(Collectors.toMap(CrossChainOfferSummary::getQortalAtAddress, CrossChainOfferSummary::getMode)));
-		}
-	}
-
 	private boolean sendOfferSummaries(Session session, List<CrossChainOfferSummary> crossChainOfferSummaries) {
 		try {
 			StringWriter stringWriter = new StringWriter();
@@ -186,25 +247,103 @@ public class TradeOffersWebSocket extends ApiWebSocket {
 		return true;
 	}
 
-	private static CrossChainOfferSummary produceSummary(Repository repository, ATStateData atState, Long timestamp) throws DataException {
-		CrossChainTradeData crossChainTradeData = BTCACCT.populateTradeData(repository, atState);
+	private static void populateCurrentSummaries(Repository repository) throws DataException {
+		// We want ALL OFFERING trades
+		Boolean isFinished = Boolean.FALSE;
+		Long expectedValue = (long) AcctMode.OFFERING.value;
+		Integer minimumFinalHeight = null;
+
+		for (SupportedBlockchain blockchain : SupportedBlockchain.values()) {
+			Map<ByteArray, Supplier<ACCT>> acctsByCodeHash = SupportedBlockchain.getFilteredAcctMap(blockchain);
+
+			CachedOfferInfo cachedInfo = cachedInfoByBlockchain.computeIfAbsent(blockchain.name(), k -> new CachedOfferInfo());
+
+			for (Map.Entry<ByteArray, Supplier<ACCT>> acctInfo : acctsByCodeHash.entrySet()) {
+				byte[] codeHash = acctInfo.getKey().value;
+				ACCT acct = acctInfo.getValue().get();
+
+				Integer dataByteOffset = acct.getModeByteOffset();
+				List<ATStateData> initialAtStates = repository.getATRepository().getMatchingFinalATStates(codeHash,
+					isFinished, dataByteOffset, expectedValue, minimumFinalHeight,
+					null, null, null);
+
+				if (initialAtStates == null)
+					throw new DataException("Couldn't fetch current trades from repository");
+
+				// Save initial AT modes
+				cachedInfo.previousAtModes.putAll(initialAtStates.stream().collect(Collectors.toMap(ATStateData::getATAddress, atState -> AcctMode.OFFERING)));
+
+				// Convert to offer summaries
+				cachedInfo.currentSummaries.putAll(produceSummaries(repository, acct, initialAtStates, null).stream()
+										.collect(Collectors.toMap(CrossChainOfferSummary::getQortalAtAddress, offerSummary -> offerSummary)));
+			}
+		}
+	}
+
+	private static void populateHistoricSummaries(Repository repository) throws DataException {
+		// We want REDEEMED/REFUNDED/CANCELLED trades over the last 24 hours
+		long timestamp = System.currentTimeMillis() - 24 * 60 * 60 * 1000L;
+		int minimumFinalHeight = repository.getBlockRepository().getHeightFromTimestamp(timestamp);
+
+		if (minimumFinalHeight == 0)
+			throw new DataException("Couldn't fetch block timestamp from repository");
+
+		Boolean isFinished = Boolean.TRUE;
+		Integer dataByteOffset = null;
+		Long expectedValue = null;
+		++minimumFinalHeight; // because height is just *before* timestamp
+
+		for (SupportedBlockchain blockchain : SupportedBlockchain.values()) {
+			Map<ByteArray, Supplier<ACCT>> acctsByCodeHash = SupportedBlockchain.getFilteredAcctMap(blockchain);
+
+			CachedOfferInfo cachedInfo = cachedInfoByBlockchain.computeIfAbsent(blockchain.name(), k -> new CachedOfferInfo());
+
+			for (Map.Entry<ByteArray, Supplier<ACCT>> acctInfo : acctsByCodeHash.entrySet()) {
+				byte[] codeHash = acctInfo.getKey().value;
+				ACCT acct = acctInfo.getValue().get();
+
+				List<ATStateData> historicAtStates = repository.getATRepository().getMatchingFinalATStates(codeHash,
+					isFinished, dataByteOffset, expectedValue, minimumFinalHeight,
+					null, null, null);
+
+				if (historicAtStates == null)
+					throw new DataException("Couldn't fetch historic trades from repository");
+
+				for (ATStateData historicAtState : historicAtStates) {
+					CrossChainOfferSummary historicOfferSummary = produceSummary(repository, acct, historicAtState, null);
+
+					if (!isHistoric.test(historicOfferSummary))
+						continue;
+
+					// Add summary to initial burst
+					cachedInfo.historicSummaries.put(historicOfferSummary.getQortalAtAddress(), historicOfferSummary);
+
+					// Save initial AT mode
+					cachedInfo.previousAtModes.put(historicOfferSummary.getQortalAtAddress(), historicOfferSummary.getMode());
+				}
+			}
+		}
+	}
+
+	private static CrossChainOfferSummary produceSummary(Repository repository, ACCT acct, ATStateData atState, Long timestamp) throws DataException {
+		CrossChainTradeData crossChainTradeData = acct.populateTradeData(repository, atState);
 
 		long atStateTimestamp;
 
-		if (crossChainTradeData.mode == BTCACCT.Mode.OFFERING)
+		if (crossChainTradeData.mode == AcctMode.OFFERING)
 			// We want when trade was created, not when it was last updated
-			atStateTimestamp = atState.getCreation();
+			atStateTimestamp = crossChainTradeData.creationTimestamp;
 		else
 			atStateTimestamp = timestamp != null ? timestamp : repository.getBlockRepository().getTimestampFromHeight(atState.getHeight());
 
 		return new CrossChainOfferSummary(crossChainTradeData, atStateTimestamp);
 	}
 
-	private static List<CrossChainOfferSummary> produceSummaries(Repository repository, List<ATStateData> atStates, Long timestamp) throws DataException {
+	private static List<CrossChainOfferSummary> produceSummaries(Repository repository, ACCT acct, List<ATStateData> atStates, Long timestamp) throws DataException {
 		List<CrossChainOfferSummary> offerSummaries = new ArrayList<>();
 
 		for (ATStateData atState : atStates)
-			offerSummaries.add(produceSummary(repository, atState, timestamp));
+			offerSummaries.add(produceSummary(repository, acct, atState, timestamp));
 
 		return offerSummaries;
 	}

src/main/java/org/qortal/at/AT.java

@@ -51,16 +51,17 @@ public class AT {
 
 		MachineState machineState = new MachineState(api, loggerFactory, deployATTransactionData.getCreationBytes());
 
-		byte[] codeHash = Crypto.digest(machineState.getCodeBytes());
+		byte[] codeBytes = machineState.getCodeBytes();
+		byte[] codeHash = Crypto.digest(codeBytes);
 
-		this.atData = new ATData(atAddress, creatorPublicKey, creation, machineState.version, assetId, machineState.getCodeBytes(), codeHash,
+		this.atData = new ATData(atAddress, creatorPublicKey, creation, machineState.version, assetId, codeBytes, codeHash,
 				machineState.isSleeping(), machineState.getSleepUntilHeight(), machineState.isFinished(), machineState.hadFatalError(),
 				machineState.isFrozen(), machineState.getFrozenBalance());
 
 		byte[] stateData = machineState.toBytes();
 		byte[] stateHash = Crypto.digest(stateData);
 
-		this.atStateData = new ATStateData(atAddress, height, creation, stateData, stateHash, 0L, true);
+		this.atStateData = new ATStateData(atAddress, height, stateData, stateHash, 0L, true);
 	}
 
 	// Getters / setters
@@ -106,23 +107,18 @@ public class AT {
 			throw new DataException(String.format("Uncaught exception while running AT '%s'", atAddress), e);
 		}
 
-		long creation = this.atData.getCreation();
 		byte[] stateData = state.toBytes();
 		byte[] stateHash = Crypto.digest(stateData);
 		long atFees = api.calcFinalFees(state);
 
-		this.atStateData = new ATStateData(atAddress, blockHeight, creation, stateData, stateHash, atFees, false);
+		this.atStateData = new ATStateData(atAddress, blockHeight, stateData, stateHash, atFees, false);
 
 		return api.getTransactions();
 	}
 
 	public void update(int blockHeight, long blockTimestamp) throws DataException {
-		// [Re]create AT machine state using AT state data or from scratch as applicable
-		QortalATAPI api = new QortalATAPI(repository, this.atData, blockTimestamp);
-		QortalAtLoggerFactory loggerFactory = QortalAtLoggerFactory.getInstance();
-
-		byte[] codeBytes = this.atData.getCodeBytes();
-		MachineState state = MachineState.fromBytes(api, loggerFactory, this.atStateData.getStateData(), codeBytes);
+		// Extract minimal/flags-only AT machine state using AT state data
+		MachineState state = MachineState.flagsOnlyfromBytes(this.atStateData.getStateData());
 
 		// Save latest AT state data
 		this.repository.getATRepository().save(this.atStateData);
@@ -151,12 +147,8 @@ public class AT {
 		if (previousStateData == null)
 			throw new DataException("Can't find previous AT state data for " + atAddress);
 
-		// [Re]create AT machine state using AT state data or from scratch as applicable
-		QortalATAPI api = new QortalATAPI(repository, this.atData, blockTimestamp);
-		QortalAtLoggerFactory loggerFactory = QortalAtLoggerFactory.getInstance();
-
-		byte[] codeBytes = this.atData.getCodeBytes();
-		MachineState state = MachineState.fromBytes(api, loggerFactory, previousStateData.getStateData(), codeBytes);
+		// Extract minimal/flags-only AT machine state using AT state data
+		MachineState state = MachineState.flagsOnlyfromBytes(previousStateData.getStateData());
 
 		// Update AT info in repository
 		this.atData.setIsSleeping(state.isSleeping());

src/main/java/org/qortal/at/QortalATAPI.java

@@ -146,7 +146,11 @@ public class QortalATAPI extends API {
 		String atAddress = this.atData.getATAddress();
 
 		int height = timestamp.blockHeight;
-		int sequence = timestamp.transactionSequence + 1;
+		int sequence = timestamp.transactionSequence;
+
+		if (state.getCurrentBlockHeight() < BlockChain.getInstance().getAtFindNextTransactionFixHeight())
+			// Off-by-one bug still in effect
+			sequence += 1;
 
 		ATRepository.NextTransactionInfo nextTransactionInfo;
 		try {

src/main/java/org/qortal/at/QortalAtLogger.java

@@ -691,6 +691,11 @@ public final class QortalAtLogger extends ExtendedLoggerWrapper implements org.c
         logger.logIfEnabled(FQCN, ERROR, null, msgSupplier, (Throwable) null);
     }
 
+    /** Java 8 version */
+    public void error(final java.util.function.Supplier<String> msgSupplier) {
+        logger.logIfEnabled(FQCN, ERROR, null, () -> msgSupplier.get(), (Throwable) null);
+    }
+
     /**
      * Logs a message (only to be constructed if the logging level is the {@code ERROR}
      * level) including the stack trace of the {@link Throwable} <code>t</code> passed as parameter.
@@ -1375,6 +1380,11 @@ public final class QortalAtLogger extends ExtendedLoggerWrapper implements org.c
         logger.logIfEnabled(FQCN, DEBUG, null, msgSupplier, (Throwable) null);
     }
 
+    /** Java 8 version */
+    public void debug(final java.util.function.Supplier<String> msgSupplier) {
+        logger.logIfEnabled(FQCN, DEBUG, null, () -> msgSupplier.get(), (Throwable) null);
+    }
+
     /**
      * Logs a message (only to be constructed if the logging level is the {@code DEBUG}
      * level) including the stack trace of the {@link Throwable} <code>t</code> passed as parameter.
@@ -2059,6 +2069,11 @@ public final class QortalAtLogger extends ExtendedLoggerWrapper implements org.c
         logger.logIfEnabled(FQCN, ECHO, null, msgSupplier, (Throwable) null);
     }
 
+    /** Java 8 version */
+    public void echo(final java.util.function.Supplier<String> msgSupplier) {
+        logger.logIfEnabled(FQCN, ECHO, null, () -> msgSupplier.get(), (Throwable) null);
+    }
+
     /**
      * Logs a message (only to be constructed if the logging level is the {@code ECHO}
      * level) including the stack trace of the {@link Throwable} <code>t</code> passed as parameter.

src/main/java/org/qortal/at/QortalFunctionCode.java

@@ -10,7 +10,7 @@ import org.ciyam.at.ExecutionException;
 import org.ciyam.at.FunctionData;
 import org.ciyam.at.IllegalFunctionCodeException;
 import org.ciyam.at.MachineState;
-import org.qortal.crosschain.BTC;
+import org.qortal.crosschain.Bitcoin;
 import org.qortal.crypto.Crypto;
 import org.qortal.data.transaction.TransactionData;
 import org.qortal.settings.Settings;
@@ -108,7 +108,7 @@ public enum QortalFunctionCode {
 	CONVERT_B_TO_P2SH(0x0511, 0, false) {
 		@Override
 		protected void postCheckExecute(FunctionData functionData, MachineState state, short rawFunctionCode) throws ExecutionException {
-			byte addressPrefix = Settings.getInstance().getBitcoinNet() == BTC.BitcoinNet.MAIN ? 0x05 : (byte) 0xc4;
+			byte addressPrefix = Settings.getInstance().getBitcoinNet() == Bitcoin.BitcoinNet.MAIN ? 0x05 : (byte) 0xc4;
 
 			convertAddressInB(addressPrefix, state);
 		}

src/main/java/org/qortal/block/Block.java

@@ -6,6 +6,8 @@ import static java.util.stream.Collectors.toMap;
 import java.math.BigDecimal;
 import java.math.BigInteger;
 import java.math.RoundingMode;
+import java.text.DecimalFormat;
+import java.text.NumberFormat;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.HashMap;
@@ -15,6 +17,7 @@ import java.util.Map;
 import java.util.Set;
 import java.util.stream.Collectors;
 
+import org.apache.logging.log4j.Level;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.qortal.account.Account;
@@ -29,6 +32,7 @@ import org.qortal.controller.Controller;
 import org.qortal.crypto.Crypto;
 import org.qortal.data.account.AccountBalanceData;
 import org.qortal.data.account.AccountData;
+import org.qortal.data.account.EligibleQoraHolderData;
 import org.qortal.data.account.QortFromQoraData;
 import org.qortal.data.account.RewardShareData;
 import org.qortal.data.at.ATData;
@@ -53,7 +57,6 @@ import org.qortal.transform.transaction.TransactionTransformer;
 import org.qortal.utils.Amounts;
 import org.qortal.utils.Base58;
 import org.qortal.utils.NTP;
-import org.roaringbitmap.IntIterator;
 
 import com.google.common.primitives.Bytes;
 import com.google.common.primitives.Longs;
@@ -128,7 +131,7 @@ public class Block {
 
 	@FunctionalInterface
 	private interface BlockRewardDistributor {
-		long distribute(long amount, Map<Account, Long> balanceChanges) throws DataException;
+		long distribute(long amount, Map<String, Long> balanceChanges) throws DataException;
 	}
 
 	/** Lazy-instantiated expanded info on block's online accounts. */
@@ -144,8 +147,8 @@ public class Block {
 		private final Account recipientAccount;
 		private final AccountData recipientAccountData;
 
-		ExpandedAccount(Repository repository, int accountIndex) throws DataException {
-			this.rewardShareData = repository.getAccountRepository().getRewardShareByIndex(accountIndex);
+		ExpandedAccount(Repository repository, RewardShareData rewardShareData) throws DataException {
+			this.rewardShareData = rewardShareData;
 			this.sharePercent = this.rewardShareData.getSharePercent();
 
 			this.mintingAccount = new Account(repository, this.rewardShareData.getMinter());
@@ -173,27 +176,34 @@ public class Block {
 		 * 
 		 *  @return account-level share "bin" from blockchain config, or null if founder / none found
 		 */
-		public AccountLevelShareBin getShareBin() {
+		public AccountLevelShareBin getShareBin(int blockHeight) {
 			if (this.isMinterFounder)
 				return null;
 
 			final int accountLevel = this.mintingAccountData.getLevel();
 			if (accountLevel <= 0)
-					return null;
+				return null; // level 0 isn't included in any share bins
 
-			final AccountLevelShareBin[] shareBinsByLevel = BlockChain.getInstance().getShareBinsByAccountLevel();
+			final BlockChain blockChain = BlockChain.getInstance();
+			final AccountLevelShareBin[] shareBinsByLevel = blockChain.getShareBinsByAccountLevel();
 			if (accountLevel > shareBinsByLevel.length)
 				return null;
 
-			return shareBinsByLevel[accountLevel];
+			if (blockHeight < blockChain.getShareBinFixHeight())
+				// Off-by-one bug still in effect
+				return shareBinsByLevel[accountLevel];
+
+			// level 1 stored at index 0, level 2 stored at index 1, etc.
+			return shareBinsByLevel[accountLevel-1];
+
 		}
 
-		public long distribute(long accountAmount, Map<Account, Long> balanceChanges) {
+		public long distribute(long accountAmount, Map<String, Long> balanceChanges) {
 			if (this.isRecipientAlsoMinter) {
 				// minter & recipient the same - simpler case
 				LOGGER.trace(() -> String.format("Minter/recipient account %s share: %s", this.mintingAccount.getAddress(), Amounts.prettyAmount(accountAmount)));
 				if (accountAmount != 0)
-					balanceChanges.merge(this.mintingAccount, accountAmount, Long::sum);
+					balanceChanges.merge(this.mintingAccount.getAddress(), accountAmount, Long::sum);
 			} else {
 				// minter & recipient different - extra work needed
 				long recipientAmount = (accountAmount * this.sharePercent) / 100L / 100L; // because scaled by 2dp and 'percent' means "per 100"
@@ -201,11 +211,11 @@ public class Block {
 
 				LOGGER.trace(() -> String.format("Minter account %s share: %s", this.mintingAccount.getAddress(), Amounts.prettyAmount(minterAmount)));
 				if (minterAmount != 0)
-					balanceChanges.merge(this.mintingAccount, minterAmount, Long::sum);
+					balanceChanges.merge(this.mintingAccount.getAddress(), minterAmount, Long::sum);
 
 				LOGGER.trace(() -> String.format("Recipient account %s share: %s", this.recipientAccount.getAddress(), Amounts.prettyAmount(recipientAmount)));
 				if (recipientAmount != 0)
-					balanceChanges.merge(this.recipientAccount, recipientAmount, Long::sum);
+					balanceChanges.merge(this.recipientAccount.getAddress(), recipientAmount, Long::sum);
 			}
 
 			// We always distribute all of the amount
@@ -215,9 +225,14 @@ public class Block {
 	/** Always use getExpandedAccounts() to access this, as it's lazy-instantiated. */
 	private List<ExpandedAccount> cachedExpandedAccounts = null;
 
+	/** Opportunistic cache of this block's valid online accounts. Only created by call to isValid(). */
+	private List<OnlineAccountData> cachedValidOnlineAccounts = null;
+	/** Opportunistic cache of this block's valid online reward-shares. Only created by call to isValid(). */
+	private List<RewardShareData> cachedOnlineRewardShares = null;
+
 	// Other useful constants
 
-	private static final BigInteger MAX_DISTANCE;
+	public static final BigInteger MAX_DISTANCE;
 	static {
 		byte[] maxValue = new byte[Transformer.PUBLIC_KEY_LENGTH];
 		Arrays.fill(maxValue, (byte) 0xFF);
@@ -349,12 +364,8 @@ public class Block {
 			System.arraycopy(onlineAccountData.getSignature(), 0, onlineAccountsSignatures, i * Transformer.SIGNATURE_LENGTH, Transformer.SIGNATURE_LENGTH);
 		}
 
-		byte[] minterSignature;
-		try {
-			minterSignature = minter.sign(BlockTransformer.getBytesForMinterSignature(parentBlockData.getMinterSignature(), minter, encodedOnlineAccounts));
-		} catch (TransformationException e) {
-			throw new DataException("Unable to calculate next block minter signature", e);
-		}
+		byte[] minterSignature = minter.sign(BlockTransformer.getBytesForMinterSignature(parentBlockData,
+				minter.getPublicKey(), encodedOnlineAccounts));
 
 		// Qortal: minter is always a reward-share, so find actual minter and get their effective minting level
 		int minterLevel = Account.getRewardShareEffectiveMintingLevel(repository, minter.getPublicKey());
@@ -420,12 +431,8 @@ public class Block {
 		int version = this.blockData.getVersion();
 		byte[] reference = this.blockData.getReference();
 
-		byte[] minterSignature;
-		try {
-			minterSignature = minter.sign(BlockTransformer.getBytesForMinterSignature(parentBlockData.getMinterSignature(), minter, this.blockData.getEncodedOnlineAccounts()));
-		} catch (TransformationException e) {
-			throw new DataException("Unable to calculate next block's minter signature", e);
-		}
+		byte[] minterSignature = minter.sign(BlockTransformer.getBytesForMinterSignature(parentBlockData,
+				minter.getPublicKey(), this.blockData.getEncodedOnlineAccounts()));
 
 		// Qortal: minter is always a reward-share, so find actual minter and get their effective minting level
 		int minterLevel = Account.getRewardShareEffectiveMintingLevel(repository, minter.getPublicKey());
@@ -564,22 +571,28 @@ public class Block {
 	/**
 	 * Return expanded info on block's online accounts.
 	 * <p>
+	 * Typically called as part of Block.process() or Block.orphan()
+	 * so ideally after any calls to Block.isValid().
+	 * 
 	 * @throws DataException
 	 */
 	public List<ExpandedAccount> getExpandedAccounts() throws DataException {
 		if (this.cachedExpandedAccounts != null)
 			return this.cachedExpandedAccounts;
 
-		ConciseSet accountIndexes = BlockTransformer.decodeOnlineAccounts(this.blockData.getEncodedOnlineAccounts());
+		// We might already have a cache of online, reward-shares thanks to isValid()
+		if (this.cachedOnlineRewardShares == null) {
+			ConciseSet accountIndexes = BlockTransformer.decodeOnlineAccounts(this.blockData.getEncodedOnlineAccounts());
+			this.cachedOnlineRewardShares = repository.getAccountRepository().getRewardSharesByIndexes(accountIndexes.toArray());
+
+			if (this.cachedOnlineRewardShares == null)
+				throw new DataException("Online accounts invalid?");
+		}
+
 		List<ExpandedAccount> expandedAccounts = new ArrayList<>();
 
-		IntIterator iterator = accountIndexes.iterator();
-		while (iterator.hasNext()) {
-			int accountIndex = iterator.next();
-
-			ExpandedAccount accountInfo = new ExpandedAccount(repository, accountIndex);
-			expandedAccounts.add(accountInfo);
-		}
+		for (RewardShareData rewardShare : this.cachedOnlineRewardShares)
+			expandedAccounts.add(new ExpandedAccount(repository, rewardShare));
 
 		this.cachedExpandedAccounts = expandedAccounts;
 
@@ -732,11 +745,7 @@ public class Block {
 		if (!(this.minter instanceof PrivateKeyAccount))
 			throw new IllegalStateException("Block's minter is not a PrivateKeyAccount - can't sign!");
 
-		try {
-			this.blockData.setMinterSignature(((PrivateKeyAccount) this.minter).sign(BlockTransformer.getBytesForMinterSignature(this.blockData)));
-		} catch (TransformationException e) {
-			throw new RuntimeException("Unable to calculate block's minter signature", e);
-		}
+		this.blockData.setMinterSignature(((PrivateKeyAccount) this.minter).sign(BlockTransformer.getBytesForMinterSignature(this.blockData)));
 	}
 
 	/**
@@ -780,16 +789,49 @@ public class Block {
 		return BigInteger.valueOf(blockSummaryData.getOnlineAccountsCount()).shiftLeft(ACCOUNTS_COUNT_SHIFT).add(keyDistance);
 	}
 
-	public static BigInteger calcChainWeight(int commonBlockHeight, byte[] commonBlockSignature, List<BlockSummaryData> blockSummaries) {
+	public static BigInteger calcChainWeight(int commonBlockHeight, byte[] commonBlockSignature, List<BlockSummaryData> blockSummaries, int maxHeight) {
 		BigInteger cumulativeWeight = BigInteger.ZERO;
 		int parentHeight = commonBlockHeight;
 		byte[] parentBlockSignature = commonBlockSignature;
+		NumberFormat formatter = new DecimalFormat("0.###E0");
+		boolean isLogging = LOGGER.getLevel().isLessSpecificThan(Level.TRACE);
 
+		int blockCount = 0;
 		for (BlockSummaryData blockSummaryData : blockSummaries) {
-			cumulativeWeight = cumulativeWeight.shiftLeft(CHAIN_WEIGHT_SHIFT).add(calcBlockWeight(parentHeight, parentBlockSignature, blockSummaryData));
+			blockCount++;
+			StringBuilder stringBuilder = isLogging ? new StringBuilder(512) : null;
+
+			if (isLogging)
+				stringBuilder.append(formatter.format(cumulativeWeight)).append(" -> ");
+
+			cumulativeWeight = cumulativeWeight.shiftLeft(CHAIN_WEIGHT_SHIFT);
+			if (isLogging)
+				stringBuilder.append(formatter.format(cumulativeWeight)).append(" + ");
+
+			BigInteger blockWeight = calcBlockWeight(parentHeight, parentBlockSignature, blockSummaryData);
+			if (isLogging)
+				stringBuilder.append("(height: ")
+						.append(parentHeight + 1)
+						.append(", online: ")
+						.append(blockSummaryData.getOnlineAccountsCount())
+						.append(") ")
+						.append(formatter.format(blockWeight));
+
+			cumulativeWeight = cumulativeWeight.add(blockWeight);
+			if (isLogging)
+				stringBuilder.append(" -> ").append(formatter.format(cumulativeWeight));
+
+			if (isLogging && blockSummaries.size() > 1)
+				LOGGER.debug(() -> stringBuilder.toString()); //NOSONAR S1612 (false positive?)
+
 			parentHeight = blockSummaryData.getHeight();
 			parentBlockSignature = blockSummaryData.getSignature();
+
+			// After this timestamp, we only compare the same number of blocks
+			if (NTP.getTime() >= BlockChain.getInstance().getCalcChainWeightTimestamp() && parentHeight >= maxHeight)
+				break;
 		}
+		LOGGER.trace(String.format("Chain weight calculation was based on %d blocks", blockCount));
 
 		return cumulativeWeight;
 	}
@@ -914,19 +956,9 @@ public class Block {
 		if (accountIndexes.size() != this.blockData.getOnlineAccountsCount())
 			return ValidationResult.ONLINE_ACCOUNTS_INVALID;
 
-		List<RewardShareData> expandedAccounts = new ArrayList<>();
-
-		IntIterator iterator = accountIndexes.iterator();
-		while (iterator.hasNext()) {
-			int accountIndex = iterator.next();
-			RewardShareData rewardShareData = repository.getAccountRepository().getRewardShareByIndex(accountIndex);
-
-			// Check that claimed online account actually exists
-			if (rewardShareData == null)
-				return ValidationResult.ONLINE_ACCOUNT_UNKNOWN;
-
-			expandedAccounts.add(rewardShareData);
-		}
+		List<RewardShareData> onlineRewardShares = repository.getAccountRepository().getRewardSharesByIndexes(accountIndexes.toArray());
+		if (onlineRewardShares == null)
+			return ValidationResult.ONLINE_ACCOUNT_UNKNOWN;
 
 		// If block is past a certain age then we simply assume the signatures were correct
 		long signatureRequirementThreshold = NTP.getTime() - BlockChain.getInstance().getOnlineAccountSignaturesMinLifetime();
@@ -936,28 +968,51 @@ public class Block {
 		if (this.blockData.getOnlineAccountsSignatures() == null || this.blockData.getOnlineAccountsSignatures().length == 0)
 			return ValidationResult.ONLINE_ACCOUNT_SIGNATURES_MISSING;
 
-		if (this.blockData.getOnlineAccountsSignatures().length != expandedAccounts.size() * Transformer.SIGNATURE_LENGTH)
+		if (this.blockData.getOnlineAccountsSignatures().length != onlineRewardShares.size() * Transformer.SIGNATURE_LENGTH)
 			return ValidationResult.ONLINE_ACCOUNT_SIGNATURES_MALFORMED;
 
 		// Check signatures
-		List<byte[]> onlineAccountsSignatures = BlockTransformer.decodeTimestampSignatures(this.blockData.getOnlineAccountsSignatures());
 		long onlineTimestamp = this.blockData.getOnlineAccountsTimestamp();
 		byte[] onlineTimestampBytes = Longs.toByteArray(onlineTimestamp);
-		List<OnlineAccountData> onlineAccounts = Controller.getInstance().getOnlineAccounts();
+
+		// If this block is much older than current online timestamp, then there's no point checking current online accounts
+		List<OnlineAccountData> currentOnlineAccounts = onlineTimestamp < NTP.getTime() - Controller.ONLINE_TIMESTAMP_MODULUS
+				? null
+				: Controller.getInstance().getOnlineAccounts();
+		List<OnlineAccountData> latestBlocksOnlineAccounts = Controller.getInstance().getLatestBlocksOnlineAccounts();
+
+		// Extract online accounts' timestamp signatures from block data
+		List<byte[]> onlineAccountsSignatures = BlockTransformer.decodeTimestampSignatures(this.blockData.getOnlineAccountsSignatures());
+
+		// We'll build up a list of online accounts to hand over to Controller if block is added to chain
+		// and this will become latestBlocksOnlineAccounts (above) to reduce CPU load when we process next block...
+		List<OnlineAccountData> ourOnlineAccounts = new ArrayList<>();
 
 		for (int i = 0; i < onlineAccountsSignatures.size(); ++i) {
 			byte[] signature = onlineAccountsSignatures.get(i);
-			byte[] publicKey = expandedAccounts.get(i).getRewardSharePublicKey();
+			byte[] publicKey = onlineRewardShares.get(i).getRewardSharePublicKey();
+
+			OnlineAccountData onlineAccountData = new OnlineAccountData(onlineTimestamp, signature, publicKey);
+			ourOnlineAccounts.add(onlineAccountData);
 
 			// If signature is still current then no need to perform Ed25519 verify
-			OnlineAccountData onlineAccountData = new OnlineAccountData(onlineTimestamp, signature, publicKey);
-			if (onlineAccounts.remove(onlineAccountData)) // remove() is like contains() but also reduces the number to check next time
+			if (currentOnlineAccounts != null && currentOnlineAccounts.remove(onlineAccountData))
+				// remove() returned true, so online account still current
+				// and one less entry in currentOnlineAccounts to check next time
+				continue;
+
+			// If signature was okay in latest block then no need to perform Ed25519 verify
+			if (latestBlocksOnlineAccounts != null && latestBlocksOnlineAccounts.contains(onlineAccountData))
 				continue;
 
 			if (!Crypto.verify(publicKey, signature, onlineTimestampBytes))
 				return ValidationResult.ONLINE_ACCOUNT_SIGNATURE_INCORRECT;
 		}
 
+		// All online accounts valid, so save our list of online accounts for potential later use
+		this.cachedValidOnlineAccounts = ourOnlineAccounts;
+		this.cachedOnlineRewardShares = onlineRewardShares;
+
 		return ValidationResult.OK;
 	}
 
@@ -1037,6 +1092,10 @@ public class Block {
 			// Create repository savepoint here so we can rollback to it after testing transactions
 			repository.setSavepoint();
 
+			if (this.blockData.getHeight() == 212937)
+				// Apply fix for block 212937 but fix will be rolled back before we exit method
+				Block212937.processFix(this);
+
 			for (Transaction transaction : this.getTransactions()) {
 				TransactionData transactionData = transaction.getTransactionData();
 
@@ -1240,6 +1299,10 @@ public class Block {
 
 			// Distribute block rewards, including transaction fees, before transactions processed
 			processBlockRewards();
+
+			if (this.blockData.getHeight() == 212937)
+				// Apply fix for block 212937
+				Block212937.processFix(this);
 		}
 
 		// We're about to (test-)process a batch of transactions,
@@ -1271,6 +1334,12 @@ public class Block {
 		linkTransactionsToBlock();
 
 		postBlockTidy();
+
+		// Give Controller our cached, valid online accounts data (if any) to help reduce CPU load for next block
+		Controller.getInstance().pushLatestBlocksOnlineAccounts(this.cachedValidOnlineAccounts);
+
+		// Log some debugging info relating to the block weight calculation
+		this.logDebugInfo();
 	}
 
 	protected void increaseAccountLevels() throws DataException {
@@ -1288,13 +1357,16 @@ public class Block {
 				allUniqueExpandedAccounts.add(expandedAccount.recipientAccountData);
 		}
 
-		// Decrease blocks minted count for all accounts
+		// Increase blocks minted count for all accounts
+
+		// Batch update in repository
+		repository.getAccountRepository().modifyMintedBlockCounts(allUniqueExpandedAccounts.stream().map(AccountData::getAddress).collect(Collectors.toList()), +1);
+
+		// Local changes and also checks for level bump
 		for (AccountData accountData : allUniqueExpandedAccounts) {
 			// Adjust count locally (in Java)
 			accountData.setBlocksMinted(accountData.getBlocksMinted() + 1);
-
-			int rowCount = repository.getAccountRepository().modifyMintedBlockCount(accountData.getAddress(), +1);
-			LOGGER.trace(() -> String.format("Block minter %s up to %d minted block%s (rowCount: %d)", accountData.getAddress(), accountData.getBlocksMinted(), (accountData.getBlocksMinted() != 1 ? "s" : ""), rowCount));
+			LOGGER.trace(() -> String.format("Block minter %s up to %d minted block%s", accountData.getAddress(), accountData.getBlocksMinted(), (accountData.getBlocksMinted() != 1 ? "s" : "")));
 
 			final int effectiveBlocksMinted = accountData.getBlocksMinted() + accountData.getBlocksMintedAdjustment();
 
@@ -1449,6 +1521,9 @@ public class Block {
 	public void orphan() throws DataException {
 		LOGGER.trace(() -> String.format("Orphaning block %d", this.blockData.getHeight()));
 
+		// Log some debugging info relating to the block weight calculation
+		this.logDebugInfo();
+
 		// Return AT fees and delete AT states from repository
 		orphanAtFeesAndStates();
 
@@ -1462,6 +1537,10 @@ public class Block {
 			// Invalidate expandedAccounts as they may have changed due to orphaning TRANSFER_PRIVS transactions, etc.
 			this.cachedExpandedAccounts = null;
 
+			if (this.blockData.getHeight() == 212937)
+				// Revert fix for block 212937
+				Block212937.orphanFix(this);
+
 			// Block rewards, including transaction fees, removed after transactions undone
 			orphanBlockRewards();
 
@@ -1474,6 +1553,9 @@ public class Block {
 		this.blockData.setHeight(null);
 
 		postBlockTidy();
+
+		// Remove any cached, valid online accounts data from Controller
+		Controller.getInstance().popLatestBlocksOnlineAccounts();
 	}
 
 	protected void orphanTransactionsFromBlock() throws DataException {
@@ -1581,12 +1663,14 @@ public class Block {
 		}
 
 		// Decrease blocks minted count for all accounts
+
+		// Batch update in repository
+		repository.getAccountRepository().modifyMintedBlockCounts(allUniqueExpandedAccounts.stream().map(AccountData::getAddress).collect(Collectors.toList()), -1);
+
 		for (AccountData accountData : allUniqueExpandedAccounts) {
 			// Adjust count locally (in Java)
 			accountData.setBlocksMinted(accountData.getBlocksMinted() - 1);
-
-			int rowCount = repository.getAccountRepository().modifyMintedBlockCount(accountData.getAddress(), -1);
-			LOGGER.trace(() -> String.format("Block minter %s down to %d minted block%s (rowCount: %d)", accountData.getAddress(), accountData.getBlocksMinted(), (accountData.getBlocksMinted() != 1 ? "s" : ""), rowCount));
+			LOGGER.trace(() -> String.format("Block minter %s down to %d minted block%s", accountData.getAddress(), accountData.getBlocksMinted(), (accountData.getBlocksMinted() != 1 ? "s" : "")));
 
 			final int effectiveBlocksMinted = accountData.getBlocksMinted() + accountData.getBlocksMintedAdjustment();
 
@@ -1615,7 +1699,7 @@ public class Block {
 			this.distributionMethod = distributionMethod;
 		}
 
-		public long distribute(long distibutionAmount, Map<Account, Long> balanceChanges) throws DataException {
+		public long distribute(long distibutionAmount, Map<String, Long> balanceChanges) throws DataException {
 			return this.distributionMethod.distribute(distibutionAmount, balanceChanges);
 		}
 	}
@@ -1632,7 +1716,7 @@ public class Block {
 		// Now distribute to candidates
 
 		// Collate all balance changes and then apply in one final step
-		Map<Account, Long> balanceChanges = new HashMap<>();
+		Map<String, Long> balanceChanges = new HashMap<>();
 
 		long remainingAmount = totalAmount;
 		for (int r = 0; r < rewardCandidates.size(); ++r) {
@@ -1657,8 +1741,10 @@ public class Block {
 		}
 
 		// Apply balance changes
-		for (Map.Entry<Account, Long> balanceChange : balanceChanges.entrySet())
-			balanceChange.getKey().modifyAssetBalance(Asset.QORT, balanceChange.getValue());
+		List<AccountBalanceData> accountBalanceDeltas = balanceChanges.entrySet().stream()
+				.map(entry -> new AccountBalanceData(entry.getKey(), Asset.QORT, entry.getValue()))
+				.collect(Collectors.toList());
+		this.repository.getAccountRepository().modifyAssetBalances(accountBalanceDeltas);
 	}
 
 	protected List<BlockRewardCandidate> determineBlockRewardCandidates(boolean isProcessingNotOrphaning) throws DataException {
@@ -1712,7 +1798,7 @@ public class Block {
 			// Find all accounts in share bin. getShareBin() returns null for minter accounts that are also founders, so they are effectively filtered out.
 			AccountLevelShareBin accountLevelShareBin = accountLevelShareBins.get(binIndex);
 			// Object reference compare is OK as all references are read-only from blockchain config.
-			List<ExpandedAccount> binnedAccounts = expandedAccounts.stream().filter(accountInfo -> accountInfo.getShareBin() == accountLevelShareBin).collect(Collectors.toList());
+			List<ExpandedAccount> binnedAccounts = expandedAccounts.stream().filter(accountInfo -> accountInfo.getShareBin(this.blockData.getHeight()) == accountLevelShareBin).collect(Collectors.toList());
 
 			// No online accounts in this bin? Skip to next one
 			if (binnedAccounts.isEmpty())
@@ -1728,7 +1814,7 @@ public class Block {
 		}
 
 		// Fetch list of legacy QORA holders who haven't reached their cap of QORT reward.
-		List<AccountBalanceData> qoraHolders = this.repository.getAccountRepository().getEligibleLegacyQoraHolders(isProcessingNotOrphaning ? null : this.blockData.getHeight());
+		List<EligibleQoraHolderData> qoraHolders = this.repository.getAccountRepository().getEligibleLegacyQoraHolders(isProcessingNotOrphaning ? null : this.blockData.getHeight());
 		final boolean haveQoraHolders = !qoraHolders.isEmpty();
 		final long qoraHoldersShare = BlockChain.getInstance().getQoraHoldersShare();
 
@@ -1781,7 +1867,7 @@ public class Block {
 		return rewardCandidates;
 	}
 
-	private static long distributeBlockRewardShare(long distributionAmount, List<ExpandedAccount> accounts, Map<Account, Long> balanceChanges) {
+	private static long distributeBlockRewardShare(long distributionAmount, List<ExpandedAccount> accounts, Map<String, Long> balanceChanges) {
 		// Collate all expanded accounts by minting account
 		Map<String, List<ExpandedAccount>> accountsByMinter = new HashMap<>();
 
@@ -1810,7 +1896,7 @@ public class Block {
 		return sharedAmount;
 	}
 
-	private static long distributeBlockRewardToQoraHolders(long qoraHoldersAmount, List<AccountBalanceData> qoraHolders, Map<Account, Long> balanceChanges, Block block) throws DataException {
+	private static long distributeBlockRewardToQoraHolders(long qoraHoldersAmount, List<EligibleQoraHolderData> qoraHolders, Map<String, Long> balanceChanges, Block block) throws DataException {
 		final boolean isProcessingNotOrphaning = qoraHoldersAmount >= 0;
 
 		long qoraPerQortReward = BlockChain.getInstance().getQoraPerQortReward();
@@ -1818,7 +1904,7 @@ public class Block {
 
 		long totalQoraHeld = 0;
 		for (int i = 0; i < qoraHolders.size(); ++i)
-			totalQoraHeld += qoraHolders.get(i).getBalance();
+			totalQoraHeld += qoraHolders.get(i).getQoraBalance();
 
 		long finalTotalQoraHeld = totalQoraHeld;
 		LOGGER.trace(() -> String.format("Total legacy QORA held: %s", Amounts.prettyAmount(finalTotalQoraHeld)));
@@ -1831,9 +1917,13 @@ public class Block {
 		BigInteger totalQoraHeldBI = BigInteger.valueOf(totalQoraHeld);
 
 		long sharedAmount = 0;
+		// For batched update of QORT_FROM_QORA balances
+		List<AccountBalanceData> newQortFromQoraBalances = new ArrayList<>();
+
 		for (int h = 0; h < qoraHolders.size(); ++h) {
-			AccountBalanceData qoraHolder = qoraHolders.get(h);
-			BigInteger qoraHolderBalanceBI = BigInteger.valueOf(qoraHolder.getBalance());
+			EligibleQoraHolderData qoraHolder = qoraHolders.get(h);
+			BigInteger qoraHolderBalanceBI = BigInteger.valueOf(qoraHolder.getQoraBalance());
+			String qoraHolderAddress = qoraHolder.getAddress();
 
 			// This is where a 128bit integer library could help:
 			// long holderReward = (qoraHoldersAmount * qoraHolder.getBalance()) / totalQoraHeld;
@@ -1841,15 +1931,13 @@ public class Block {
 
 			final long holderRewardForLogging = holderReward;
 			LOGGER.trace(() -> String.format("QORA holder %s has %s / %s QORA so share: %s",
-					qoraHolder.getAddress(), Amounts.prettyAmount(qoraHolder.getBalance()), finalTotalQoraHeld, Amounts.prettyAmount(holderRewardForLogging)));
+					qoraHolderAddress, Amounts.prettyAmount(qoraHolder.getQoraBalance()), finalTotalQoraHeld, Amounts.prettyAmount(holderRewardForLogging)));
 
 			// Too small to register this time?
 			if (holderReward == 0)
 				continue;
 
-			Account qoraHolderAccount = new Account(block.repository, qoraHolder.getAddress());
-
-			long newQortFromQoraBalance = qoraHolderAccount.getConfirmedBalance(Asset.QORT_FROM_QORA) + holderReward;
+			long newQortFromQoraBalance = qoraHolder.getQortFromQoraBalance() + holderReward;
 
 			// If processing, make sure we don't overpay
 			if (isProcessingNotOrphaning) {
@@ -1863,44 +1951,43 @@ public class Block {
 					newQortFromQoraBalance -= adjustment;
 
 					// This is also the QORA holder's final QORT-from-QORA block
-					QortFromQoraData qortFromQoraData = new QortFromQoraData(qoraHolder.getAddress(), holderReward, block.blockData.getHeight());
+					QortFromQoraData qortFromQoraData = new QortFromQoraData(qoraHolderAddress, holderReward, block.blockData.getHeight());
 					block.repository.getAccountRepository().save(qortFromQoraData);
 
 					long finalAdjustedHolderReward = holderReward;
 					LOGGER.trace(() -> String.format("QORA holder %s final share %s at height %d",
-							qoraHolder.getAddress(), Amounts.prettyAmount(finalAdjustedHolderReward), block.blockData.getHeight()));
+							qoraHolderAddress, Amounts.prettyAmount(finalAdjustedHolderReward), block.blockData.getHeight()));
 				}
 			} else {
 				// Orphaning
-				QortFromQoraData qortFromQoraData = block.repository.getAccountRepository().getQortFromQoraInfo(qoraHolder.getAddress());
-				if (qortFromQoraData != null) {
+				if (qoraHolder.getFinalBlockHeight() != null) {
 					// Final QORT-from-QORA amount from repository was stored during processing, and hence positive.
 					// So we use + here as qortFromQora is negative during orphaning.
 					// More efficient than "holderReward - (0 - final-qort-from-qora)"
-					long adjustment = holderReward + qortFromQoraData.getFinalQortFromQora();
+					long adjustment = holderReward + qoraHolder.getFinalQortFromQora();
 
 					holderReward -= adjustment;
 					newQortFromQoraBalance -= adjustment;
 
-					block.repository.getAccountRepository().deleteQortFromQoraInfo(qoraHolder.getAddress());
+					block.repository.getAccountRepository().deleteQortFromQoraInfo(qoraHolderAddress);
 
 					long finalAdjustedHolderReward = holderReward;
 					LOGGER.trace(() -> String.format("QORA holder %s final share %s was at height %d",
-							qoraHolder.getAddress(), Amounts.prettyAmount(finalAdjustedHolderReward), block.blockData.getHeight()));
+							qoraHolderAddress, Amounts.prettyAmount(finalAdjustedHolderReward), block.blockData.getHeight()));
 				}
 			}
 
-			balanceChanges.merge(qoraHolderAccount, holderReward, Long::sum);
+			balanceChanges.merge(qoraHolderAddress, holderReward, Long::sum);
 
-			if (newQortFromQoraBalance > 0)
-				qoraHolderAccount.setConfirmedBalance(Asset.QORT_FROM_QORA, newQortFromQoraBalance);
-			else
-				// Remove QORT_FROM_QORA balance as it's zero
-				qoraHolderAccount.deleteBalance(Asset.QORT_FROM_QORA);
+			// Add to batched QORT_FROM_QORA balance update list
+			newQortFromQoraBalances.add(new AccountBalanceData(qoraHolderAddress, Asset.QORT_FROM_QORA, newQortFromQoraBalance));
 
 			sharedAmount += holderReward;
 		}
 
+		// Perform batched update of QORT_FROM_QORA balances
+		block.repository.getAccountRepository().setAssetBalances(newQortFromQoraBalances);
+
 		return sharedAmount;
 	}
 
@@ -1909,4 +1996,38 @@ public class Block {
 		this.repository.getAccountRepository().tidy();
 	}
 
+	private void logDebugInfo() {
+		try {
+			// Avoid calculations if possible. We have to check against INFO here, since Level.isMoreSpecificThan() confusingly uses <= rather than just <
+			if (LOGGER.getLevel().isMoreSpecificThan(Level.INFO))
+				return;
+
+			if (this.repository == null || this.getMinter() == null || this.getBlockData() == null)
+				return;
+
+			int minterLevel = Account.getRewardShareEffectiveMintingLevel(this.repository, this.getMinter().getPublicKey());
+
+			LOGGER.debug(String.format("======= BLOCK %d (%.8s) =======", this.getBlockData().getHeight(), Base58.encode(this.getSignature())));
+			LOGGER.debug(String.format("Timestamp: %d", this.getBlockData().getTimestamp()));
+			LOGGER.debug(String.format("Minter level: %d", minterLevel));
+			LOGGER.debug(String.format("Online accounts: %d", this.getBlockData().getOnlineAccountsCount()));
+			LOGGER.debug(String.format("AT count: %d", this.getBlockData().getATCount()));
+
+			BlockSummaryData blockSummaryData = new BlockSummaryData(this.getBlockData());
+			if (this.getParent() == null || this.getParent().getSignature() == null || blockSummaryData == null || minterLevel == 0)
+				return;
+
+			blockSummaryData.setMinterLevel(minterLevel);
+			BigInteger blockWeight = calcBlockWeight(this.getParent().getHeight(), this.getParent().getSignature(), blockSummaryData);
+			BigInteger keyDistance = calcKeyDistance(this.getParent().getHeight(), this.getParent().getSignature(), blockSummaryData.getMinterPublicKey(), blockSummaryData.getMinterLevel());
+			NumberFormat formatter = new DecimalFormat("0.###E0");
+
+			LOGGER.debug(String.format("Key distance: %s", formatter.format(keyDistance)));
+			LOGGER.debug(String.format("Weight: %s", formatter.format(blockWeight)));
+
+		} catch (DataException e) {
+			LOGGER.info(() -> String.format("Unable to log block debugging info: %s", e.getMessage()));
+		}
+	}
+
 }

src/main/java/org/qortal/block/Block212937.java

@@ -0,0 +1,153 @@
+package org.qortal.block;
+
+import java.io.InputStream;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import javax.xml.bind.JAXBContext;
+import javax.xml.bind.JAXBException;
+import javax.xml.bind.UnmarshalException;
+import javax.xml.bind.Unmarshaller;
+import javax.xml.transform.stream.StreamSource;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.eclipse.persistence.jaxb.JAXBContextFactory;
+import org.eclipse.persistence.jaxb.UnmarshallerProperties;
+import org.qortal.data.account.AccountBalanceData;
+import org.qortal.repository.DataException;
+
+/**
+ * Block 212937
+ * <p>
+ * Somehow a node minted a version of block 212937 that contained one transaction:
+ * a PAYMENT transaction that attempted to spend more QORT than that account had as QORT balance.
+ * <p>
+ * This invalid transaction made block 212937 (rightly) invalid to several nodes,
+ * which refused to use that block.
+ * However, it seems there were no other nodes minting an alternative, valid block at that time
+ * and so the chain stalled for several nodes in the network.
+ * <p>
+ * Additionally, the invalid block 212937 affected all new installations, regardless of whether
+ * they synchronized from scratch (block 1) or used an 'official release' bootstrap.
+ * <p>
+ * After lengthy diagnosis, it was discovered that
+ * the invalid transaction seemed to rely on incorrect balances in a corrupted database.
+ * Copies of DB files containing the broken chain were also shared around, exacerbating the problem.
+ * <p>
+ * There were three options:
+ * <ol>
+ * <li>roll back the chain to last known valid block 212936 and re-mint empty blocks to current height</li>
+ * <li>keep existing chain, but apply database edits at block 212937 to allow current chain to be valid</li>
+ * <li>attempt to mint an alternative chain, retaining as many valid transactions as possible</li>
+ * </ol>
+ * <p>
+ * Option 1 was highly undesirable due to knock-on effects from wiping 700+ transactions, some of which
+ * might have affect cross-chain trades, although there were no cross-chain trade completed during
+ * the decision period.
+ * <p>
+ * Option 3 was essentially a slightly better version of option 1 and rejected for similar reasons.
+ * Attempts at option 3 also rapidly hit cumulative problems with every replacement block due to
+ * differing block timestamps making some transactions, and then even some blocks themselves, invalid.
+ * <p>
+ * This class is the implementation of option 2.
+ * <p>
+ * The change in account balances are relatively small, see <tt>block-212937-deltas.json</tt> resource
+ * for actual values. These values were obtained by exporting the <tt>AccountBalances</tt> table from
+ * both versions of the database with chain at block 212936, and then comparing. The values were also
+ * tested by syncing both databases up to block 225500, re-exporting and re-comparing.
+ * <p>
+ * The invalid block 212937 signature is: <tt>2J3GVJjv...qavh6KkQ</tt>.
+ * <p>
+ * The invalid transaction in block 212937 is:
+ * <p>
+ * <code><pre>
+   {
+      "amount" : "0.10788294",
+      "approvalStatus" : "NOT_REQUIRED",
+      "blockHeight" : 212937,
+      "creatorAddress" : "QLdw5uabviLJgRGkRiydAFmAtZzxHfNXSs",
+      "fee" : "0.00100000",
+      "recipient" : "QZi1mNHDbiLvsytxTgxDr9nhJe4pNZaWpw",
+      "reference" : "J6JukdTVuXZ3JYbHatfZzwxG2vSiZwVCPDzW5K7PsVQKRj8XZeDtqnkGCGGjaSQZ9bQMtV44ky88NnGM4YBQKU6",
+      "senderPublicKey" : "DBFfbD2M3uh4jPE5PaUcZVvNPfrrJzVB7seeEtBn5SPs",
+      "signature" : "qkitxdCEEnKt8w6wRfFixtErbXsxWE6zG2ESNhpqBdScikV1WxeA6WZTTMJVV4tCeZdBFXw3V1X5NVztv6LirWK",
+      "timestamp" : 1607863074904,
+      "txGroupId" : 0,
+      "type" : "PAYMENT"
+   }
+   </pre></code>
+ * <p>
+ * Account <tt>QLdw5uabviLJgRGkRiydAFmAtZzxHfNXSs</tt> attempted to spend <tt>0.10888294</tt> (including fees)
+ * when their QORT balance was really only <tt>0.10886665</tt>.
+ * <p>
+ * However, on the broken DB nodes, their balance
+ * seemed to be <tt>0.10890293</tt> which was sufficient to make the transaction valid.
+ */
+public final class Block212937 {
+
+	private static final Logger LOGGER = LogManager.getLogger(Block212937.class);
+	private static final String ACCOUNT_DELTAS_SOURCE = "block-212937-deltas.json";
+
+	private static final List<AccountBalanceData> accountDeltas = readAccountDeltas();
+
+	private Block212937() {
+		/* Do not instantiate */
+	}
+
+	@SuppressWarnings("unchecked")
+	private static List<AccountBalanceData> readAccountDeltas() {
+		Unmarshaller unmarshaller;
+
+		try {
+			// Create JAXB context aware of classes we need to unmarshal
+			JAXBContext jc = JAXBContextFactory.createContext(new Class[] {
+				AccountBalanceData.class
+			}, null);
+
+			// Create unmarshaller
+			unmarshaller = jc.createUnmarshaller();
+
+			// Set the unmarshaller media type to JSON
+			unmarshaller.setProperty(UnmarshallerProperties.MEDIA_TYPE, "application/json");
+
+			// Tell unmarshaller that there's no JSON root element in the JSON input
+			unmarshaller.setProperty(UnmarshallerProperties.JSON_INCLUDE_ROOT, false);
+		} catch (JAXBException e) {
+			String message = "Failed to setup unmarshaller to read block 212937 deltas";
+			LOGGER.error(message, e);
+			throw new RuntimeException(message, e);
+		}
+
+		ClassLoader classLoader = BlockChain.class.getClassLoader();
+		InputStream in = classLoader.getResourceAsStream(ACCOUNT_DELTAS_SOURCE);
+		StreamSource jsonSource = new StreamSource(in);
+
+		try  {
+			// Attempt to unmarshal JSON stream to BlockChain config
+			return (List<AccountBalanceData>) unmarshaller.unmarshal(jsonSource, AccountBalanceData.class).getValue();
+		} catch (UnmarshalException e) {
+			String message = "Failed to parse block 212937 deltas";
+			LOGGER.error(message, e);
+			throw new RuntimeException(message, e);
+		} catch (JAXBException e) {
+			String message = "Unexpected JAXB issue while processing block 212937 deltas";
+			LOGGER.error(message, e);
+			throw new RuntimeException(message, e);
+		}
+	}
+
+	public static void processFix(Block block) throws DataException {
+		block.repository.getAccountRepository().modifyAssetBalances(accountDeltas);
+	}
+
+	public static void orphanFix(Block block) throws DataException {
+		// Create inverse deltas
+		List<AccountBalanceData> inverseDeltas = accountDeltas.stream()
+				.map(delta -> new AccountBalanceData(delta.getAddress(), delta.getAssetId(), 0 - delta.getBalance()))
+				.collect(Collectors.toList());
+
+		block.repository.getAccountRepository().modifyAssetBalances(inverseDeltas);
+	}
+
+}

src/main/java/org/qortal/block/BlockChain.java

@@ -32,7 +32,6 @@ import org.qortal.repository.DataException;
 import org.qortal.repository.Repository;
 import org.qortal.repository.RepositoryManager;
 import org.qortal.settings.Settings;
-import org.qortal.utils.NTP;
 import org.qortal.utils.StringLongMapXmlAdapter;
 
 /**
@@ -71,6 +70,10 @@ public class BlockChain {
 	private GenesisBlock.GenesisInfo genesisInfo;
 
 	public enum FeatureTrigger {
+		atFindNextTransactionFix,
+		newBlockSigHeight,
+		shareBinFix,
+		calcChainWeightTimestamp;
 	}
 
 	/** Map of which blockchain features are enabled when (height/timestamp) */
@@ -372,6 +375,22 @@ public class BlockChain {
 
 	// Convenience methods for specific blockchain feature triggers
 
+	public int getAtFindNextTransactionFixHeight() {
+		return this.featureTriggers.get(FeatureTrigger.atFindNextTransactionFix.name()).intValue();
+	}
+
+	public int getNewBlockSigHeight() {
+		return this.featureTriggers.get(FeatureTrigger.newBlockSigHeight.name()).intValue();
+	}
+
+	public int getShareBinFixHeight() {
+		return this.featureTriggers.get(FeatureTrigger.shareBinFix.name()).intValue();
+	}
+
+	public long getCalcChainWeightTimestamp() {
+		return this.featureTriggers.get(FeatureTrigger.calcChainWeightTimestamp.name()).longValue();
+	}
+
 	// More complex getters for aspects that change by height or timestamp
 
 	public long getRewardAtHeight(int ourHeight) {
@@ -482,7 +501,7 @@ public class BlockChain {
 	}
 
 	/**
-	 * Some sort start-up/initialization/checking method.
+	 * Some sort of start-up/initialization/checking method.
 	 * 
 	 * @throws SQLException
 	 */
@@ -492,7 +511,11 @@ public class BlockChain {
 			rebuildBlockchain();
 
 		try (final Repository repository = RepositoryManager.getRepository()) {
-			BlockData detachedBlockData = repository.getBlockRepository().getDetachedBlockSignature();
+			repository.checkConsistency();
+
+			int startHeight = Math.max(repository.getBlockRepository().getBlockchainHeight() - 1440, 1);
+
+			BlockData detachedBlockData = repository.getBlockRepository().getDetachedBlockSignature(startHeight);
 
 			if (detachedBlockData != null) {
 				LOGGER.error(String.format("Block %d's reference does not match any block's signature", detachedBlockData.getHeight()));
@@ -530,7 +553,8 @@ public class BlockChain {
 
 	private static void rebuildBlockchain() throws DataException {
 		// (Re)build repository
-		RepositoryManager.rebuild();
+		if (!RepositoryManager.wasPristineAtOpen())
+			RepositoryManager.rebuild();
 
 		try (final Repository repository = RepositoryManager.getRepository()) {
 			GenesisBlock genesisBlock = GenesisBlock.getInstance(repository);
@@ -552,17 +576,23 @@ public class BlockChain {
 
 		try {
 			try (final Repository repository = RepositoryManager.getRepository()) {
-				for (int height = repository.getBlockRepository().getBlockchainHeight(); height > targetHeight; --height) {
+				int height = repository.getBlockRepository().getBlockchainHeight();
+				BlockData orphanBlockData = repository.getBlockRepository().fromHeight(height);
+
+				while (height > targetHeight) {
 					LOGGER.info(String.format("Forcably orphaning block %d", height));
 
-					BlockData blockData = repository.getBlockRepository().fromHeight(height);
-					Block block = new Block(repository, blockData);
+					Block block = new Block(repository, orphanBlockData);
 					block.orphan();
-					repository.saveChanges();
-				}
 
-				BlockData lastBlockData = repository.getBlockRepository().getLastBlock();
-				Controller.getInstance().setChainTip(lastBlockData);
+					repository.saveChanges();
+
+					--height;
+					orphanBlockData = repository.getBlockRepository().fromHeight(height);
+
+					repository.discardChanges(); // clear transaction status to prevent deadlocks
+					Controller.getInstance().onOrphanedBlock(orphanBlockData);
+				}
 
 				return true;
 			}
@@ -571,33 +601,4 @@ public class BlockChain {
 		}
 	}
 
-	public static void trimOldOnlineAccountsSignatures() {
-		final Long now = NTP.getTime();
-		if (now == null)
-			return;
-
-		ReentrantLock blockchainLock = Controller.getInstance().getBlockchainLock();
-		if (!blockchainLock.tryLock())
-			// Too busy to trim right now, try again later
-			return;
-
-		try {
-			try (final Repository repository = RepositoryManager.tryRepository()) {
-				if (repository == null)
-					return;
-
-				int numBlocksTrimmed = repository.getBlockRepository().trimOldOnlineAccountsSignatures(now - BlockChain.getInstance().getOnlineAccountSignaturesMaxLifetime());
-
-				if (numBlocksTrimmed > 0)
-					LOGGER.debug(String.format("Trimmed old online accounts signatures from %d block%s", numBlocksTrimmed, (numBlocksTrimmed != 1 ? "s" : "")));
-
-				repository.saveChanges();
-			} catch (DataException e) {
-				LOGGER.warn(String.format("Repository issue trying to trim old online accounts signatures: %s", e.getMessage()));
-			}
-		} finally {
-			blockchainLock.unlock();
-		}
-	}
-
 }

src/main/java/org/qortal/controller/AtStatesTrimmer.java

@@ -0,0 +1,80 @@
+package org.qortal.controller;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.qortal.data.block.BlockData;
+import org.qortal.repository.DataException;
+import org.qortal.repository.Repository;
+import org.qortal.repository.RepositoryManager;
+import org.qortal.settings.Settings;
+import org.qortal.utils.NTP;
+
+public class AtStatesTrimmer implements Runnable {
+
+	private static final Logger LOGGER = LogManager.getLogger(AtStatesTrimmer.class);
+
+	@Override
+	public void run() {
+		Thread.currentThread().setName("AT States trimmer");
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			int trimStartHeight = repository.getATRepository().getAtTrimHeight();
+
+			repository.getATRepository().prepareForAtStateTrimming();
+			repository.saveChanges();
+
+			while (!Controller.isStopping()) {
+				repository.discardChanges();
+
+				Thread.sleep(Settings.getInstance().getAtStatesTrimInterval());
+
+				BlockData chainTip = Controller.getInstance().getChainTip();
+				if (chainTip == null || NTP.getTime() == null)
+					continue;
+
+				// Don't even attempt if we're mid-sync as our repository requests will be delayed for ages
+				if (Controller.getInstance().isSynchronizing())
+					continue;
+
+				long currentTrimmableTimestamp = NTP.getTime() - Settings.getInstance().getAtStatesMaxLifetime();
+				// We want to keep AT states near the tip of our copy of blockchain so we can process/orphan nearby blocks
+				long chainTrimmableTimestamp = chainTip.getTimestamp() - Settings.getInstance().getAtStatesMaxLifetime();
+
+				long upperTrimmableTimestamp = Math.min(currentTrimmableTimestamp, chainTrimmableTimestamp);
+				int upperTrimmableHeight = repository.getBlockRepository().getHeightFromTimestamp(upperTrimmableTimestamp);
+
+				int upperBatchHeight = trimStartHeight + Settings.getInstance().getAtStatesTrimBatchSize();
+				int upperTrimHeight = Math.min(upperBatchHeight, upperTrimmableHeight);
+
+				if (trimStartHeight >= upperTrimHeight)
+					continue;
+
+				int numAtStatesTrimmed = repository.getATRepository().trimAtStates(trimStartHeight, upperTrimHeight, Settings.getInstance().getAtStatesTrimLimit());
+				repository.saveChanges();
+
+				if (numAtStatesTrimmed > 0) {
+					final int finalTrimStartHeight = trimStartHeight;
+					LOGGER.debug(() -> String.format("Trimmed %d AT state%s between blocks %d and %d",
+							numAtStatesTrimmed, (numAtStatesTrimmed != 1 ? "s" : ""),
+							finalTrimStartHeight, upperTrimHeight));
+				} else {
+					// Can we move onto next batch?
+					if (upperTrimmableHeight > upperBatchHeight) {
+						trimStartHeight = upperBatchHeight;
+						repository.getATRepository().setAtTrimHeight(trimStartHeight);
+						repository.getATRepository().prepareForAtStateTrimming();
+						repository.saveChanges();
+
+						final int finalTrimStartHeight = trimStartHeight;
+						LOGGER.debug(() -> String.format("Bumping AT state base trim height to %d", finalTrimStartHeight));
+					}
+				}
+			}
+		} catch (DataException e) {
+			LOGGER.warn(String.format("Repository issue trying to trim AT states: %s", e.getMessage()));
+		} catch (InterruptedException e) {
+			// Time to exit
+		}
+	}
+
+}

src/main/java/org/qortal/controller/AutoUpdate.java

@@ -214,8 +214,9 @@ public class AutoUpdate extends Thread {
 			return false; // failed - try another repo
 		}
 
-		// Give repository a chance to backup in case things go badly wrong
-		RepositoryManager.backup(true);
+		// Give repository a chance to backup in case things go badly wrong (if enabled)
+		if (Settings.getInstance().getRepositoryBackupInterval() > 0)
+			RepositoryManager.backup(true);
 
 		// Call ApplyUpdate to end this process (unlocking current JAR so it can be replaced)
 		String javaHome = System.getProperty("java.home");

src/main/java/org/qortal/controller/BlockMinter.java

@@ -1,4 +1,4 @@
-package org.qortal.block;
+package org.qortal.controller;
 
 import java.math.BigInteger;
 import java.util.ArrayList;
@@ -13,8 +13,9 @@ import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.qortal.account.Account;
 import org.qortal.account.PrivateKeyAccount;
+import org.qortal.block.Block;
 import org.qortal.block.Block.ValidationResult;
-import org.qortal.controller.Controller;
+import org.qortal.block.BlockChain;
 import org.qortal.data.account.MintingAccountData;
 import org.qortal.data.account.RewardShareData;
 import org.qortal.data.block.BlockData;
@@ -60,7 +61,7 @@ public class BlockMinter extends Thread {
 				List<TransactionData> unconfirmedTransactions = repository.getTransactionRepository().getUnconfirmedTransactions();
 
 				for (TransactionData transactionData : unconfirmedTransactions) {
-					LOGGER.trace(String.format("Deleting unconfirmed transaction %s", Base58.encode(transactionData.getSignature())));
+					LOGGER.trace(() -> String.format("Deleting unconfirmed transaction %s", Base58.encode(transactionData.getSignature())));
 					repository.getTransactionRepository().delete(transactionData);
 				}
 
@@ -69,7 +70,7 @@ public class BlockMinter extends Thread {
 
 			// Going to need this a lot...
 			BlockRepository blockRepository = repository.getBlockRepository();
-			Block previousBlock = null;
+			BlockData previousBlockData = null;
 
 			List<Block> newBlocks = new ArrayList<>();
 
@@ -115,7 +116,7 @@ public class BlockMinter extends Thread {
 
 					RewardShareData rewardShareData = repository.getAccountRepository().getRewardShare(mintingAccountData.getPublicKey());
 					if (rewardShareData == null) {
-						// Reward-share doesn't even exist - probably not a good sign
+						// Reward-share doesn't exist - probably cancelled but not yet removed from node's list of minting accounts
 						madi.remove();
 						continue;
 					}
@@ -134,24 +135,27 @@ public class BlockMinter extends Thread {
 				// Disregard peers that have "misbehaved" recently
 				peers.removeIf(Controller.hasMisbehaved);
 
-				// Disregard peers that don't have a recent block
-				peers.removeIf(Controller.hasNoRecentBlock);
+				// Disregard peers that don't have a recent block, but only if we're not in recovery mode.
+				// In that mode, we want to allow minting on top of older blocks, to recover stalled networks.
+				if (Controller.getInstance().getRecoveryMode() == false)
+					peers.removeIf(Controller.hasNoRecentBlock);
 
 				// Don't mint if we don't have enough up-to-date peers as where would the transactions/consensus come from?
 				if (peers.size() < Settings.getInstance().getMinBlockchainPeers())
 					continue;
 
-				// If our latest block isn't recent then we need to synchronize instead of minting.
+				// If our latest block isn't recent then we need to synchronize instead of minting, unless we're in recovery mode.
 				if (!peers.isEmpty() && lastBlockData.getTimestamp() < minLatestBlockTimestamp)
-					continue;
+					if (Controller.getInstance().getRecoveryMode() == false)
+						continue;
 
 				// There are enough peers with a recent block and our latest block is recent
 				// so go ahead and mint a block if possible.
 				isMintingPossible = true;
 
 				// Check blockchain hasn't changed
-				if (previousBlock == null || !Arrays.equals(previousBlock.getSignature(), lastBlockData.getSignature())) {
-					previousBlock = new Block(repository, lastBlockData);
+				if (previousBlockData == null || !Arrays.equals(previousBlockData.getSignature(), lastBlockData.getSignature())) {
+					previousBlockData = lastBlockData;
 					newBlocks.clear();
 
 					// Reduce log timeout
@@ -162,12 +166,20 @@ public class BlockMinter extends Thread {
 				mintingAccountsData.removeIf(mintingAccountData -> newBlocks.stream().anyMatch(newBlock -> Arrays.equals(newBlock.getBlockData().getMinterPublicKey(), mintingAccountData.getPublicKey())));
 
 				// Do we need to build any potential new blocks?
-				List<PrivateKeyAccount> mintingAccounts = mintingAccountsData.stream().map(accountData -> new PrivateKeyAccount(repository, accountData.getPrivateKey())).collect(Collectors.toList());
+				List<PrivateKeyAccount> newBlocksMintingAccounts = mintingAccountsData.stream().map(accountData -> new PrivateKeyAccount(repository, accountData.getPrivateKey())).collect(Collectors.toList());
 
-				for (PrivateKeyAccount mintingAccount : mintingAccounts) {
+				// We might need to sit the next block out, if one of our minting accounts signed the previous one
+				final byte[] previousBlockMinter = previousBlockData.getMinterPublicKey();
+				final boolean mintedLastBlock = mintingAccountsData.stream().anyMatch(mintingAccount -> Arrays.equals(mintingAccount.getPublicKey(), previousBlockMinter));
+				if (mintedLastBlock) {
+					LOGGER.trace(String.format("One of our keys signed the last block, so we won't sign the next one"));
+					continue;
+				}
+
+				for (PrivateKeyAccount mintingAccount : newBlocksMintingAccounts) {
 					// First block does the AT heavy-lifting
 					if (newBlocks.isEmpty()) {
-						Block newBlock = Block.mint(repository, previousBlock.getBlockData(), mintingAccount);
+						Block newBlock = Block.mint(repository, previousBlockData, mintingAccount);
 						if (newBlock == null) {
 							// For some reason we can't mint right now
 							moderatedLog(() -> LOGGER.error("Couldn't build a to-be-minted block"));
@@ -195,7 +207,7 @@ public class BlockMinter extends Thread {
 				// Make sure we're the only thread modifying the blockchain
 				ReentrantLock blockchainLock = Controller.getInstance().getBlockchainLock();
 				if (!blockchainLock.tryLock(30, TimeUnit.SECONDS)) {
-					LOGGER.warn("Couldn't acquire blockchain lock even after waiting 30 seconds");
+					LOGGER.debug("Couldn't acquire blockchain lock even after waiting 30 seconds");
 					continue;
 				}
 
@@ -233,8 +245,8 @@ public class BlockMinter extends Thread {
 						continue;
 
 					// Pick best block
-					final int parentHeight = previousBlock.getBlockData().getHeight();
-					final byte[] parentBlockSignature = previousBlock.getSignature();
+					final int parentHeight = previousBlockData.getHeight();
+					final byte[] parentBlockSignature = previousBlockData.getSignature();
 
 					BigInteger bestWeight = null;
 
@@ -274,28 +286,33 @@ public class BlockMinter extends Thread {
 					try {
 						newBlock.process();
 
-						LOGGER.info(String.format("Minted new block: %d", newBlock.getBlockData().getHeight()));
 						repository.saveChanges();
 
+						LOGGER.info(String.format("Minted new block: %d", newBlock.getBlockData().getHeight()));
+
 						RewardShareData rewardShareData = repository.getAccountRepository().getRewardShare(newBlock.getBlockData().getMinterPublicKey());
 
 						if (rewardShareData != null) {
-							LOGGER.info(String.format("Minted block %d, sig %.8s by %s on behalf of %s",
+							LOGGER.info(String.format("Minted block %d, sig %.8s, parent sig: %.8s by %s on behalf of %s",
 									newBlock.getBlockData().getHeight(),
 									Base58.encode(newBlock.getBlockData().getSignature()),
+									Base58.encode(newBlock.getParent().getSignature()),
 									rewardShareData.getMinter(),
 									rewardShareData.getRecipient()));
 						} else {
-							LOGGER.info(String.format("Minted block %d, sig %.8s by %s",
+							LOGGER.info(String.format("Minted block %d, sig %.8s, parent sig: %.8s by %s",
 									newBlock.getBlockData().getHeight(),
 									Base58.encode(newBlock.getBlockData().getSignature()),
+									Base58.encode(newBlock.getParent().getSignature()),
 									newBlock.getMinter().getAddress()));
 						}
 
-						repository.saveChanges();
-
-						// Notify controller
+						// Notify network after we're released blockchain lock
 						newBlockMinted = true;
+
+						// Notify Controller
+						repository.discardChanges(); // clear transaction status to prevent deadlocks
+						Controller.getInstance().onNewBlock(newBlock.getBlockData());
 					} catch (DataException e) {
 						// Unable to process block - report and discard
 						LOGGER.error("Unable to process newly minted block?", e);
@@ -305,8 +322,13 @@ public class BlockMinter extends Thread {
 					blockchainLock.unlock();
 				}
 
-				if (newBlockMinted)
-					Controller.getInstance().onNewBlock(newBlock.getBlockData());
+				if (newBlockMinted) {
+					// Broadcast our new chain to network
+					BlockData newBlockData = newBlock.getBlockData();
+
+					Network network = Network.getInstance();
+					network.broadcast(broadcastPeer -> network.buildHeightMessage(broadcastPeer, newBlockData));
+				}
 			}
 		} catch (DataException e) {
 			LOGGER.warn("Repository issue while running block minter", e);

src/main/java/org/qortal/controller/BlockNotifier.java

@@ -1,61 +0,0 @@
-package org.qortal.controller;
-
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.HashMap;
-import java.util.Map;
-
-import org.eclipse.jetty.websocket.api.Session;
-import org.qortal.api.model.BlockInfo;
-import org.qortal.data.block.BlockData;
-
-public class BlockNotifier {
-
-	private static BlockNotifier instance;
-
-	@FunctionalInterface
-	public interface Listener {
-		void notify(BlockInfo blockInfo);
-	}
-
-	private Map<Session, Listener> listenersBySession = new HashMap<>();
-
-	private BlockNotifier() {
-	}
-
-	public static synchronized BlockNotifier getInstance() {
-		if (instance == null)
-			instance = new BlockNotifier();
-
-		return instance;
-	}
-
-	public void register(Session session, Listener listener) {
-		synchronized (this.listenersBySession) {
-			this.listenersBySession.put(session, listener);
-		}
-	}
-
-	public void deregister(Session session) {
-		synchronized (this.listenersBySession) {
-			this.listenersBySession.remove(session);
-		}
-	}
-
-	public void onNewBlock(BlockData blockData) {
-		// Convert BlockData to BlockInfo
-		BlockInfo blockInfo = new BlockInfo(blockData);
-
-		for (Listener listener : getAllListeners())
-			listener.notify(blockInfo);
-	}
-
-	private Collection<Listener> getAllListeners() {
-		// Make a copy of listeners to both avoid concurrent modification
-		// and reduce synchronization time
-		synchronized (this.listenersBySession) {
-			return new ArrayList<>(this.listenersBySession.values());
-		}
-	}
-
-}

src/main/java/org/qortal/controller/Controller.java

@@ -9,21 +9,31 @@ import java.security.Security;
 import java.time.LocalDateTime;
 import java.time.ZoneOffset;
 import java.time.format.DateTimeFormatter;
+import java.util.ArrayDeque;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.Deque;
 import java.util.HashMap;
 import java.util.Iterator;
+import java.util.LinkedHashMap;
+import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
 import java.util.Properties;
 import java.util.Random;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicLong;
 import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
 import java.util.function.Predicate;
 import java.util.stream.Collectors;
 
+import javax.xml.bind.annotation.XmlAccessType;
+import javax.xml.bind.annotation.XmlAccessorType;
+
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.bouncycastle.jce.provider.BouncyCastleProvider;
@@ -34,9 +44,9 @@ import org.qortal.account.PublicKeyAccount;
 import org.qortal.api.ApiService;
 import org.qortal.block.Block;
 import org.qortal.block.BlockChain;
-import org.qortal.block.BlockMinter;
 import org.qortal.block.BlockChain.BlockTimingByHeight;
 import org.qortal.controller.Synchronizer.SynchronizationResult;
+import org.qortal.controller.tradebot.TradeBot;
 import org.qortal.crypto.Crypto;
 import org.qortal.data.account.MintingAccountData;
 import org.qortal.data.account.RewardShareData;
@@ -48,6 +58,8 @@ import org.qortal.data.network.PeerData;
 import org.qortal.data.transaction.ArbitraryTransactionData;
 import org.qortal.data.transaction.TransactionData;
 import org.qortal.data.transaction.ArbitraryTransactionData.DataType;
+import org.qortal.event.Event;
+import org.qortal.event.EventBus;
 import org.qortal.data.transaction.ChatTransactionData;
 import org.qortal.globalization.Translator;
 import org.qortal.gui.Gui;
@@ -55,8 +67,8 @@ import org.qortal.gui.SysTray;
 import org.qortal.network.Network;
 import org.qortal.network.Peer;
 import org.qortal.network.message.ArbitraryDataMessage;
-import org.qortal.network.message.BlockMessage;
 import org.qortal.network.message.BlockSummariesMessage;
+import org.qortal.network.message.CachedBlockMessage;
 import org.qortal.network.message.GetArbitraryDataMessage;
 import org.qortal.network.message.GetBlockMessage;
 import org.qortal.network.message.GetBlockSummariesMessage;
@@ -83,6 +95,7 @@ import org.qortal.transaction.Transaction.TransactionType;
 import org.qortal.transaction.Transaction.ValidationResult;
 import org.qortal.utils.Base58;
 import org.qortal.utils.ByteArray;
+import org.qortal.utils.DaemonThreadFactory;
 import org.qortal.utils.NTP;
 import org.qortal.utils.Triple;
 
@@ -108,12 +121,15 @@ public class Controller extends Thread {
 	private static final long NTP_PRE_SYNC_CHECK_PERIOD = 5 * 1000L; // ms
 	private static final long NTP_POST_SYNC_CHECK_PERIOD = 5 * 60 * 1000L; // ms
 	private static final long DELETE_EXPIRED_INTERVAL = 5 * 60 * 1000L; // ms
+	private static final long RECOVERY_MODE_TIMEOUT = 10 * 60 * 1000L; // ms
 
 	// To do with online accounts list
 	private static final long ONLINE_ACCOUNTS_TASKS_INTERVAL = 10 * 1000L; // ms
 	private static final long ONLINE_ACCOUNTS_BROADCAST_INTERVAL = 1 * 60 * 1000L; // ms
-	private static final long ONLINE_TIMESTAMP_MODULUS = 5 * 60 * 1000L;
+	public static final long ONLINE_TIMESTAMP_MODULUS = 5 * 60 * 1000L;
 	private static final long LAST_SEEN_EXPIRY_PERIOD = (ONLINE_TIMESTAMP_MODULUS * 2) + (1 * 60 * 1000L);
+	/** How many (latest) blocks' worth of online accounts we cache */
+	private static final int MAX_BLOCKS_CACHED_ONLINE_ACCOUNTS = 2;
 
 	private static volatile boolean isStopping = false;
 	private static BlockMinter blockMinter = null;
@@ -128,16 +144,30 @@ public class Controller extends Thread {
 	private ExecutorService callbackExecutor = Executors.newFixedThreadPool(3);
 	private volatile boolean notifyGroupMembershipChange = false;
 
-	private volatile BlockData chainTip = null;
+	/** Latest blocks on our chain. Note: tail/last is the latest block. */
+	private final Deque<BlockData> latestBlocks = new LinkedList<>();
+
+	/** Cache of BlockMessages, indexed by block signature */
+	@SuppressWarnings("serial")
+	private final LinkedHashMap<ByteArray, CachedBlockMessage> blockMessageCache = new LinkedHashMap<>() {
+		@Override
+		protected boolean removeEldestEntry(Map.Entry<ByteArray, CachedBlockMessage> eldest) {
+			return this.size() > Settings.getInstance().getBlockCacheSize();
+		}
+	};
 
 	private long repositoryBackupTimestamp = startTime; // ms
+	private long repositoryCheckpointTimestamp = startTime; // ms
 	private long ntpCheckTimestamp = startTime; // ms
 	private long deleteExpiredTimestamp = startTime + DELETE_EXPIRED_INTERVAL; // ms
+
 	private long onlineAccountsTasksTimestamp = startTime + ONLINE_ACCOUNTS_TASKS_INTERVAL; // ms
 
 	/** Whether we can mint new blocks, as reported by BlockMinter. */
 	private volatile boolean isMintingPossible = false;
 
+	/** Synchronization object for sync variables below */
+	private final Object syncLock = new Object();
 	/** Whether we are attempting to synchronize. */
 	private volatile boolean isSynchronizing = false;
 	/** Temporary estimate of synchronization progress for SysTray use. */
@@ -146,6 +176,11 @@ public class Controller extends Thread {
 	/** Latest block signatures from other peers that we know are on inferior chains. */
 	List<ByteArray> inferiorChainSignatures = new ArrayList<>();
 
+	/** Recovery mode, which is used to bring back a stalled network */
+	private boolean recoveryMode = false;
+	private boolean peersAvailable = true; // peersAvailable must default to true
+	private long timePeersLastAvailable = 0;
+
 	/**
 	 * Map of recent requests for ARBITRARY transaction data payloads.
 	 * <p>
@@ -168,8 +203,51 @@ public class Controller extends Thread {
 	/** Lock for only allowing one blockchain-modifying codepath at a time. e.g. synchronization or newly minted block. */
 	private final ReentrantLock blockchainLock = new ReentrantLock();
 
-	/** Cache of 'online accounts' */
+	/** Cache of current 'online accounts' */
 	List<OnlineAccountData> onlineAccounts = new ArrayList<>();
+	/** Cache of latest blocks' online accounts */
+	Deque<List<OnlineAccountData>> latestBlocksOnlineAccounts = new ArrayDeque<>(MAX_BLOCKS_CACHED_ONLINE_ACCOUNTS);
+
+	// Stats
+	@XmlAccessorType(XmlAccessType.FIELD)
+	public static class StatsSnapshot {
+		public static class GetBlockMessageStats {
+			public AtomicLong requests = new AtomicLong();
+			public AtomicLong cacheHits = new AtomicLong();
+			public AtomicLong unknownBlocks = new AtomicLong();
+			public AtomicLong cacheFills = new AtomicLong();
+
+			public GetBlockMessageStats() {
+			}
+		}
+		public GetBlockMessageStats getBlockMessageStats = new GetBlockMessageStats();
+
+		public static class GetBlockSummariesStats {
+			public AtomicLong requests = new AtomicLong();
+			public AtomicLong cacheHits = new AtomicLong();
+			public AtomicLong fullyFromCache = new AtomicLong();
+
+			public GetBlockSummariesStats() {
+			}
+		}
+		public GetBlockSummariesStats getBlockSummariesStats = new GetBlockSummariesStats();
+
+		public static class GetBlockSignaturesV2Stats {
+			public AtomicLong requests = new AtomicLong();
+			public AtomicLong cacheHits = new AtomicLong();
+			public AtomicLong fullyFromCache = new AtomicLong();
+
+			public GetBlockSignaturesV2Stats() {
+			}
+		}
+		public GetBlockSignaturesV2Stats getBlockSignaturesV2Stats = new GetBlockSignaturesV2Stats();
+
+		public AtomicLong latestBlocksCacheRefills = new AtomicLong();
+
+		public StatsSnapshot() {
+		}
+	}
+	private final StatsSnapshot stats = new StatsSnapshot();
 
 	// Constructors
 
@@ -226,21 +304,37 @@ public class Controller extends Thread {
 
 	/** Returns current blockchain height, or 0 if it's not available. */
 	public int getChainHeight() {
-		BlockData blockData = this.chainTip;
-		if (blockData == null)
-			return 0;
+		synchronized (this.latestBlocks) {
+			BlockData blockData = this.latestBlocks.peekLast();
+			if (blockData == null)
+				return 0;
 
-		return blockData.getHeight();
+			return blockData.getHeight();
+		}
 	}
 
 	/** Returns highest block, or null if it's not available. */
 	public BlockData getChainTip() {
-		return this.chainTip;
+		synchronized (this.latestBlocks) {
+			return this.latestBlocks.peekLast();
+		}
 	}
 
-	/** Cache new blockchain tip. */
-	public void setChainTip(BlockData blockData) {
-		this.chainTip = blockData;
+	public void refillLatestBlocksCache() throws DataException {
+		// Set initial chain height/tip
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			BlockData blockData = repository.getBlockRepository().getLastBlock();
+			int blockCacheSize = Settings.getInstance().getBlockCacheSize();
+
+			synchronized (this.latestBlocks) {
+				this.latestBlocks.clear();
+
+				for (int i = 0; i < blockCacheSize && blockData != null; ++i) {
+					this.latestBlocks.addFirst(blockData);
+					blockData = repository.getBlockRepository().fromHeight(blockData.getHeight() - 1);
+				}
+			}
+		}
 	}
 
 	public ReentrantLock getBlockchainLock() {
@@ -265,7 +359,13 @@ public class Controller extends Thread {
 	}
 
 	public Integer getSyncPercent() {
-		return this.isSynchronizing ? this.syncPercent : null;
+		synchronized (this.syncLock) {
+			return this.isSynchronizing ? this.syncPercent : null;
+		}
+	}
+
+	public boolean getRecoveryMode() {
+		return this.recoveryMode;
 	}
 
 	// Entry point
@@ -320,13 +420,8 @@ public class Controller extends Thread {
 		try {
 			BlockChain.validate();
 
-			// Set initial chain height/tip
-			try (final Repository repository = RepositoryManager.getRepository()) {
-				BlockData blockData = repository.getBlockRepository().getLastBlock();
-
-				Controller.getInstance().setChainTip(blockData);
-				LOGGER.info(String.format("Our chain height at start-up: %d", blockData.getHeight()));
-			}
+			Controller.getInstance().refillLatestBlocksCache();
+			LOGGER.info(String.format("Our chain height at start-up: %d", Controller.getInstance().getChainHeight()));
 		} catch (DataException e) {
 			LOGGER.error("Couldn't validate blockchain", e);
 			Gui.getInstance().fatalError("Blockchain validation issue", e);
@@ -360,6 +455,9 @@ public class Controller extends Thread {
 		blockMinter = new BlockMinter();
 		blockMinter.start();
 
+		LOGGER.info("Starting trade-bot");
+		TradeBot.getInstance();
+
 		// Arbitrary transaction data manager
 		// LOGGER.info("Starting arbitrary-transaction data manager");
 		// ArbitraryDataManager.getInstance().start();
@@ -398,6 +496,11 @@ public class Controller extends Thread {
 		Thread.currentThread().setName("Controller");
 
 		final long repositoryBackupInterval = Settings.getInstance().getRepositoryBackupInterval();
+		final long repositoryCheckpointInterval = Settings.getInstance().getRepositoryCheckpointInterval();
+
+		ExecutorService trimExecutor = Executors.newCachedThreadPool(new DaemonThreadFactory());
+		trimExecutor.execute(new AtStatesTrimmer());
+		trimExecutor.execute(new OnlineAccountsSignaturesTrimmer());
 
 		try {
 			while (!isStopping) {
@@ -439,6 +542,13 @@ public class Controller extends Thread {
 				final long requestMinimumTimestamp = now - ARBITRARY_REQUEST_TIMEOUT;
 				arbitraryDataRequests.entrySet().removeIf(entry -> entry.getValue().getC() < requestMinimumTimestamp);
 
+				// Time to 'checkpoint' uncommitted repository writes?
+				if (now >= repositoryCheckpointTimestamp + repositoryCheckpointInterval) {
+					repositoryCheckpointTimestamp = now + repositoryCheckpointInterval;
+
+					RepositoryManager.setRequestedCheckpoint(Boolean.TRUE);
+				}
+
 				// Give repository a chance to backup (if enabled)
 				if (repositoryBackupInterval > 0 && now >= repositoryBackupTimestamp + repositoryBackupInterval) {
 					repositoryBackupTimestamp = now + repositoryBackupInterval;
@@ -471,7 +581,17 @@ public class Controller extends Thread {
 				}
 			}
 		} catch (InterruptedException e) {
+			// Clear interrupted flag so we can shutdown trim threads
+			Thread.interrupted();
 			// Fall-through to exit
+		} finally {
+			trimExecutor.shutdownNow();
+
+			try {
+				trimExecutor.awaitTermination(2L, TimeUnit.SECONDS);
+			} catch (InterruptedException e) {
+				// We tried...
+			}
 		}
 	}
 
@@ -503,7 +623,16 @@ public class Controller extends Thread {
 		return peerChainTipData == null || peerChainTipData.getLastBlockSignature() == null || inferiorChainTips.contains(new ByteArray(peerChainTipData.getLastBlockSignature()));
 	};
 
+	public static final Predicate<Peer> hasOldVersion = peer -> {
+		final String minPeerVersion = Settings.getInstance().getMinPeerVersion();
+		return peer.isAtLeastVersion(minPeerVersion) == false;
+	};
+
 	private void potentiallySynchronize() throws InterruptedException {
+		// Already synchronizing via another thread?
+		if (this.isSynchronizing)
+			return;
+
 		List<Peer> peers = Network.getInstance().getHandshakedPeers();
 
 		// Disregard peers that have "misbehaved" recently
@@ -515,6 +644,17 @@ public class Controller extends Thread {
 		// Disregard peers that don't have a recent block
 		peers.removeIf(hasNoRecentBlock);
 
+		// Disregard peers that are on an old version
+		peers.removeIf(hasOldVersion);
+
+		checkRecoveryModeForPeers(peers);
+		if (recoveryMode) {
+			peers = Network.getInstance().getHandshakedPeers();
+			peers.removeIf(hasOnlyGenesisBlock);
+			peers.removeIf(hasMisbehaved);
+			peers.removeIf(hasOldVersion);
+		}
+
 		// Check we have enough peers to potentially synchronize
 		if (peers.size() < Settings.getInstance().getMinBlockchainPeers())
 			return;
@@ -525,9 +665,31 @@ public class Controller extends Thread {
 		// Disregard peers that are on the same block as last sync attempt and we didn't like their chain
 		peers.removeIf(hasInferiorChainTip);
 
+		final int peersBeforeComparison = peers.size();
+
+		// Request recent block summaries from the remaining peers, and locate our common block with each
+		Synchronizer.getInstance().findCommonBlocksWithPeers(peers);
+
+		// Compare the peers against each other, and against our chain, which will return an updated list excluding those without common blocks
+		peers = Synchronizer.getInstance().comparePeers(peers);
+
+		// We may have added more inferior chain tips when comparing peers, so remove any peers that are currently on those chains
+		peers.removeIf(hasInferiorChainTip);
+
+		final int peersRemoved = peersBeforeComparison - peers.size();
+		if (peersRemoved > 0 && peers.size() > 0)
+			LOGGER.info(String.format("Ignoring %d peers on inferior chains. Peers remaining: %d", peersRemoved, peers.size()));
+
 		if (peers.isEmpty())
 			return;
 
+		if (peers.size() > 1) {
+			StringBuilder finalPeersString = new StringBuilder();
+			for (Peer peer : peers)
+				finalPeersString = finalPeersString.length() > 0 ? finalPeersString.append(", ").append(peer) : finalPeersString.append(peer);
+			LOGGER.info(String.format("Choosing random peer from: [%s]", finalPeersString.toString()));
+		}
+
 		// Pick random peer to sync with
 		int index = new SecureRandom().nextInt(peers.size());
 		Peer peer = peers.get(index);
@@ -536,14 +698,21 @@ public class Controller extends Thread {
 	}
 
 	public SynchronizationResult actuallySynchronize(Peer peer, boolean force) throws InterruptedException {
-		syncPercent = (this.chainTip.getHeight() * 100) / peer.getChainTipData().getLastHeight();
-		// Only update SysTray if we're potentially changing height
-		if (syncPercent < 100) {
-			isSynchronizing = true;
-			updateSysTray();
+		boolean hasStatusChanged = false;
+		BlockData priorChainTip = this.getChainTip();
+
+		synchronized (this.syncLock) {
+			this.syncPercent = (priorChainTip.getHeight() * 100) / peer.getChainTipData().getLastHeight();
+
+			// Only update SysTray if we're potentially changing height
+			if (this.syncPercent < 100) {
+				this.isSynchronizing = true;
+				hasStatusChanged = true;
+			}
 		}
 
-		BlockData priorChainTip = this.chainTip;
+		if (hasStatusChanged)
+			updateSysTray();
 
 		try {
 			SynchronizationResult syncResult = Synchronizer.getInstance().synchronize(peer, force);
@@ -613,8 +782,8 @@ public class Controller extends Thread {
 				// Reset our cache of inferior chains
 				inferiorChainSignatures.clear();
 
-				// Update chain-tip, systray, notify peers, websockets, etc.
-				this.onNewBlock(newChainTip);
+				Network network = Network.getInstance();
+				network.broadcast(broadcastPeer -> network.buildHeightMessage(broadcastPeer, newChainTip));
 			}
 
 			return syncResult;
@@ -623,6 +792,51 @@ public class Controller extends Thread {
 		}
 	}
 
+	private boolean checkRecoveryModeForPeers(List<Peer> qualifiedPeers) {
+		List<Peer> handshakedPeers = Network.getInstance().getHandshakedPeers();
+
+		if (handshakedPeers.size() > 0) {
+			// There is at least one handshaked peer
+			if (qualifiedPeers.isEmpty()) {
+				// There are no 'qualified' peers - i.e. peers that have a recent block we can sync to
+				boolean werePeersAvailable = peersAvailable;
+				peersAvailable = false;
+
+				// If peers only just became unavailable, update our record of the time they were last available
+				if (werePeersAvailable)
+					timePeersLastAvailable = NTP.getTime();
+
+				// If enough time has passed, enter recovery mode, which lifts some restrictions on who we can sync with and when we can mint
+				if (NTP.getTime() - timePeersLastAvailable > RECOVERY_MODE_TIMEOUT) {
+					if (recoveryMode == false) {
+						LOGGER.info(String.format("Peers have been unavailable for %d minutes. Entering recovery mode...", RECOVERY_MODE_TIMEOUT/60/1000));
+						recoveryMode = true;
+					}
+				}
+			} else {
+				// We now have at least one peer with a recent block, so we can exit recovery mode and sync normally
+				peersAvailable = true;
+				if (recoveryMode) {
+					LOGGER.info("Peers have become available again. Exiting recovery mode...");
+					recoveryMode = false;
+				}
+			}
+		}
+		return recoveryMode;
+	}
+
+	public void addInferiorChainSignature(byte[] inferiorSignature) {
+		// Update our list of inferior chain tips
+		ByteArray inferiorChainSignature = new ByteArray(inferiorSignature);
+		if (!inferiorChainSignatures.contains(inferiorChainSignature))
+			inferiorChainSignatures.add(inferiorChainSignature);
+	}
+
+	public static class StatusChangeEvent implements Event {
+		public StatusChangeEvent() {
+		}
+	}
+
 	private void updateSysTray() {
 		if (NTP.getTime() == null) {
 			SysTray.getInstance().setToolTipText(Translator.INSTANCE.translate("SysTray", "SYNCHRONIZING_CLOCK"));
@@ -637,20 +851,23 @@ public class Controller extends Thread {
 		String heightText = Translator.INSTANCE.translate("SysTray", "BLOCK_HEIGHT");
 
 		String actionText;
-		if (isMintingPossible)
-			actionText = Translator.INSTANCE.translate("SysTray", "MINTING_ENABLED");
-		else if (isSynchronizing)
-			actionText = String.format("%s - %d%%", Translator.INSTANCE.translate("SysTray", "SYNCHRONIZING_BLOCKCHAIN"), syncPercent);
-		else if (numberOfPeers < Settings.getInstance().getMinBlockchainPeers())
-			actionText = Translator.INSTANCE.translate("SysTray", "CONNECTING");
-		else
-			actionText = Translator.INSTANCE.translate("SysTray", "MINTING_DISABLED");
 
-		String tooltip = String.format("%s - %d %s - %s %d", actionText, numberOfPeers, connectionsText, heightText, height);
+		synchronized (this.syncLock) {
+			if (this.isMintingPossible)
+				actionText = Translator.INSTANCE.translate("SysTray", "MINTING_ENABLED");
+			else if (this.isSynchronizing)
+				actionText = String.format("%s - %d%%", Translator.INSTANCE.translate("SysTray", "SYNCHRONIZING_BLOCKCHAIN"), this.syncPercent);
+			else if (numberOfPeers < Settings.getInstance().getMinBlockchainPeers())
+				actionText = Translator.INSTANCE.translate("SysTray", "CONNECTING");
+			else
+				actionText = Translator.INSTANCE.translate("SysTray", "MINTING_DISABLED");
+		}
+
+		String tooltip = String.format("%s - %d %s - %s %d", actionText, numberOfPeers, connectionsText, heightText, height) + "\n" + String.format("Build version: %s", this.buildVersion);
 		SysTray.getInstance().setToolTipText(tooltip);
 
 		this.callbackExecutor.execute(() -> {
-			StatusNotifier.getInstance().onStatusChange(NTP.getTime());
+			EventBus.INSTANCE.notify(new StatusChangeEvent());
 		});
 	}
 
@@ -666,15 +883,21 @@ public class Controller extends Thread {
 
 			List<TransactionData> transactions = repository.getTransactionRepository().getUnconfirmedTransactions();
 
-			for (TransactionData transactionData : transactions)
-				if (now >= Transaction.getDeadline(transactionData)) {
-					LOGGER.info(String.format("Deleting expired, unconfirmed transaction %s", Base58.encode(transactionData.getSignature())));
+			for (TransactionData transactionData : transactions) {
+				Transaction transaction = Transaction.fromData(repository, transactionData);
+
+				if (now >= transaction.getDeadline()) {
+					LOGGER.info(() -> String.format("Deleting expired, unconfirmed transaction %s", Base58.encode(transactionData.getSignature())));
 					repository.getTransactionRepository().delete(transactionData);
 				}
+			}
 
 			repository.saveChanges();
 		} catch (DataException e) {
-			LOGGER.error("Repository issue while deleting expired unconfirmed transactions", e);
+			if (RepositoryManager.isDeadlockRelated(e))
+				LOGGER.info("Couldn't delete some expired, unconfirmed transactions this round");
+			else
+				LOGGER.error("Repository issue while deleting expired unconfirmed transactions", e);
 		}
 	}
 
@@ -777,32 +1000,154 @@ public class Controller extends Thread {
 		requestSysTrayUpdate = true;
 	}
 
-	public void onNewBlock(BlockData latestBlockData) {
-		this.setChainTip(latestBlockData);
-		requestSysTrayUpdate = true;
+	public static class NewBlockEvent implements Event {
+		private final BlockData blockData;
 
-		// Broadcast our new height info and notify websocket listeners
-		this.callbackExecutor.execute(() -> {
-			Network network = Network.getInstance();
-			network.broadcast(peer -> network.buildHeightMessage(peer, latestBlockData));
+		public NewBlockEvent(BlockData blockData) {
+			this.blockData = blockData;
+		}
 
-			BlockNotifier.getInstance().onNewBlock(latestBlockData);
-
-			if (this.notifyGroupMembershipChange) {
-				this.notifyGroupMembershipChange = false;
-				ChatNotifier.getInstance().onGroupMembershipChange();
-			}
-
-			// Trade-bot might want to perform some actions too
-			TradeBot.getInstance().onChainTipChange();
-		});
+		public BlockData getBlockData() {
+			return this.blockData;
+		}
 	}
 
-	/** Callback for when we've received a new transaction via API or peer. */
-	public void onNewTransaction(TransactionData transactionData, Peer peer) {
+	/**
+	 * Callback for when we've received a new block.
+	 * <p>
+	 * See <b>WARNING</b> for {@link EventBus#notify(Event)}
+	 * to prevent deadlocks.
+	 */
+	public void onNewBlock(BlockData latestBlockData) {
+		// Protective copy
+		BlockData blockDataCopy = new BlockData(latestBlockData);
+		int blockCacheSize = Settings.getInstance().getBlockCacheSize();
+
+		synchronized (this.latestBlocks) {
+			BlockData cachedChainTip = this.latestBlocks.peekLast();
+
+			if (cachedChainTip != null && Arrays.equals(cachedChainTip.getSignature(), blockDataCopy.getReference())) {
+				// Chain tip is parent for new latest block, so we can safely add new latest block
+				this.latestBlocks.addLast(latestBlockData);
+
+				// Trim if necessary
+				if (this.latestBlocks.size() >= blockCacheSize)
+					this.latestBlocks.pollFirst();
+			} else {
+				if (cachedChainTip != null)
+					// Chain tip didn't match - potentially abnormal behaviour?
+					LOGGER.debug(() -> String.format("Cached chain tip %.8s not parent for new latest block %.8s (reference %.8s)",
+							Base58.encode(cachedChainTip.getSignature()),
+							Base58.encode(blockDataCopy.getSignature()),
+							Base58.encode(blockDataCopy.getReference())));
+
+				// Defensively rebuild cache
+				try {
+					this.stats.latestBlocksCacheRefills.incrementAndGet();
+
+					this.refillLatestBlocksCache();
+				} catch (DataException e) {
+					LOGGER.warn(() -> "Couldn't refill latest blocks cache?", e);
+				}
+			}
+		}
+
+		this.onNewOrOrphanedBlock(blockDataCopy, NewBlockEvent::new);
+	}
+
+	public static class OrphanedBlockEvent implements Event {
+		private final BlockData blockData;
+
+		public OrphanedBlockEvent(BlockData blockData) {
+			this.blockData = blockData;
+		}
+
+		public BlockData getBlockData() {
+			return this.blockData;
+		}
+	}
+
+	/**
+	 * Callback for when we've orphaned a block.
+	 * <p>
+	 * See <b>WARNING</b> for {@link EventBus#notify(Event)}
+	 * to prevent deadlocks.
+	 */
+	public void onOrphanedBlock(BlockData latestBlockData) {
+		// Protective copy
+		BlockData blockDataCopy = new BlockData(latestBlockData);
+
+		synchronized (this.latestBlocks) {
+			BlockData cachedChainTip = this.latestBlocks.pollLast();
+			boolean refillNeeded = false;
+
+			if (cachedChainTip != null && Arrays.equals(cachedChainTip.getReference(), blockDataCopy.getSignature())) {
+				// Chain tip was parent for new latest block that has been orphaned, so we're good
+
+				// However, if we've emptied the cache then we will need to refill it
+				refillNeeded = this.latestBlocks.isEmpty();
+			} else {
+				if (cachedChainTip != null)
+					// Chain tip didn't match - potentially abnormal behaviour?
+					LOGGER.debug(() -> String.format("Cached chain tip %.8s (reference %.8s) was not parent for new latest block %.8s",
+							Base58.encode(cachedChainTip.getSignature()),
+							Base58.encode(cachedChainTip.getReference()),
+							Base58.encode(blockDataCopy.getSignature())));
+
+				// Defensively rebuild cache
+				refillNeeded = true;
+			}
+
+			if (refillNeeded)
+				try {
+					this.stats.latestBlocksCacheRefills.incrementAndGet();
+
+					this.refillLatestBlocksCache();
+				} catch (DataException e) {
+					LOGGER.warn(() -> "Couldn't refill latest blocks cache?", e);
+				}
+		}
+
+		this.onNewOrOrphanedBlock(blockDataCopy, OrphanedBlockEvent::new);
+	}
+
+	private void onNewOrOrphanedBlock(BlockData blockDataCopy, Function<BlockData, Event> eventConstructor) {
+		requestSysTrayUpdate = true;
+
+		// Notify listeners, trade-bot, etc.
+		EventBus.INSTANCE.notify(eventConstructor.apply(blockDataCopy));
+
+		if (this.notifyGroupMembershipChange) {
+			this.notifyGroupMembershipChange = false;
+			ChatNotifier.getInstance().onGroupMembershipChange();
+		}
+	}
+
+	public static class NewTransactionEvent implements Event {
+		private final TransactionData transactionData;
+
+		public NewTransactionEvent(TransactionData transactionData) {
+			this.transactionData = transactionData;
+		}
+
+		public TransactionData getTransactionData() {
+			return this.transactionData;
+		}
+	}
+
+	/**
+	 * Callback for when we've received a new transaction via API or peer.
+	 * <p>
+	 * @implSpec performs actions in a new thread
+	 */
+	public void onNewTransaction(TransactionData transactionData) {
 		this.callbackExecutor.execute(() -> {
-			// Notify all peers (except maybe peer that sent it to us if applicable)
-			Network.getInstance().broadcast(broadcastPeer -> broadcastPeer == peer ? null : new TransactionSignaturesMessage(Arrays.asList(transactionData.getSignature())));
+			// Notify all peers
+			Message newTransactionSignatureMessage = new TransactionSignaturesMessage(Arrays.asList(transactionData.getSignature()));
+			Network.getInstance().broadcast(broadcastPeer -> newTransactionSignatureMessage);
+
+			// Notify listeners
+			EventBus.INSTANCE.notify(new NewTransactionEvent(transactionData));
 
 			// If this is a CHAT transaction, there may be extra listeners to notify
 			if (transactionData.getType() == TransactionType.CHAT)
@@ -890,21 +1235,62 @@ public class Controller extends Thread {
 	private void onNetworkGetBlockMessage(Peer peer, Message message) {
 		GetBlockMessage getBlockMessage = (GetBlockMessage) message;
 		byte[] signature = getBlockMessage.getSignature();
+		this.stats.getBlockMessageStats.requests.incrementAndGet();
+
+		ByteArray signatureAsByteArray = new ByteArray(signature);
+
+		CachedBlockMessage cachedBlockMessage = this.blockMessageCache.get(signatureAsByteArray);
+		int blockCacheSize = Settings.getInstance().getBlockCacheSize();
+
+		// Check cached latest block message
+		if (cachedBlockMessage != null) {
+			this.stats.getBlockMessageStats.cacheHits.incrementAndGet();
+
+			// We need to duplicate it to prevent multiple threads setting ID on the same message
+			CachedBlockMessage clonedBlockMessage = cachedBlockMessage.cloneWithNewId(message.getId());
+
+			if (!peer.sendMessage(clonedBlockMessage))
+				peer.disconnect("failed to send block");
+
+			return;
+		}
 
 		try (final Repository repository = RepositoryManager.getRepository()) {
 			BlockData blockData = repository.getBlockRepository().fromSignature(signature);
+
 			if (blockData == null) {
-				LOGGER.debug(() -> String.format("Ignoring GET_BLOCK request from peer %s for unknown block %s", peer, Base58.encode(signature)));
-				// Send no response at all???
+				// We don't have this block
+				this.stats.getBlockMessageStats.unknownBlocks.getAndIncrement();
+
+				// Send valid, yet unexpected message type in response, so peer's synchronizer doesn't have to wait for timeout
+				LOGGER.debug(() -> String.format("Sending 'block unknown' response to peer %s for GET_BLOCK request for unknown block %s", peer, Base58.encode(signature)));
+
+				// We'll send empty block summaries message as it's very short
+				Message blockUnknownMessage = new BlockSummariesMessage(Collections.emptyList());
+				blockUnknownMessage.setId(message.getId());
+				if (!peer.sendMessage(blockUnknownMessage))
+					peer.disconnect("failed to send block-unknown response");
 				return;
 			}
 
 			Block block = new Block(repository, blockData);
 
-			Message blockMessage = new BlockMessage(block);
+			CachedBlockMessage blockMessage = new CachedBlockMessage(block);
 			blockMessage.setId(message.getId());
-			if (!peer.sendMessage(blockMessage))
+
+			// This call also causes the other needed data to be pulled in from repository
+			if (!peer.sendMessage(blockMessage)) {
 				peer.disconnect("failed to send block");
+				// Don't fall-through to caching because failure to send might be from failure to build message
+				return;
+			}
+
+			// If request is for a recent block, cache it
+			if (getChainHeight() - blockData.getHeight() <= blockCacheSize) {
+				this.stats.getBlockMessageStats.cacheFills.incrementAndGet();
+
+				this.blockMessageCache.put(new ByteArray(blockData.getSignature()), blockMessage);
+			}
 		} catch (DataException e) {
 			LOGGER.error(String.format("Repository issue while send block %s to peer %s", Base58.encode(signature), peer), e);
 		}
@@ -914,6 +1300,18 @@ public class Controller extends Thread {
 		TransactionMessage transactionMessage = (TransactionMessage) message;
 		TransactionData transactionData = transactionMessage.getTransactionData();
 
+		/*
+		 *  If we can't obtain blockchain lock immediately,
+		 *  e.g. Synchronizer is active, or another transaction is taking a while to validate,
+		 *  then we're using up a network thread for ages and clogging things up
+		 *  so bail out early
+		 */
+		ReentrantLock blockchainLock = Controller.getInstance().getBlockchainLock();
+		if (!blockchainLock.tryLock()) {
+			LOGGER.trace(() -> String.format("Too busy to import %s transaction %s from peer %s", transactionData.getType().name(), Base58.encode(transactionData.getSignature()), peer));
+			return;
+		}
+
 		try (final Repository repository = RepositoryManager.getRepository()) {
 			Transaction transaction = Transaction.fromData(repository, transactionData);
 
@@ -943,67 +1341,117 @@ public class Controller extends Thread {
 			LOGGER.debug(() -> String.format("Imported %s transaction %s from peer %s", transactionData.getType().name(), Base58.encode(transactionData.getSignature()), peer));
 		} catch (DataException e) {
 			LOGGER.error(String.format("Repository issue while processing transaction %s from peer %s", Base58.encode(transactionData.getSignature()), peer), e);
+		} finally {
+			blockchainLock.unlock();
 		}
-
-		// Notify controller so it can notify other peers, etc.
-		Controller.getInstance().onNewTransaction(transactionData, peer);
 	}
 
 	private void onNetworkGetBlockSummariesMessage(Peer peer, Message message) {
 		GetBlockSummariesMessage getBlockSummariesMessage = (GetBlockSummariesMessage) message;
-		byte[] parentSignature = getBlockSummariesMessage.getParentSignature();
+		final byte[] parentSignature = getBlockSummariesMessage.getParentSignature();
+		this.stats.getBlockSummariesStats.requests.incrementAndGet();
 
-		try (final Repository repository = RepositoryManager.getRepository()) {
-			List<BlockSummaryData> blockSummaries = new ArrayList<>();
-
-			int numberRequested = Math.min(Network.MAX_BLOCK_SUMMARIES_PER_REPLY, getBlockSummariesMessage.getNumberRequested());
-
-			do {
-				BlockData blockData = repository.getBlockRepository().fromReference(parentSignature);
-
-				if (blockData == null)
-					// No more blocks to send to peer
-					break;
-
-				BlockSummaryData blockSummary = new BlockSummaryData(blockData);
-				blockSummaries.add(blockSummary);
-				parentSignature = blockData.getSignature();
-			} while (blockSummaries.size() < numberRequested);
-
-			Message blockSummariesMessage = new BlockSummariesMessage(blockSummaries);
+		// If peer's parent signature matches our latest block signature
+		// then we can short-circuit with an empty response
+		BlockData chainTip = getChainTip();
+		if (chainTip != null && Arrays.equals(parentSignature, chainTip.getSignature())) {
+			Message blockSummariesMessage = new BlockSummariesMessage(Collections.emptyList());
 			blockSummariesMessage.setId(message.getId());
 			if (!peer.sendMessage(blockSummariesMessage))
 				peer.disconnect("failed to send block summaries");
-		} catch (DataException e) {
-			LOGGER.error(String.format("Repository issue while sending block summaries after %s to peer %s", Base58.encode(parentSignature), peer), e);
+
+			return;
 		}
+
+		List<BlockSummaryData> blockSummaries = new ArrayList<>();
+
+		// Attempt to serve from our cache of latest blocks
+		synchronized (this.latestBlocks) {
+			blockSummaries = this.latestBlocks.stream()
+					.dropWhile(cachedBlockData -> !Arrays.equals(cachedBlockData.getReference(), parentSignature))
+					.map(BlockSummaryData::new)
+					.collect(Collectors.toList());
+		}
+
+		if (blockSummaries.isEmpty()) {
+			try (final Repository repository = RepositoryManager.getRepository()) {
+				int numberRequested = Math.min(Network.MAX_BLOCK_SUMMARIES_PER_REPLY, getBlockSummariesMessage.getNumberRequested());
+
+				BlockData blockData = repository.getBlockRepository().fromReference(parentSignature);
+
+				while (blockData != null && blockSummaries.size() < numberRequested) {
+					BlockSummaryData blockSummary = new BlockSummaryData(blockData);
+					blockSummaries.add(blockSummary);
+
+					blockData = repository.getBlockRepository().fromReference(blockData.getSignature());
+				}
+			} catch (DataException e) {
+				LOGGER.error(String.format("Repository issue while sending block summaries after %s to peer %s", Base58.encode(parentSignature), peer), e);
+			}
+		} else {
+			this.stats.getBlockSummariesStats.cacheHits.incrementAndGet();
+
+			if (blockSummaries.size() >= getBlockSummariesMessage.getNumberRequested())
+				this.stats.getBlockSummariesStats.fullyFromCache.incrementAndGet();
+		}
+
+		Message blockSummariesMessage = new BlockSummariesMessage(blockSummaries);
+		blockSummariesMessage.setId(message.getId());
+		if (!peer.sendMessage(blockSummariesMessage))
+			peer.disconnect("failed to send block summaries");
 	}
 
 	private void onNetworkGetSignaturesV2Message(Peer peer, Message message) {
 		GetSignaturesV2Message getSignaturesMessage = (GetSignaturesV2Message) message;
-		byte[] parentSignature = getSignaturesMessage.getParentSignature();
+		final byte[] parentSignature = getSignaturesMessage.getParentSignature();
+		this.stats.getBlockSignaturesV2Stats.requests.incrementAndGet();
 
-		try (final Repository repository = RepositoryManager.getRepository()) {
-			List<byte[]> signatures = new ArrayList<>();
-
-			do {
-				BlockData blockData = repository.getBlockRepository().fromReference(parentSignature);
-
-				if (blockData == null)
-					// No more signatures to send to peer
-					break;
-
-				parentSignature = blockData.getSignature();
-				signatures.add(parentSignature);
-			} while (signatures.size() < getSignaturesMessage.getNumberRequested());
-
-			Message signaturesMessage = new SignaturesMessage(signatures);
+		// If peer's parent signature matches our latest block signature
+		// then we can short-circuit with an empty response
+		BlockData chainTip = getChainTip();
+		if (chainTip != null && Arrays.equals(parentSignature, chainTip.getSignature())) {
+			Message signaturesMessage = new SignaturesMessage(Collections.emptyList());
 			signaturesMessage.setId(message.getId());
 			if (!peer.sendMessage(signaturesMessage))
 				peer.disconnect("failed to send signatures (v2)");
-		} catch (DataException e) {
-			LOGGER.error(String.format("Repository issue while sending V2 signatures after %s to peer %s", Base58.encode(parentSignature), peer), e);
+
+			return;
 		}
+
+		List<byte[]> signatures = new ArrayList<>();
+
+		// Attempt to serve from our cache of latest blocks
+		synchronized (this.latestBlocks) {
+			signatures = this.latestBlocks.stream()
+					.dropWhile(cachedBlockData -> !Arrays.equals(cachedBlockData.getReference(), parentSignature))
+					.map(BlockData::getSignature)
+					.collect(Collectors.toList());
+		}
+
+		if (signatures.isEmpty()) {
+			try (final Repository repository = RepositoryManager.getRepository()) {
+				int numberRequested = getSignaturesMessage.getNumberRequested();
+				BlockData blockData = repository.getBlockRepository().fromReference(parentSignature);
+
+				while (blockData != null && signatures.size() < numberRequested) {
+					signatures.add(blockData.getSignature());
+
+					blockData = repository.getBlockRepository().fromReference(blockData.getSignature());
+				}
+			} catch (DataException e) {
+				LOGGER.error(String.format("Repository issue while sending V2 signatures after %s to peer %s", Base58.encode(parentSignature), peer), e);
+			}
+		} else {
+			this.stats.getBlockSignaturesV2Stats.cacheHits.incrementAndGet();
+
+			if (signatures.size() >= getSignaturesMessage.getNumberRequested())
+				this.stats.getBlockSignaturesV2Stats.fullyFromCache.incrementAndGet();
+		}
+
+		Message signaturesMessage = new SignaturesMessage(signatures);
+		signaturesMessage.setId(message.getId());
+		if (!peer.sendMessage(signaturesMessage))
+			peer.disconnect("failed to send signatures (v2)");
 	}
 
 	private void onNetworkHeightV2Message(Peer peer, Message message) {
@@ -1353,9 +1801,6 @@ public class Controller extends Thread {
 
 		// Refresh our online accounts signatures?
 		sendOurOnlineAccountsInfo();
-
-		// Trim blockchain by removing 'old' online accounts signatures
-		BlockChain.trimOldOnlineAccountsSignatures();
 	}
 
 	private void sendOurOnlineAccountsInfo() {
@@ -1457,6 +1902,32 @@ public class Controller extends Thread {
 		}
 	}
 
+	/** Returns cached, unmodifiable list of latest block's online accounts. */
+	public List<OnlineAccountData> getLatestBlocksOnlineAccounts() {
+		synchronized (this.latestBlocksOnlineAccounts) {
+			return this.latestBlocksOnlineAccounts.peekFirst();
+		}
+	}
+
+	/** Caches list of latest block's online accounts. Typically called by Block.process() */
+	public void pushLatestBlocksOnlineAccounts(List<OnlineAccountData> latestBlocksOnlineAccounts) {
+		synchronized (this.latestBlocksOnlineAccounts) {
+			if (this.latestBlocksOnlineAccounts.size() == MAX_BLOCKS_CACHED_ONLINE_ACCOUNTS)
+				this.latestBlocksOnlineAccounts.pollLast();
+
+			this.latestBlocksOnlineAccounts.addFirst(latestBlocksOnlineAccounts == null
+					? Collections.emptyList()
+					: Collections.unmodifiableList(latestBlocksOnlineAccounts));
+		}
+	}
+
+	/** Reverts list of latest block's online accounts. Typically called by Block.orphan() */
+	public void popLatestBlocksOnlineAccounts() {
+		synchronized (this.latestBlocksOnlineAccounts) {
+			this.latestBlocksOnlineAccounts.pollFirst();
+		}
+	}
+
 	public byte[] fetchArbitraryData(byte[] signature) throws InterruptedException {
 		// Build request
 		Message getArbitraryDataMessage = new GetArbitraryDataMessage(signature);
@@ -1591,4 +2062,8 @@ public class Controller extends Thread {
 		return now - offset;
 	}
 
+	public StatsSnapshot getStatsSnapshot() {
+		return this.stats;
+	}
+
 }

src/main/java/org/qortal/controller/OnlineAccountsSignaturesTrimmer.java

@@ -0,0 +1,79 @@
+package org.qortal.controller;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.qortal.block.BlockChain;
+import org.qortal.data.block.BlockData;
+import org.qortal.repository.DataException;
+import org.qortal.repository.Repository;
+import org.qortal.repository.RepositoryManager;
+import org.qortal.settings.Settings;
+import org.qortal.utils.NTP;
+
+public class OnlineAccountsSignaturesTrimmer implements Runnable {
+
+	private static final Logger LOGGER = LogManager.getLogger(OnlineAccountsSignaturesTrimmer.class);
+
+	private static final long INITIAL_SLEEP_PERIOD = 5 * 60 * 1000L + 1234L; // ms
+
+	public void run() {
+		Thread.currentThread().setName("Online Accounts trimmer");
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			// Don't even start trimming until initial rush has ended
+			Thread.sleep(INITIAL_SLEEP_PERIOD);
+
+			int trimStartHeight = repository.getBlockRepository().getOnlineAccountsSignaturesTrimHeight();
+
+			while (!Controller.isStopping()) {
+				repository.discardChanges();
+
+				Thread.sleep(Settings.getInstance().getOnlineSignaturesTrimInterval());
+
+				BlockData chainTip = Controller.getInstance().getChainTip();
+				if (chainTip == null || NTP.getTime() == null)
+					continue;
+
+				// Don't even attempt if we're mid-sync as our repository requests will be delayed for ages
+				if (Controller.getInstance().isSynchronizing())
+					continue;
+
+				// Trim blockchain by removing 'old' online accounts signatures
+				long upperTrimmableTimestamp = NTP.getTime() - BlockChain.getInstance().getOnlineAccountSignaturesMaxLifetime();
+				int upperTrimmableHeight = repository.getBlockRepository().getHeightFromTimestamp(upperTrimmableTimestamp);
+
+				int upperBatchHeight = trimStartHeight + Settings.getInstance().getOnlineSignaturesTrimBatchSize();
+				int upperTrimHeight = Math.min(upperBatchHeight, upperTrimmableHeight);
+
+				if (trimStartHeight >= upperTrimHeight)
+					continue;
+
+				int numSigsTrimmed = repository.getBlockRepository().trimOldOnlineAccountsSignatures(trimStartHeight, upperTrimHeight);
+				repository.saveChanges();
+
+				if (numSigsTrimmed > 0) {
+					final int finalTrimStartHeight = trimStartHeight;
+					LOGGER.debug(() -> String.format("Trimmed %d online accounts signature%s between blocks %d and %d",
+							numSigsTrimmed, (numSigsTrimmed != 1 ? "s" : ""),
+							finalTrimStartHeight, upperTrimHeight));
+				} else {
+					// Can we move onto next batch?
+					if (upperTrimmableHeight > upperBatchHeight) {
+						trimStartHeight = upperBatchHeight;
+
+						repository.getBlockRepository().setOnlineAccountsSignaturesTrimHeight(trimStartHeight);
+						repository.saveChanges();
+
+						final int finalTrimStartHeight = trimStartHeight;
+						LOGGER.debug(() -> String.format("Bumping online accounts signatures base trim height to %d", finalTrimStartHeight));
+					}
+				}
+			}
+		} catch (DataException e) {
+			LOGGER.warn(String.format("Repository issue trying to trim online accounts signatures: %s", e.getMessage()));
+		} catch (InterruptedException e) {
+			// Time to exit
+		}
+	}
+
+}

src/main/java/org/qortal/controller/StatusNotifier.java

@@ -1,56 +0,0 @@
-package org.qortal.controller;
-
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.HashMap;
-import java.util.Map;
-
-import org.eclipse.jetty.websocket.api.Session;
-
-public class StatusNotifier {
-
-	private static StatusNotifier instance;
-
-	@FunctionalInterface
-	public interface Listener {
-		void notify(long timestamp);
-	}
-
-	private Map<Session, Listener> listenersBySession = new HashMap<>();
-
-	private StatusNotifier() {
-	}
-
-	public static synchronized StatusNotifier getInstance() {
-		if (instance == null)
-			instance = new StatusNotifier();
-
-		return instance;
-	}
-
-	public void register(Session session, Listener listener) {
-		synchronized (this.listenersBySession) {
-			this.listenersBySession.put(session, listener);
-		}
-	}
-
-	public void deregister(Session session) {
-		synchronized (this.listenersBySession) {
-			this.listenersBySession.remove(session);
-		}
-	}
-
-	public void onStatusChange(long now) {
-		for (Listener listener : getAllListeners())
-			listener.notify(now);
-	}
-
-	private Collection<Listener> getAllListeners() {
-		// Make a copy of listeners to both avoid concurrent modification
-		// and reduce synchronization time
-		synchronized (this.listenersBySession) {
-			return new ArrayList<>(this.listenersBySession.values());
-		}
-	}
-
-}

src/main/java/org/qortal/controller/tradebot/AcctTradeBot.java

@@ -0,0 +1,30 @@
+package org.qortal.controller.tradebot;
+
+import java.util.List;
+
+import org.qortal.api.model.crosschain.TradeBotCreateRequest;
+import org.qortal.crosschain.ACCT;
+import org.qortal.crosschain.ForeignBlockchainException;
+import org.qortal.data.at.ATData;
+import org.qortal.data.crosschain.CrossChainTradeData;
+import org.qortal.data.crosschain.TradeBotData;
+import org.qortal.repository.DataException;
+import org.qortal.repository.Repository;
+
+public interface AcctTradeBot {
+
+	public enum ResponseResult { OK, BALANCE_ISSUE, NETWORK_ISSUE, TRADE_ALREADY_EXISTS }
+
+	/** Returns list of state names for trade-bot entries that have ended, e.g. redeemed, refunded or cancelled. */
+	public List<String> getEndStates();
+
+	public byte[] createTrade(Repository repository, TradeBotCreateRequest tradeBotCreateRequest) throws DataException;
+
+	public ResponseResult startResponse(Repository repository, ATData atData, ACCT acct,
+			CrossChainTradeData crossChainTradeData, String foreignKey, String receivingAddress) throws DataException;
+
+	public boolean canDelete(Repository repository, TradeBotData tradeBotData) throws DataException;
+
+	public void progress(Repository repository, TradeBotData tradeBotData) throws DataException, ForeignBlockchainException;
+
+}

src/main/java/org/qortal/controller/tradebot/LitecoinACCTv1TradeBot.java

@@ -0,0 +1,903 @@
+package org.qortal.controller.tradebot;
+
+import static java.util.Arrays.stream;
+import static java.util.stream.Collectors.toMap;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.bitcoinj.core.Address;
+import org.bitcoinj.core.AddressFormatException;
+import org.bitcoinj.core.Coin;
+import org.bitcoinj.core.ECKey;
+import org.bitcoinj.core.Transaction;
+import org.bitcoinj.core.TransactionOutput;
+import org.bitcoinj.script.Script.ScriptType;
+import org.qortal.account.PrivateKeyAccount;
+import org.qortal.account.PublicKeyAccount;
+import org.qortal.api.model.crosschain.TradeBotCreateRequest;
+import org.qortal.asset.Asset;
+import org.qortal.crosschain.ACCT;
+import org.qortal.crosschain.AcctMode;
+import org.qortal.crosschain.ForeignBlockchainException;
+import org.qortal.crosschain.Litecoin;
+import org.qortal.crosschain.LitecoinACCTv1;
+import org.qortal.crosschain.SupportedBlockchain;
+import org.qortal.crosschain.BitcoinyHTLC;
+import org.qortal.crypto.Crypto;
+import org.qortal.data.at.ATData;
+import org.qortal.data.crosschain.CrossChainTradeData;
+import org.qortal.data.crosschain.TradeBotData;
+import org.qortal.data.transaction.BaseTransactionData;
+import org.qortal.data.transaction.DeployAtTransactionData;
+import org.qortal.data.transaction.MessageTransactionData;
+import org.qortal.group.Group;
+import org.qortal.repository.DataException;
+import org.qortal.repository.Repository;
+import org.qortal.transaction.DeployAtTransaction;
+import org.qortal.transaction.MessageTransaction;
+import org.qortal.transaction.Transaction.ValidationResult;
+import org.qortal.transform.TransformationException;
+import org.qortal.transform.transaction.DeployAtTransactionTransformer;
+import org.qortal.utils.Base58;
+import org.qortal.utils.NTP;
+
+/**
+ * Performing cross-chain trading steps on behalf of user.
+ * <p>
+ * We deal with three different independent state-spaces here:
+ * <ul>
+ * 	<li>Qortal blockchain</li>
+ * 	<li>Foreign blockchain</li>
+ * 	<li>Trade-bot entries</li>
+ * </ul>
+ */
+public class LitecoinACCTv1TradeBot implements AcctTradeBot {
+
+	private static final Logger LOGGER = LogManager.getLogger(LitecoinACCTv1TradeBot.class);
+
+	public enum State implements TradeBot.StateNameAndValueSupplier {
+		BOB_WAITING_FOR_AT_CONFIRM(10, false, false),
+		BOB_WAITING_FOR_MESSAGE(15, true, true),
+		BOB_WAITING_FOR_AT_REDEEM(25, true, true),
+		BOB_DONE(30, false, false),
+		BOB_REFUNDED(35, false, false),
+
+		ALICE_WAITING_FOR_AT_LOCK(85, true, true),
+		ALICE_DONE(95, false, false),
+		ALICE_REFUNDING_A(105, true, true),
+		ALICE_REFUNDED(110, false, false);
+
+		private static final Map<Integer, State> map = stream(State.values()).collect(toMap(state -> state.value, state -> state));
+
+		public final int value;
+		public final boolean requiresAtData;
+		public final boolean requiresTradeData;
+
+		State(int value, boolean requiresAtData, boolean requiresTradeData) {
+			this.value = value;
+			this.requiresAtData = requiresAtData;
+			this.requiresTradeData = requiresTradeData;
+		}
+
+		public static State valueOf(int value) {
+			return map.get(value);
+		}
+
+		@Override
+		public String getState() {
+			return this.name();
+		}
+
+		@Override
+		public int getStateValue() {
+			return this.value;
+		}
+	}
+
+	/** Maximum time Bob waits for his AT creation transaction to be confirmed into a block. (milliseconds) */
+	private static final long MAX_AT_CONFIRMATION_PERIOD = 24 * 60 * 60 * 1000L; // ms
+
+	private static LitecoinACCTv1TradeBot instance;
+
+	private final List<String> endStates = Arrays.asList(State.BOB_DONE, State.BOB_REFUNDED, State.ALICE_DONE, State.ALICE_REFUNDING_A, State.ALICE_REFUNDED).stream()
+			.map(State::name)
+			.collect(Collectors.toUnmodifiableList());
+
+	private LitecoinACCTv1TradeBot() {
+	}
+
+	public static synchronized LitecoinACCTv1TradeBot getInstance() {
+		if (instance == null)
+			instance = new LitecoinACCTv1TradeBot();
+
+		return instance;
+	}
+
+	@Override
+	public List<String> getEndStates() {
+		return this.endStates;
+	}
+
+	/**
+	 * Creates a new trade-bot entry from the "Bob" viewpoint, i.e. OFFERing QORT in exchange for LTC.
+	 * <p>
+	 * Generates:
+	 * <ul>
+	 * 	<li>new 'trade' private key</li>
+	 * </ul>
+	 * Derives:
+	 * <ul>
+	 * 	<li>'native' (as in Qortal) public key, public key hash, address (starting with Q)</li>
+	 * 	<li>'foreign' (as in Litecoin) public key, public key hash</li>
+	 * </ul>
+	 * A Qortal AT is then constructed including the following as constants in the 'data segment':
+	 * <ul>
+	 * 	<li>'native'/Qortal 'trade' address - used as a MESSAGE contact</li>
+	 * 	<li>'foreign'/Litecoin public key hash - used by Alice's P2SH scripts to allow redeem</li>
+	 * 	<li>QORT amount on offer by Bob</li>
+	 * 	<li>LTC amount expected in return by Bob (from Alice)</li>
+	 * 	<li>trading timeout, in case things go wrong and everyone needs to refund</li>
+	 * </ul>
+	 * Returns a DEPLOY_AT transaction that needs to be signed and broadcast to the Qortal network.
+	 * <p>
+	 * Trade-bot will wait for Bob's AT to be deployed before taking next step.
+	 * <p>
+	 * @param repository
+	 * @param tradeBotCreateRequest
+	 * @return raw, unsigned DEPLOY_AT transaction
+	 * @throws DataException
+	 */
+	public byte[] createTrade(Repository repository, TradeBotCreateRequest tradeBotCreateRequest) throws DataException {
+		byte[] tradePrivateKey = TradeBot.generateTradePrivateKey();
+
+		byte[] tradeNativePublicKey = TradeBot.deriveTradeNativePublicKey(tradePrivateKey);
+		byte[] tradeNativePublicKeyHash = Crypto.hash160(tradeNativePublicKey);
+		String tradeNativeAddress = Crypto.toAddress(tradeNativePublicKey);
+
+		byte[] tradeForeignPublicKey = TradeBot.deriveTradeForeignPublicKey(tradePrivateKey);
+		byte[] tradeForeignPublicKeyHash = Crypto.hash160(tradeForeignPublicKey);
+
+		// Convert Litecoin receiving address into public key hash (we only support P2PKH at this time)
+		Address litecoinReceivingAddress;
+		try {
+			litecoinReceivingAddress = Address.fromString(Litecoin.getInstance().getNetworkParameters(), tradeBotCreateRequest.receivingAddress);
+		} catch (AddressFormatException e) {
+			throw new DataException("Unsupported Litecoin receiving address: " + tradeBotCreateRequest.receivingAddress);
+		}
+		if (litecoinReceivingAddress.getOutputScriptType() != ScriptType.P2PKH)
+			throw new DataException("Unsupported Litecoin receiving address: " + tradeBotCreateRequest.receivingAddress);
+
+		byte[] litecoinReceivingAccountInfo = litecoinReceivingAddress.getHash();
+
+		PublicKeyAccount creator = new PublicKeyAccount(repository, tradeBotCreateRequest.creatorPublicKey);
+
+		// Deploy AT
+		long timestamp = NTP.getTime();
+		byte[] reference = creator.getLastReference();
+		long fee = 0L;
+		byte[] signature = null;
+		BaseTransactionData baseTransactionData = new BaseTransactionData(timestamp, Group.NO_GROUP, reference, creator.getPublicKey(), fee, signature);
+
+		String name = "QORT/LTC ACCT";
+		String description = "QORT/LTC cross-chain trade";
+		String aTType = "ACCT";
+		String tags = "ACCT QORT LTC";
+		byte[] creationBytes = LitecoinACCTv1.buildQortalAT(tradeNativeAddress, tradeForeignPublicKeyHash, tradeBotCreateRequest.qortAmount,
+				tradeBotCreateRequest.foreignAmount, tradeBotCreateRequest.tradeTimeout);
+		long amount = tradeBotCreateRequest.fundingQortAmount;
+
+		DeployAtTransactionData deployAtTransactionData = new DeployAtTransactionData(baseTransactionData, name, description, aTType, tags, creationBytes, amount, Asset.QORT);
+
+		DeployAtTransaction deployAtTransaction = new DeployAtTransaction(repository, deployAtTransactionData);
+		fee = deployAtTransaction.calcRecommendedFee();
+		deployAtTransactionData.setFee(fee);
+
+		DeployAtTransaction.ensureATAddress(deployAtTransactionData);
+		String atAddress = deployAtTransactionData.getAtAddress();
+
+		TradeBotData tradeBotData =  new TradeBotData(tradePrivateKey, LitecoinACCTv1.NAME,
+				State.BOB_WAITING_FOR_AT_CONFIRM.name(), State.BOB_WAITING_FOR_AT_CONFIRM.value,
+				creator.getAddress(), atAddress, timestamp, tradeBotCreateRequest.qortAmount,
+				tradeNativePublicKey, tradeNativePublicKeyHash, tradeNativeAddress,
+				null, null,
+				SupportedBlockchain.LITECOIN.name(),
+				tradeForeignPublicKey, tradeForeignPublicKeyHash,
+				tradeBotCreateRequest.foreignAmount, null, null, null, litecoinReceivingAccountInfo);
+
+		TradeBot.updateTradeBotState(repository, tradeBotData, () -> String.format("Built AT %s. Waiting for deployment", atAddress));
+
+		// Attempt to backup the trade bot data
+		TradeBot.backupTradeBotData(repository);
+
+		// Return to user for signing and broadcast as we don't have their Qortal private key
+		try {
+			return DeployAtTransactionTransformer.toBytes(deployAtTransactionData);
+		} catch (TransformationException e) {
+			throw new DataException("Failed to transform DEPLOY_AT transaction?", e);
+		}
+	}
+
+	/**
+	 * Creates a trade-bot entry from the 'Alice' viewpoint, i.e. matching LTC to an existing offer.
+	 * <p>
+	 * Requires a chosen trade offer from Bob, passed by <tt>crossChainTradeData</tt>
+	 * and access to a Litecoin wallet via <tt>xprv58</tt>.
+	 * <p>
+	 * The <tt>crossChainTradeData</tt> contains the current trade offer state
+	 * as extracted from the AT's data segment.
+	 * <p>
+	 * Access to a funded wallet is via a Litecoin BIP32 hierarchical deterministic key,
+	 * passed via <tt>xprv58</tt>.
+	 * <b>This key will be stored in your node's database</b>
+	 * to allow trade-bot to create/fund the necessary P2SH transactions!
+	 * However, due to the nature of BIP32 keys, it is possible to give the trade-bot
+	 * only a subset of wallet access (see BIP32 for more details).
+	 * <p>
+	 * As an example, the xprv58 can be extract from a <i>legacy, password-less</i>
+	 * Electrum wallet by going to the console tab and entering:<br>
+	 * <tt>wallet.keystore.xprv</tt><br>
+	 * which should result in a base58 string starting with either 'xprv' (for Litecoin main-net)
+	 * or 'tprv' for (Litecoin test-net).
+	 * <p>
+	 * It is envisaged that the value in <tt>xprv58</tt> will actually come from a Qortal-UI-managed wallet.
+	 * <p>
+	 * If sufficient funds are available, <b>this method will actually fund the P2SH-A</b>
+	 * with the Litecoin amount expected by 'Bob'.
+	 * <p>
+	 * If the Litecoin transaction is successfully broadcast to the network then
+	 * we also send a MESSAGE to Bob's trade-bot to let them know.
+	 * <p>
+	 * The trade-bot entry is saved to the repository and the cross-chain trading process commences.
+	 * <p>
+	 * @param repository
+	 * @param crossChainTradeData chosen trade OFFER that Alice wants to match
+	 * @param xprv58 funded wallet xprv in base58
+	 * @return true if P2SH-A funding transaction successfully broadcast to Litecoin network, false otherwise
+	 * @throws DataException
+	 */
+	public ResponseResult startResponse(Repository repository, ATData atData, ACCT acct, CrossChainTradeData crossChainTradeData, String xprv58, String receivingAddress) throws DataException {
+		byte[] tradePrivateKey = TradeBot.generateTradePrivateKey();
+		byte[] secretA = TradeBot.generateSecret();
+		byte[] hashOfSecretA = Crypto.hash160(secretA);
+
+		byte[] tradeNativePublicKey = TradeBot.deriveTradeNativePublicKey(tradePrivateKey);
+		byte[] tradeNativePublicKeyHash = Crypto.hash160(tradeNativePublicKey);
+		String tradeNativeAddress = Crypto.toAddress(tradeNativePublicKey);
+
+		byte[] tradeForeignPublicKey = TradeBot.deriveTradeForeignPublicKey(tradePrivateKey);
+		byte[] tradeForeignPublicKeyHash = Crypto.hash160(tradeForeignPublicKey);
+		byte[] receivingPublicKeyHash = Base58.decode(receivingAddress); // Actually the whole address, not just PKH
+
+		// We need to generate lockTime-A: add tradeTimeout to now
+		long now = NTP.getTime();
+		int lockTimeA = crossChainTradeData.tradeTimeout * 60 + (int) (now / 1000L);
+
+		TradeBotData tradeBotData =  new TradeBotData(tradePrivateKey, LitecoinACCTv1.NAME,
+				State.ALICE_WAITING_FOR_AT_LOCK.name(), State.ALICE_WAITING_FOR_AT_LOCK.value,
+				receivingAddress, crossChainTradeData.qortalAtAddress, now, crossChainTradeData.qortAmount,
+				tradeNativePublicKey, tradeNativePublicKeyHash, tradeNativeAddress,
+				secretA, hashOfSecretA,
+				SupportedBlockchain.LITECOIN.name(),
+				tradeForeignPublicKey, tradeForeignPublicKeyHash,
+				crossChainTradeData.expectedForeignAmount, xprv58, null, lockTimeA, receivingPublicKeyHash);
+
+		// Attempt to backup the trade bot data
+		TradeBot.backupTradeBotData(repository);
+
+		// Check we have enough funds via xprv58 to fund P2SH to cover expectedForeignAmount
+		long p2shFee;
+		try {
+			p2shFee = Litecoin.getInstance().getP2shFee(now);
+		} catch (ForeignBlockchainException e) {
+			LOGGER.debug("Couldn't estimate Litecoin fees?");
+			return ResponseResult.NETWORK_ISSUE;
+		}
+
+		// Fee for redeem/refund is subtracted from P2SH-A balance.
+		// Do not include fee for funding transaction as this is covered by buildSpend()
+		long amountA = crossChainTradeData.expectedForeignAmount + p2shFee /*redeeming/refunding P2SH-A*/;
+
+		// P2SH-A to be funded
+		byte[] redeemScriptBytes = BitcoinyHTLC.buildScript(tradeForeignPublicKeyHash, lockTimeA, crossChainTradeData.creatorForeignPKH, hashOfSecretA);
+		String p2shAddress = Litecoin.getInstance().deriveP2shAddress(redeemScriptBytes);
+
+		// Build transaction for funding P2SH-A
+		Transaction p2shFundingTransaction = Litecoin.getInstance().buildSpend(tradeBotData.getForeignKey(), p2shAddress, amountA);
+		if (p2shFundingTransaction == null) {
+			LOGGER.debug("Unable to build P2SH-A funding transaction - lack of funds?");
+			return ResponseResult.BALANCE_ISSUE;
+		}
+
+		try {
+			Litecoin.getInstance().broadcastTransaction(p2shFundingTransaction);
+		} catch (ForeignBlockchainException e) {
+			// We couldn't fund P2SH-A at this time
+			LOGGER.debug("Couldn't broadcast P2SH-A funding transaction?");
+			return ResponseResult.NETWORK_ISSUE;
+		}
+
+		// Attempt to send MESSAGE to Bob's Qortal trade address
+		byte[] messageData = LitecoinACCTv1.buildOfferMessage(tradeBotData.getTradeForeignPublicKeyHash(), tradeBotData.getHashOfSecret(), tradeBotData.getLockTimeA());
+		String messageRecipient = crossChainTradeData.qortalCreatorTradeAddress;
+
+		boolean isMessageAlreadySent = repository.getMessageRepository().exists(tradeBotData.getTradeNativePublicKey(), messageRecipient, messageData);
+		if (!isMessageAlreadySent) {
+			PrivateKeyAccount sender = new PrivateKeyAccount(repository, tradeBotData.getTradePrivateKey());
+			MessageTransaction messageTransaction = MessageTransaction.build(repository, sender, Group.NO_GROUP, messageRecipient, messageData, false, false);
+
+			messageTransaction.computeNonce();
+			messageTransaction.sign(sender);
+
+			// reset repository state to prevent deadlock
+			repository.discardChanges();
+			ValidationResult result = messageTransaction.importAsUnconfirmed();
+
+			if (result != ValidationResult.OK) {
+				LOGGER.warn(() -> String.format("Unable to send MESSAGE to Bob's trade-bot %s: %s", messageRecipient, result.name()));
+				return ResponseResult.NETWORK_ISSUE;
+			}
+		}
+
+		TradeBot.updateTradeBotState(repository, tradeBotData, () -> String.format("Funding P2SH-A %s. Messaged Bob. Waiting for AT-lock", p2shAddress));
+
+		return ResponseResult.OK;
+	}
+
+	@Override
+	public boolean canDelete(Repository repository, TradeBotData tradeBotData) throws DataException {
+		State tradeBotState = State.valueOf(tradeBotData.getStateValue());
+		if (tradeBotState == null)
+			return true;
+
+		// If the AT doesn't exist then we might as well let the user tidy up
+		if (!repository.getATRepository().exists(tradeBotData.getAtAddress()))
+			return true;
+
+		switch (tradeBotState) {
+			case BOB_WAITING_FOR_AT_CONFIRM:
+			case ALICE_DONE:
+			case BOB_DONE:
+			case ALICE_REFUNDED:
+			case BOB_REFUNDED:
+				return true;
+
+			default:
+				return false;
+		}
+	}
+
+	@Override
+	public void progress(Repository repository, TradeBotData tradeBotData) throws DataException, ForeignBlockchainException {
+		State tradeBotState = State.valueOf(tradeBotData.getStateValue());
+		if (tradeBotState == null) {
+			LOGGER.info(() -> String.format("Trade-bot entry for AT %s has invalid state?", tradeBotData.getAtAddress()));
+			return;
+		}
+
+		ATData atData = null;
+		CrossChainTradeData tradeData = null;
+
+		if (tradeBotState.requiresAtData) {
+			// Attempt to fetch AT data
+			atData = repository.getATRepository().fromATAddress(tradeBotData.getAtAddress());
+			if (atData == null) {
+				LOGGER.debug(() -> String.format("Unable to fetch trade AT %s from repository", tradeBotData.getAtAddress()));
+
+				// If it has been over 24 hours since we last updated this trade-bot entry then assume AT is never coming back
+				// and so wipe the trade-bot entry
+				if (tradeBotData.getTimestamp() + MAX_AT_CONFIRMATION_PERIOD < NTP.getTime()) {
+					LOGGER.info(() -> String.format("AT %s has been gone for too long - deleting trade-bot entry", tradeBotData.getAtAddress()));
+					repository.getCrossChainRepository().delete(tradeBotData.getTradePrivateKey());
+					repository.saveChanges();
+				}
+
+				return;
+			}
+
+			if (tradeBotState.requiresTradeData) {
+				tradeData = LitecoinACCTv1.getInstance().populateTradeData(repository, atData);
+				if (tradeData == null) {
+					LOGGER.warn(() -> String.format("Unable to fetch ACCT trade data for AT %s from repository", tradeBotData.getAtAddress()));
+					return;
+				}
+			}
+		}
+
+		switch (tradeBotState) {
+			case BOB_WAITING_FOR_AT_CONFIRM:
+				handleBobWaitingForAtConfirm(repository, tradeBotData);
+				break;
+
+			case BOB_WAITING_FOR_MESSAGE:
+				TradeBot.getInstance().updatePresence(repository, tradeBotData, tradeData);
+				handleBobWaitingForMessage(repository, tradeBotData, atData, tradeData);
+				break;
+
+			case ALICE_WAITING_FOR_AT_LOCK:
+				TradeBot.getInstance().updatePresence(repository, tradeBotData, tradeData);
+				handleAliceWaitingForAtLock(repository, tradeBotData, atData, tradeData);
+				break;
+
+			case BOB_WAITING_FOR_AT_REDEEM:
+				TradeBot.getInstance().updatePresence(repository, tradeBotData, tradeData);
+				handleBobWaitingForAtRedeem(repository, tradeBotData, atData, tradeData);
+				break;
+
+			case ALICE_DONE:
+			case BOB_DONE:
+				break;
+
+			case ALICE_REFUNDING_A:
+				TradeBot.getInstance().updatePresence(repository, tradeBotData, tradeData);
+				handleAliceRefundingP2shA(repository, tradeBotData, atData, tradeData);
+				break;
+
+			case ALICE_REFUNDED:
+			case BOB_REFUNDED:
+				break;
+		}
+	}
+
+	/**
+	 * Trade-bot is waiting for Bob's AT to deploy.
+	 * <p>
+	 * If AT is deployed, then trade-bot's next step is to wait for MESSAGE from Alice.
+	 */
+	private void handleBobWaitingForAtConfirm(Repository repository, TradeBotData tradeBotData) throws DataException {
+		if (!repository.getATRepository().exists(tradeBotData.getAtAddress())) {
+			if (NTP.getTime() - tradeBotData.getTimestamp() <= MAX_AT_CONFIRMATION_PERIOD)
+				return;
+
+			// We've waited ages for AT to be confirmed into a block but something has gone awry.
+			// After this long we assume transaction loss so give up with trade-bot entry too.
+			tradeBotData.setState(State.BOB_REFUNDED.name());
+			tradeBotData.setStateValue(State.BOB_REFUNDED.value);
+			tradeBotData.setTimestamp(NTP.getTime());
+			// We delete trade-bot entry here instead of saving, hence not using updateTradeBotState()
+			repository.getCrossChainRepository().delete(tradeBotData.getTradePrivateKey());
+			repository.saveChanges();
+
+			LOGGER.info(() -> String.format("AT %s never confirmed. Giving up on trade", tradeBotData.getAtAddress()));
+			TradeBot.notifyStateChange(tradeBotData);
+			return;
+		}
+
+		TradeBot.updateTradeBotState(repository, tradeBotData, State.BOB_WAITING_FOR_MESSAGE,
+				() -> String.format("AT %s confirmed ready. Waiting for trade message", tradeBotData.getAtAddress()));
+	}
+
+	/**
+	 * Trade-bot is waiting for MESSAGE from Alice's trade-bot, containing Alice's trade info.
+	 * <p>
+	 * It's possible Bob has cancelling his trade offer, receiving an automatic QORT refund,
+	 * in which case trade-bot is done with this specific trade and finalizes on refunded state.
+	 * <p>
+	 * Assuming trade is still on offer, trade-bot checks the contents of MESSAGE from Alice's trade-bot.
+	 * <p>
+	 * Details from Alice are used to derive P2SH-A address and this is checked for funding balance.
+	 * <p>
+	 * Assuming P2SH-A has at least expected Litecoin balance,
+	 * Bob's trade-bot constructs a zero-fee, PoW MESSAGE to send to Bob's AT with more trade details.
+	 * <p>
+	 * On processing this MESSAGE, Bob's AT should switch into 'TRADE' mode and only trade with Alice.
+	 * <p>
+	 * Trade-bot's next step is to wait for Alice to redeem the AT, which will allow Bob to
+	 * extract secret-A needed to redeem Alice's P2SH.
+	 * @throws ForeignBlockchainException
+	 */
+	private void handleBobWaitingForMessage(Repository repository, TradeBotData tradeBotData,
+			ATData atData, CrossChainTradeData crossChainTradeData) throws DataException, ForeignBlockchainException {
+		// If AT has finished then Bob likely cancelled his trade offer
+		if (atData.getIsFinished()) {
+			TradeBot.updateTradeBotState(repository, tradeBotData, State.BOB_REFUNDED,
+					() -> String.format("AT %s cancelled - trading aborted", tradeBotData.getAtAddress()));
+			return;
+		}
+
+		Litecoin litecoin = Litecoin.getInstance();
+
+		String address = tradeBotData.getTradeNativeAddress();
+		List<MessageTransactionData> messageTransactionsData = repository.getMessageRepository().getMessagesByParticipants(null, address, null, null, null);
+
+		for (MessageTransactionData messageTransactionData : messageTransactionsData) {
+			if (messageTransactionData.isText())
+				continue;
+
+			// We're expecting: HASH160(secret-A), Alice's Litecoin pubkeyhash and lockTime-A
+			byte[] messageData = messageTransactionData.getData();
+			LitecoinACCTv1.OfferMessageData offerMessageData = LitecoinACCTv1.extractOfferMessageData(messageData);
+			if (offerMessageData == null)
+				continue;
+
+			byte[] aliceForeignPublicKeyHash = offerMessageData.partnerLitecoinPKH;
+			byte[] hashOfSecretA = offerMessageData.hashOfSecretA;
+			int lockTimeA = (int) offerMessageData.lockTimeA;
+			long messageTimestamp = messageTransactionData.getTimestamp();
+			int refundTimeout = LitecoinACCTv1.calcRefundTimeout(messageTimestamp, lockTimeA);
+
+			// Determine P2SH-A address and confirm funded
+			byte[] redeemScriptA = BitcoinyHTLC.buildScript(aliceForeignPublicKeyHash, lockTimeA, tradeBotData.getTradeForeignPublicKeyHash(), hashOfSecretA);
+			String p2shAddressA = litecoin.deriveP2shAddress(redeemScriptA);
+
+			long feeTimestamp = calcFeeTimestamp(lockTimeA, crossChainTradeData.tradeTimeout);
+			long p2shFee = Litecoin.getInstance().getP2shFee(feeTimestamp);
+			final long minimumAmountA = tradeBotData.getForeignAmount() + p2shFee;
+
+			BitcoinyHTLC.Status htlcStatusA = BitcoinyHTLC.determineHtlcStatus(litecoin.getBlockchainProvider(), p2shAddressA, minimumAmountA);
+
+			switch (htlcStatusA) {
+				case UNFUNDED:
+				case FUNDING_IN_PROGRESS:
+					// There might be another MESSAGE from someone else with an actually funded P2SH-A...
+					continue;
+
+				case REDEEM_IN_PROGRESS:
+				case REDEEMED:
+					// We've already redeemed this?
+					TradeBot.updateTradeBotState(repository, tradeBotData, State.BOB_DONE,
+							() -> String.format("P2SH-A %s already spent? Assuming trade complete", p2shAddressA));
+					return;
+
+				case REFUND_IN_PROGRESS:
+				case REFUNDED:
+					// This P2SH-A is burnt, but there might be another MESSAGE from someone else with an actually funded P2SH-A...
+					continue;
+
+				case FUNDED:
+					// Fall-through out of switch...
+					break;
+			}
+
+			// Good to go - send MESSAGE to AT
+
+			String aliceNativeAddress = Crypto.toAddress(messageTransactionData.getCreatorPublicKey());
+
+			// Build outgoing message, padding each part to 32 bytes to make it easier for AT to consume
+			byte[] outgoingMessageData = LitecoinACCTv1.buildTradeMessage(aliceNativeAddress, aliceForeignPublicKeyHash, hashOfSecretA, lockTimeA, refundTimeout);
+			String messageRecipient = tradeBotData.getAtAddress();
+
+			boolean isMessageAlreadySent = repository.getMessageRepository().exists(tradeBotData.getTradeNativePublicKey(), messageRecipient, outgoingMessageData);
+			if (!isMessageAlreadySent) {
+				PrivateKeyAccount sender = new PrivateKeyAccount(repository, tradeBotData.getTradePrivateKey());
+				MessageTransaction outgoingMessageTransaction = MessageTransaction.build(repository, sender, Group.NO_GROUP, messageRecipient, outgoingMessageData, false, false);
+
+				outgoingMessageTransaction.computeNonce();
+				outgoingMessageTransaction.sign(sender);
+
+				// reset repository state to prevent deadlock
+				repository.discardChanges();
+				ValidationResult result = outgoingMessageTransaction.importAsUnconfirmed();
+
+				if (result != ValidationResult.OK) {
+					LOGGER.warn(() -> String.format("Unable to send MESSAGE to AT %s: %s", messageRecipient, result.name()));
+					return;
+				}
+			}
+
+			TradeBot.updateTradeBotState(repository, tradeBotData, State.BOB_WAITING_FOR_AT_REDEEM,
+					() -> String.format("Locked AT %s to %s. Waiting for AT redeem", tradeBotData.getAtAddress(), aliceNativeAddress));
+
+			return;
+		}
+	}
+
+	/**
+	 * Trade-bot is waiting for Bob's AT to switch to TRADE mode and lock trade to Alice only.
+	 * <p>
+	 * It's possible that Bob has cancelled his trade offer in the mean time, or that somehow
+	 * this process has taken so long that we've reached P2SH-A's locktime, or that someone else
+	 * has managed to trade with Bob. In any of these cases, trade-bot switches to begin the refunding process.
+	 * <p>
+	 * Assuming Bob's AT is locked to Alice, trade-bot checks AT's state data to make sure it is correct.
+	 * <p>
+	 * If all is well, trade-bot then redeems AT using Alice's secret-A, releasing Bob's QORT to Alice.
+	 * <p>
+	 * In revealing a valid secret-A, Bob can then redeem the LTC funds from P2SH-A.
+	 * <p>
+	 * @throws ForeignBlockchainException
+	 */
+	private void handleAliceWaitingForAtLock(Repository repository, TradeBotData tradeBotData,
+			ATData atData, CrossChainTradeData crossChainTradeData) throws DataException, ForeignBlockchainException {
+		if (aliceUnexpectedState(repository, tradeBotData, atData, crossChainTradeData))
+			return;
+
+		Litecoin litecoin = Litecoin.getInstance();
+		int lockTimeA = tradeBotData.getLockTimeA();
+
+		// Refund P2SH-A if we've passed lockTime-A
+		if (NTP.getTime() >= lockTimeA * 1000L) {
+			byte[] redeemScriptA = BitcoinyHTLC.buildScript(tradeBotData.getTradeForeignPublicKeyHash(), lockTimeA, crossChainTradeData.creatorForeignPKH, tradeBotData.getHashOfSecret());
+			String p2shAddressA = litecoin.deriveP2shAddress(redeemScriptA);
+
+			long feeTimestamp = calcFeeTimestamp(lockTimeA, crossChainTradeData.tradeTimeout);
+			long p2shFee = Litecoin.getInstance().getP2shFee(feeTimestamp);
+			long minimumAmountA = crossChainTradeData.expectedForeignAmount + p2shFee;
+
+			BitcoinyHTLC.Status htlcStatusA = BitcoinyHTLC.determineHtlcStatus(litecoin.getBlockchainProvider(), p2shAddressA, minimumAmountA);
+
+			switch (htlcStatusA) {
+				case UNFUNDED:
+				case FUNDING_IN_PROGRESS:
+				case FUNDED:
+					break;
+
+				case REDEEM_IN_PROGRESS:
+				case REDEEMED:
+					// Already redeemed?
+					TradeBot.updateTradeBotState(repository, tradeBotData, State.ALICE_DONE,
+							() -> String.format("P2SH-A %s already spent? Assuming trade completed", p2shAddressA));
+					return;
+
+				case REFUND_IN_PROGRESS:
+				case REFUNDED:
+					TradeBot.updateTradeBotState(repository, tradeBotData, State.ALICE_REFUNDED,
+							() -> String.format("P2SH-A %s already refunded. Trade aborted", p2shAddressA));
+					return;
+
+			}
+
+			TradeBot.updateTradeBotState(repository, tradeBotData, State.ALICE_REFUNDING_A,
+					() -> atData.getIsFinished()
+					? String.format("AT %s cancelled. Refunding P2SH-A %s - aborting trade", tradeBotData.getAtAddress(), p2shAddressA)
+					: String.format("LockTime-A reached, refunding P2SH-A %s - aborting trade", p2shAddressA));
+
+			return;
+		}
+
+		// We're waiting for AT to be in TRADE mode
+		if (crossChainTradeData.mode != AcctMode.TRADING)
+			return;
+
+		// AT is in TRADE mode and locked to us as checked by aliceUnexpectedState() above
+
+		// Find our MESSAGE to AT from previous state
+		List<MessageTransactionData> messageTransactionsData = repository.getMessageRepository().getMessagesByParticipants(tradeBotData.getTradeNativePublicKey(),
+				crossChainTradeData.qortalCreatorTradeAddress, null, null, null);
+		if (messageTransactionsData == null || messageTransactionsData.isEmpty()) {
+			LOGGER.warn(() -> String.format("Unable to find our message to trade creator %s?", crossChainTradeData.qortalCreatorTradeAddress));
+			return;
+		}
+
+		long recipientMessageTimestamp = messageTransactionsData.get(0).getTimestamp();
+		int refundTimeout = LitecoinACCTv1.calcRefundTimeout(recipientMessageTimestamp, lockTimeA);
+
+		// Our calculated refundTimeout should match AT's refundTimeout
+		if (refundTimeout != crossChainTradeData.refundTimeout) {
+			LOGGER.debug(() -> String.format("Trade AT refundTimeout '%d' doesn't match our refundTimeout '%d'", crossChainTradeData.refundTimeout, refundTimeout));
+			// We'll eventually refund
+			return;
+		}
+
+		// We're good to redeem AT
+
+		// Send 'redeem' MESSAGE to AT using both secret
+		byte[] secretA = tradeBotData.getSecret();
+		String qortalReceivingAddress = Base58.encode(tradeBotData.getReceivingAccountInfo()); // Actually contains whole address, not just PKH
+		byte[] messageData = LitecoinACCTv1.buildRedeemMessage(secretA, qortalReceivingAddress);
+		String messageRecipient = tradeBotData.getAtAddress();
+
+		boolean isMessageAlreadySent = repository.getMessageRepository().exists(tradeBotData.getTradeNativePublicKey(), messageRecipient, messageData);
+		if (!isMessageAlreadySent) {
+			PrivateKeyAccount sender = new PrivateKeyAccount(repository, tradeBotData.getTradePrivateKey());
+			MessageTransaction messageTransaction = MessageTransaction.build(repository, sender, Group.NO_GROUP, messageRecipient, messageData, false, false);
+
+			messageTransaction.computeNonce();
+			messageTransaction.sign(sender);
+
+			// Reset repository state to prevent deadlock
+			repository.discardChanges();
+			ValidationResult result = messageTransaction.importAsUnconfirmed();
+
+			if (result != ValidationResult.OK) {
+				LOGGER.warn(() -> String.format("Unable to send MESSAGE to AT %s: %s", messageRecipient, result.name()));
+				return;
+			}
+		}
+
+		TradeBot.updateTradeBotState(repository, tradeBotData, State.ALICE_DONE,
+				() -> String.format("Redeeming AT %s. Funds should arrive at %s",
+						tradeBotData.getAtAddress(), qortalReceivingAddress));
+	}
+
+	/**
+	 * Trade-bot is waiting for Alice to redeem Bob's AT, thus revealing secret-A which is required to spend the LTC funds from P2SH-A.
+	 * <p>
+	 * It's possible that Bob's AT has reached its trading timeout and automatically refunded QORT back to Bob. In which case,
+	 * trade-bot is done with this specific trade and finalizes in refunded state.
+	 * <p>
+	 * Assuming trade-bot can extract a valid secret-A from Alice's MESSAGE then trade-bot uses that to redeem the LTC funds from P2SH-A
+	 * to Bob's 'foreign'/Litecoin trade legacy-format address, as derived from trade private key.
+	 * <p>
+	 * (This could potentially be 'improved' to send LTC to any address of Bob's choosing by changing the transaction output).
+	 * <p>
+	 * If trade-bot successfully broadcasts the transaction, then this specific trade is done.
+	 * @throws ForeignBlockchainException
+	 */
+	private void handleBobWaitingForAtRedeem(Repository repository, TradeBotData tradeBotData,
+			ATData atData, CrossChainTradeData crossChainTradeData) throws DataException, ForeignBlockchainException {
+		// AT should be 'finished' once Alice has redeemed QORT funds
+		if (!atData.getIsFinished())
+			// Not finished yet
+			return;
+
+		// If AT is not REDEEMED then something has gone wrong
+		if (crossChainTradeData.mode != AcctMode.REDEEMED) {
+			// Not redeemed so must be refunded/cancelled
+			TradeBot.updateTradeBotState(repository, tradeBotData, State.BOB_REFUNDED,
+					() -> String.format("AT %s has auto-refunded - trade aborted", tradeBotData.getAtAddress()));
+
+			return;
+		}
+
+		byte[] secretA = LitecoinACCTv1.findSecretA(repository, crossChainTradeData);
+		if (secretA == null) {
+			LOGGER.debug(() -> String.format("Unable to find secret-A from redeem message to AT %s?", tradeBotData.getAtAddress()));
+			return;
+		}
+
+		// Use secret-A to redeem P2SH-A
+
+		Litecoin litecoin = Litecoin.getInstance();
+
+		byte[] receivingAccountInfo = tradeBotData.getReceivingAccountInfo();
+		int lockTimeA = crossChainTradeData.lockTimeA;
+		byte[] redeemScriptA = BitcoinyHTLC.buildScript(crossChainTradeData.partnerForeignPKH, lockTimeA, crossChainTradeData.creatorForeignPKH, crossChainTradeData.hashOfSecretA);
+		String p2shAddressA = litecoin.deriveP2shAddress(redeemScriptA);
+
+		// Fee for redeem/refund is subtracted from P2SH-A balance.
+		long feeTimestamp = calcFeeTimestamp(lockTimeA, crossChainTradeData.tradeTimeout);
+		long p2shFee = Litecoin.getInstance().getP2shFee(feeTimestamp);
+		long minimumAmountA = crossChainTradeData.expectedForeignAmount + p2shFee;
+		BitcoinyHTLC.Status htlcStatusA = BitcoinyHTLC.determineHtlcStatus(litecoin.getBlockchainProvider(), p2shAddressA, minimumAmountA);
+
+		switch (htlcStatusA) {
+			case UNFUNDED:
+			case FUNDING_IN_PROGRESS:
+				// P2SH-A suddenly not funded? Our best bet at this point is to hope for AT auto-refund
+				return;
+
+			case REDEEM_IN_PROGRESS:
+			case REDEEMED:
+				// Double-check that we have redeemed P2SH-A...
+				break;
+
+			case REFUND_IN_PROGRESS:
+			case REFUNDED:
+				// Wait for AT to auto-refund
+				return;
+
+			case FUNDED: {
+				Coin redeemAmount = Coin.valueOf(crossChainTradeData.expectedForeignAmount);
+				ECKey redeemKey = ECKey.fromPrivate(tradeBotData.getTradePrivateKey());
+				List<TransactionOutput> fundingOutputs = litecoin.getUnspentOutputs(p2shAddressA);
+
+				Transaction p2shRedeemTransaction = BitcoinyHTLC.buildRedeemTransaction(litecoin.getNetworkParameters(), redeemAmount, redeemKey,
+						fundingOutputs, redeemScriptA, secretA, receivingAccountInfo);
+
+				litecoin.broadcastTransaction(p2shRedeemTransaction);
+				break;
+			}
+		}
+
+		String receivingAddress = litecoin.pkhToAddress(receivingAccountInfo);
+
+		TradeBot.updateTradeBotState(repository, tradeBotData, State.BOB_DONE,
+				() -> String.format("P2SH-A %s redeemed. Funds should arrive at %s", tradeBotData.getAtAddress(), receivingAddress));
+	}
+
+	/**
+	 * Trade-bot is attempting to refund P2SH-A.
+	 * @throws ForeignBlockchainException
+	 */
+	private void handleAliceRefundingP2shA(Repository repository, TradeBotData tradeBotData,
+			ATData atData, CrossChainTradeData crossChainTradeData) throws DataException, ForeignBlockchainException {
+		int lockTimeA = tradeBotData.getLockTimeA();
+
+		// We can't refund P2SH-A until lockTime-A has passed
+		if (NTP.getTime() <= lockTimeA * 1000L)
+			return;
+
+		Litecoin litecoin = Litecoin.getInstance();
+
+		// We can't refund P2SH-A until median block time has passed lockTime-A (see BIP113)
+		int medianBlockTime = litecoin.getMedianBlockTime();
+		if (medianBlockTime <= lockTimeA)
+			return;
+
+		byte[] redeemScriptA = BitcoinyHTLC.buildScript(tradeBotData.getTradeForeignPublicKeyHash(), lockTimeA, crossChainTradeData.creatorForeignPKH, tradeBotData.getHashOfSecret());
+		String p2shAddressA = litecoin.deriveP2shAddress(redeemScriptA);
+
+		// Fee for redeem/refund is subtracted from P2SH-A balance.
+		long feeTimestamp = calcFeeTimestamp(lockTimeA, crossChainTradeData.tradeTimeout);
+		long p2shFee = Litecoin.getInstance().getP2shFee(feeTimestamp);
+		long minimumAmountA = crossChainTradeData.expectedForeignAmount + p2shFee;
+		BitcoinyHTLC.Status htlcStatusA = BitcoinyHTLC.determineHtlcStatus(litecoin.getBlockchainProvider(), p2shAddressA, minimumAmountA);
+
+		switch (htlcStatusA) {
+			case UNFUNDED:
+			case FUNDING_IN_PROGRESS:
+				// Still waiting for P2SH-A to be funded...
+				return;
+
+			case REDEEM_IN_PROGRESS:
+			case REDEEMED:
+				// Too late!
+				TradeBot.updateTradeBotState(repository, tradeBotData, State.ALICE_DONE,
+						() -> String.format("P2SH-A %s already spent!", p2shAddressA));
+				return;
+
+			case REFUND_IN_PROGRESS:
+			case REFUNDED:
+				break;
+
+			case FUNDED:{
+				Coin refundAmount = Coin.valueOf(crossChainTradeData.expectedForeignAmount);
+				ECKey refundKey = ECKey.fromPrivate(tradeBotData.getTradePrivateKey());
+				List<TransactionOutput> fundingOutputs = litecoin.getUnspentOutputs(p2shAddressA);
+
+				// Determine receive address for refund
+				String receiveAddress = litecoin.getUnusedReceiveAddress(tradeBotData.getForeignKey());
+				Address receiving = Address.fromString(litecoin.getNetworkParameters(), receiveAddress);
+
+				Transaction p2shRefundTransaction = BitcoinyHTLC.buildRefundTransaction(litecoin.getNetworkParameters(), refundAmount, refundKey,
+						fundingOutputs, redeemScriptA, lockTimeA, receiving.getHash());
+
+				litecoin.broadcastTransaction(p2shRefundTransaction);
+				break;
+			}
+		}
+
+		TradeBot.updateTradeBotState(repository, tradeBotData, State.ALICE_REFUNDED,
+				() -> String.format("LockTime-A reached. Refunded P2SH-A %s. Trade aborted", p2shAddressA));
+	}
+
+	/**
+	 * Returns true if Alice finds AT unexpectedly cancelled, refunded, redeemed or locked to someone else.
+	 * <p>
+	 * Will automatically update trade-bot state to <tt>ALICE_REFUNDING_A</tt> or <tt>ALICE_DONE</tt> as necessary.
+	 * 
+	 * @throws DataException
+	 * @throws ForeignBlockchainException
+	 */
+	private boolean aliceUnexpectedState(Repository repository, TradeBotData tradeBotData,
+			ATData atData, CrossChainTradeData crossChainTradeData) throws DataException, ForeignBlockchainException {
+		// This is OK
+		if (!atData.getIsFinished() && crossChainTradeData.mode == AcctMode.OFFERING)
+			return false;
+
+		boolean isAtLockedToUs = tradeBotData.getTradeNativeAddress().equals(crossChainTradeData.qortalPartnerAddress);
+
+		if (!atData.getIsFinished() && crossChainTradeData.mode == AcctMode.TRADING)
+			if (isAtLockedToUs) {
+				// AT is trading with us - OK
+				return false;
+			} else {
+				TradeBot.updateTradeBotState(repository, tradeBotData, State.ALICE_REFUNDING_A,
+						() -> String.format("AT %s trading with someone else: %s. Refunding & aborting trade", tradeBotData.getAtAddress(), crossChainTradeData.qortalPartnerAddress));
+
+				return true;
+			}
+
+		if (atData.getIsFinished() && crossChainTradeData.mode == AcctMode.REDEEMED && isAtLockedToUs) {
+			// We've redeemed already?
+			TradeBot.updateTradeBotState(repository, tradeBotData, State.ALICE_DONE,
+					() -> String.format("AT %s already redeemed by us. Trade completed", tradeBotData.getAtAddress()));
+		} else {
+			// Any other state is not good, so start defensive refund
+			TradeBot.updateTradeBotState(repository, tradeBotData, State.ALICE_REFUNDING_A,
+					() -> String.format("AT %s cancelled/refunded/redeemed by someone else/invalid state. Refunding & aborting trade", tradeBotData.getAtAddress()));
+		}
+
+		return true;
+	}
+
+	private long calcFeeTimestamp(int lockTimeA, int tradeTimeout) {
+		return (lockTimeA - tradeTimeout * 60) * 1000L;
+	}
+
+}

src/main/java/org/qortal/controller/tradebot/TradeBot.java

@@ -0,0 +1,373 @@
+package org.qortal.controller.tradebot;
+
+import java.awt.TrayIcon.MessageType;
+import java.security.SecureRandom;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Random;
+import java.util.concurrent.locks.ReentrantLock;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.apache.logging.log4j.util.Supplier;
+import org.bitcoinj.core.ECKey;
+import org.qortal.account.PrivateKeyAccount;
+import org.qortal.api.model.crosschain.TradeBotCreateRequest;
+import org.qortal.controller.Controller;
+import org.qortal.controller.tradebot.AcctTradeBot.ResponseResult;
+import org.qortal.crosschain.ACCT;
+import org.qortal.crosschain.BitcoinACCTv1;
+import org.qortal.crosschain.ForeignBlockchainException;
+import org.qortal.crosschain.LitecoinACCTv1;
+import org.qortal.crosschain.SupportedBlockchain;
+import org.qortal.data.at.ATData;
+import org.qortal.data.crosschain.CrossChainTradeData;
+import org.qortal.data.crosschain.TradeBotData;
+import org.qortal.data.transaction.BaseTransactionData;
+import org.qortal.data.transaction.PresenceTransactionData;
+import org.qortal.event.Event;
+import org.qortal.event.EventBus;
+import org.qortal.event.Listener;
+import org.qortal.group.Group;
+import org.qortal.gui.SysTray;
+import org.qortal.repository.DataException;
+import org.qortal.repository.Repository;
+import org.qortal.repository.RepositoryManager;
+import org.qortal.settings.Settings;
+import org.qortal.transaction.PresenceTransaction;
+import org.qortal.transaction.PresenceTransaction.PresenceType;
+import org.qortal.transaction.Transaction.ValidationResult;
+import org.qortal.transform.transaction.TransactionTransformer;
+import org.qortal.utils.NTP;
+
+import com.google.common.primitives.Longs;
+
+/**
+ * Performing cross-chain trading steps on behalf of user.
+ * <p>
+ * We deal with three different independent state-spaces here:
+ * <ul>
+ * 	<li>Qortal blockchain</li>
+ * 	<li>Foreign blockchain</li>
+ * 	<li>Trade-bot entries</li>
+ * </ul>
+ */
+public class TradeBot implements Listener {
+
+	private static final Logger LOGGER = LogManager.getLogger(TradeBot.class);
+	private static final Random RANDOM = new SecureRandom();
+
+	public interface StateNameAndValueSupplier {
+		public String getState();
+		public int getStateValue();
+	}
+
+	public static class StateChangeEvent implements Event {
+		private final TradeBotData tradeBotData;
+
+		public StateChangeEvent(TradeBotData tradeBotData) {
+			this.tradeBotData = tradeBotData;
+		}
+
+		public TradeBotData getTradeBotData() {
+			return this.tradeBotData;
+		}
+	}
+
+	private static final Map<Class<? extends ACCT>, Supplier<AcctTradeBot>> acctTradeBotSuppliers = new HashMap<>();
+	static {
+		acctTradeBotSuppliers.put(BitcoinACCTv1.class, BitcoinACCTv1TradeBot::getInstance);
+		acctTradeBotSuppliers.put(LitecoinACCTv1.class, LitecoinACCTv1TradeBot::getInstance);
+	}
+
+	private static TradeBot instance;
+
+	private final Map<String, Long> presenceTimestampsByAtAddress = Collections.synchronizedMap(new HashMap<>());
+
+	private TradeBot() {
+		EventBus.INSTANCE.addListener(event -> TradeBot.getInstance().listen(event));
+	}
+
+	public static synchronized TradeBot getInstance() {
+		if (instance == null)
+			instance = new TradeBot();
+
+		return instance;
+	}
+
+	public ACCT getAcctUsingAtData(ATData atData) {
+		byte[] codeHash = atData.getCodeHash();
+		if (codeHash == null)
+			return null;
+
+		return SupportedBlockchain.getAcctByCodeHash(codeHash);
+	}
+
+	public CrossChainTradeData populateTradeData(Repository repository, ATData atData) throws DataException {
+		ACCT acct = this.getAcctUsingAtData(atData);
+		if (acct == null)
+			return null;
+
+		return acct.populateTradeData(repository, atData);
+	}
+
+	/**
+	 * Creates a new trade-bot entry from the "Bob" viewpoint,
+	 * i.e. OFFERing QORT in exchange for foreign blockchain currency.
+	 * <p>
+	 * Generates:
+	 * <ul>
+	 * 	<li>new 'trade' private key</li>
+	 * 	<li>secret(s)</li>
+	 * </ul>
+	 * Derives:
+	 * <ul>
+	 * 	<li>'native' (as in Qortal) public key, public key hash, address (starting with Q)</li>
+	 * 	<li>'foreign' public key, public key hash</li>
+	 *	<li>hash(es) of secret(s)</li>
+	 * </ul>
+	 * A Qortal AT is then constructed including the following as constants in the 'data segment':
+	 * <ul>
+	 * 	<li>'native' (Qortal) 'trade' address - used to MESSAGE AT</li>
+	 * 	<li>'foreign' public key hash - used by Alice's to allow redeem of currency on foreign blockchain</li>
+	 * 	<li>hash(es) of secret(s) - used by AT (optional) and foreign blockchain as needed</li>
+	 * 	<li>QORT amount on offer by Bob</li>
+	 * 	<li>foreign currency amount expected in return by Bob (from Alice)</li>
+	 * 	<li>trading timeout, in case things go wrong and everyone needs to refund</li>
+	 * </ul>
+	 * Returns a DEPLOY_AT transaction that needs to be signed and broadcast to the Qortal network.
+	 * <p>
+	 * Trade-bot will wait for Bob's AT to be deployed before taking next step.
+	 * <p>
+	 * @param repository
+	 * @param tradeBotCreateRequest
+	 * @return raw, unsigned DEPLOY_AT transaction
+	 * @throws DataException
+	 */
+	public byte[] createTrade(Repository repository, TradeBotCreateRequest tradeBotCreateRequest) throws DataException {
+		// Fetch latest ACCT version for requested foreign blockchain
+		ACCT acct = tradeBotCreateRequest.foreignBlockchain.getLatestAcct();
+
+		AcctTradeBot acctTradeBot = findTradeBotForAcct(acct);
+		if (acctTradeBot == null)
+			return null;
+
+		return acctTradeBot.createTrade(repository, tradeBotCreateRequest);
+	}
+
+	/**
+	 * Creates a trade-bot entry from the 'Alice' viewpoint,
+	 * i.e. matching foreign blockchain currency to an existing QORT offer.
+	 * <p>
+	 * Requires a chosen trade offer from Bob, passed by <tt>crossChainTradeData</tt>
+	 * and access to a foreign blockchain wallet via <tt>foreignKey</tt>.
+	 * <p>
+	 * @param repository
+	 * @param crossChainTradeData chosen trade OFFER that Alice wants to match
+	 * @param foreignKey foreign blockchain wallet key
+	 * @throws DataException
+	 */
+	public ResponseResult startResponse(Repository repository, ATData atData, ACCT acct,
+			CrossChainTradeData crossChainTradeData, String foreignKey, String receivingAddress) throws DataException {
+		AcctTradeBot acctTradeBot = findTradeBotForAcct(acct);
+		if (acctTradeBot == null) {
+			LOGGER.debug(() -> String.format("Couldn't find ACCT trade-bot for AT %s", atData.getATAddress()));
+			return ResponseResult.NETWORK_ISSUE;
+		}
+
+		// Check Alice doesn't already have an existing, on-going trade-bot entry for this AT.
+		if (repository.getCrossChainRepository().existsTradeWithAtExcludingStates(atData.getATAddress(), acctTradeBot.getEndStates()))
+			return ResponseResult.TRADE_ALREADY_EXISTS;
+
+		return acctTradeBot.startResponse(repository, atData, acct, crossChainTradeData, foreignKey, receivingAddress);
+	}
+
+	public boolean deleteEntry(Repository repository, byte[] tradePrivateKey) throws DataException {
+		TradeBotData tradeBotData = repository.getCrossChainRepository().getTradeBotData(tradePrivateKey);
+		if (tradeBotData == null)
+			// Can't delete what we don't have!
+			return false;
+
+		boolean canDelete = false;
+
+		ACCT acct = SupportedBlockchain.getAcctByName(tradeBotData.getAcctName());
+		if (acct == null)
+			// We can't/no longer support this ACCT
+			canDelete = true;
+		else {
+			AcctTradeBot acctTradeBot = findTradeBotForAcct(acct);
+			canDelete = acctTradeBot == null || acctTradeBot.canDelete(repository, tradeBotData);
+		}
+
+		if (canDelete) {
+			repository.getCrossChainRepository().delete(tradePrivateKey);
+			repository.saveChanges();
+		}
+
+		return canDelete;
+	}
+
+	@Override
+	public void listen(Event event) {
+		if (!(event instanceof Controller.NewBlockEvent))
+			return;
+
+		synchronized (this) {
+			List<TradeBotData> allTradeBotData;
+
+			try (final Repository repository = RepositoryManager.getRepository()) {
+				allTradeBotData = repository.getCrossChainRepository().getAllTradeBotData();
+			} catch (DataException e) {
+				LOGGER.error("Couldn't run trade bot due to repository issue", e);
+				return;
+			}
+
+			for (TradeBotData tradeBotData : allTradeBotData)
+				try (final Repository repository = RepositoryManager.getRepository()) {
+					// Find ACCT-specific trade-bot for this entry
+					ACCT acct = SupportedBlockchain.getAcctByName(tradeBotData.getAcctName());
+					if (acct == null) {
+						LOGGER.debug(() -> String.format("Couldn't find ACCT matching name %s", tradeBotData.getAcctName()));
+						continue;
+					}
+
+					AcctTradeBot acctTradeBot = findTradeBotForAcct(acct);
+					if (acctTradeBot == null) {
+						LOGGER.debug(() -> String.format("Couldn't find ACCT trade-bot matching name %s", tradeBotData.getAcctName()));
+						continue;
+					}
+
+					acctTradeBot.progress(repository, tradeBotData);
+				} catch (DataException e) {
+					LOGGER.error("Couldn't run trade bot due to repository issue", e);
+				} catch (ForeignBlockchainException e) {
+					LOGGER.warn(() -> String.format("Foreign blockchain issue processing trade-bot entry for AT %s: %s", tradeBotData.getAtAddress(), e.getMessage()));
+				}
+		}
+	}
+
+	/*package*/ static byte[] generateTradePrivateKey() {
+		// The private key is used for both Curve25519 and secp256k1 so needs to be valid for both.
+		// Curve25519 accepts any seed, so generate a valid secp256k1 key and use that.
+		return new ECKey().getPrivKeyBytes();
+	}
+
+	/*package*/ static byte[] deriveTradeNativePublicKey(byte[] privateKey) {
+		return PrivateKeyAccount.toPublicKey(privateKey);
+	}
+
+	/*package*/ static byte[] deriveTradeForeignPublicKey(byte[] privateKey) {
+		return ECKey.fromPrivate(privateKey).getPubKey();
+	}
+
+	/*package*/ static byte[] generateSecret() {
+		byte[] secret = new byte[32];
+		RANDOM.nextBytes(secret);
+		return secret;
+	}
+
+	/*package*/ static void backupTradeBotData(Repository repository) {
+		// Attempt to backup the trade bot data. This an optional step and doesn't impact trading, so don't throw an exception on failure
+		try {
+			LOGGER.info("About to backup trade bot data...");
+			repository.exportNodeLocalData();
+		} catch (DataException e) {
+			LOGGER.info(String.format("Repository issue when exporting trade bot data: %s", e.getMessage()));
+		}
+	}
+
+	/** Updates trade-bot entry to new state, with current timestamp, logs message and notifies state-change listeners. */
+	/*package*/ static void updateTradeBotState(Repository repository, TradeBotData tradeBotData,
+			String newState, int newStateValue, Supplier<String> logMessageSupplier) throws DataException {
+		tradeBotData.setState(newState);
+		tradeBotData.setStateValue(newStateValue);
+		tradeBotData.setTimestamp(NTP.getTime());
+		repository.getCrossChainRepository().save(tradeBotData);
+		repository.saveChanges();
+
+		if (Settings.getInstance().isTradebotSystrayEnabled())
+			SysTray.getInstance().showMessage("Trade-Bot", String.format("%s: %s", tradeBotData.getAtAddress(), newState), MessageType.INFO);
+
+		if (logMessageSupplier != null)
+			LOGGER.info(logMessageSupplier);
+
+		LOGGER.debug(() -> String.format("new state for trade-bot entry based on AT %s: %s", tradeBotData.getAtAddress(), newState));
+
+		notifyStateChange(tradeBotData);
+	}
+
+	/** Updates trade-bot entry to new state, with current timestamp, logs message and notifies state-change listeners. */
+	/*package*/ static void updateTradeBotState(Repository repository, TradeBotData tradeBotData, StateNameAndValueSupplier newStateSupplier, Supplier<String> logMessageSupplier) throws DataException {
+		updateTradeBotState(repository, tradeBotData, newStateSupplier.getState(), newStateSupplier.getStateValue(), logMessageSupplier);
+	}
+
+	/** Updates trade-bot entry to new state, with current timestamp, logs message and notifies state-change listeners. */
+	/*package*/ static void updateTradeBotState(Repository repository, TradeBotData tradeBotData, Supplier<String> logMessageSupplier) throws DataException {
+		updateTradeBotState(repository, tradeBotData, tradeBotData.getState(), tradeBotData.getStateValue(), logMessageSupplier);
+	}
+
+	/*package*/ static void notifyStateChange(TradeBotData tradeBotData) {
+		StateChangeEvent stateChangeEvent = new StateChangeEvent(tradeBotData);
+		EventBus.INSTANCE.notify(stateChangeEvent);
+	}
+
+	/*package*/ static AcctTradeBot findTradeBotForAcct(ACCT acct) {
+		Supplier<AcctTradeBot> acctTradeBotSupplier = acctTradeBotSuppliers.get(acct.getClass());
+		if (acctTradeBotSupplier == null)
+			return null;
+
+		return acctTradeBotSupplier.get();
+	}
+
+	// PRESENCE-related
+	/*package*/ void updatePresence(Repository repository, TradeBotData tradeBotData, CrossChainTradeData tradeData)
+			throws DataException {
+		String atAddress = tradeBotData.getAtAddress();
+
+		PrivateKeyAccount tradeNativeAccount = new PrivateKeyAccount(repository, tradeBotData.getTradePrivateKey());
+		String signerAddress = tradeNativeAccount.getAddress();
+
+		/*
+		 * There's no point in Alice trying to build a PRESENCE transaction
+		 * for an AT that isn't locked to her, as other peers won't be able
+		 * to validate the PRESENCE transaction as signing public key won't
+		 * be visible.
+		 */
+		if (!signerAddress.equals(tradeData.qortalCreatorTradeAddress) && !signerAddress.equals(tradeData.qortalPartnerAddress))
+			// Signer is neither Bob, nor Alice, or trade not yet locked to Alice
+			return;
+
+		long now = NTP.getTime();
+		long threshold = now - PresenceType.TRADE_BOT.getLifetime();
+
+		long timestamp = presenceTimestampsByAtAddress.compute(atAddress, (k, v) -> (v == null || v < threshold) ? now : v);
+
+		// If timestamp hasn't been updated then nothing to do
+		if (timestamp != now)
+			return;
+
+		int txGroupId = Group.NO_GROUP;
+		byte[] reference = new byte[TransactionTransformer.SIGNATURE_LENGTH];
+		byte[] creatorPublicKey = tradeNativeAccount.getPublicKey();
+		long fee = 0L;
+
+		BaseTransactionData baseTransactionData = new BaseTransactionData(timestamp, txGroupId, reference, creatorPublicKey, fee, null);
+
+		int nonce = 0;
+		byte[] timestampSignature = tradeNativeAccount.sign(Longs.toByteArray(timestamp));
+
+		PresenceTransactionData transactionData = new PresenceTransactionData(baseTransactionData, nonce, PresenceType.TRADE_BOT, timestampSignature);
+
+		PresenceTransaction presenceTransaction = new PresenceTransaction(repository, transactionData);
+		presenceTransaction.computeNonce();
+
+		presenceTransaction.sign(tradeNativeAccount);
+
+		ValidationResult result = presenceTransaction.importAsUnconfirmed();
+		if (result != ValidationResult.OK)
+			LOGGER.debug(() -> String.format("Unable to build trade-bot PRESENCE transaction for %s: %s", tradeBotData.getAtAddress(), result.name()));
+	}
+
+}

src/main/java/org/qortal/crosschain/ACCT.java

@@ -0,0 +1,23 @@
+package org.qortal.crosschain;
+
+import org.qortal.data.at.ATData;
+import org.qortal.data.at.ATStateData;
+import org.qortal.data.crosschain.CrossChainTradeData;
+import org.qortal.repository.DataException;
+import org.qortal.repository.Repository;
+
+public interface ACCT {
+
+	public byte[] getCodeBytesHash();
+
+	public int getModeByteOffset();
+
+	public ForeignBlockchain getBlockchain();
+
+	public CrossChainTradeData populateTradeData(Repository repository, ATData atData) throws DataException;
+
+	public CrossChainTradeData populateTradeData(Repository repository, ATStateData atStateData) throws DataException;
+
+	public byte[] buildCancelMessage(String creatorQortalAddress);
+
+}

src/main/java/org/qortal/crosschain/AcctMode.java

@@ -0,0 +1,21 @@
+package org.qortal.crosschain;
+
+import static java.util.Arrays.stream;
+import static java.util.stream.Collectors.toMap;
+
+import java.util.Map;
+
+public enum AcctMode {
+	OFFERING(0), TRADING(1), CANCELLED(2), REFUNDED(3), REDEEMED(4);
+
+	public final int value;
+	private static final Map<Integer, AcctMode> map = stream(AcctMode.values()).collect(toMap(mode -> mode.value, mode -> mode));
+
+	AcctMode(int value) {
+		this.value = value;
+	}
+
+	public static AcctMode valueOf(int value) {
+		return map.get(value);
+	}
+}

src/main/java/org/qortal/crosschain/BTC.java

@@ -1,381 +0,0 @@
-package org.qortal.crosschain;
-
-import java.util.ArrayList;
-import java.util.HashSet;
-import java.util.List;
-import java.util.Set;
-import java.util.stream.Collectors;
-
-import org.apache.logging.log4j.LogManager;
-import org.apache.logging.log4j.Logger;
-import org.bitcoinj.core.Address;
-import org.bitcoinj.core.Coin;
-import org.bitcoinj.core.ECKey;
-import org.bitcoinj.core.InsufficientMoneyException;
-import org.bitcoinj.core.LegacyAddress;
-import org.bitcoinj.core.NetworkParameters;
-import org.bitcoinj.core.Sha256Hash;
-import org.bitcoinj.core.Transaction;
-import org.bitcoinj.core.TransactionOutput;
-import org.bitcoinj.core.UTXO;
-import org.bitcoinj.core.UTXOProvider;
-import org.bitcoinj.core.UTXOProviderException;
-import org.bitcoinj.crypto.DeterministicHierarchy;
-import org.bitcoinj.crypto.DeterministicKey;
-import org.bitcoinj.params.MainNetParams;
-import org.bitcoinj.params.RegTestParams;
-import org.bitcoinj.params.TestNet3Params;
-import org.bitcoinj.script.Script.ScriptType;
-import org.bitcoinj.script.ScriptBuilder;
-import org.bitcoinj.utils.MonetaryFormat;
-import org.bitcoinj.wallet.DeterministicKeyChain;
-import org.bitcoinj.wallet.SendRequest;
-import org.bitcoinj.wallet.Wallet;
-import org.qortal.crosschain.ElectrumX.UnspentOutput;
-import org.qortal.crypto.Crypto;
-import org.qortal.settings.Settings;
-import org.qortal.utils.BitTwiddling;
-
-import com.google.common.hash.HashCode;
-
-public class BTC {
-
-	public static final long NO_LOCKTIME_NO_RBF_SEQUENCE = 0xFFFFFFFFL;
-	public static final long LOCKTIME_NO_RBF_SEQUENCE = NO_LOCKTIME_NO_RBF_SEQUENCE - 1;
-	public static final int HASH160_LENGTH = 20;
-
-	protected static final Logger LOGGER = LogManager.getLogger(BTC.class);
-
-	private static final int TIMESTAMP_OFFSET = 4 + 32 + 32;
-	private static final MonetaryFormat FORMAT = new MonetaryFormat().minDecimals(8).postfixCode();
-
-	public enum BitcoinNet {
-		MAIN {
-			@Override
-			public NetworkParameters getParams() {
-				return MainNetParams.get();
-			}
-		},
-		TEST3 {
-			@Override
-			public NetworkParameters getParams() {
-				return TestNet3Params.get();
-			}
-		},
-		REGTEST {
-			@Override
-			public NetworkParameters getParams() {
-				return RegTestParams.get();
-			}
-		};
-
-		public abstract NetworkParameters getParams();
-	}
-
-	private static BTC instance;
-	private final NetworkParameters params;
-	private final ElectrumX electrumX;
-
-	// Let ECKey.equals() do the hard work
-	private final Set<ECKey> spentKeys = new HashSet<>();
-
-	// Constructors and instance
-
-	private BTC() {
-		BitcoinNet bitcoinNet = Settings.getInstance().getBitcoinNet();
-		this.params = bitcoinNet.getParams();
-
-		LOGGER.info(() -> String.format("Starting Bitcoin support using %s", bitcoinNet.name()));
-
-		this.electrumX = ElectrumX.getInstance(bitcoinNet.name());
-	}
-
-	public static synchronized BTC getInstance() {
-		if (instance == null)
-			instance = new BTC();
-
-		return instance;
-	}
-
-	// Getters & setters
-
-	public NetworkParameters getNetworkParameters() {
-		return this.params;
-	}
-
-	public static synchronized void resetForTesting() {
-		instance = null;
-	}
-
-	// Actual useful methods for use by other classes
-
-	public static String format(Coin amount) {
-		return BTC.FORMAT.format(amount).toString();
-	}
-
-	public static String format(long amount) {
-		return format(Coin.valueOf(amount));
-	}
-
-	public boolean isValidXprv(String xprv58) {
-		try {
-			DeterministicKey.deserializeB58(null, xprv58, this.params);
-			return true;
-		} catch (IllegalArgumentException e) {
-			return false;
-		}
-	}
-
-	/** Returns P2PKH Bitcoin address using passed public key hash. */
-	public String pkhToAddress(byte[] publicKeyHash) {
-		return LegacyAddress.fromPubKeyHash(this.params, publicKeyHash).toString();
-	}
-
-	public String deriveP2shAddress(byte[] redeemScriptBytes) {
-		byte[] redeemScriptHash = Crypto.hash160(redeemScriptBytes);
-		Address p2shAddress = LegacyAddress.fromScriptHash(params, redeemScriptHash);
-		return p2shAddress.toString();
-	}
-
-	/** Returns median timestamp from latest 11 blocks, in seconds. */
-	public Integer getMedianBlockTime() {
-		Integer height = this.electrumX.getCurrentHeight();
-		if (height == null)
-			return null;
-
-		// Grab latest 11 blocks
-		List<byte[]> blockHeaders = this.electrumX.getBlockHeaders(height - 11, 11);
-		if (blockHeaders == null || blockHeaders.size() < 11)
-			return null;
-
-		List<Integer> blockTimestamps = blockHeaders.stream().map(blockHeader -> BitTwiddling.intFromLEBytes(blockHeader, TIMESTAMP_OFFSET)).collect(Collectors.toList());
-
-		// Descending order
-		blockTimestamps.sort((a, b) -> Integer.compare(b, a));
-
-		// Pick median
-		return blockTimestamps.get(5);
-	}
-
-	public Long getBalance(String base58Address) {
-		return this.electrumX.getBalance(addressToScript(base58Address));
-	}
-
-	public List<TransactionOutput> getUnspentOutputs(String base58Address) {
-		List<UnspentOutput> unspentOutputs = this.electrumX.getUnspentOutputs(addressToScript(base58Address));
-		if (unspentOutputs == null)
-			return null;
-
-		List<TransactionOutput> unspentTransactionOutputs = new ArrayList<>();
-		for (UnspentOutput unspentOutput : unspentOutputs) {
-			List<TransactionOutput> transactionOutputs = getOutputs(unspentOutput.hash);
-			if (transactionOutputs == null)
-				return null;
-
-			unspentTransactionOutputs.add(transactionOutputs.get(unspentOutput.index));
-		}
-
-		return unspentTransactionOutputs;
-	}
-
-	public List<TransactionOutput> getOutputs(byte[] txHash) {
-		byte[] rawTransactionBytes = this.electrumX.getRawTransaction(txHash);
-		if (rawTransactionBytes == null)
-			return null;
-
-		Transaction transaction = new Transaction(this.params, rawTransactionBytes);
-		return transaction.getOutputs();
-	}
-
-	/** Returns list of raw transactions spending passed address. */
-	public List<byte[]> getAddressTransactions(String base58Address) {
-		return this.electrumX.getAddressTransactions(addressToScript(base58Address));
-	}
-
-	public boolean broadcastTransaction(Transaction transaction) {
-		return this.electrumX.broadcastTransaction(transaction.bitcoinSerialize());
-	}
-
-	/**
-	 * Returns bitcoinj transaction sending <tt>amount</tt> to <tt>recipient</tt>.
-	 * 
-	 * @param xprv58 BIP32 extended Bitcoin private key
-	 * @param recipient P2PKH address
-	 * @param amount unscaled amount
-	 * @return transaction, or null if insufficient funds
-	 */
-	public Transaction buildSpend(String xprv58, String recipient, long amount) {
-		Wallet wallet = Wallet.fromSpendingKeyB58(this.params, xprv58, DeterministicHierarchy.BIP32_STANDARDISATION_TIME_SECS);
-		wallet.setUTXOProvider(new WalletAwareUTXOProvider(this, wallet, WalletAwareUTXOProvider.KeySearchMode.REQUEST_MORE_IF_ALL_SPENT));
-
-		Address destination = Address.fromString(this.params, recipient);
-		SendRequest sendRequest = SendRequest.to(destination, Coin.valueOf(amount));
-
-		if (this.params == TestNet3Params.get())
-			// Much smaller fee for TestNet3
-			sendRequest.feePerKb = Coin.valueOf(2000L);
-
-		try {
-			wallet.completeTx(sendRequest);
-			return sendRequest.tx;
-		} catch (InsufficientMoneyException e) {
-			return null;
-		}
-	}
-
-	/**
-	 * Returns unspent Bitcoin balance given 'm' BIP32 key.
-	 *
-	 * @param xprv58 BIP32 extended Bitcoin private key
-	 * @return unspent BTC balance, or null if unable to determine balance
-	 */
-	public Long getWalletBalance(String xprv58) {
-		Wallet wallet = Wallet.fromSpendingKeyB58(this.params, xprv58, DeterministicHierarchy.BIP32_STANDARDISATION_TIME_SECS);
-		wallet.setUTXOProvider(new WalletAwareUTXOProvider(this, wallet, WalletAwareUTXOProvider.KeySearchMode.REQUEST_MORE_IF_ANY_SPENT));
-
-		Coin balance = wallet.getBalance();
-		if (balance == null)
-			return null;
-
-		return balance.value;
-	}
-
-	// UTXOProvider support
-
-	static class WalletAwareUTXOProvider implements UTXOProvider {
-		private static final int LOOKAHEAD_INCREMENT = 3;
-
-		private final BTC btc;
-		private final Wallet wallet;
-
-		enum KeySearchMode {
-			REQUEST_MORE_IF_ALL_SPENT, REQUEST_MORE_IF_ANY_SPENT;
-		}
-		private final KeySearchMode keySearchMode;
-		private final DeterministicKeyChain keyChain;
-
-		public WalletAwareUTXOProvider(BTC btc, Wallet wallet, KeySearchMode keySearchMode) {
-			this.btc = btc;
-			this.wallet = wallet;
-			this.keySearchMode = keySearchMode;
-			this.keyChain = this.wallet.getActiveKeyChain();
-
-			// Set up wallet's key chain
-			this.keyChain.setLookaheadSize(LOOKAHEAD_INCREMENT);
-			this.keyChain.maybeLookAhead();
-		}
-
-		public List<UTXO> getOpenTransactionOutputs(List<ECKey> keys) throws UTXOProviderException {
-			List<UTXO> allUnspentOutputs = new ArrayList<>();
-			final boolean coinbase = false;
-
-			int ki = 0;
-			do {
-				boolean areAllKeysUnspent = true;
-				boolean areAllKeysSpent = true;
-
-				for (; ki < keys.size(); ++ki) {
-					ECKey key = keys.get(ki);
-
-					Address address = Address.fromKey(btc.params, key, ScriptType.P2PKH);
-					byte[] script = ScriptBuilder.createOutputScript(address).getProgram();
-
-					List<UnspentOutput> unspentOutputs = btc.electrumX.getUnspentOutputs(script);
-					if (unspentOutputs == null)
-						throw new UTXOProviderException(String.format("Unable to fetch unspent outputs for %s", address));
-
-					/*
-					 * If there are no unspent outputs then either:
-					 * a) all the outputs have been spent
-					 * b) address has never been used
-					 * 
-					 * For case (a) we want to remember not to check this address (key) again.
-					 */
-
-					if (unspentOutputs.isEmpty()) {
-						// If this is a known key that has been spent before, then we can skip asking for transaction history
-						if (btc.spentKeys.contains(key)) {
-							wallet.getActiveKeyChain().markKeyAsUsed((DeterministicKey) key);
-							areAllKeysUnspent = false;
-							continue;
-						}
-
-						// Ask for transaction history - if it's empty then key has never been used
-						List<byte[]> historicTransactionHashes = btc.electrumX.getAddressTransactions(script);
-						if (historicTransactionHashes == null)
-							throw new UTXOProviderException(
-									String.format("Unable to fetch transaction history for %s", address));
-
-						if (!historicTransactionHashes.isEmpty()) {
-							// Fully spent key - case (a)
-							btc.spentKeys.add(key);
-							wallet.getActiveKeyChain().markKeyAsUsed((DeterministicKey) key);
-							areAllKeysUnspent = false;
-						} else {
-							// Key never been used - case (b)
-							areAllKeysSpent = false;
-						}
-
-						continue;
-					}
-
-					// If we reach here, then there's definitely at least one unspent key
-					areAllKeysSpent = false;
-
-					for (UnspentOutput unspentOutput : unspentOutputs) {
-						List<TransactionOutput> transactionOutputs = btc.getOutputs(unspentOutput.hash);
-						if (transactionOutputs == null)
-							throw new UTXOProviderException(String.format("Unable to fetch outputs for TX %s",
-									HashCode.fromBytes(unspentOutput.hash)));
-
-						TransactionOutput transactionOutput = transactionOutputs.get(unspentOutput.index);
-
-						UTXO utxo = new UTXO(Sha256Hash.wrap(unspentOutput.hash), unspentOutput.index,
-								Coin.valueOf(unspentOutput.value), unspentOutput.height, coinbase,
-								transactionOutput.getScriptPubKey());
-
-						allUnspentOutputs.add(utxo);
-					}
-				}
-
-				if ((this.keySearchMode == KeySearchMode.REQUEST_MORE_IF_ALL_SPENT && areAllKeysSpent)
-						|| (this.keySearchMode == KeySearchMode.REQUEST_MORE_IF_ANY_SPENT && !areAllKeysUnspent)) {
-					// Generate some more keys
-					this.keyChain.setLookaheadSize(this.keyChain.getLookaheadSize() + LOOKAHEAD_INCREMENT);
-					this.keyChain.maybeLookAhead();
-
-					// This returns all keys, including those already in 'keys'
-					List<DeterministicKey> allLeafKeys = this.keyChain.getLeafKeys();
-					// Add only new keys onto our list of keys to search
-					List<DeterministicKey> newKeys = allLeafKeys.subList(ki, allLeafKeys.size());
-					keys.addAll(newKeys);
-					// Fall-through to checking more keys as now 'ki' is smaller than 'keys.size()' again
-				}
-
-				// If we have processed all keys, then we're done
-			} while (ki < keys.size());
-
-			return allUnspentOutputs;
-		}
-
-		public int getChainHeadHeight() throws UTXOProviderException {
-			Integer height = btc.electrumX.getCurrentHeight();
-			if (height == null)
-				throw new UTXOProviderException("Unable to determine Bitcoin chain height");
-
-			return height.intValue();
-		}
-
-		public NetworkParameters getParams() {
-			return btc.params;
-		}
-	}
-
-	// Utility methods for us
-
-	private byte[] addressToScript(String base58Address) {
-		Address address = Address.fromString(this.params, base58Address);
-		return ScriptBuilder.createOutputScript(address).getProgram();
-	}
-
-}

src/main/java/org/qortal/crosschain/BTCP2SH.java

@@ -1,236 +0,0 @@
-package org.qortal.crosschain;
-
-import java.util.List;
-import java.util.function.Function;
-
-import org.bitcoinj.core.Address;
-import org.bitcoinj.core.Coin;
-import org.bitcoinj.core.ECKey;
-import org.bitcoinj.core.LegacyAddress;
-import org.bitcoinj.core.NetworkParameters;
-import org.bitcoinj.core.Transaction;
-import org.bitcoinj.core.Transaction.SigHash;
-import org.bitcoinj.core.TransactionInput;
-import org.bitcoinj.core.TransactionOutput;
-import org.bitcoinj.crypto.TransactionSignature;
-import org.bitcoinj.script.Script;
-import org.bitcoinj.script.ScriptBuilder;
-import org.bitcoinj.script.ScriptChunk;
-import org.bitcoinj.script.ScriptOpCodes;
-import org.qortal.crypto.Crypto;
-import org.qortal.utils.BitTwiddling;
-
-import com.google.common.hash.HashCode;
-import com.google.common.primitives.Bytes;
-
-public class BTCP2SH {
-
-	public static final int SECRET_LENGTH = 32;
-	public static final int MIN_LOCKTIME = 1500000000;
-
-	/*
-	 * OP_TUCK (to copy public key to before signature)
-	 * OP_CHECKSIGVERIFY (sig & pubkey must verify or script fails)
-	 * OP_HASH160 (convert public key to PKH)
-	 * OP_DUP (duplicate PKH)
-	 * <push 20 bytes> <refund PKH> OP_EQUAL (does PKH match refund PKH?)
-	 * OP_IF
-	 * 	OP_DROP (no need for duplicate PKH)
-	 * 	<push 4 bytes> <locktime>
-	 * 	OP_CHECKLOCKTIMEVERIFY (if this passes, leftover stack is <locktime> so script passes)
-	 * OP_ELSE
-	 * 	<push 20 bytes> <redeem PKH> OP_EQUALVERIFY (duplicate PKH must match redeem PKH or script fails)
-	 * 	OP_HASH160 (hash secret)
-	 * 	<push 20 bytes> <hash of secret> OP_EQUAL (do hashes of secrets match? if true, script passes else script fails)
-	 * OP_ENDIF
-	 */
-
-	private static final byte[] redeemScript1 = HashCode.fromString("7dada97614").asBytes(); // OP_TUCK OP_CHECKSIGVERIFY OP_HASH160 OP_DUP push(0x14 bytes)
-	private static final byte[] redeemScript2 = HashCode.fromString("87637504").asBytes(); // OP_EQUAL OP_IF OP_DROP push(0x4 bytes)
-	private static final byte[] redeemScript3 = HashCode.fromString("b16714").asBytes(); // OP_CHECKLOCKTIMEVERIFY OP_ELSE push(0x14 bytes)
-	private static final byte[] redeemScript4 = HashCode.fromString("88a914").asBytes(); // OP_EQUALVERIFY OP_HASH160 push(0x14 bytes)
-	private static final byte[] redeemScript5 = HashCode.fromString("8768").asBytes(); // OP_EQUAL OP_ENDIF
-
-	/**
-	 * Returns Bitcoin redeemScript used for cross-chain trading.
-	 * <p>
-	 * See comments in {@link BTCP2SH} for more details.
-	 * 
-	 * @param refunderPubKeyHash 20-byte HASH160 of P2SH funder's public key, for refunding purposes
-	 * @param lockTime seconds-since-epoch threshold, after which P2SH funder can claim refund
-	 * @param redeemerPubKeyHash 20-byte HASH160 of P2SH redeemer's public key
-	 * @param secretHash 20-byte HASH160 of secret, used by P2SH redeemer to claim funds
-	 * @return
-	 */
-	public static byte[] buildScript(byte[] refunderPubKeyHash, int lockTime, byte[] redeemerPubKeyHash, byte[] secretHash) {
-		return Bytes.concat(redeemScript1, refunderPubKeyHash, redeemScript2, BitTwiddling.toLEByteArray((int) (lockTime & 0xffffffffL)),
-				redeemScript3, redeemerPubKeyHash, redeemScript4, secretHash, redeemScript5);
-	}
-
-	/**
-	 * Builds a custom transaction to spend P2SH.
-	 * 
-	 * @param amount output amount, should be total of input amounts, less miner fees
-	 * @param spendKey key for signing transaction, and also where funds are 'sent' (output)
-	 * @param fundingOutput output from transaction that funded P2SH address
-	 * @param redeemScriptBytes the redeemScript itself, in byte[] form
-	 * @param lockTime (optional) transaction nLockTime, used in refund scenario
-	 * @param scriptSigBuilder function for building scriptSig using transaction input signature
-	 * @param outputPublicKeyHash PKH used to create P2PKH output
-	 * @return Signed Bitcoin transaction for spending P2SH
-	 */
-	public static Transaction buildP2shTransaction(Coin amount, ECKey spendKey, List<TransactionOutput> fundingOutputs, byte[] redeemScriptBytes,
-			Long lockTime, Function<byte[], Script> scriptSigBuilder, byte[] outputPublicKeyHash) {
-		NetworkParameters params = BTC.getInstance().getNetworkParameters();
-
-		Transaction transaction = new Transaction(params);
-		transaction.setVersion(2);
-
-		// Output is back to P2SH funder
-		transaction.addOutput(amount, ScriptBuilder.createP2PKHOutputScript(outputPublicKeyHash));
-
-		for (int inputIndex = 0; inputIndex < fundingOutputs.size(); ++inputIndex) {
-			TransactionOutput fundingOutput = fundingOutputs.get(inputIndex);
-
-			// Input (without scriptSig prior to signing)
-			TransactionInput input = new TransactionInput(params, null, redeemScriptBytes, fundingOutput.getOutPointFor());
-			if (lockTime != null)
-				input.setSequenceNumber(BTC.LOCKTIME_NO_RBF_SEQUENCE); // Use max-value - 1, so lockTime can be used but not RBF
-			else
-				input.setSequenceNumber(BTC.NO_LOCKTIME_NO_RBF_SEQUENCE); // Use max-value, so no lockTime and no RBF
-			transaction.addInput(input);
-		}
-
-		// Set locktime after inputs added but before input signatures are generated
-		if (lockTime != null)
-			transaction.setLockTime(lockTime);
-
-		for (int inputIndex = 0; inputIndex < fundingOutputs.size(); ++inputIndex) {
-			// Generate transaction signature for input
-			final boolean anyoneCanPay = false;
-			TransactionSignature txSig = transaction.calculateSignature(inputIndex, spendKey, redeemScriptBytes, SigHash.ALL, anyoneCanPay);
-
-			// Calculate transaction signature
-			byte[] txSigBytes = txSig.encodeToBitcoin();
-
-			// Build scriptSig using lambda and tx signature
-			Script scriptSig = scriptSigBuilder.apply(txSigBytes);
-
-			// Set input scriptSig
-			transaction.getInput(inputIndex).setScriptSig(scriptSig);
-		}
-
-		return transaction;
-	}
-
-	/**
-	 * Returns signed Bitcoin transaction claiming refund from P2SH address.
-	 * 
-	 * @param refundAmount refund amount, should be total of input amounts, less miner fees
-	 * @param refundKey key for signing transaction, and also where refund is 'sent' (output)
-	 * @param fundingOutput output from transaction that funded P2SH address
-	 * @param redeemScriptBytes the redeemScript itself, in byte[] form
-	 * @param lockTime transaction nLockTime - must be at least locktime used in redeemScript
-	 * @return Signed Bitcoin transaction for refunding P2SH
-	 */
-	public static Transaction buildRefundTransaction(Coin refundAmount, ECKey refundKey, List<TransactionOutput> fundingOutputs, byte[] redeemScriptBytes, long lockTime) {
-		Function<byte[], Script> refundSigScriptBuilder = (txSigBytes) -> {
-			// Build scriptSig with...
-			ScriptBuilder scriptBuilder = new ScriptBuilder();
-
-			// transaction signature
-			scriptBuilder.addChunk(new ScriptChunk(txSigBytes.length, txSigBytes));
-
-			// redeem public key
-			byte[] refundPubKey = refundKey.getPubKey();
-			scriptBuilder.addChunk(new ScriptChunk(refundPubKey.length, refundPubKey));
-
-			// redeem script
-			scriptBuilder.addChunk(new ScriptChunk(ScriptOpCodes.OP_PUSHDATA1, redeemScriptBytes));
-
-			return scriptBuilder.build();
-		};
-
-		// Send funds back to funding address
-		return buildP2shTransaction(refundAmount, refundKey, fundingOutputs, redeemScriptBytes, lockTime, refundSigScriptBuilder, refundKey.getPubKeyHash());
-	}
-
-	/**
-	 * Returns signed Bitcoin transaction redeeming funds from P2SH address.
-	 * 
-	 * @param redeemAmount redeem amount, should be total of input amounts, less miner fees
-	 * @param redeemKey key for signing transaction, and also where funds are 'sent' (output)
-	 * @param fundingOutput output from transaction that funded P2SH address
-	 * @param redeemScriptBytes the redeemScript itself, in byte[] form
-	 * @param secret actual 32-byte secret used when building redeemScript
-	 * @param receivingAccountInfo Bitcoin PKH used for output
-	 * @return Signed Bitcoin transaction for redeeming P2SH
-	 */
-	public static Transaction buildRedeemTransaction(Coin redeemAmount, ECKey redeemKey, List<TransactionOutput> fundingOutputs, byte[] redeemScriptBytes, byte[] secret, byte[] receivingAccountInfo) {
-		Function<byte[], Script> redeemSigScriptBuilder = (txSigBytes) -> {
-			// Build scriptSig with...
-			ScriptBuilder scriptBuilder = new ScriptBuilder();
-
-			// secret
-			scriptBuilder.addChunk(new ScriptChunk(secret.length, secret));
-
-			// transaction signature
-			scriptBuilder.addChunk(new ScriptChunk(txSigBytes.length, txSigBytes));
-
-			// redeem public key
-			byte[] redeemPubKey = redeemKey.getPubKey();
-			scriptBuilder.addChunk(new ScriptChunk(redeemPubKey.length, redeemPubKey));
-
-			// redeem script
-			scriptBuilder.addChunk(new ScriptChunk(ScriptOpCodes.OP_PUSHDATA1, redeemScriptBytes));
-
-			return scriptBuilder.build();
-		};
-
-		return buildP2shTransaction(redeemAmount, redeemKey, fundingOutputs, redeemScriptBytes, null, redeemSigScriptBuilder, receivingAccountInfo);
-	}
-
-	/** Returns 'secret', if any, given list of raw bitcoin transactions. */
-	public static byte[] findP2shSecret(String p2shAddress, List<byte[]> rawTransactions) {
-		NetworkParameters params = BTC.getInstance().getNetworkParameters();
-
-		for (byte[] rawTransaction : rawTransactions) {
-			Transaction transaction = new Transaction(params, rawTransaction);
-
-			// Cycle through inputs, looking for one that spends our P2SH
-			for (TransactionInput input : transaction.getInputs()) {
-				Script scriptSig = input.getScriptSig();
-				List<ScriptChunk> scriptChunks = scriptSig.getChunks();
-
-				// Expected number of script chunks for redeem. Refund might not have the same number.
-				int expectedChunkCount = 1 /*secret*/ + 1 /*sig*/ + 1 /*pubkey*/ + 1 /*redeemScript*/;
-				if (scriptChunks.size() != expectedChunkCount)
-					continue;
-
-				// We're expecting last chunk to contain the actual redeemScript
-				ScriptChunk lastChunk = scriptChunks.get(scriptChunks.size() - 1);
-				byte[] redeemScriptBytes = lastChunk.data;
-
-				// If non-push scripts, redeemScript will be null
-				if (redeemScriptBytes == null)
-					continue;
-
-				byte[] redeemScriptHash = Crypto.hash160(redeemScriptBytes);
-				Address inputAddress = LegacyAddress.fromScriptHash(params, redeemScriptHash);
-
-				if (!inputAddress.toString().equals(p2shAddress))
-					// Input isn't spending our P2SH
-					continue;
-
-				byte[] secret = scriptChunks.get(0).data;
-				if (secret.length != BTCP2SH.SECRET_LENGTH)
-					continue;
-
-				return secret;
-			}
-		}
-
-		return null;
-	}
-
-}

src/main/java/org/qortal/crosschain/Bitcoin.java

@@ -0,0 +1,190 @@
+package org.qortal.crosschain;
+
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.EnumMap;
+import java.util.Map;
+
+import org.bitcoinj.core.Context;
+import org.bitcoinj.core.NetworkParameters;
+import org.bitcoinj.params.MainNetParams;
+import org.bitcoinj.params.RegTestParams;
+import org.bitcoinj.params.TestNet3Params;
+import org.qortal.crosschain.ElectrumX.Server;
+import org.qortal.crosschain.ElectrumX.Server.ConnectionType;
+import org.qortal.settings.Settings;
+
+public class Bitcoin extends Bitcoiny {
+
+	public static final String CURRENCY_CODE = "BTC";
+
+	// Temporary values until a dynamic fee system is written.
+	private static final long OLD_FEE_AMOUNT = 4_000L; // Not 5000 so that existing P2SH-B can output 1000, avoiding dust issue, leaving 4000 for fees.
+	private static final long NEW_FEE_TIMESTAMP = 1598280000000L; // milliseconds since epoch
+	private static final long NEW_FEE_AMOUNT = 10_000L;
+
+	private static final long NON_MAINNET_FEE = 1000L; // enough for TESTNET3 and should be OK for REGTEST
+
+	private static final Map<ElectrumX.Server.ConnectionType, Integer> DEFAULT_ELECTRUMX_PORTS = new EnumMap<>(ElectrumX.Server.ConnectionType.class);
+	static {
+		DEFAULT_ELECTRUMX_PORTS.put(ConnectionType.TCP, 50001);
+		DEFAULT_ELECTRUMX_PORTS.put(ConnectionType.SSL, 50002);
+	}
+
+	public enum BitcoinNet {
+		MAIN {
+			@Override
+			public NetworkParameters getParams() {
+				return MainNetParams.get();
+			}
+
+			@Override
+			public Collection<ElectrumX.Server> getServers() {
+				return Arrays.asList(
+						// Servers chosen on NO BASIS WHATSOEVER from various sources!
+						new Server("128.0.190.26", Server.ConnectionType.SSL, 50002),
+						new Server("hodlers.beer", Server.ConnectionType.SSL, 50002),
+						new Server("electrumx.erbium.eu", Server.ConnectionType.TCP, 50001),
+						new Server("electrumx.erbium.eu", Server.ConnectionType.SSL, 50002),
+						new Server("btc.lastingcoin.net", Server.ConnectionType.SSL, 50002),
+						new Server("electrum.bitaroo.net", Server.ConnectionType.SSL, 50002),
+						new Server("bitcoin.grey.pw", Server.ConnectionType.SSL, 50002),
+						new Server("2electrumx.hopto.me", Server.ConnectionType.SSL, 56022),
+						new Server("185.64.116.15", Server.ConnectionType.SSL, 50002),
+						new Server("kirsche.emzy.de", Server.ConnectionType.SSL, 50002),
+						new Server("alviss.coinjoined.com", Server.ConnectionType.SSL, 50002),
+						new Server("electrum.emzy.de", Server.ConnectionType.SSL, 50002),
+						new Server("electrum.emzy.de", Server.ConnectionType.TCP, 50001),
+						new Server("vmd71287.contaboserver.net", Server.ConnectionType.SSL, 50002),
+						new Server("btc.litepay.ch", Server.ConnectionType.SSL, 50002),
+						new Server("electrum.stippy.com", Server.ConnectionType.SSL, 50002),
+						new Server("xtrum.com", Server.ConnectionType.SSL, 50002),
+						new Server("electrum.acinq.co", Server.ConnectionType.SSL, 50002),
+						new Server("electrum2.taborsky.cz", Server.ConnectionType.SSL, 50002),
+						new Server("vmd63185.contaboserver.net", Server.ConnectionType.SSL, 50002),
+						new Server("electrum2.privateservers.network", Server.ConnectionType.SSL, 50002),
+						new Server("electrumx.alexridevski.net", Server.ConnectionType.SSL, 50002),
+						new Server("192.166.219.200", Server.ConnectionType.SSL, 50002),
+						new Server("2ex.digitaleveryware.com", Server.ConnectionType.SSL, 50002),
+						new Server("dxm.no-ip.biz", Server.ConnectionType.SSL, 50002),
+						new Server("caleb.vegas", Server.ConnectionType.SSL, 50002));
+			}
+
+			@Override
+			public String getGenesisHash() {
+				return "000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f";
+			}
+
+			@Override
+			public long getP2shFee(Long timestamp) {
+				// TODO: This will need to be replaced with something better in the near future!
+				if (timestamp != null && timestamp < NEW_FEE_TIMESTAMP)
+					return OLD_FEE_AMOUNT;
+
+				return NEW_FEE_AMOUNT;
+			}
+		},
+		TEST3 {
+			@Override
+			public NetworkParameters getParams() {
+				return TestNet3Params.get();
+			}
+
+			@Override
+			public Collection<ElectrumX.Server> getServers() {
+				return Arrays.asList(
+						new Server("tn.not.fyi", Server.ConnectionType.SSL, 55002),
+						new Server("electrumx-test.1209k.com", Server.ConnectionType.SSL, 50002),
+						new Server("testnet.qtornado.com", Server.ConnectionType.SSL, 51002),
+						new Server("testnet.aranguren.org", Server.ConnectionType.TCP, 51001),
+						new Server("testnet.aranguren.org", Server.ConnectionType.SSL, 51002),
+						new Server("testnet.hsmiths.com", Server.ConnectionType.SSL, 53012));
+			}
+
+			@Override
+			public String getGenesisHash() {
+				return "000000000933ea01ad0ee984209779baaec3ced90fa3f408719526f8d77f4943";
+			}
+
+			@Override
+			public long getP2shFee(Long timestamp) {
+				return NON_MAINNET_FEE;
+			}
+		},
+		REGTEST {
+			@Override
+			public NetworkParameters getParams() {
+				return RegTestParams.get();
+			}
+
+			@Override
+			public Collection<ElectrumX.Server> getServers() {
+				return Arrays.asList(
+						new Server("localhost", Server.ConnectionType.TCP, 50001),
+						new Server("localhost", Server.ConnectionType.SSL, 50002));
+			}
+
+			@Override
+			public String getGenesisHash() {
+				// This is unique to each regtest instance
+				return null;
+			}
+
+			@Override
+			public long getP2shFee(Long timestamp) {
+				return NON_MAINNET_FEE;
+			}
+		};
+
+		public abstract NetworkParameters getParams();
+		public abstract Collection<ElectrumX.Server> getServers();
+		public abstract String getGenesisHash();
+		public abstract long getP2shFee(Long timestamp) throws ForeignBlockchainException;
+	}
+
+	private static Bitcoin instance;
+
+	private final BitcoinNet bitcoinNet;
+
+	// Constructors and instance
+
+	private Bitcoin(BitcoinNet bitcoinNet, BitcoinyBlockchainProvider blockchain, Context bitcoinjContext, String currencyCode) {
+		super(blockchain, bitcoinjContext, currencyCode);
+		this.bitcoinNet = bitcoinNet;
+
+		LOGGER.info(() -> String.format("Starting Bitcoin support using %s", this.bitcoinNet.name()));
+	}
+
+	public static synchronized Bitcoin getInstance() {
+		if (instance == null) {
+			BitcoinNet bitcoinNet = Settings.getInstance().getBitcoinNet();
+
+			BitcoinyBlockchainProvider electrumX = new ElectrumX("Bitcoin-" + bitcoinNet.name(), bitcoinNet.getGenesisHash(), bitcoinNet.getServers(), DEFAULT_ELECTRUMX_PORTS);
+			Context bitcoinjContext = new Context(bitcoinNet.getParams());
+
+			instance = new Bitcoin(bitcoinNet, electrumX, bitcoinjContext, CURRENCY_CODE);
+		}
+
+		return instance;
+	}
+
+	// Getters & setters
+
+	public static synchronized void resetForTesting() {
+		instance = null;
+	}
+
+	// Actual useful methods for use by other classes
+
+	/**
+	 * Returns estimated BTC fee, in sats per 1000bytes, optionally for historic timestamp.
+	 * 
+	 * @param timestamp optional milliseconds since epoch, or null for 'now'
+	 * @return sats per 1000bytes, or throws ForeignBlockchainException if something went wrong
+	 */
+	@Override
+	public long getP2shFee(Long timestamp) throws ForeignBlockchainException {
+		return this.bitcoinNet.getP2shFee(timestamp);
+	}
+
+}

src/main/java/org/qortal/crosschain/BitcoinACCTv1.java

@@ -1,13 +1,10 @@
 package org.qortal.crosschain;
 
-import static java.util.Arrays.stream;
-import static java.util.stream.Collectors.toMap;
 import static org.ciyam.at.OpCode.calcOffset;
 
 import java.nio.ByteBuffer;
 import java.util.Arrays;
 import java.util.List;
-import java.util.Map;
 
 import org.ciyam.at.API;
 import org.ciyam.at.CompilationException;
@@ -101,11 +98,12 @@ import com.google.common.primitives.Bytes;
  * </li>
  * </ul>
  */
-public class BTCACCT {
+public class BitcoinACCTv1 implements ACCT {
+
+	public static final String NAME = BitcoinACCTv1.class.getSimpleName();
+	public static final byte[] CODE_BYTES_HASH = HashCode.fromString("f7f419522a9aaa3c671149878f8c1374dfc59d4fd86ca43ff2a4d913cfbc9e89").asBytes(); // SHA256 of AT code bytes
 
 	public static final int SECRET_LENGTH = 32;
-	public static final int MIN_LOCKTIME = 1500000000;
-	public static final byte[] CODE_BYTES_HASH = HashCode.fromString("f7f419522a9aaa3c671149878f8c1374dfc59d4fd86ca43ff2a4d913cfbc9e89").asBytes(); // SHA256 of AT code bytes
 
 	/** <b>Value</b> offset into AT segment where 'mode' variable (long) is stored. (Multiply by MachineState.VALUE_SIZE for byte offset). */
 	private static final int MODE_VALUE_OFFSET = 68;
@@ -126,22 +124,31 @@ public class BTCACCT {
 	public static final int REDEEM_MESSAGE_LENGTH = 32 /*secret*/ + 32 /*secret*/ + 32 /*partner's Qortal receiving address padded from 25 to 32*/;
 	public static final int CANCEL_MESSAGE_LENGTH = 32 /*AT creator's Qortal address*/;
 
-	public enum Mode {
-		OFFERING(0), TRADING(1), CANCELLED(2), REFUNDED(3), REDEEMED(4);
+	private static BitcoinACCTv1 instance;
 
-		public final int value;
-		private static final Map<Integer, Mode> map = stream(Mode.values()).collect(toMap(mode -> mode.value, mode -> mode));
-
-		Mode(int value) {
-			this.value = value;
-		}
-
-		public static Mode valueOf(int value) {
-			return map.get(value);
-		}
+	private BitcoinACCTv1() {
 	}
 
-	private BTCACCT() {
+	public static synchronized BitcoinACCTv1 getInstance() {
+		if (instance == null)
+			instance = new BitcoinACCTv1();
+
+		return instance;
+	}
+
+	@Override
+	public byte[] getCodeBytesHash() {
+		return CODE_BYTES_HASH;
+	}
+
+	@Override
+	public int getModeByteOffset() {
+		return MODE_BYTE_OFFSET;
+	}
+
+	@Override
+	public ForeignBlockchain getBlockchain() {
+		return Bitcoin.getInstance();
 	}
 
 	/**
@@ -156,7 +163,6 @@ public class BTCACCT {
 	 * @param qortAmount how much QORT to pay trade partner if they send correct 32-byte secrets to AT
 	 * @param bitcoinAmount how much BTC the AT creator is expecting to trade
 	 * @param tradeTimeout suggested timeout for entire trade
-	 * @return
 	 */
 	public static byte[] buildQortalAT(String creatorTradeAddress, byte[] bitcoinPublicKeyHash, byte[] hashOfSecretB, long qortAmount, long bitcoinAmount, int tradeTimeout) {
 		// Labels for data segment addresses
@@ -419,7 +425,7 @@ public class BTCACCT {
 				codeByteBuffer.put(OpCode.BNE_DAT.compile(addrMessageSender3, addrCreatorAddress3, calcOffset(codeByteBuffer, labelNotTradeNorCancelTxn)));
 				codeByteBuffer.put(OpCode.BNE_DAT.compile(addrMessageSender4, addrCreatorAddress4, calcOffset(codeByteBuffer, labelNotTradeNorCancelTxn)));
 				// Partner address is AT creator's address, so cancel offer and finish.
-				codeByteBuffer.put(OpCode.SET_VAL.compile(addrMode, Mode.CANCELLED.value));
+				codeByteBuffer.put(OpCode.SET_VAL.compile(addrMode, AcctMode.CANCELLED.value));
 				// We're finished forever (finishing auto-refunds remaining balance to AT creator)
 				codeByteBuffer.put(OpCode.FIN_IMD.compile());
 
@@ -470,7 +476,7 @@ public class BTCACCT {
 				codeByteBuffer.put(OpCode.EXT_FUN_RET_DAT_2.compile(FunctionCode.ADD_MINUTES_TO_TIMESTAMP, addrRefundTimestamp, addrLastTxnTimestamp, addrRefundTimeout));
 
 				/* We are in 'trade mode' */
-				codeByteBuffer.put(OpCode.SET_VAL.compile(addrMode, Mode.TRADING.value));
+				codeByteBuffer.put(OpCode.SET_VAL.compile(addrMode, AcctMode.TRADING.value));
 
 				// Set restart position to after this opcode
 				codeByteBuffer.put(OpCode.SET_PCS.compile());
@@ -568,7 +574,7 @@ public class BTCACCT {
 				// Pay AT's balance to receiving address
 				codeByteBuffer.put(OpCode.EXT_FUN_DAT.compile(FunctionCode.PAY_TO_ADDRESS_IN_B, addrQortAmount));
 				// Set redeemed mode
-				codeByteBuffer.put(OpCode.SET_VAL.compile(addrMode, Mode.REDEEMED.value));
+				codeByteBuffer.put(OpCode.SET_VAL.compile(addrMode, AcctMode.REDEEMED.value));
 				// We're finished forever (finishing auto-refunds remaining balance to AT creator)
 				codeByteBuffer.put(OpCode.FIN_IMD.compile());
 
@@ -578,7 +584,7 @@ public class BTCACCT {
 				labelRefund = codeByteBuffer.position();
 
 				// Set refunded mode
-				codeByteBuffer.put(OpCode.SET_VAL.compile(addrMode, Mode.REFUNDED.value));
+				codeByteBuffer.put(OpCode.SET_VAL.compile(addrMode, AcctMode.REFUNDED.value));
 				// We're finished forever (finishing auto-refunds remaining balance to AT creator)
 				codeByteBuffer.put(OpCode.FIN_IMD.compile());
 			} catch (CompilationException e) {
@@ -591,7 +597,7 @@ public class BTCACCT {
 		byte[] codeBytes = new byte[codeByteBuffer.limit()];
 		codeByteBuffer.get(codeBytes);
 
-		assert Arrays.equals(Crypto.digest(codeBytes), BTCACCT.CODE_BYTES_HASH)
+		assert Arrays.equals(Crypto.digest(codeBytes), BitcoinACCTv1.CODE_BYTES_HASH)
 			: String.format("BTCACCT.CODE_BYTES_HASH mismatch: expected %s, actual %s", HashCode.fromBytes(CODE_BYTES_HASH), HashCode.fromBytes(Crypto.digest(codeBytes)));
 
 		final short ciyamAtVersion = 2;
@@ -604,44 +610,37 @@ public class BTCACCT {
 
 	/**
 	 * Returns CrossChainTradeData with useful info extracted from AT.
-	 * 
-	 * @param repository
-	 * @param atAddress
-	 * @throws DataException
 	 */
-	public static CrossChainTradeData populateTradeData(Repository repository, ATData atData) throws DataException {
+	@Override
+	public CrossChainTradeData populateTradeData(Repository repository, ATData atData) throws DataException {
 		ATStateData atStateData = repository.getATRepository().getLatestATState(atData.getATAddress());
-		return populateTradeData(repository, atData.getCreatorPublicKey(), atStateData);
+		return populateTradeData(repository, atData.getCreatorPublicKey(), atData.getCreation(), atStateData);
 	}
 
 	/**
 	 * Returns CrossChainTradeData with useful info extracted from AT.
-	 * 
-	 * @param repository
-	 * @param atAddress
-	 * @throws DataException
 	 */
-	public static CrossChainTradeData populateTradeData(Repository repository, ATStateData atStateData) throws DataException {
-		byte[] creatorPublicKey = repository.getATRepository().getCreatorPublicKey(atStateData.getATAddress());
-		return populateTradeData(repository, creatorPublicKey, atStateData);
+	@Override
+	public CrossChainTradeData populateTradeData(Repository repository, ATStateData atStateData) throws DataException {
+		ATData atData = repository.getATRepository().fromATAddress(atStateData.getATAddress());
+		return populateTradeData(repository, atData.getCreatorPublicKey(), atData.getCreation(), atStateData);
 	}
 
 	/**
 	 * Returns CrossChainTradeData with useful info extracted from AT.
-	 * 
-	 * @param repository
-	 * @param atAddress
-	 * @throws DataException
 	 */
-	public static CrossChainTradeData populateTradeData(Repository repository, byte[] creatorPublicKey, ATStateData atStateData) throws DataException {
+	public CrossChainTradeData populateTradeData(Repository repository, byte[] creatorPublicKey, long creationTimestamp, ATStateData atStateData) throws DataException {
 		byte[] addressBytes = new byte[25]; // for general use
 		String atAddress = atStateData.getATAddress();
 
 		CrossChainTradeData tradeData = new CrossChainTradeData();
 
+		tradeData.foreignBlockchain = SupportedBlockchain.BITCOIN.name();
+		tradeData.acctName = NAME;
+
 		tradeData.qortalAtAddress = atAddress;
 		tradeData.qortalCreator = Crypto.toAddress(creatorPublicKey);
-		tradeData.creationTimestamp = atStateData.getCreation();
+		tradeData.creationTimestamp = creationTimestamp;
 
 		Account atAccount = new Account(repository, atAddress);
 		tradeData.qortBalance = atAccount.getConfirmedBalance(Asset.QORT);
@@ -658,9 +657,9 @@ public class BTCACCT {
 		dataByteBuffer.position(dataByteBuffer.position() + 32 - addressBytes.length);
 
 		// Creator's Bitcoin/foreign public key hash
-		tradeData.creatorBitcoinPKH = new byte[20];
-		dataByteBuffer.get(tradeData.creatorBitcoinPKH);
-		dataByteBuffer.position(dataByteBuffer.position() + 32 - tradeData.creatorBitcoinPKH.length); // skip to 32 bytes
+		tradeData.creatorForeignPKH = new byte[20];
+		dataByteBuffer.get(tradeData.creatorForeignPKH);
+		dataByteBuffer.position(dataByteBuffer.position() + 32 - tradeData.creatorForeignPKH.length); // skip to 32 bytes
 
 		// Hash of secret B
 		tradeData.hashOfSecretB = new byte[20];
@@ -671,7 +670,7 @@ public class BTCACCT {
 		tradeData.qortAmount = dataByteBuffer.getLong();
 
 		// Expected BTC amount
-		tradeData.expectedBitcoin = dataByteBuffer.getLong();
+		tradeData.expectedForeignAmount = dataByteBuffer.getLong();
 
 		// Trade timeout
 		tradeData.tradeTimeout = (int) dataByteBuffer.getLong();
@@ -784,26 +783,28 @@ public class BTCACCT {
 
 		// Trade AT's 'mode'
 		long modeValue = dataByteBuffer.getLong();
-		Mode mode = Mode.valueOf((int) (modeValue & 0xffL));
+		AcctMode acctMode = AcctMode.valueOf((int) (modeValue & 0xffL));
 
 		/* End of variables */
 
-		if (mode != null && mode != Mode.OFFERING) {
-			tradeData.mode = mode;
+		if (acctMode != null && acctMode != AcctMode.OFFERING) {
+			tradeData.mode = acctMode;
 			tradeData.refundTimeout = refundTimeout;
 			tradeData.tradeRefundHeight = new Timestamp(tradeRefundTimestamp).blockHeight;
 			tradeData.qortalPartnerAddress = qortalRecipient;
 			tradeData.hashOfSecretA = hashOfSecretA;
-			tradeData.partnerBitcoinPKH = partnerBitcoinPKH;
+			tradeData.partnerForeignPKH = partnerBitcoinPKH;
 			tradeData.lockTimeA = lockTimeA;
 			tradeData.lockTimeB = lockTimeB;
 
-			if (mode == Mode.REDEEMED)
+			if (acctMode == AcctMode.REDEEMED)
 				tradeData.qortalPartnerReceivingAddress = Base58.encode(partnerReceivingAddress);
 		} else {
-			tradeData.mode = Mode.OFFERING;
+			tradeData.mode = AcctMode.OFFERING;
 		}
 
+		tradeData.duplicateDeprecated();
+
 		return tradeData;
 	}
 
@@ -843,7 +844,8 @@ public class BTCACCT {
 	}
 
 	/** Returns 'cancel' MESSAGE payload for AT creator to cancel trade AT. */
-	public static byte[] buildCancelMessage(String creatorQortalAddress) {
+	@Override
+	public byte[] buildCancelMessage(String creatorQortalAddress) {
 		byte[] data = new byte[CANCEL_MESSAGE_LENGTH];
 		byte[] creatorQortalAddressBytes = Base58.decode(creatorQortalAddress);
 
@@ -866,7 +868,7 @@ public class BTCACCT {
 
 	/** Returns P2SH-B lockTime (epoch seconds) based on trade partner's 'offer' MESSAGE timestamp and P2SH-A locktime. */
 	public static int calcLockTimeB(long offerMessageTimestamp, int lockTimeA) {
-		// lockTimeB is halfway between offerMessageTimesamp and lockTimeA
+		// lockTimeB is halfway between offerMessageTimestamp and lockTimeA
 		return (int) ((lockTimeA + (offerMessageTimestamp / 1000L)) / 2L);
 	}
 
@@ -874,7 +876,8 @@ public class BTCACCT {
 		String atAddress = crossChainTradeData.qortalAtAddress;
 		String redeemerAddress = crossChainTradeData.qortalPartnerAddress;
 
-		List<MessageTransactionData> messageTransactionsData = repository.getTransactionRepository().getMessagesByRecipient(atAddress, null, null, null);
+		// We don't have partner's public key so we check every message to AT
+		List<MessageTransactionData> messageTransactionsData = repository.getMessageRepository().getMessagesByParticipants(null, atAddress, null, null, null);
 		if (messageTransactionsData == null)
 			return null;
 

src/main/java/org/qortal/crosschain/Bitcoiny.java

@@ -0,0 +1,740 @@
+package org.qortal.crosschain;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.bitcoinj.core.Address;
+import org.bitcoinj.core.AddressFormatException;
+import org.bitcoinj.core.Coin;
+import org.bitcoinj.core.Context;
+import org.bitcoinj.core.ECKey;
+import org.bitcoinj.core.InsufficientMoneyException;
+import org.bitcoinj.core.LegacyAddress;
+import org.bitcoinj.core.NetworkParameters;
+import org.bitcoinj.core.Sha256Hash;
+import org.bitcoinj.core.Transaction;
+import org.bitcoinj.core.TransactionOutput;
+import org.bitcoinj.core.UTXO;
+import org.bitcoinj.core.UTXOProvider;
+import org.bitcoinj.core.UTXOProviderException;
+import org.bitcoinj.crypto.ChildNumber;
+import org.bitcoinj.crypto.DeterministicHierarchy;
+import org.bitcoinj.crypto.DeterministicKey;
+import org.bitcoinj.script.Script.ScriptType;
+import org.bitcoinj.script.ScriptBuilder;
+import org.bitcoinj.wallet.DeterministicKeyChain;
+import org.bitcoinj.wallet.SendRequest;
+import org.bitcoinj.wallet.Wallet;
+import org.qortal.api.model.SimpleForeignTransaction;
+import org.qortal.crypto.Crypto;
+import org.qortal.utils.Amounts;
+import org.qortal.utils.BitTwiddling;
+
+import com.google.common.hash.HashCode;
+
+/** Bitcoin-like (Bitcoin, Litecoin, etc.) support */
+public abstract class Bitcoiny implements ForeignBlockchain {
+
+	protected static final Logger LOGGER = LogManager.getLogger(Bitcoiny.class);
+
+	public static final int HASH160_LENGTH = 20;
+
+	protected final BitcoinyBlockchainProvider blockchain;
+	protected final Context bitcoinjContext;
+	protected final String currencyCode;
+
+	protected final NetworkParameters params;
+
+	/** Keys that have been previously marked as fully spent,<br>
+	 * i.e. keys with transactions but with no unspent outputs. */
+	protected final Set<ECKey> spentKeys = Collections.synchronizedSet(new HashSet<>());
+
+	/** How many bitcoinj wallet keys to generate in each batch. */
+	private static final int WALLET_KEY_LOOKAHEAD_INCREMENT = 3;
+
+	/** Byte offset into raw block headers to block timestamp. */
+	private static final int TIMESTAMP_OFFSET = 4 + 32 + 32;
+
+	// Constructors and instance
+
+	protected Bitcoiny(BitcoinyBlockchainProvider blockchain, Context bitcoinjContext, String currencyCode) {
+		this.blockchain = blockchain;
+		this.bitcoinjContext = bitcoinjContext;
+		this.currencyCode = currencyCode;
+
+		this.params = this.bitcoinjContext.getParams();
+	}
+
+	// Getters & setters
+
+	public BitcoinyBlockchainProvider getBlockchainProvider() {
+		return this.blockchain;
+	}
+
+	public Context getBitcoinjContext() {
+		return this.bitcoinjContext;
+	}
+
+	public String getCurrencyCode() {
+		return this.currencyCode;
+	}
+
+	public NetworkParameters getNetworkParameters() {
+		return this.params;
+	}
+
+	// Interface obligations
+
+	@Override
+	public boolean isValidAddress(String address) {
+		try {
+			ScriptType addressType = Address.fromString(this.params, address).getOutputScriptType();
+
+			return addressType == ScriptType.P2PKH || addressType == ScriptType.P2SH;
+		} catch (AddressFormatException e) {
+			return false;
+		}
+	}
+
+	@Override
+	public boolean isValidWalletKey(String walletKey) {
+		return this.isValidDeterministicKey(walletKey);
+	}
+
+	// Actual useful methods for use by other classes
+
+	public String format(Coin amount) {
+		return this.format(amount.value);
+	}
+
+	public String format(long amount) {
+		return Amounts.prettyAmount(amount) + " " + this.currencyCode;
+	}
+
+	public boolean isValidDeterministicKey(String key58) {
+		try {
+			Context.propagate(this.bitcoinjContext);
+			DeterministicKey.deserializeB58(null, key58, this.params);
+			return true;
+		} catch (IllegalArgumentException e) {
+			return false;
+		}
+	}
+
+	/** Returns P2PKH address using passed public key hash. */
+	public String pkhToAddress(byte[] publicKeyHash) {
+		Context.propagate(this.bitcoinjContext);
+		return LegacyAddress.fromPubKeyHash(this.params, publicKeyHash).toString();
+	}
+
+	/** Returns P2SH address using passed redeem script. */
+	public String deriveP2shAddress(byte[] redeemScriptBytes) {
+		Context.propagate(bitcoinjContext);
+		byte[] redeemScriptHash = Crypto.hash160(redeemScriptBytes);
+		return LegacyAddress.fromScriptHash(this.params, redeemScriptHash).toString();
+	}
+
+	/**
+	 * Returns median timestamp from latest 11 blocks, in seconds.
+	 * <p>
+	 * @throws ForeignBlockchainException if error occurs
+	 */
+	public int getMedianBlockTime() throws ForeignBlockchainException {
+		int height = this.blockchain.getCurrentHeight();
+
+		// Grab latest 11 blocks
+		List<byte[]> blockHeaders = this.blockchain.getRawBlockHeaders(height - 11, 11);
+		if (blockHeaders.size() < 11)
+			throw new ForeignBlockchainException("Not enough blocks to determine median block time");
+
+		List<Integer> blockTimestamps = blockHeaders.stream().map(blockHeader -> BitTwiddling.intFromLEBytes(blockHeader, TIMESTAMP_OFFSET)).collect(Collectors.toList());
+
+		// Descending order
+		blockTimestamps.sort((a, b) -> Integer.compare(b, a));
+
+		// Pick median
+		return blockTimestamps.get(5);
+	}
+
+	/** Returns fee per transaction KB. To be overridden for testnet/regtest. */
+	public Coin getFeePerKb() {
+		return this.bitcoinjContext.getFeePerKb();
+	}
+
+	/**
+	 * Returns fixed P2SH spending fee, in sats per 1000bytes, optionally for historic timestamp.
+	 *
+	 * @param timestamp optional milliseconds since epoch, or null for 'now'
+	 * @return sats per 1000bytes
+	 * @throws ForeignBlockchainException if something went wrong
+	 */
+	public abstract long getP2shFee(Long timestamp) throws ForeignBlockchainException;
+
+	/**
+	 * Returns confirmed balance, based on passed payment script.
+	 * <p>
+	 * @return confirmed balance, or zero if script unknown
+	 * @throws ForeignBlockchainException if there was an error
+	 */
+	public long getConfirmedBalance(String base58Address) throws ForeignBlockchainException {
+		return this.blockchain.getConfirmedBalance(addressToScriptPubKey(base58Address));
+	}
+
+	/**
+	 * Returns list of unspent outputs pertaining to passed address.
+	 * <p>
+	 * @return list of unspent outputs, or empty list if address unknown
+	 * @throws ForeignBlockchainException if there was an error.
+	 */
+	// TODO: don't return bitcoinj-based objects like TransactionOutput, use BitcoinyTransaction.Output instead
+	public List<TransactionOutput> getUnspentOutputs(String base58Address) throws ForeignBlockchainException {
+		List<UnspentOutput> unspentOutputs = this.blockchain.getUnspentOutputs(addressToScriptPubKey(base58Address), false);
+
+		List<TransactionOutput> unspentTransactionOutputs = new ArrayList<>();
+		for (UnspentOutput unspentOutput : unspentOutputs) {
+			List<TransactionOutput> transactionOutputs = this.getOutputs(unspentOutput.hash);
+
+			unspentTransactionOutputs.add(transactionOutputs.get(unspentOutput.index));
+		}
+
+		return unspentTransactionOutputs;
+	}
+
+	/**
+	 * Returns list of outputs pertaining to passed transaction hash.
+	 * <p>
+	 * @return list of outputs, or empty list if transaction unknown
+	 * @throws ForeignBlockchainException if there was an error.
+	 */
+	// TODO: don't return bitcoinj-based objects like TransactionOutput, use BitcoinyTransaction.Output instead
+	public List<TransactionOutput> getOutputs(byte[] txHash) throws ForeignBlockchainException {
+		byte[] rawTransactionBytes = this.blockchain.getRawTransaction(txHash);
+
+		Context.propagate(bitcoinjContext);
+		Transaction transaction = new Transaction(this.params, rawTransactionBytes);
+		return transaction.getOutputs();
+	}
+
+	/**
+	 * Returns list of transaction hashes pertaining to passed address.
+	 * <p>
+	 * @return list of unspent outputs, or empty list if script unknown
+	 * @throws ForeignBlockchainException if there was an error.
+	 */
+	public List<TransactionHash> getAddressTransactions(String base58Address, boolean includeUnconfirmed) throws ForeignBlockchainException {
+		return this.blockchain.getAddressTransactions(addressToScriptPubKey(base58Address), includeUnconfirmed);
+	}
+
+	/**
+	 * Returns list of raw, confirmed transactions involving given address.
+	 * <p>
+	 * @throws ForeignBlockchainException if there was an error
+	 */
+	public List<byte[]> getAddressTransactions(String base58Address) throws ForeignBlockchainException {
+		List<TransactionHash> transactionHashes = this.blockchain.getAddressTransactions(addressToScriptPubKey(base58Address), false);
+
+		List<byte[]> rawTransactions = new ArrayList<>();
+		for (TransactionHash transactionInfo : transactionHashes) {
+			byte[] rawTransaction = this.blockchain.getRawTransaction(HashCode.fromString(transactionInfo.txHash).asBytes());
+			rawTransactions.add(rawTransaction);
+		}
+
+		return rawTransactions;
+	}
+
+	/**
+	 * Returns transaction info for passed transaction hash.
+	 * <p>
+	 * @throws ForeignBlockchainException.NotFoundException if transaction unknown
+	 * @throws ForeignBlockchainException if error occurs
+	 */
+	public BitcoinyTransaction getTransaction(String txHash) throws ForeignBlockchainException {
+		return this.blockchain.getTransaction(txHash);
+	}
+
+	/**
+	 * Broadcasts raw transaction to network.
+	 * <p>
+	 * @throws ForeignBlockchainException if error occurs
+	 */
+	public void broadcastTransaction(Transaction transaction) throws ForeignBlockchainException {
+		this.blockchain.broadcastTransaction(transaction.bitcoinSerialize());
+	}
+
+	/**
+	 * Returns bitcoinj transaction sending <tt>amount</tt> to <tt>recipient</tt>.
+	 *
+	 * @param xprv58 BIP32 private key
+	 * @param recipient P2PKH address
+	 * @param amount unscaled amount
+	 * @param feePerByte unscaled fee per byte, or null to use default fees
+	 * @return transaction, or null if insufficient funds
+	 */
+	public Transaction buildSpend(String xprv58, String recipient, long amount, Long feePerByte) {
+		Context.propagate(bitcoinjContext);
+
+		Wallet wallet = Wallet.fromSpendingKeyB58(this.params, xprv58, DeterministicHierarchy.BIP32_STANDARDISATION_TIME_SECS);
+		wallet.setUTXOProvider(new WalletAwareUTXOProvider(this, wallet));
+
+		Address destination = Address.fromString(this.params, recipient);
+		SendRequest sendRequest = SendRequest.to(destination, Coin.valueOf(amount));
+
+		if (feePerByte != null)
+			sendRequest.feePerKb = Coin.valueOf(feePerByte * 1000L); // Note: 1000 not 1024
+		else
+			// Allow override of default for TestNet3, etc.
+			sendRequest.feePerKb = this.getFeePerKb();
+
+		try {
+			wallet.completeTx(sendRequest);
+			return sendRequest.tx;
+		} catch (InsufficientMoneyException e) {
+			return null;
+		}
+	}
+
+	/**
+	 * Returns bitcoinj transaction sending <tt>amount</tt> to <tt>recipient</tt> using default fees.
+	 *
+	 * @param xprv58 BIP32 private key
+	 * @param recipient P2PKH address
+	 * @param amount unscaled amount
+	 * @return transaction, or null if insufficient funds
+	 */
+	public Transaction buildSpend(String xprv58, String recipient, long amount) {
+		return buildSpend(xprv58, recipient, amount, null);
+	}
+
+	/**
+	 * Returns unspent Bitcoin balance given 'm' BIP32 key.
+	 *
+	 * @param key58 BIP32/HD extended Bitcoin private/public key
+	 * @return unspent BTC balance, or null if unable to determine balance
+	 */
+	public Long getWalletBalance(String key58) {
+		Context.propagate(bitcoinjContext);
+
+		Wallet wallet = walletFromDeterministicKey58(key58);
+		wallet.setUTXOProvider(new WalletAwareUTXOProvider(this, wallet));
+
+		Coin balance = wallet.getBalance();
+		if (balance == null)
+			return null;
+
+		return balance.value;
+	}
+
+	public List<SimpleTransaction> getWalletTransactions(String key58) throws ForeignBlockchainException {
+		Context.propagate(bitcoinjContext);
+
+		Wallet wallet = walletFromDeterministicKey58(key58);
+		DeterministicKeyChain keyChain = wallet.getActiveKeyChain();
+
+		keyChain.setLookaheadSize(Bitcoiny.WALLET_KEY_LOOKAHEAD_INCREMENT);
+		keyChain.maybeLookAhead();
+
+		List<DeterministicKey> keys = new ArrayList<>(keyChain.getLeafKeys());
+
+		Set<BitcoinyTransaction> walletTransactions = new HashSet<>();
+		Set<String> keySet = new HashSet<>();
+
+		int ki = 0;
+		do {
+			boolean areAllKeysUnused = true;
+
+			for (; ki < keys.size(); ++ki) {
+				DeterministicKey dKey = keys.get(ki);
+
+				// Check for transactions
+				Address address = Address.fromKey(this.params, dKey, ScriptType.P2PKH);
+				keySet.add(address.toString());
+				byte[] script = ScriptBuilder.createOutputScript(address).getProgram();
+
+				// Ask for transaction history - if it's empty then key has never been used
+				List<TransactionHash> historicTransactionHashes = this.blockchain.getAddressTransactions(script, false);
+
+				if (!historicTransactionHashes.isEmpty()) {
+					areAllKeysUnused = false;
+
+					for (TransactionHash transactionHash : historicTransactionHashes)
+						walletTransactions.add(this.getTransaction(transactionHash.txHash));
+				}
+			}
+
+			if (areAllKeysUnused)
+				// No transactions for this batch of keys so assume we're done searching.
+				break;
+
+			// Generate some more keys
+			keys.addAll(generateMoreKeys(keyChain));
+
+			// Process new keys
+		} while (true);
+
+		Comparator<SimpleTransaction> newestTimestampFirstComparator = Comparator.comparingInt(SimpleTransaction::getTimestamp).reversed();
+
+		return walletTransactions.stream().map(t -> convertToSimpleTransaction(t, keySet)).sorted(newestTimestampFirstComparator).collect(Collectors.toList());
+	}
+
+	protected SimpleTransaction convertToSimpleTransaction(BitcoinyTransaction t, Set<String> keySet) {
+		long amount = 0;
+		long total = 0L;
+		for (BitcoinyTransaction.Input input : t.inputs) {
+			try {
+				BitcoinyTransaction t2 = getTransaction(input.outputTxHash);
+				List<String> senders = t2.outputs.get(input.outputVout).addresses;
+				for (String sender : senders) {
+					if (keySet.contains(sender)) {
+						total += t2.outputs.get(input.outputVout).value;
+					}
+				}
+			} catch (ForeignBlockchainException e) {
+				LOGGER.trace("Failed to retrieve transaction information {}", input.outputTxHash);
+			}
+		}
+		if (t.outputs != null && !t.outputs.isEmpty()) {
+			for (BitcoinyTransaction.Output output : t.outputs) {
+				for (String address : output.addresses) {
+					if (keySet.contains(address)) {
+						if (total > 0L) {
+							amount -= (total - output.value);
+						} else {
+							amount += output.value;
+						}
+					}
+				}
+			}
+		}
+		return new SimpleTransaction(t.txHash, t.timestamp, amount);
+	}
+
+	/**
+	 * Returns first unused receive address given 'm' BIP32 key.
+	 *
+	 * @param key58 BIP32/HD extended Bitcoin private/public key
+	 * @return P2PKH address
+	 * @throws ForeignBlockchainException if something went wrong
+	 */
+	public String getUnusedReceiveAddress(String key58) throws ForeignBlockchainException {
+		Context.propagate(bitcoinjContext);
+
+		Wallet wallet = walletFromDeterministicKey58(key58);
+		DeterministicKeyChain keyChain = wallet.getActiveKeyChain();
+
+		keyChain.setLookaheadSize(Bitcoiny.WALLET_KEY_LOOKAHEAD_INCREMENT);
+		keyChain.maybeLookAhead();
+
+		final int keyChainPathSize = keyChain.getAccountPath().size();
+		List<DeterministicKey> keys = new ArrayList<>(keyChain.getLeafKeys());
+
+		int ki = 0;
+		do {
+			for (; ki < keys.size(); ++ki) {
+				DeterministicKey dKey = keys.get(ki);
+				List<ChildNumber> dKeyPath = dKey.getPath();
+
+				// If keyChain is based on 'm', then make sure dKey is m/0/ki - i.e. a 'receive' address, not 'change' (m/1/ki)
+				if (dKeyPath.size() != keyChainPathSize + 2 || dKeyPath.get(dKeyPath.size() - 2) != ChildNumber.ZERO)
+					continue;
+
+				// Check unspent
+				Address address = Address.fromKey(this.params, dKey, ScriptType.P2PKH);
+				byte[] script = ScriptBuilder.createOutputScript(address).getProgram();
+
+				List<UnspentOutput> unspentOutputs = this.blockchain.getUnspentOutputs(script, false);
+
+				/*
+				 * If there are no unspent outputs then either:
+				 * a) all the outputs have been spent
+				 * b) address has never been used
+				 *
+				 * For case (a) we want to remember not to check this address (key) again.
+				 */
+
+				if (unspentOutputs.isEmpty()) {
+					// If this is a known key that has been spent before, then we can skip asking for transaction history
+					if (this.spentKeys.contains(dKey)) {
+						wallet.getActiveKeyChain().markKeyAsUsed(dKey);
+						continue;
+					}
+
+					// Ask for transaction history - if it's empty then key has never been used
+					List<TransactionHash> historicTransactionHashes = this.blockchain.getAddressTransactions(script, false);
+
+					if (!historicTransactionHashes.isEmpty()) {
+						// Fully spent key - case (a)
+						this.spentKeys.add(dKey);
+						wallet.getActiveKeyChain().markKeyAsUsed(dKey);
+						continue;
+					}
+
+					// Key never been used - case (b)
+					return address.toString();
+				}
+
+				// Key has unspent outputs, hence used, so no good to us
+				this.spentKeys.remove(dKey);
+			}
+
+			// Generate some more keys
+			keys.addAll(generateMoreKeys(keyChain));
+
+			// Process new keys
+		} while (true);
+	}
+
+	// UTXOProvider support
+
+	static class WalletAwareUTXOProvider implements UTXOProvider {
+		private final Bitcoiny bitcoiny;
+		private final Wallet wallet;
+
+		private final DeterministicKeyChain keyChain;
+
+		public WalletAwareUTXOProvider(Bitcoiny bitcoiny, Wallet wallet) {
+			this.bitcoiny = bitcoiny;
+			this.wallet = wallet;
+			this.keyChain = this.wallet.getActiveKeyChain();
+
+			// Set up wallet's key chain
+			this.keyChain.setLookaheadSize(Bitcoiny.WALLET_KEY_LOOKAHEAD_INCREMENT);
+			this.keyChain.maybeLookAhead();
+		}
+
+		@Override
+		public List<UTXO> getOpenTransactionOutputs(List<ECKey> keys) throws UTXOProviderException {
+			List<UTXO> allUnspentOutputs = new ArrayList<>();
+			final boolean coinbase = false;
+
+			int ki = 0;
+			do {
+				boolean areAllKeysUnspent = true;
+
+				for (; ki < keys.size(); ++ki) {
+					ECKey key = keys.get(ki);
+
+					Address address = Address.fromKey(this.bitcoiny.params, key, ScriptType.P2PKH);
+					byte[] script = ScriptBuilder.createOutputScript(address).getProgram();
+
+					List<UnspentOutput> unspentOutputs;
+					try {
+						unspentOutputs = this.bitcoiny.blockchain.getUnspentOutputs(script, false);
+					} catch (ForeignBlockchainException e) {
+						throw new UTXOProviderException(String.format("Unable to fetch unspent outputs for %s", address));
+					}
+
+					/*
+					 * If there are no unspent outputs then either:
+					 * a) all the outputs have been spent
+					 * b) address has never been used
+					 *
+					 * For case (a) we want to remember not to check this address (key) again.
+					 */
+
+					if (unspentOutputs.isEmpty()) {
+						// If this is a known key that has been spent before, then we can skip asking for transaction history
+						if (this.bitcoiny.spentKeys.contains(key)) {
+							this.wallet.getActiveKeyChain().markKeyAsUsed((DeterministicKey) key);
+							areAllKeysUnspent = false;
+							continue;
+						}
+
+						// Ask for transaction history - if it's empty then key has never been used
+						List<TransactionHash> historicTransactionHashes;
+						try {
+							historicTransactionHashes = this.bitcoiny.blockchain.getAddressTransactions(script, false);
+						} catch (ForeignBlockchainException e) {
+							throw new UTXOProviderException(String.format("Unable to fetch transaction history for %s", address));
+						}
+
+						if (!historicTransactionHashes.isEmpty()) {
+							// Fully spent key - case (a)
+							this.bitcoiny.spentKeys.add(key);
+							this.wallet.getActiveKeyChain().markKeyAsUsed((DeterministicKey) key);
+							areAllKeysUnspent = false;
+						} else {
+							// Key never been used - case (b)
+						}
+
+						continue;
+					}
+
+					// If we reach here, then there's definitely at least one unspent key
+					this.bitcoiny.spentKeys.remove(key);
+
+					for (UnspentOutput unspentOutput : unspentOutputs) {
+						List<TransactionOutput> transactionOutputs;
+						try {
+							transactionOutputs = this.bitcoiny.getOutputs(unspentOutput.hash);
+						} catch (ForeignBlockchainException e) {
+							throw new UTXOProviderException(String.format("Unable to fetch outputs for TX %s",
+									HashCode.fromBytes(unspentOutput.hash)));
+						}
+
+						TransactionOutput transactionOutput = transactionOutputs.get(unspentOutput.index);
+
+						UTXO utxo = new UTXO(Sha256Hash.wrap(unspentOutput.hash), unspentOutput.index,
+								Coin.valueOf(unspentOutput.value), unspentOutput.height, coinbase,
+								transactionOutput.getScriptPubKey());
+
+						allUnspentOutputs.add(utxo);
+					}
+				}
+
+				if (areAllKeysUnspent)
+					// No transactions for this batch of keys so assume we're done searching.
+					return allUnspentOutputs;
+
+				// Generate some more keys
+				keys.addAll(Bitcoiny.generateMoreKeys(this.keyChain));
+
+				// Process new keys
+			} while (true);
+		}
+
+		@Override
+		public int getChainHeadHeight() throws UTXOProviderException {
+			try {
+				return this.bitcoiny.blockchain.getCurrentHeight();
+			} catch (ForeignBlockchainException e) {
+				throw new UTXOProviderException("Unable to determine Bitcoiny chain height");
+			}
+		}
+
+		@Override
+		public NetworkParameters getParams() {
+			return this.bitcoiny.params;
+		}
+	}
+
+	// Utility methods for others
+
+	public static List<SimpleForeignTransaction> simplifyWalletTransactions(List<BitcoinyTransaction> transactions) {
+		// Sort by oldest timestamp first
+		transactions.sort(Comparator.comparingInt(t -> t.timestamp));
+
+		// Manual 2nd-level sort same-timestamp transactions so that a transaction's input comes first
+		int fromIndex = 0;
+		do {
+			int timestamp = transactions.get(fromIndex).timestamp;
+
+			int toIndex;
+			for (toIndex = fromIndex + 1; toIndex < transactions.size(); ++toIndex)
+				if (transactions.get(toIndex).timestamp != timestamp)
+					break;
+
+			// Process same-timestamp sub-list
+			List<BitcoinyTransaction> subList = transactions.subList(fromIndex, toIndex);
+
+			// Only if necessary
+			if (subList.size() > 1) {
+				// Quick index lookup
+				Map<String, Integer> indexByTxHash = subList.stream().collect(Collectors.toMap(t -> t.txHash, t -> t.timestamp));
+
+				int restartIndex = 0;
+				boolean isSorted;
+				do {
+					isSorted = true;
+
+					for (int ourIndex = restartIndex; ourIndex < subList.size(); ++ourIndex) {
+						BitcoinyTransaction ourTx = subList.get(ourIndex);
+
+						for (BitcoinyTransaction.Input input : ourTx.inputs) {
+							Integer inputIndex = indexByTxHash.get(input.outputTxHash);
+
+							if (inputIndex != null && inputIndex > ourIndex) {
+								// Input tx is currently after current tx, so swap
+								BitcoinyTransaction tmpTx = subList.get(inputIndex);
+								subList.set(inputIndex, ourTx);
+								subList.set(ourIndex, tmpTx);
+
+								// Update index lookup too
+								indexByTxHash.put(ourTx.txHash, inputIndex);
+								indexByTxHash.put(tmpTx.txHash, ourIndex);
+
+								if (isSorted)
+									restartIndex = Math.max(restartIndex, ourIndex);
+
+								isSorted = false;
+								break;
+							}
+						}
+					}
+				} while (!isSorted);
+			}
+
+			fromIndex = toIndex;
+		} while (fromIndex < transactions.size());
+
+		// Simplify
+		List<SimpleForeignTransaction> simpleTransactions = new ArrayList<>();
+
+		// Quick lookup of txs in our wallet
+		Set<String> walletTxHashes = transactions.stream().map(t -> t.txHash).collect(Collectors.toSet());
+
+		for (BitcoinyTransaction transaction : transactions) {
+			SimpleForeignTransaction.Builder builder = new SimpleForeignTransaction.Builder();
+			builder.txHash(transaction.txHash);
+			builder.timestamp(transaction.timestamp);
+
+			builder.isSentNotReceived(false);
+
+			for (BitcoinyTransaction.Input input : transaction.inputs) {
+				// TODO: add input via builder
+
+				if (walletTxHashes.contains(input.outputTxHash))
+					builder.isSentNotReceived(true);
+			}
+
+			for (BitcoinyTransaction.Output output : transaction.outputs)
+				builder.output(output.addresses, output.value);
+
+			simpleTransactions.add(builder.build());
+		}
+
+		return simpleTransactions;
+	}
+
+	// Utility methods for us
+
+	protected static List<DeterministicKey> generateMoreKeys(DeterministicKeyChain keyChain) {
+		int existingLeafKeyCount = keyChain.getLeafKeys().size();
+
+		// Increase lookahead size...
+		keyChain.setLookaheadSize(keyChain.getLookaheadSize() + Bitcoiny.WALLET_KEY_LOOKAHEAD_INCREMENT);
+		// ...and lookahead threshold (minimum number of keys to generate)...
+		keyChain.setLookaheadThreshold(0);
+		// ...so that this call will generate more keys
+		keyChain.maybeLookAhead();
+
+		// This returns *all* keys
+		List<DeterministicKey> allLeafKeys = keyChain.getLeafKeys();
+
+		// Only return newly generated keys
+		return allLeafKeys.subList(existingLeafKeyCount, allLeafKeys.size());
+	}
+
+	protected byte[] addressToScriptPubKey(String base58Address) {
+		Context.propagate(this.bitcoinjContext);
+		Address address = Address.fromString(this.params, base58Address);
+		return ScriptBuilder.createOutputScript(address).getProgram();
+	}
+
+	protected Wallet walletFromDeterministicKey58(String key58) {
+		DeterministicKey dKey = DeterministicKey.deserializeB58(null, key58, this.params);
+
+		if (dKey.hasPrivKey())
+			return Wallet.fromSpendingKeyB58(this.params, key58, DeterministicHierarchy.BIP32_STANDARDISATION_TIME_SECS);
+		else
+			return Wallet.fromWatchingKeyB58(this.params, key58, DeterministicHierarchy.BIP32_STANDARDISATION_TIME_SECS);
+	}
+
+}

src/main/java/org/qortal/crosschain/BitcoinyBlockchainProvider.java

@@ -0,0 +1,40 @@
+package org.qortal.crosschain;
+
+import java.util.List;
+
+public abstract class BitcoinyBlockchainProvider {
+
+	public static final boolean INCLUDE_UNCONFIRMED = true;
+	public static final boolean EXCLUDE_UNCONFIRMED = false;
+
+	/** Returns ID unique to bitcoiny network (e.g. "Litecoin-TEST3") */
+	public abstract String getNetId();
+
+	/** Returns current blockchain height. */
+	public abstract int getCurrentHeight() throws ForeignBlockchainException;
+
+	/** Returns a list of raw block headers, starting at <tt>startHeight</tt> (inclusive), up to <tt>count</tt> max. */
+	public abstract List<byte[]> getRawBlockHeaders(int startHeight, int count) throws ForeignBlockchainException;
+
+	/** Returns balance of address represented by <tt>scriptPubKey</tt>. */
+	public abstract long getConfirmedBalance(byte[] scriptPubKey) throws ForeignBlockchainException;
+
+	/** Returns raw, serialized, transaction bytes given <tt>txHash</tt>. */
+	public abstract byte[] getRawTransaction(String txHash) throws ForeignBlockchainException;
+
+	/** Returns raw, serialized, transaction bytes given <tt>txHash</tt>. */
+	public abstract byte[] getRawTransaction(byte[] txHash) throws ForeignBlockchainException;
+
+	/** Returns unpacked transaction given <tt>txHash</tt>. */
+	public abstract BitcoinyTransaction getTransaction(String txHash) throws ForeignBlockchainException;
+
+	/** Returns list of transaction hashes (and heights) for address represented by <tt>scriptPubKey</tt>, optionally including unconfirmed transactions. */
+	public abstract List<TransactionHash> getAddressTransactions(byte[] scriptPubKey, boolean includeUnconfirmed) throws ForeignBlockchainException;
+
+	/** Returns list of unspent transaction outputs for address represented by <tt>scriptPubKey</tt>, optionally including unconfirmed transactions. */
+	public abstract List<UnspentOutput> getUnspentOutputs(byte[] scriptPubKey, boolean includeUnconfirmed) throws ForeignBlockchainException;
+
+	/** Broadcasts raw, serialized, transaction bytes to network, returning success/failure. */
+	public abstract void broadcastTransaction(byte[] rawTransaction) throws ForeignBlockchainException;
+
+}

src/main/java/org/qortal/crosschain/BitcoinyHTLC.java

@@ -0,0 +1,438 @@
+package org.qortal.crosschain;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.function.Function;
+
+import org.bitcoinj.core.Address;
+import org.bitcoinj.core.Coin;
+import org.bitcoinj.core.ECKey;
+import org.bitcoinj.core.LegacyAddress;
+import org.bitcoinj.core.NetworkParameters;
+import org.bitcoinj.core.Transaction;
+import org.bitcoinj.core.Transaction.SigHash;
+import org.bitcoinj.core.TransactionInput;
+import org.bitcoinj.core.TransactionOutput;
+import org.bitcoinj.crypto.TransactionSignature;
+import org.bitcoinj.script.Script;
+import org.bitcoinj.script.ScriptBuilder;
+import org.bitcoinj.script.ScriptChunk;
+import org.bitcoinj.script.ScriptOpCodes;
+import org.qortal.crypto.Crypto;
+import org.qortal.utils.Base58;
+import org.qortal.utils.BitTwiddling;
+
+import com.google.common.hash.HashCode;
+import com.google.common.primitives.Bytes;
+
+public class BitcoinyHTLC {
+
+	public enum Status {
+		UNFUNDED, FUNDING_IN_PROGRESS, FUNDED, REDEEM_IN_PROGRESS, REDEEMED, REFUND_IN_PROGRESS, REFUNDED
+	}
+
+	public static final int SECRET_LENGTH = 32;
+	public static final int MIN_LOCKTIME = 1500000000;
+
+	public static final long NO_LOCKTIME_NO_RBF_SEQUENCE = 0xFFFFFFFFL;
+	public static final long LOCKTIME_NO_RBF_SEQUENCE = NO_LOCKTIME_NO_RBF_SEQUENCE - 1;
+
+	// Assuming node's trade-bot has no more than 100 entries?
+	private static final int MAX_CACHE_ENTRIES = 100;
+
+	// Max time-to-live for cache entries (milliseconds)
+	private static final long CACHE_TIMEOUT = 30_000L;
+
+	@SuppressWarnings("serial")
+	private static final Map<String, byte[]> SECRET_CACHE = new LinkedHashMap<>(MAX_CACHE_ENTRIES + 1, 0.75F, true) {
+		// This method is called just after a new entry has been added
+		@Override
+		public boolean removeEldestEntry(Map.Entry<String, byte[]> eldest) {
+			return size() > MAX_CACHE_ENTRIES;
+		}
+	};
+	private static final byte[] NO_SECRET_CACHE_ENTRY = new byte[0];
+
+	@SuppressWarnings("serial")
+	private static final Map<String, Status> STATUS_CACHE = new LinkedHashMap<>(MAX_CACHE_ENTRIES + 1, 0.75F, true) {
+		// This method is called just after a new entry has been added
+		@Override
+		public boolean removeEldestEntry(Map.Entry<String, Status> eldest) {
+			return size() > MAX_CACHE_ENTRIES;
+		}
+	};
+
+	/*
+	 * OP_TUCK (to copy public key to before signature)
+	 * OP_CHECKSIGVERIFY (sig & pubkey must verify or script fails)
+	 * OP_HASH160 (convert public key to PKH)
+	 * OP_DUP (duplicate PKH)
+	 * <push 20 bytes> <refund PKH> OP_EQUAL (does PKH match refund PKH?)
+	 * OP_IF
+	 * 	OP_DROP (no need for duplicate PKH)
+	 * 	<push 4 bytes> <locktime>
+	 * 	OP_CHECKLOCKTIMEVERIFY (if this passes, leftover stack is <locktime> so script passes)
+	 * OP_ELSE
+	 * 	<push 20 bytes> <redeem PKH> OP_EQUALVERIFY (duplicate PKH must match redeem PKH or script fails)
+	 * 	OP_HASH160 (hash secret)
+	 * 	<push 20 bytes> <hash of secret> OP_EQUAL (do hashes of secrets match? if true, script passes else script fails)
+	 * OP_ENDIF
+	 */
+
+	private static final byte[] redeemScript1 = HashCode.fromString("7dada97614").asBytes(); // OP_TUCK OP_CHECKSIGVERIFY OP_HASH160 OP_DUP push(0x14 bytes)
+	private static final byte[] redeemScript2 = HashCode.fromString("87637504").asBytes(); // OP_EQUAL OP_IF OP_DROP push(0x4 bytes)
+	private static final byte[] redeemScript3 = HashCode.fromString("b16714").asBytes(); // OP_CHECKLOCKTIMEVERIFY OP_ELSE push(0x14 bytes)
+	private static final byte[] redeemScript4 = HashCode.fromString("88a914").asBytes(); // OP_EQUALVERIFY OP_HASH160 push(0x14 bytes)
+	private static final byte[] redeemScript5 = HashCode.fromString("8768").asBytes(); // OP_EQUAL OP_ENDIF
+
+	/**
+	 * Returns redeemScript used for cross-chain trading.
+	 * <p>
+	 * See comments in {@link BitcoinyHTLC} for more details.
+	 * 
+	 * @param refunderPubKeyHash 20-byte HASH160 of P2SH funder's public key, for refunding purposes
+	 * @param lockTime seconds-since-epoch threshold, after which P2SH funder can claim refund
+	 * @param redeemerPubKeyHash 20-byte HASH160 of P2SH redeemer's public key
+	 * @param hashOfSecret 20-byte HASH160 of secret, used by P2SH redeemer to claim funds
+	 */
+	public static byte[] buildScript(byte[] refunderPubKeyHash, int lockTime, byte[] redeemerPubKeyHash, byte[] hashOfSecret) {
+		return Bytes.concat(redeemScript1, refunderPubKeyHash, redeemScript2, BitTwiddling.toLEByteArray((int) (lockTime & 0xffffffffL)),
+				redeemScript3, redeemerPubKeyHash, redeemScript4, hashOfSecret, redeemScript5);
+	}
+
+	/**
+	 * Builds a custom transaction to spend HTLC P2SH.
+	 * 
+	 * @param params blockchain network parameters
+	 * @param amount output amount, should be total of input amounts, less miner fees
+	 * @param spendKey key for signing transaction, and also where funds are 'sent' (output)
+	 * @param fundingOutput output from transaction that funded P2SH address
+	 * @param redeemScriptBytes the redeemScript itself, in byte[] form
+	 * @param lockTime (optional) transaction nLockTime, used in refund scenario
+	 * @param scriptSigBuilder function for building scriptSig using transaction input signature
+	 * @param outputPublicKeyHash PKH used to create P2PKH output
+	 * @return Signed transaction for spending P2SH
+	 */
+	public static Transaction buildP2shTransaction(NetworkParameters params, Coin amount, ECKey spendKey,
+			List<TransactionOutput> fundingOutputs, byte[] redeemScriptBytes,
+			Long lockTime, Function<byte[], Script> scriptSigBuilder, byte[] outputPublicKeyHash) {
+		Transaction transaction = new Transaction(params);
+		transaction.setVersion(2);
+
+		// Output is back to P2SH funder
+		transaction.addOutput(amount, ScriptBuilder.createP2PKHOutputScript(outputPublicKeyHash));
+
+		for (int inputIndex = 0; inputIndex < fundingOutputs.size(); ++inputIndex) {
+			TransactionOutput fundingOutput = fundingOutputs.get(inputIndex);
+
+			// Input (without scriptSig prior to signing)
+			TransactionInput input = new TransactionInput(params, null, redeemScriptBytes, fundingOutput.getOutPointFor());
+			if (lockTime != null)
+				input.setSequenceNumber(LOCKTIME_NO_RBF_SEQUENCE); // Use max-value - 1, so lockTime can be used but not RBF
+			else
+				input.setSequenceNumber(NO_LOCKTIME_NO_RBF_SEQUENCE); // Use max-value, so no lockTime and no RBF
+			transaction.addInput(input);
+		}
+
+		// Set locktime after inputs added but before input signatures are generated
+		if (lockTime != null)
+			transaction.setLockTime(lockTime);
+
+		for (int inputIndex = 0; inputIndex < fundingOutputs.size(); ++inputIndex) {
+			// Generate transaction signature for input
+			final boolean anyoneCanPay = false;
+			TransactionSignature txSig = transaction.calculateSignature(inputIndex, spendKey, redeemScriptBytes, SigHash.ALL, anyoneCanPay);
+
+			// Calculate transaction signature
+			byte[] txSigBytes = txSig.encodeToBitcoin();
+
+			// Build scriptSig using lambda and tx signature
+			Script scriptSig = scriptSigBuilder.apply(txSigBytes);
+
+			// Set input scriptSig
+			transaction.getInput(inputIndex).setScriptSig(scriptSig);
+		}
+
+		return transaction;
+	}
+
+	/**
+	 * Returns signed transaction claiming refund from HTLC P2SH.
+	 * 
+	 * @param params blockchain network parameters
+	 * @param refundAmount refund amount, should be total of input amounts, less miner fees
+	 * @param refundKey key for signing transaction
+	 * @param fundingOutputs outputs from transaction that funded P2SH address
+	 * @param redeemScriptBytes the redeemScript itself, in byte[] form
+	 * @param lockTime transaction nLockTime - must be at least locktime used in redeemScript
+	 * @param receivingAccountInfo public-key-hash used for P2PKH output
+	 * @return Signed transaction for refunding P2SH
+	 */
+	public static Transaction buildRefundTransaction(NetworkParameters params, Coin refundAmount, ECKey refundKey,
+			List<TransactionOutput> fundingOutputs, byte[] redeemScriptBytes, long lockTime, byte[] receivingAccountInfo) {
+		Function<byte[], Script> refundSigScriptBuilder = (txSigBytes) -> {
+			// Build scriptSig with...
+			ScriptBuilder scriptBuilder = new ScriptBuilder();
+
+			// transaction signature
+			scriptBuilder.addChunk(new ScriptChunk(txSigBytes.length, txSigBytes));
+
+			// redeem public key
+			byte[] refundPubKey = refundKey.getPubKey();
+			scriptBuilder.addChunk(new ScriptChunk(refundPubKey.length, refundPubKey));
+
+			// redeem script
+			scriptBuilder.addChunk(new ScriptChunk(ScriptOpCodes.OP_PUSHDATA1, redeemScriptBytes));
+
+			return scriptBuilder.build();
+		};
+
+		// Send funds back to funding address
+		return buildP2shTransaction(params, refundAmount, refundKey, fundingOutputs, redeemScriptBytes, lockTime, refundSigScriptBuilder, receivingAccountInfo);
+	}
+
+	/**
+	 * Returns signed transaction redeeming funds from P2SH address.
+	 * 
+	 * @param params blockchain network parameters
+	 * @param redeemAmount redeem amount, should be total of input amounts, less miner fees
+	 * @param redeemKey key for signing transaction
+	 * @param fundingOutputs outputs from transaction that funded P2SH address
+	 * @param redeemScriptBytes the redeemScript itself, in byte[] form
+	 * @param secret actual 32-byte secret used when building redeemScript
+	 * @param receivingAccountInfo Bitcoin PKH used for output
+	 * @return Signed transaction for redeeming P2SH
+	 */
+	public static Transaction buildRedeemTransaction(NetworkParameters params, Coin redeemAmount, ECKey redeemKey,
+			List<TransactionOutput> fundingOutputs, byte[] redeemScriptBytes, byte[] secret, byte[] receivingAccountInfo) {
+		Function<byte[], Script> redeemSigScriptBuilder = (txSigBytes) -> {
+			// Build scriptSig with...
+			ScriptBuilder scriptBuilder = new ScriptBuilder();
+
+			// secret
+			scriptBuilder.addChunk(new ScriptChunk(secret.length, secret));
+
+			// transaction signature
+			scriptBuilder.addChunk(new ScriptChunk(txSigBytes.length, txSigBytes));
+
+			// redeem public key
+			byte[] redeemPubKey = redeemKey.getPubKey();
+			scriptBuilder.addChunk(new ScriptChunk(redeemPubKey.length, redeemPubKey));
+
+			// redeem script
+			scriptBuilder.addChunk(new ScriptChunk(ScriptOpCodes.OP_PUSHDATA1, redeemScriptBytes));
+
+			return scriptBuilder.build();
+		};
+
+		return buildP2shTransaction(params, redeemAmount, redeemKey, fundingOutputs, redeemScriptBytes, null, redeemSigScriptBuilder, receivingAccountInfo);
+	}
+
+	/**
+	 * Returns 'secret', if any, given HTLC's P2SH address.
+	 * <p>
+	 * @throws ForeignBlockchainException
+	 */
+	public static byte[] findHtlcSecret(Bitcoiny bitcoiny, String p2shAddress) throws ForeignBlockchainException {
+		NetworkParameters params = bitcoiny.getNetworkParameters();
+		String compoundKey = String.format("%s-%s-%d", params.getId(), p2shAddress, System.currentTimeMillis() / CACHE_TIMEOUT);
+
+		byte[] secret = SECRET_CACHE.getOrDefault(compoundKey, NO_SECRET_CACHE_ENTRY);
+		if (secret != NO_SECRET_CACHE_ENTRY)
+			return secret;
+
+		List<byte[]> rawTransactions = bitcoiny.getAddressTransactions(p2shAddress);
+
+		for (byte[] rawTransaction : rawTransactions) {
+			Transaction transaction = new Transaction(params, rawTransaction);
+
+			// Cycle through inputs, looking for one that spends our HTLC
+			for (TransactionInput input : transaction.getInputs()) {
+				Script scriptSig = input.getScriptSig();
+				List<ScriptChunk> scriptChunks = scriptSig.getChunks();
+
+				// Expected number of script chunks for redeem. Refund might not have the same number.
+				int expectedChunkCount = 1 /*secret*/ + 1 /*sig*/ + 1 /*pubkey*/ + 1 /*redeemScript*/;
+				if (scriptChunks.size() != expectedChunkCount)
+					continue;
+
+				// We're expecting last chunk to contain the actual redeemScript
+				ScriptChunk lastChunk = scriptChunks.get(scriptChunks.size() - 1);
+				byte[] redeemScriptBytes = lastChunk.data;
+
+				// If non-push scripts, redeemScript will be null
+				if (redeemScriptBytes == null)
+					continue;
+
+				byte[] redeemScriptHash = Crypto.hash160(redeemScriptBytes);
+				Address inputAddress = LegacyAddress.fromScriptHash(params, redeemScriptHash);
+
+				if (!inputAddress.toString().equals(p2shAddress))
+					// Input isn't spending our HTLC
+					continue;
+
+				secret = scriptChunks.get(0).data;
+				if (secret.length != BitcoinyHTLC.SECRET_LENGTH)
+					continue;
+
+				// Cache secret for a while
+				SECRET_CACHE.put(compoundKey, secret);
+
+				return secret;
+			}
+		}
+
+		// Cache negative result
+		SECRET_CACHE.put(compoundKey, null);
+
+		return null;
+	}
+
+	/**
+	 * Returns HTLC status, given P2SH address and expected redeem/refund amount
+	 * <p>
+	 * @throws ForeignBlockchainException if error occurs
+	 */
+	public static Status determineHtlcStatus(BitcoinyBlockchainProvider blockchain, String p2shAddress, long minimumAmount) throws ForeignBlockchainException {
+		String compoundKey = String.format("%s-%s-%d", blockchain.getNetId(), p2shAddress, System.currentTimeMillis() / CACHE_TIMEOUT);
+
+		Status cachedStatus = STATUS_CACHE.getOrDefault(compoundKey, null);
+		if (cachedStatus != null)
+			return cachedStatus;
+
+		byte[] ourScriptPubKey = addressToScriptPubKey(p2shAddress);
+		List<TransactionHash> transactionHashes = blockchain.getAddressTransactions(ourScriptPubKey, BitcoinyBlockchainProvider.INCLUDE_UNCONFIRMED);
+
+		// Sort by confirmed first, followed by ascending height
+		transactionHashes.sort(TransactionHash.CONFIRMED_FIRST.thenComparing(TransactionHash::getHeight));
+
+		// Transaction cache
+		Map<String, BitcoinyTransaction> transactionsByHash = new HashMap<>();
+		// HASH160(redeem script) for this p2shAddress
+		byte[] ourRedeemScriptHash = addressToRedeemScriptHash(p2shAddress);
+
+		// Check for spends first, caching full transaction info as we progress just in case we don't return in this loop
+		for (TransactionHash transactionInfo : transactionHashes) {
+			BitcoinyTransaction bitcoinyTransaction = blockchain.getTransaction(transactionInfo.txHash);
+
+			// Cache for possible later reuse
+			transactionsByHash.put(transactionInfo.txHash, bitcoinyTransaction);
+
+			// Acceptable funding is one transaction output, so we're expecting only one input
+			if (bitcoinyTransaction.inputs.size() != 1)
+				// Wrong number of inputs
+				continue;
+
+			String scriptSig = bitcoinyTransaction.inputs.get(0).scriptSig;
+
+			List<byte[]> scriptSigChunks = extractScriptSigChunks(HashCode.fromString(scriptSig).asBytes());
+			if (scriptSigChunks.size() < 3 || scriptSigChunks.size() > 4)
+				// Not valid chunks for our form of HTLC
+				continue;
+
+			// Last chunk is redeem script
+			byte[] redeemScriptBytes = scriptSigChunks.get(scriptSigChunks.size() - 1);
+			byte[] redeemScriptHash = Crypto.hash160(redeemScriptBytes);
+			if (!Arrays.equals(redeemScriptHash, ourRedeemScriptHash))
+				// Not spending our specific HTLC redeem script
+				continue;
+
+			if (scriptSigChunks.size() == 4)
+				// If we have 4 chunks, then secret is present, hence redeem
+				cachedStatus = transactionInfo.height == 0 ? Status.REDEEM_IN_PROGRESS : Status.REDEEMED;
+			else
+				cachedStatus = transactionInfo.height == 0 ? Status.REFUND_IN_PROGRESS : Status.REFUNDED;
+
+			STATUS_CACHE.put(compoundKey, cachedStatus);
+			return cachedStatus;
+		}
+
+		String ourScriptPubKeyHex = HashCode.fromBytes(ourScriptPubKey).toString();
+
+		// Check for funding
+		for (TransactionHash transactionInfo : transactionHashes) {
+			BitcoinyTransaction bitcoinyTransaction = transactionsByHash.get(transactionInfo.txHash);
+			if (bitcoinyTransaction == null)
+				// Should be present in map!
+				throw new ForeignBlockchainException("Cached Bitcoin transaction now missing?");
+
+			// Check outputs for our specific P2SH
+			for (BitcoinyTransaction.Output output : bitcoinyTransaction.outputs) {
+				// Check amount
+				if (output.value < minimumAmount)
+					// Output amount too small (not taking fees into account)
+					continue;
+
+				String scriptPubKeyHex = output.scriptPubKey;
+				if (!scriptPubKeyHex.equals(ourScriptPubKeyHex))
+					// Not funding our specific P2SH
+					continue;
+
+				cachedStatus = transactionInfo.height == 0 ? Status.FUNDING_IN_PROGRESS : Status.FUNDED;
+				STATUS_CACHE.put(compoundKey, cachedStatus);
+				return cachedStatus;
+			}
+		}
+
+		cachedStatus = Status.UNFUNDED;
+		STATUS_CACHE.put(compoundKey, cachedStatus);
+		return cachedStatus;
+	}
+
+	private static List<byte[]> extractScriptSigChunks(byte[] scriptSigBytes) {
+		List<byte[]> chunks = new ArrayList<>();
+
+		int offset = 0;
+		int previousOffset = 0;
+		while (offset < scriptSigBytes.length) {
+			byte pushOp = scriptSigBytes[offset++];
+
+			if (pushOp < 0 || pushOp > 0x4c)
+				// Unacceptable OP
+				return Collections.emptyList();
+
+			// Special treatment for OP_PUSHDATA1
+			if (pushOp == 0x4c) {
+				if (offset >= scriptSigBytes.length)
+					// Run out of scriptSig bytes?
+					return Collections.emptyList();
+
+				pushOp = scriptSigBytes[offset++];
+			}
+
+			previousOffset = offset;
+			offset += Byte.toUnsignedInt(pushOp);
+
+			byte[] chunk = Arrays.copyOfRange(scriptSigBytes, previousOffset, offset);
+			chunks.add(chunk);
+		}
+
+		return chunks;
+	}
+
+	private static byte[] addressToScriptPubKey(String p2shAddress) {
+		// We want the HASH160 part of the P2SH address
+		byte[] p2shAddressBytes = Base58.decode(p2shAddress);
+
+		byte[] scriptPubKey = new byte[1 + 1 + 20 + 1];
+		scriptPubKey[0x00] = (byte) 0xa9; /* OP_HASH160 */
+		scriptPubKey[0x01] = (byte) 0x14; /* PUSH 0x14 bytes */
+		System.arraycopy(p2shAddressBytes, 1, scriptPubKey, 2, 0x14);
+		scriptPubKey[0x16] = (byte) 0x87; /* OP_EQUAL */
+
+		return scriptPubKey;
+	}
+
+	private static byte[] addressToRedeemScriptHash(String p2shAddress) {
+		// We want the HASH160 part of the P2SH address
+		byte[] p2shAddressBytes = Base58.decode(p2shAddress);
+
+		return Arrays.copyOfRange(p2shAddressBytes, 1, 1 + 20);
+	}
+
+}

src/main/java/org/qortal/crosschain/BitcoinyTransaction.java

@@ -0,0 +1,146 @@
+package org.qortal.crosschain;
+
+import java.util.List;
+import java.util.stream.Collectors;
+
+import javax.xml.bind.annotation.XmlAccessType;
+import javax.xml.bind.annotation.XmlAccessorType;
+import javax.xml.bind.annotation.XmlTransient;
+
+@XmlAccessorType(XmlAccessType.FIELD)
+public class BitcoinyTransaction {
+
+	public final String txHash;
+
+	@XmlTransient
+	public final int size;
+
+	@XmlTransient
+	public final int locktime;
+
+	// Not present if transaction is unconfirmed
+	public final Integer timestamp;
+
+	public static class Input {
+		@XmlTransient
+		public final String scriptSig;
+
+		@XmlTransient
+		public final int sequence;
+
+		public final String outputTxHash;
+
+		public final int outputVout;
+
+		// For JAXB
+		protected Input() {
+			this.scriptSig = null;
+			this.sequence = 0;
+			this.outputTxHash = null;
+			this.outputVout = 0;
+		}
+
+		public Input(String scriptSig, int sequence, String outputTxHash, int outputVout) {
+			this.scriptSig = scriptSig;
+			this.sequence = sequence;
+			this.outputTxHash = outputTxHash;
+			this.outputVout = outputVout;
+		}
+
+		public String toString() {
+			return String.format("{output %s:%d, sequence %d, scriptSig %s}",
+					this.outputTxHash, this.outputVout, this.sequence, this.scriptSig);
+		}
+	}
+	@XmlTransient
+	public final List<Input> inputs;
+
+	public static class Output {
+		@XmlTransient
+		public final String scriptPubKey;
+
+		public final long value;
+
+		public final List<String> addresses;
+
+		// For JAXB
+		protected Output() {
+			this.scriptPubKey = null;
+			this.value = 0;
+			this.addresses = null;
+		}
+
+		public Output(String scriptPubKey, long value) {
+			this.scriptPubKey = scriptPubKey;
+			this.value = value;
+			this.addresses = null;
+		}
+
+		public Output(String scriptPubKey, long value, List<String> addresses) {
+			this.scriptPubKey = scriptPubKey;
+			this.value = value;
+			this.addresses = addresses;
+		}
+
+		public String toString() {
+			return String.format("{value %d, scriptPubKey %s}", this.value, this.scriptPubKey);
+		}
+	}
+	public final List<Output> outputs;
+
+	public final long totalAmount;
+
+	// For JAXB
+	protected BitcoinyTransaction() {
+		this.txHash = null;
+		this.size = 0;
+		this.locktime = 0;
+		this.timestamp = 0;
+		this.inputs = null;
+		this.outputs = null;
+		this.totalAmount = 0;
+	}
+
+	public BitcoinyTransaction(String txHash, int size, int locktime, Integer timestamp,
+			List<Input> inputs, List<Output> outputs) {
+		this.txHash = txHash;
+		this.size = size;
+		this.locktime = locktime;
+		this.timestamp = timestamp;
+		this.inputs = inputs;
+		this.outputs = outputs;
+
+		this.totalAmount = outputs.stream().map(output -> output.value).reduce(0L, Long::sum);
+	}
+
+	public String toString() {
+		return String.format("txHash %s, size %d, locktime %d, timestamp %d\n"
+				+ "\tinputs: [%s]\n"
+				+ "\toutputs: [%s]\n",
+				this.txHash,
+				this.size,
+				this.locktime,
+				this.timestamp,
+				this.inputs.stream().map(Input::toString).collect(Collectors.joining(",\n\t\t")),
+				this.outputs.stream().map(Output::toString).collect(Collectors.joining(",\n\t\t")));
+	}
+
+	@Override
+	public boolean equals(Object other) {
+		if (other == this)
+			return true;
+
+		if (!(other instanceof BitcoinyTransaction))
+			return false;
+
+		BitcoinyTransaction otherTransaction = (BitcoinyTransaction) other;
+
+		return this.txHash.equals(otherTransaction.txHash);
+	}
+
+	@Override
+	public int hashCode() {
+		return this.txHash.hashCode();
+	}
+
+}

src/main/java/org/qortal/crosschain/ElectrumX.java

@@ -1,21 +1,26 @@
 package org.qortal.crosschain;
 
 import java.io.IOException;
+import java.math.BigDecimal;
 import java.net.InetSocketAddress;
 import java.net.Socket;
 import java.net.SocketAddress;
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.HashMap;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.EnumMap;
 import java.util.HashSet;
+import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.NoSuchElementException;
 import java.util.Random;
 import java.util.Scanner;
 import java.util.Set;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 
-import javax.net.ssl.SSLSocket;
 import javax.net.ssl.SSLSocketFactory;
 
 import org.apache.logging.log4j.LogManager;
@@ -29,23 +34,25 @@ import org.qortal.crypto.TrustlessSSLSocketFactory;
 import com.google.common.hash.HashCode;
 import com.google.common.primitives.Bytes;
 
-/** ElectrumX network support for querying Bitcoin-related info like block headers, transaction outputs, etc. */
-public class ElectrumX {
+/** ElectrumX network support for querying Bitcoiny-related info like block headers, transaction outputs, etc. */
+public class ElectrumX extends BitcoinyBlockchainProvider {
 
 	private static final Logger LOGGER = LogManager.getLogger(ElectrumX.class);
 	private static final Random RANDOM = new Random();
 
-	private static final int DEFAULT_TCP_PORT = 50001;
-	private static final int DEFAULT_SSL_PORT = 50002;
-
+	private static final double MIN_PROTOCOL_VERSION = 1.2;
 	private static final int BLOCK_HEADER_LENGTH = 80;
 
-	private static final Map<String, ElectrumX> instances = new HashMap<>();
+	// "message": "daemon error: DaemonError({'code': -5, 'message': 'No such mempool or blockchain transaction. Use gettransaction for wallet transactions.'})"
+	private static final Pattern DAEMON_ERROR_REGEX = Pattern.compile("DaemonError\\(\\{.*'code': ?(-?[0-9]+).*\\}\\)\\z"); // Capture 'code' inside curly-brace content
 
-	static class Server {
+	/** Error message sent by some ElectrumX servers when they don't support returning verbose transactions. */
+	private static final String VERBOSE_TRANSACTIONS_UNSUPPORTED_MESSAGE = "verbose transactions are currently unsupported";
+
+	public static class Server {
 		String hostname;
 
-		enum ConnectionType { TCP, SSL };
+		public enum ConnectionType { TCP, SSL }
 		ConnectionType connectionType;
 
 		int port;
@@ -82,96 +89,91 @@ public class ElectrumX {
 		}
 	}
 	private Set<Server> servers = new HashSet<>();
+	private List<Server> remainingServers = new ArrayList<>();
+	private Set<Server> uselessServers = Collections.synchronizedSet(new HashSet<>());
 
+	private final String netId;
+	private final String expectedGenesisHash;
+	private final Map<Server.ConnectionType, Integer> defaultPorts = new EnumMap<>(Server.ConnectionType.class);
+
+	private final Object serverLock = new Object();
 	private Server currentServer;
 	private Socket socket;
 	private Scanner scanner;
 	private int nextId = 1;
 
+	private static final int TX_CACHE_SIZE = 200;
+	@SuppressWarnings("serial")
+	private final Map<String, BitcoinyTransaction> transactionCache = Collections.synchronizedMap(new LinkedHashMap<>(TX_CACHE_SIZE + 1, 0.75F, true) {
+		// This method is called just after a new entry has been added
+		@Override
+		public boolean removeEldestEntry(Map.Entry<String, BitcoinyTransaction> eldest) {
+			return size() > TX_CACHE_SIZE;
+		}
+	});
+
 	// Constructors
 
-	private ElectrumX(String bitcoinNetwork) {
-		switch (bitcoinNetwork) {
-			case "MAIN":
-				servers.addAll(Arrays.asList(
-						// Servers chosen on NO BASIS WHATSOEVER from various sources!
-						new Server("tardis.bauerj.eu", Server.ConnectionType.SSL, 50002),
-						new Server("rbx.curalle.ovh", Server.ConnectionType.SSL, 50002),
-						new Server("quick.electumx.live", Server.ConnectionType.SSL, 50002),
-						new Server("enode.duckdns.org", Server.ConnectionType.SSL, 50002),
-						new Server("electrumx.ddns.net", Server.ConnectionType.SSL, 50002),
-						new Server("electrumx.ml", Server.ConnectionType.SSL, 50002),
-						new Server("electrum.eff.ro", Server.ConnectionType.SSL, 50002),
-						new Server("electrum.bitkoins.nl", Server.ConnectionType.SSL, 50512),
-						new Server("E-X.not.fyi", Server.ConnectionType.SSL, 50002),
-						new Server("btc.electroncash.dk", Server.ConnectionType.SSL, 60002),
-						new Server("electrum.blockstream.info", Server.ConnectionType.TCP, 50001),
-						new Server("electrum.blockstream.info", Server.ConnectionType.SSL, 50002),
-						new Server("bitcoin.aranguren.org", Server.ConnectionType.TCP, 50001)));
-				break;
-
-			case "TEST3":
-				servers.addAll(Arrays.asList(
-						new Server("tn.not.fyi", Server.ConnectionType.TCP, 55001),
-						new Server("tn.not.fyi", Server.ConnectionType.SSL, 55002),
-						new Server("testnet.aranguren.org", Server.ConnectionType.TCP, 51001),
-						new Server("testnet.aranguren.org", Server.ConnectionType.SSL, 51002),
-						new Server("testnet.hsmiths.com", Server.ConnectionType.SSL, 53012)));
-				break;
-
-			case "REGTEST":
-				servers.addAll(Arrays.asList(
-						new Server("localhost", Server.ConnectionType.TCP, DEFAULT_TCP_PORT),
-						new Server("localhost", Server.ConnectionType.SSL, DEFAULT_SSL_PORT)));
-				break;
-
-			default:
-				throw new IllegalArgumentException(String.format("Bitcoin network '%s' unknown", bitcoinNetwork));
-		}
-
-		LOGGER.debug(() -> String.format("Starting ElectrumX support for %s Bitcoin network", bitcoinNetwork));
-		rpc("server.banner");
-	}
-
-	/** Returns ElectrumX instance linked to passed Bitcoin network, one of "MAIN", "TEST3" or "REGTEST". */
-	public static synchronized ElectrumX getInstance(String bitcoinNetwork) {
-		if (!instances.containsKey(bitcoinNetwork))
-			instances.put(bitcoinNetwork, new ElectrumX(bitcoinNetwork));
-
-		return instances.get(bitcoinNetwork);
+	public ElectrumX(String netId, String genesisHash, Collection<Server> initialServerList, Map<Server.ConnectionType, Integer> defaultPorts) {
+		this.netId = netId;
+		this.expectedGenesisHash = genesisHash;
+		this.servers.addAll(initialServerList);
+		this.defaultPorts.putAll(defaultPorts);
 	}
 
 	// Methods for use by other classes
 
-	public Integer getCurrentHeight() {
-		Object blockObj = this.rpc("blockchain.headers.subscribe");
-		if (!(blockObj instanceof JSONObject))
-			return null;
-
-		JSONObject blockJson = (JSONObject) blockObj;
-
-		if (!blockJson.containsKey("height"))
-			return null;
-
-		return ((Long) blockJson.get("height")).intValue();
+	@Override
+	public String getNetId() {
+		return this.netId;
 	}
 
-	public List<byte[]> getBlockHeaders(int startHeight, long count) {
-		Object blockObj = this.rpc("blockchain.block.headers", startHeight, count);
+	/**
+	 * Returns current blockchain height.
+	 * <p>
+	 * @throws ForeignBlockchainException if error occurs
+	 */
+	@Override
+	public int getCurrentHeight() throws ForeignBlockchainException {
+		Object blockObj = this.rpc("blockchain.headers.subscribe");
 		if (!(blockObj instanceof JSONObject))
-			return null;
+			throw new ForeignBlockchainException.NetworkException("Unexpected output from ElectrumX blockchain.headers.subscribe RPC");
 
 		JSONObject blockJson = (JSONObject) blockObj;
 
-		if (!blockJson.containsKey("count") || !blockJson.containsKey("hex"))
-			return null;
+		Object heightObj = blockJson.get("height");
 
-		Long returnedCount = (Long) blockJson.get("count");
-		String hex = (String) blockJson.get("hex");
+		if (!(heightObj instanceof Long))
+			throw new ForeignBlockchainException.NetworkException("Missing/invalid 'height' in JSON from ElectrumX blockchain.headers.subscribe RPC");
+
+		return ((Long) heightObj).intValue();
+	}
+
+	/**
+	 * Returns list of raw block headers, starting from <tt>startHeight</tt> inclusive.
+	 * <p>
+	 * @throws ForeignBlockchainException if error occurs
+	 */
+	@Override
+	public List<byte[]> getRawBlockHeaders(int startHeight, int count) throws ForeignBlockchainException {
+		Object blockObj = this.rpc("blockchain.block.headers", startHeight, count);
+		if (!(blockObj instanceof JSONObject))
+			throw new ForeignBlockchainException.NetworkException("Unexpected output from ElectrumX blockchain.block.headers RPC");
+
+		JSONObject blockJson = (JSONObject) blockObj;
+
+		Object countObj = blockJson.get("count");
+		Object hexObj = blockJson.get("hex");
+
+		if (!(countObj instanceof Long) || !(hexObj instanceof String))
+			throw new ForeignBlockchainException.NetworkException("Missing/invalid 'count' or 'hex' entries in JSON from ElectrumX blockchain.block.headers RPC");
+
+		Long returnedCount = (Long) countObj;
+		String hex = (String) hexObj;
 
 		byte[] raw = HashCode.fromString(hex).asBytes();
 		if (raw.length != returnedCount * BLOCK_HEADER_LENGTH)
-			return null;
+			throw new ForeignBlockchainException.NetworkException("Unexpected raw header length in JSON from ElectrumX blockchain.block.headers RPC");
 
 		List<byte[]> rawBlockHeaders = new ArrayList<>(returnedCount.intValue());
 		for (int i = 0; i < returnedCount; ++i)
@@ -180,46 +182,45 @@ public class ElectrumX {
 		return rawBlockHeaders;
 	}
 
-	/** Returns confirmed balance, based on passed payment script, or null if there was an error or no known balance. */
-	public Long getBalance(byte[] script) {
+	/**
+	 * Returns confirmed balance, based on passed payment script.
+	 * <p>
+	 * @return confirmed balance, or zero if script unknown
+	 * @throws ForeignBlockchainException if there was an error
+	 */
+	@Override
+	public long getConfirmedBalance(byte[] script) throws ForeignBlockchainException {
 		byte[] scriptHash = Crypto.digest(script);
 		Bytes.reverse(scriptHash);
 
 		Object balanceObj = this.rpc("blockchain.scripthash.get_balance", HashCode.fromBytes(scriptHash).toString());
 		if (!(balanceObj instanceof JSONObject))
-			return null;
+			throw new ForeignBlockchainException.NetworkException("Unexpected output from ElectrumX blockchain.scripthash.get_balance RPC");
 
 		JSONObject balanceJson = (JSONObject) balanceObj;
 
-		if (!balanceJson.containsKey("confirmed"))
-			return null;
+		Object confirmedBalanceObj = balanceJson.get("confirmed");
+
+		if (!(confirmedBalanceObj instanceof Long))
+			throw new ForeignBlockchainException.NetworkException("Missing confirmed balance from ElectrumX blockchain.scripthash.get_balance RPC");
 
 		return (Long) balanceJson.get("confirmed");
 	}
 
-	/** Unspent output info as returned by ElectrumX network. */
-	public static class UnspentOutput {
-		public final byte[] hash;
-		public final int index;
-		public final int height;
-		public final long value;
-
-		public UnspentOutput(byte[] hash, int index, int height, long value) {
-			this.hash = hash;
-			this.index = index;
-			this.height = height;
-			this.value = value;
-		}
-	}
-
-	/** Returns list of unspent outputs pertaining to passed payment script, or null if there was an error. */
-	public List<UnspentOutput> getUnspentOutputs(byte[] script) {
+	/**
+	 * Returns list of unspent outputs pertaining to passed payment script.
+	 * <p>
+	 * @return list of unspent outputs, or empty list if script unknown
+	 * @throws ForeignBlockchainException if there was an error.
+	 */
+	@Override
+	public List<UnspentOutput> getUnspentOutputs(byte[] script, boolean includeUnconfirmed) throws ForeignBlockchainException {
 		byte[] scriptHash = Crypto.digest(script);
 		Bytes.reverse(scriptHash);
 
 		Object unspentJson = this.rpc("blockchain.scripthash.listunspent", HashCode.fromBytes(scriptHash).toString());
 		if (!(unspentJson instanceof JSONArray))
-			return null;
+			throw new ForeignBlockchainException("Expected array output from ElectrumX blockchain.scripthash.listunspent RPC");
 
 		List<UnspentOutput> unspentOutputs = new ArrayList<>();
 		for (Object rawUnspent : (JSONArray) unspentJson) {
@@ -227,7 +228,7 @@ public class ElectrumX {
 
 			int height = ((Long) unspent.get("height")).intValue();
 			// We only want unspent outputs from confirmed transactions (and definitely not mempool duplicates with height 0)
-			if (height <= 0)
+			if (!includeUnconfirmed && height <= 0)
 				continue;
 
 			byte[] txHash = HashCode.fromString((String) unspent.get("tx_hash")).asBytes();
@@ -240,68 +241,215 @@ public class ElectrumX {
 		return unspentOutputs;
 	}
 
-	/** Returns raw transaction for passed transaction hash, or null if not found. */
-	public byte[] getRawTransaction(byte[] txHash) {
-		Object rawTransactionHex = this.rpc("blockchain.transaction.get", HashCode.fromBytes(txHash).toString());
+	/**
+	 * Returns raw transaction for passed transaction hash.
+	 * <p>
+	 * NOTE: Do not mutate returned byte[]!
+	 * 
+	 * @throws ForeignBlockchainException.NotFoundException if transaction not found
+	 * @throws ForeignBlockchainException if error occurs
+	 */
+	@Override
+	public byte[] getRawTransaction(String txHash) throws ForeignBlockchainException {
+		Object rawTransactionHex;
+		try {
+			rawTransactionHex = this.rpc("blockchain.transaction.get", txHash, false);
+		} catch (ForeignBlockchainException.NetworkException e) {
+			// DaemonError({'code': -5, 'message': 'No such mempool or blockchain transaction. Use gettransaction for wallet transactions.'})
+			if (Integer.valueOf(-5).equals(e.getDaemonErrorCode()))
+				throw new ForeignBlockchainException.NotFoundException(e.getMessage());
+
+			throw e;
+		}
+
 		if (!(rawTransactionHex instanceof String))
-			return null;
+			throw new ForeignBlockchainException.NetworkException("Expected hex string as raw transaction from ElectrumX blockchain.transaction.get RPC");
 
 		return HashCode.fromString((String) rawTransactionHex).asBytes();
 	}
 
-	/** Returns list of raw transactions, relating to passed payment script, if null if there's an error. */
-	public List<byte[]> getAddressTransactions(byte[] script) {
+	/**
+	 * Returns raw transaction for passed transaction hash.
+	 * <p>
+	 * NOTE: Do not mutate returned byte[]!
+	 * 
+	 * @throws ForeignBlockchainException.NotFoundException if transaction not found
+	 * @throws ForeignBlockchainException if error occurs
+	 */
+	@Override
+	public byte[] getRawTransaction(byte[] txHash) throws ForeignBlockchainException {
+		return getRawTransaction(HashCode.fromBytes(txHash).toString());
+	}
+
+	/**
+	 * Returns transaction info for passed transaction hash.
+	 * <p>
+	 * @throws ForeignBlockchainException.NotFoundException if transaction not found
+	 * @throws ForeignBlockchainException if error occurs
+	 */
+	@Override
+	public BitcoinyTransaction getTransaction(String txHash) throws ForeignBlockchainException {
+		// Check cache first
+		BitcoinyTransaction transaction = transactionCache.get(txHash);
+		if (transaction != null)
+			return transaction;
+
+		Object transactionObj = null;
+
+		do {
+			try {
+				transactionObj = this.rpc("blockchain.transaction.get", txHash, true);
+			} catch (ForeignBlockchainException.NetworkException e) {
+				// DaemonError({'code': -5, 'message': 'No such mempool or blockchain transaction. Use gettransaction for wallet transactions.'})
+				if (Integer.valueOf(-5).equals(e.getDaemonErrorCode()))
+					throw new ForeignBlockchainException.NotFoundException(e.getMessage());
+
+				// Some servers also return non-standard responses like this:
+				// {"error":"verbose transactions are currently unsupported","id":3,"jsonrpc":"2.0"}
+				// We should probably not use this server any more
+				if (e.getServer() != null && e.getMessage() != null && e.getMessage().contains(VERBOSE_TRANSACTIONS_UNSUPPORTED_MESSAGE)) {
+					Server uselessServer = (Server) e.getServer();
+					LOGGER.trace(() -> String.format("Server %s doesn't support verbose transactions - barring use of that server", uselessServer));
+					this.uselessServers.add(uselessServer);
+					this.closeServer(uselessServer);
+					continue;
+				}
+
+				throw e;
+			}
+		} while (transactionObj == null);
+
+		if (!(transactionObj instanceof JSONObject))
+			throw new ForeignBlockchainException.NetworkException("Expected JSONObject as response from ElectrumX blockchain.transaction.get RPC");
+
+		JSONObject transactionJson = (JSONObject) transactionObj;
+
+		Object inputsObj = transactionJson.get("vin");
+		if (!(inputsObj instanceof JSONArray))
+			throw new ForeignBlockchainException.NetworkException("Expected JSONArray for 'vin' from ElectrumX blockchain.transaction.get RPC");
+
+		Object outputsObj = transactionJson.get("vout");
+		if (!(outputsObj instanceof JSONArray))
+			throw new ForeignBlockchainException.NetworkException("Expected JSONArray for 'vout' from ElectrumX blockchain.transaction.get RPC");
+
+		try {
+			int size = ((Long) transactionJson.get("size")).intValue();
+			int locktime = ((Long) transactionJson.get("locktime")).intValue();
+
+			// Timestamp might not be present, e.g. for unconfirmed transaction
+			Object timeObj = transactionJson.get("time");
+			Integer timestamp = timeObj != null
+					? ((Long) timeObj).intValue()
+					: null;
+
+			List<BitcoinyTransaction.Input> inputs = new ArrayList<>();
+			for (Object inputObj : (JSONArray) inputsObj) {
+				JSONObject inputJson = (JSONObject) inputObj;
+
+				String scriptSig = (String) ((JSONObject) inputJson.get("scriptSig")).get("hex");
+				int sequence = ((Long) inputJson.get("sequence")).intValue();
+				String outputTxHash = (String) inputJson.get("txid");
+				int outputVout = ((Long) inputJson.get("vout")).intValue();
+
+				inputs.add(new BitcoinyTransaction.Input(scriptSig, sequence, outputTxHash, outputVout));
+			}
+
+			List<BitcoinyTransaction.Output> outputs = new ArrayList<>();
+			for (Object outputObj : (JSONArray) outputsObj) {
+				JSONObject outputJson = (JSONObject) outputObj;
+
+				String scriptPubKey = (String) ((JSONObject) outputJson.get("scriptPubKey")).get("hex");
+				long value = BigDecimal.valueOf((Double) outputJson.get("value")).setScale(8).unscaledValue().longValue();
+
+				// address too, if present
+				List<String> addresses = null;
+				Object addressesObj = ((JSONObject) outputJson.get("scriptPubKey")).get("addresses");
+				if (addressesObj instanceof JSONArray) {
+					addresses = new ArrayList<>();
+					for (Object addressObj : (JSONArray) addressesObj)
+						addresses.add((String) addressObj);
+				}
+
+				outputs.add(new BitcoinyTransaction.Output(scriptPubKey, value, addresses));
+			}
+
+			transaction = new BitcoinyTransaction(txHash, size, locktime, timestamp, inputs, outputs);
+
+			// Save into cache
+			transactionCache.put(txHash, transaction);
+
+			return transaction;
+		} catch (NullPointerException | ClassCastException e) {
+			// Unexpected / invalid response from ElectrumX server
+		}
+
+		throw new ForeignBlockchainException.NetworkException("Unexpected JSON format from ElectrumX blockchain.transaction.get RPC");
+	}
+
+	/**
+	 * Returns list of transactions, relating to passed payment script.
+	 * <p>
+	 * @return list of related transactions, or empty list if script unknown
+	 * @throws ForeignBlockchainException if error occurs
+	 */
+	@Override
+	public List<TransactionHash> getAddressTransactions(byte[] script, boolean includeUnconfirmed) throws ForeignBlockchainException {
 		byte[] scriptHash = Crypto.digest(script);
 		Bytes.reverse(scriptHash);
 
 		Object transactionsJson = this.rpc("blockchain.scripthash.get_history", HashCode.fromBytes(scriptHash).toString());
 		if (!(transactionsJson instanceof JSONArray))
-			return null;
+			throw new ForeignBlockchainException.NetworkException("Expected array output from ElectrumX blockchain.scripthash.get_history RPC");
 
-		List<byte[]> rawTransactions = new ArrayList<>();
+		List<TransactionHash> transactionHashes = new ArrayList<>();
 
 		for (Object rawTransactionInfo : (JSONArray) transactionsJson) {
 			JSONObject transactionInfo = (JSONObject) rawTransactionInfo;
 
-			// We only want confirmed transactions
-			if (!transactionInfo.containsKey("height"))
+			Long height = (Long) transactionInfo.get("height");
+			if (!includeUnconfirmed && (height == null || height == 0))
+				// We only want confirmed transactions
 				continue;
 
 			String txHash = (String) transactionInfo.get("tx_hash");
-			String rawTransactionHex = (String) this.rpc("blockchain.transaction.get", txHash);
-			if (rawTransactionHex == null)
-				return null;
 
-			rawTransactions.add(HashCode.fromString(rawTransactionHex).asBytes());
+			transactionHashes.add(new TransactionHash(height.intValue(), txHash));
 		}
 
-		return rawTransactions;
+		return transactionHashes;
 	}
 
-	/** Returns true if raw transaction successfully broadcast. */
-	public boolean broadcastTransaction(byte[] transactionBytes) {
+	/**
+	 * Broadcasts raw transaction to network.
+	 * <p>
+	 * @throws ForeignBlockchainException if error occurs
+	 */
+	@Override
+	public void broadcastTransaction(byte[] transactionBytes) throws ForeignBlockchainException {
 		Object rawBroadcastResult = this.rpc("blockchain.transaction.broadcast", HashCode.fromBytes(transactionBytes).toString());
-		if (rawBroadcastResult == null)
-			return false;
 
-		// If result is a String, then it is simply transaction hash.
-		// Otherwise result is JSON and probably contains error info instead.
-		return rawBroadcastResult instanceof String;
+		// We're expecting a simple string that is the transaction hash
+		if (!(rawBroadcastResult instanceof String))
+			throw new ForeignBlockchainException.NetworkException("Unexpected response from ElectrumX blockchain.transaction.broadcast RPC");
 	}
 
 	// Class-private utility methods
 
-	/** Query current server for its list of peer servers, and return those we can parse. */
-	private Set<Server> serverPeersSubscribe() {
+	/**
+	 * Query current server for its list of peer servers, and return those we can parse.
+	 * <p>
+	 * @throws ForeignBlockchainException
+	 * @throws ClassCastException to be handled by caller
+	 */
+	private Set<Server> serverPeersSubscribe() throws ForeignBlockchainException {
 		Set<Server> newServers = new HashSet<>();
 
 		Object peers = this.connectedRpc("server.peers.subscribe");
-		if (!(peers instanceof JSONArray))
-			return newServers;
 
 		for (Object rawPeer : (JSONArray) peers) {
 			JSONArray peer = (JSONArray) rawPeer;
 			if (peer.size() < 3)
+				// We're expecting at least 3 fields for each peer entry: IP, hostname, features
 				continue;
 
 			String hostname = (String) peer.get(1);
@@ -310,21 +458,26 @@ public class ElectrumX {
 			for (Object rawFeature : features) {
 				String feature = (String) rawFeature;
 				Server.ConnectionType connectionType = null;
-				int port = -1;
+				Integer port = null;
 
 				switch (feature.charAt(0)) {
 					case 's':
 						connectionType = Server.ConnectionType.SSL;
-						port = DEFAULT_SSL_PORT;
+						port = this.defaultPorts.get(connectionType);
 						break;
 
 					case 't':
 						connectionType = Server.ConnectionType.TCP;
-						port = DEFAULT_TCP_PORT;
+						port = this.defaultPorts.get(connectionType);
+						break;
+
+					default:
+						// e.g. could be 'v' for protocol version, or 'p' for pruning limit
 						break;
 				}
 
-				if (connectionType == null)
+				if (connectionType == null || port == null)
+					// We couldn't extract any peer connection info?
 					continue;
 
 				// Possible non-default port?
@@ -344,34 +497,38 @@ public class ElectrumX {
 		return newServers;
 	}
 
-	/** Return output from RPC call, with automatic reconnection to different server if needed. */
-	private synchronized Object rpc(String method, Object...params) {
-		while (haveConnection()) {
-			Object response = connectedRpc(method, params);
-			if (response != null)
-				return response;
+	/**
+	 * Performs RPC call, with automatic reconnection to different server if needed.
+	 * <p>
+	 * @return "result" object from within JSON output
+	 * @throws ForeignBlockchainException if server returns error or something goes wrong
+	 */
+	private Object rpc(String method, Object...params) throws ForeignBlockchainException {
+		synchronized (this.serverLock) {
+			if (this.remainingServers.isEmpty())
+				this.remainingServers.addAll(this.servers);
 
-			this.currentServer = null;
-			try {
-				this.socket.close();
-			} catch (IOException e) {
-				/* ignore */
+			while (haveConnection()) {
+				Object response = connectedRpc(method, params);
+				if (response != null)
+					return response;
+
+				// Didn't work, try another server...
+				this.closeServer();
 			}
-			this.scanner = null;
-		}
 
-		return null;
+			// Failed to perform RPC - maybe lack of servers?
+			throw new ForeignBlockchainException.NetworkException(String.format("Failed to perform ElectrumX RPC %s", method));
+		}
 	}
 
 	/** Returns true if we have, or create, a connection to an ElectrumX server. */
-	private boolean haveConnection() {
+	private boolean haveConnection() throws ForeignBlockchainException {
 		if (this.currentServer != null)
 			return true;
 
-		List<Server> remainingServers = new ArrayList<>(this.servers);
-
-		while (!remainingServers.isEmpty()) {
-			Server server = remainingServers.remove(RANDOM.nextInt(remainingServers.size()));
+		while (!this.remainingServers.isEmpty()) {
+			Server server = this.remainingServers.remove(RANDOM.nextInt(this.remainingServers.size()));
 			LOGGER.trace(() -> String.format("Connecting to %s", server));
 
 			try {
@@ -384,36 +541,55 @@ public class ElectrumX {
 
 				if (server.connectionType == Server.ConnectionType.SSL) {
 					SSLSocketFactory factory = TrustlessSSLSocketFactory.getSocketFactory();
-					this.socket = (SSLSocket) factory.createSocket(this.socket, server.hostname, server.port, true);
+					this.socket = factory.createSocket(this.socket, server.hostname, server.port, true);
 				}
 
 				this.scanner = new Scanner(this.socket.getInputStream());
 				this.scanner.useDelimiter("\n");
 
-				// Check connection works by asking for more servers
+				// Check connection is suitable by asking for server features, including genesis block hash
+				JSONObject featuresJson = (JSONObject) this.connectedRpc("server.features");
+
+				if (featuresJson == null || Double.valueOf((String) featuresJson.get("protocol_min")) < MIN_PROTOCOL_VERSION)
+					continue;
+
+				if (this.expectedGenesisHash != null && !((String) featuresJson.get("genesis_hash")).equals(this.expectedGenesisHash))
+					continue;
+
+				// Ask for more servers
 				Set<Server> moreServers = serverPeersSubscribe();
+				// Discard duplicate servers we already know
 				moreServers.removeAll(this.servers);
-				remainingServers.addAll(moreServers);
+				// Add to both lists
+				this.remainingServers.addAll(moreServers);
 				this.servers.addAll(moreServers);
 
 				LOGGER.debug(() -> String.format("Connected to %s", server));
 				this.currentServer = server;
 				return true;
-			} catch (IOException e) {
-				// Try another server...
-				this.socket = null;
-				this.scanner = null;
+			} catch (IOException | ForeignBlockchainException | ClassCastException | NullPointerException e) {
+				// Didn't work, try another server...
+				closeServer();
 			}
 		}
 
 		return false;
 	}
 
+	/**
+	 * Perform RPC using currently connected server.
+	 * <p>
+	 * @param method
+	 * @param params
+	 * @return response Object, or null if server fails to respond
+	 * @throws ForeignBlockchainException if server returns error
+	 */
 	@SuppressWarnings("unchecked")
-	private Object connectedRpc(String method, Object...params) {
+	private Object connectedRpc(String method, Object...params) throws ForeignBlockchainException {
 		JSONObject requestJson = new JSONObject();
 		requestJson.put("id", this.nextId++);
 		requestJson.put("method", method);
+		requestJson.put("jsonrpc", "2.0");
 
 		JSONArray requestParams = new JSONArray();
 		requestParams.addAll(Arrays.asList(params));
@@ -428,21 +604,85 @@ public class ElectrumX {
 			this.socket.getOutputStream().write(request.getBytes());
 			response = scanner.next();
 		} catch (IOException | NoSuchElementException e) {
+			// Unable to send, or receive -- try another server?
 			return null;
 		}
 
 		LOGGER.trace(() -> String.format("Response: %s", response));
 
 		if (response.isEmpty())
+			// Empty response - try another server?
 			return null;
 
 		Object responseObj = JSONValue.parse(response);
 		if (!(responseObj instanceof JSONObject))
+			// Unexpected response - try another server?
 			return null;
 
 		JSONObject responseJson = (JSONObject) responseObj;
 
+		Object errorObj = responseJson.get("error");
+		if (errorObj != null) {
+			if (errorObj instanceof String)
+				throw new ForeignBlockchainException.NetworkException(String.format("Unexpected error message from ElectrumX RPC %s: %s", method, (String) errorObj), this.currentServer);
+
+			if (!(errorObj instanceof JSONObject))
+				throw new ForeignBlockchainException.NetworkException(String.format("Unexpected error response from ElectrumX RPC %s", method), this.currentServer);
+
+			JSONObject errorJson = (JSONObject) errorObj;
+
+			Object messageObj = errorJson.get("message");
+
+			if (!(messageObj instanceof String))
+				throw new ForeignBlockchainException.NetworkException(String.format("Missing/invalid message in error response from ElectrumX RPC %s", method), this.currentServer);
+
+			String message = (String) messageObj;
+
+			// Some error 'messages' are actually wrapped upstream bitcoind errors:
+			// "message": "daemon error: DaemonError({'code': -5, 'message': 'No such mempool or blockchain transaction. Use gettransaction for wallet transactions.'})"
+			// We want to detect these and extract the upstream error code for caller's use
+			Matcher messageMatcher = DAEMON_ERROR_REGEX.matcher(message);
+			if (messageMatcher.find())
+				try {
+					int daemonErrorCode = Integer.parseInt(messageMatcher.group(1));
+					throw new ForeignBlockchainException.NetworkException(daemonErrorCode, message, this.currentServer);
+				} catch (NumberFormatException e) {
+					// We couldn't parse the error code integer? Fall-through to generic exception...
+				}
+
+			throw new ForeignBlockchainException.NetworkException(message, this.currentServer);
+		}
+
 		return responseJson.get("result");
 	}
 
+	/**
+	 * Closes connection to <tt>server</tt> if it is currently connected server.
+	 * @param server
+	 */
+	private void closeServer(Server server) {
+		synchronized (this.serverLock) {
+			if (this.currentServer == null || !this.currentServer.equals(server))
+				return;
+
+			if (this.socket != null && !this.socket.isClosed())
+				try {
+					this.socket.close();
+				} catch (IOException e) {
+					// We did try...
+				}
+
+			this.socket = null;
+			this.scanner = null;
+			this.currentServer = null;
+		}
+	}
+
+	/** Closes connection to currently connected server (if any). */
+	private void closeServer() {
+		synchronized (this.serverLock) {
+			this.closeServer(this.currentServer);
+		}
+	}
+
 }

src/main/java/org/qortal/crosschain/ForeignBlockchain.java

@@ -0,0 +1,9 @@
+package org.qortal.crosschain;
+
+public interface ForeignBlockchain {
+
+	public boolean isValidAddress(String address);
+
+	public boolean isValidWalletKey(String walletKey);
+
+}

src/main/java/org/qortal/crosschain/ForeignBlockchainException.java

@@ -0,0 +1,77 @@
+package org.qortal.crosschain;
+
+@SuppressWarnings("serial")
+public class ForeignBlockchainException extends Exception {
+
+	public ForeignBlockchainException() {
+		super();
+	}
+
+	public ForeignBlockchainException(String message) {
+		super(message);
+	}
+
+	public static class NetworkException extends ForeignBlockchainException {
+		private final Integer daemonErrorCode;
+		private final transient Object server;
+
+		public NetworkException() {
+			super();
+			this.daemonErrorCode = null;
+			this.server = null;
+		}
+
+		public NetworkException(String message) {
+			super(message);
+			this.daemonErrorCode = null;
+			this.server = null;
+		}
+
+		public NetworkException(int errorCode, String message) {
+			super(message);
+			this.daemonErrorCode = errorCode;
+			this.server = null;
+		}
+
+		public NetworkException(String message, Object server) {
+			super(message);
+			this.daemonErrorCode = null;
+			this.server = server;
+		}
+
+		public NetworkException(int errorCode, String message, Object server) {
+			super(message);
+			this.daemonErrorCode = errorCode;
+			this.server = server;
+		}
+
+		public Integer getDaemonErrorCode() {
+			return this.daemonErrorCode;
+		}
+
+		public Object getServer() {
+			return this.server;
+		}
+	}
+
+	public static class NotFoundException extends ForeignBlockchainException {
+		public NotFoundException() {
+			super();
+		}
+
+		public NotFoundException(String message) {
+			super(message);
+		}
+	}
+
+	public static class InsufficientFundsException extends ForeignBlockchainException {
+		public InsufficientFundsException() {
+			super();
+		}
+
+		public InsufficientFundsException(String message) {
+			super(message);
+		}
+	}
+
+}

src/main/java/org/qortal/crosschain/Litecoin.java

@@ -0,0 +1,175 @@
+package org.qortal.crosschain;
+
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.EnumMap;
+import java.util.Map;
+
+import org.bitcoinj.core.Coin;
+import org.bitcoinj.core.Context;
+import org.bitcoinj.core.NetworkParameters;
+import org.libdohj.params.LitecoinMainNetParams;
+import org.libdohj.params.LitecoinRegTestParams;
+import org.libdohj.params.LitecoinTestNet3Params;
+import org.qortal.crosschain.ElectrumX.Server;
+import org.qortal.crosschain.ElectrumX.Server.ConnectionType;
+import org.qortal.settings.Settings;
+
+public class Litecoin extends Bitcoiny {
+
+	public static final String CURRENCY_CODE = "LTC";
+
+	private static final Coin DEFAULT_FEE_PER_KB = Coin.valueOf(10000); // 0.0001 LTC per 1000 bytes
+
+	// Temporary values until a dynamic fee system is written.
+	private static final long MAINNET_FEE = 1000L;
+	private static final long NON_MAINNET_FEE = 1000L; // enough for TESTNET3 and should be OK for REGTEST
+
+	private static final Map<ElectrumX.Server.ConnectionType, Integer> DEFAULT_ELECTRUMX_PORTS = new EnumMap<>(ElectrumX.Server.ConnectionType.class);
+	static {
+		DEFAULT_ELECTRUMX_PORTS.put(ConnectionType.TCP, 50001);
+		DEFAULT_ELECTRUMX_PORTS.put(ConnectionType.SSL, 50002);
+	}
+
+	public enum LitecoinNet {
+		MAIN {
+			@Override
+			public NetworkParameters getParams() {
+				return LitecoinMainNetParams.get();
+			}
+
+			@Override
+			public Collection<ElectrumX.Server> getServers() {
+				return Arrays.asList(
+						// Servers chosen on NO BASIS WHATSOEVER from various sources!
+						new Server("electrum-ltc.someguy123.net", Server.ConnectionType.SSL, 50002),
+						new Server("backup.electrum-ltc.org", Server.ConnectionType.TCP, 50001),
+						new Server("backup.electrum-ltc.org", Server.ConnectionType.SSL, 443),
+						new Server("electrum.ltc.xurious.com", Server.ConnectionType.TCP, 50001),
+						new Server("electrum.ltc.xurious.com", Server.ConnectionType.SSL, 50002),
+						new Server("electrum-ltc.bysh.me", Server.ConnectionType.SSL, 50002),
+						new Server("ltc.rentonisk.com", Server.ConnectionType.TCP, 50001),
+						new Server("ltc.rentonisk.com", Server.ConnectionType.SSL, 50002),
+						new Server("electrum-ltc.petrkr.net", Server.ConnectionType.SSL, 60002),
+						new Server("ltc.litepay.ch", Server.ConnectionType.SSL, 50022));
+			}
+
+			@Override
+			public String getGenesisHash() {
+				return "12a765e31ffd4059bada1e25190f6e98c99d9714d334efa41a195a7e7e04bfe2";
+			}
+
+			@Override
+			public long getP2shFee(Long timestamp) {
+				// TODO: This will need to be replaced with something better in the near future!
+				return MAINNET_FEE;
+			}
+		},
+		TEST3 {
+			@Override
+			public NetworkParameters getParams() {
+				return LitecoinTestNet3Params.get();
+			}
+
+			@Override
+			public Collection<ElectrumX.Server> getServers() {
+				return Arrays.asList(
+						new Server("electrum-ltc.bysh.me", Server.ConnectionType.TCP, 51001),
+						new Server("electrum-ltc.bysh.me", Server.ConnectionType.SSL, 51002),
+						new Server("electrum.ltc.xurious.com", Server.ConnectionType.TCP, 51001),
+						new Server("electrum.ltc.xurious.com", Server.ConnectionType.SSL, 51002));
+			}
+
+			@Override
+			public String getGenesisHash() {
+				return "4966625a4b2851d9fdee139e56211a0d88575f59ed816ff5e6a63deb4e3e29a0";
+			}
+
+			@Override
+			public long getP2shFee(Long timestamp) {
+				return NON_MAINNET_FEE;
+			}
+		},
+		REGTEST {
+			@Override
+			public NetworkParameters getParams() {
+				return LitecoinRegTestParams.get();
+			}
+
+			@Override
+			public Collection<ElectrumX.Server> getServers() {
+				return Arrays.asList(
+						new Server("localhost", Server.ConnectionType.TCP, 50001),
+						new Server("localhost", Server.ConnectionType.SSL, 50002));
+			}
+
+			@Override
+			public String getGenesisHash() {
+				// This is unique to each regtest instance
+				return null;
+			}
+
+			@Override
+			public long getP2shFee(Long timestamp) {
+				return NON_MAINNET_FEE;
+			}
+		};
+
+		public abstract NetworkParameters getParams();
+		public abstract Collection<ElectrumX.Server> getServers();
+		public abstract String getGenesisHash();
+		public abstract long getP2shFee(Long timestamp) throws ForeignBlockchainException;
+	}
+
+	private static Litecoin instance;
+
+	private final LitecoinNet litecoinNet;
+
+	// Constructors and instance
+
+	private Litecoin(LitecoinNet litecoinNet, BitcoinyBlockchainProvider blockchain, Context bitcoinjContext, String currencyCode) {
+		super(blockchain, bitcoinjContext, currencyCode);
+		this.litecoinNet = litecoinNet;
+
+		LOGGER.info(() -> String.format("Starting Litecoin support using %s", this.litecoinNet.name()));
+	}
+
+	public static synchronized Litecoin getInstance() {
+		if (instance == null) {
+			LitecoinNet litecoinNet = Settings.getInstance().getLitecoinNet();
+
+			BitcoinyBlockchainProvider electrumX = new ElectrumX("Litecoin-" + litecoinNet.name(), litecoinNet.getGenesisHash(), litecoinNet.getServers(), DEFAULT_ELECTRUMX_PORTS);
+			Context bitcoinjContext = new Context(litecoinNet.getParams());
+
+			instance = new Litecoin(litecoinNet, electrumX, bitcoinjContext, CURRENCY_CODE);
+		}
+
+		return instance;
+	}
+
+	// Getters & setters
+
+	public static synchronized void resetForTesting() {
+		instance = null;
+	}
+
+	// Actual useful methods for use by other classes
+
+	/** Default Litecoin fee is lower than Bitcoin: only 10sats/byte. */
+	@Override
+	public Coin getFeePerKb() {
+		return DEFAULT_FEE_PER_KB;
+	}
+
+	/**
+	 * Returns estimated LTC fee, in sats per 1000bytes, optionally for historic timestamp.
+	 * 
+	 * @param timestamp optional milliseconds since epoch, or null for 'now'
+	 * @return sats per 1000bytes, or throws ForeignBlockchainException if something went wrong
+	 */
+	@Override
+	public long getP2shFee(Long timestamp) throws ForeignBlockchainException {
+		return this.litecoinNet.getP2shFee(timestamp);
+	}
+
+}