Return file lists via /arbitrary/metadata/* endpoints, but exclude it from /arbitrary/resources/* endpoints.

isTooDivergent will be true or false if a definitive decision has been made, or missing from the response if not yet known. Therefore it should be safe to treat `"isTooDivergent": false` as a peer that is on the same chain.

TestNets.md

@@ -52,14 +52,13 @@
 
 ## Single-node testnet
 
-A single-node testnet is possible with code modifications, for basic testing, or to more easily start a new testnet.
-To do so, follow these steps:
-- Comment out the `if (mintedLastBlock) { }` conditional in BlockMinter.java
-- Comment out the `minBlockchainPeers` validation in Settings.validate()
-- Set `minBlockchainPeers` to 0 in settings.json
-- Set `Synchronizer.RECOVERY_MODE_TIMEOUT` to `0`
-- All other steps should remain the same. Only a single reward share key is needed.
-- Remember to put these values back after introducing other nodes
+A single-node testnet is possible with an additional settings, or to more easily start a new testnet.
+Just add this setting:
+```
+"singleNodeTestnet": true
+```
+This will automatically allow multiple consecutive blocks to be minted, as well as setting minBlockchainPeers to 0.
+Remember to put these values back after introducing other nodes
 
 ## Fixed network
 
@@ -93,3 +92,32 @@ Your options are:
 - `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
 
+## Example settings-test.json
+```
+{
+  "isTestNet": true,
+  "bitcoinNet": "TEST3",
+  "repositoryPath": "db-testnet",
+  "blockchainConfig": "testchain.json",
+  "minBlockchainPeers": 1,
+  "apiDocumentationEnabled": true,
+  "apiRestricted": false,
+  "bootstrap": false,
+  "maxPeerConnectionTime": 999999999,
+  "localAuthBypassEnabled": true,
+  "singleNodeTestnet": true,
+  "recoveryModeTimeout": 0
+}
+```
+
+## Quick start
+Here are some steps to quickly get a single node testnet up and running with a generic minting account:
+1. Start with template `settings-test.json`, and create a `testchain.json` based on mainnet's blockchain.json (or obtain one from Qortal developers). These should be in the same directory as the jar.
+2. Make sure feature triggers and other timestamp/height activations are correctly set. Generally these would be `0` so that they are enabled from the start.
+3. Set a recent genesis `timestamp` in testchain.json, and add this reward share entry:
+`{ "type": "REWARD_SHARE", "minterPublicKey": "DwcUnhxjamqppgfXCLgbYRx8H9XFPUc2qYRy3CEvQWEw", "recipient": "QbTDMss7NtRxxQaSqBZtSLSNdSYgvGaqFf", "rewardSharePublicKey": "CRvQXxFfUMfr4q3o1PcUZPA4aPCiubBsXkk47GzRo754", "sharePercent": 0 },`
+4. Start the node, passing in settings-test.json, e.g: `java -jar qortal.jar settings-test.json`
+5. Once started, add the corresponding minting key to the node:
+`curl -X POST "http://localhost:62391/admin/mintingaccounts" -d "F48mYJycFgRdqtc58kiovwbcJgVukjzRE4qRRtRsK9ix"`
+6. Alternatively you can use your own minting account instead of the generic one above.
+7. After a short while, blocks should be minted from the genesis timestamp until the current time.

WindowsInstaller/Qortal.aip

@@ -17,10 +17,10 @@
     <ROW Property="Manufacturer" Value="Qortal"/>
     <ROW Property="MsiLogging" MultiBuildValue="DefaultBuild:vp"/>
     <ROW Property="NTP_GOOD" Value="false"/>
-    <ROW Property="ProductCode" Value="1033:{E5597539-098E-4BA6-99DF-4D22018BC0D3} 1049:{2B5E55A2-142A-4BED-B3B9-5657162282B7} 2052:{6F19171F-4743-4127-B191-AAFA3FA885D2} 2057:{A1B3108D-EC5D-47A1-AEE4-DBD956E682FB} " Type="16"/>
+    <ROW Property="ProductCode" Value="1033:{6C93A96C-E3AF-42FD-BE11-7EC3734905C6} 1049:{754F5347-82E5-4251-AED0-F4141CDD11F5} 2052:{413BD7B3-A3F8-47D0-BCA4-5C7694A40936} 2057:{71450AC8-1E6F-4469-852D-0591FA693680} " Type="16"/>
     <ROW Property="ProductLanguage" Value="2057"/>
     <ROW Property="ProductName" Value="Qortal"/>
-    <ROW Property="ProductVersion" Value="3.4.3" Type="32"/>
+    <ROW Property="ProductVersion" Value="3.8.3" Type="32"/>
     <ROW Property="RECONFIG_NTP" Value="true"/>
     <ROW Property="REMOVE_BLOCKCHAIN" Value="YES" Type="4"/>
     <ROW Property="REPAIR_BLOCKCHAIN" Value="YES" Type="4"/>
@@ -212,7 +212,7 @@
     <ROW Component="ADDITIONAL_LICENSE_INFO_71" ComponentId="{12A3ADBE-BB7A-496C-8869-410681E6232F}" Directory_="jdk.zipfs_Dir" Attributes="0" KeyPath="ADDITIONAL_LICENSE_INFO_71" Type="0"/>
     <ROW Component="ADDITIONAL_LICENSE_INFO_8" ComponentId="{D53AD95E-CF96-4999-80FC-5812277A7456}" Directory_="java.naming_Dir" Attributes="0" KeyPath="ADDITIONAL_LICENSE_INFO_8" Type="0"/>
     <ROW Component="ADDITIONAL_LICENSE_INFO_9" ComponentId="{6B7EA9B0-5D17-47A8-B78C-FACE86D15E01}" Directory_="java.net.http_Dir" Attributes="0" KeyPath="ADDITIONAL_LICENSE_INFO_9" Type="0"/>
-    <ROW Component="AI_CustomARPName" ComponentId="{F17029E8-CCC4-456D-B4AC-1854C81C46B6}" Directory_="APPDIR" Attributes="260" KeyPath="DisplayName" Options="1"/>
+    <ROW Component="AI_CustomARPName" ComponentId="{EC7B4AD9-F2D9-48C4-A586-C4697D9C380C}" Directory_="APPDIR" Attributes="260" KeyPath="DisplayName" Options="1"/>
     <ROW Component="AI_ExePath" ComponentId="{3644948D-AE0B-41BB-9FAF-A79E70490A08}" Directory_="APPDIR" Attributes="260" KeyPath="AI_ExePath"/>
     <ROW Component="APPDIR" ComponentId="{680DFDDE-3FB4-47A5-8FF5-934F576C6F91}" Directory_="APPDIR" Attributes="0"/>
     <ROW Component="AccessBridgeCallbacks.h" ComponentId="{288055D1-1062-47A3-AA44-5601B4E38AED}" Directory_="bridge_Dir" Attributes="0" KeyPath="AccessBridgeCallbacks.h" Type="0"/>
@@ -1173,7 +1173,7 @@
     <ROW Action="AI_STORE_LOCATION" Type="51" Source="ARPINSTALLLOCATION" Target="[APPDIR]"/>
     <ROW Action="AI_SetPermissions" Type="11265" Source="userAccounts.dll" Target="OnSetPermissions" WithoutSeq="true"/>
     <ROW Action="CustomizeLog4j2PropertiesScript" Type="3109" Target="Script Text" TargetUnformatted="var actionData = Session.Property(&quot;CustomActionData&quot;);&#13;&#10;var actionDataArray = actionData.split(&quot;|&quot;);&#13;&#10;var appDir = actionDataArray[0];&#13;&#10;var dataFolder = actionDataArray[1] + actionDataArray[2] + &quot;\\&quot;;&#13;&#10;&#13;&#10;var ForReading = 1, ForWriting = 2, ForAppending = 8;&#13;&#10;var fso = new ActiveXObject(&quot;Scripting.FileSystemObject&quot;);&#13;&#10;&#13;&#10;// Make copy&#13;&#10;fso.CopyFile(appDir + &quot;log4j2.properties&quot;, appDir + &quot;log4j2-orig.properties&quot;, true); // overwrite&#13;&#10;&#13;&#10;// Rewrite %AppDir%\log4j2.properties to update logfile storage path&#13;&#10;var fin = fso.OpenTextFile(appDir + &quot;log4j2-orig.properties&quot;, ForReading, false); // no create&#13;&#10;var fout = fso.OpenTextFile(appDir + &quot;log4j2.properties&quot;, ForWriting, true); // can create&#13;&#10;&#13;&#10;// Copy lines with rewriting where necessary&#13;&#10;while( !fin.AtEndOfStream ) {&#13;&#10;&#9;var line = fin.ReadLine();&#13;&#10;&#13;&#10;&#9;var start = line.indexOf(&quot;property.dirname&quot;);&#13;&#10;&#9;if (start &gt; 0) {&#13;&#10;&#9;&#9;// line: # property.dirname = ...appdata...&#13;&#10;&#9;&#9;// uncomment/replace this line for Windows&#13;&#10;&#9;&#9;fout.WriteLine( &quot;property.dirname = &quot; + dataFolder.split(&apos;\\&apos;).join(&apos;\\\\&apos;) );&#13;&#10;&#9;} else {&#13;&#10;&#9;&#9;// not found - output verbatim&#13;&#10;&#9;&#9;fout.WriteLine( line );&#13;&#10;&#9;}&#13;&#10;}&#13;&#10;&#13;&#10;fin.Close();&#13;&#10;fout.Close();&#13;&#10;" AdditionalSeq="AI_DATA_SETTER_4"/>
-    <ROW Action="CustomizeSettingsJsonScript" Type="3109" Target="Script Text" TargetUnformatted="var actionData = Session.Property(&quot;CustomActionData&quot;);&#13;&#10;var actionDataArray = actionData.split(&quot;|&quot;);&#13;&#10;var appDir = actionDataArray[0];&#13;&#10;var dataFolder = actionDataArray[1] + actionDataArray[2] + &quot;\\&quot;;&#13;&#10;&#13;&#10;var ForReading = 1, ForWriting = 2, ForAppending = 8;&#13;&#10;var fso = new ActiveXObject(&quot;Scripting.FileSystemObject&quot;);&#13;&#10;&#13;&#10;// Create basic %APPDIR%\settings.json with path to real settings.json in dataFolder&#13;&#10;var fts = fso.OpenTextFile(appDir + &quot;settings.json&quot;, ForWriting, true);&#13;&#10;&#13;&#10;fts.WriteLine( &quot;{&quot; );&#13;&#10;// We need to escape Windows path backslashes to keep JSON valid&#13;&#10;fts.WriteLine( &quot;  \&quot;userPath\&quot;: \&quot;&quot; + dataFolder.split(&apos;\\&apos;).join(&apos;\\\\&apos;) + &quot;\&quot;&quot; );&#13;&#10;fts.WriteLine( &quot;}&quot; );&#13;&#10;&#13;&#10;fts.Close();&#13;&#10;&#13;&#10;// Make copy&#13;&#10;fso.CopyFile(dataFolder + &quot;settings.json&quot;, dataFolder + &quot;settings-orig.json&quot;, true); // overwrite&#13;&#10;&#13;&#10;// Rewrite settings.json to update repository path&#13;&#10;var fin = fso.OpenTextFile(dataFolder + &quot;settings-orig.json&quot;, ForReading, false);&#13;&#10;var fout = fso.OpenTextFile(dataFolder + &quot;settings.json&quot;, ForWriting, true);&#13;&#10;&#13;&#10;// First line should contain opening brace&#13;&#10;fout.WriteLine( fin.ReadLine() );&#13;&#10;&#13;&#10;// Append our entries&#13;&#10;fout.WriteLine( &quot;  \&quot;repositoryPath\&quot;: \&quot;&quot; + dataFolder.split(&apos;\\&apos;).join(&apos;\\\\&apos;) + &quot;db\&quot;,&quot; );&#13;&#10;fout.WriteLine( &quot;  \&quot;dataPath\&quot;: \&quot;&quot; + dataFolder.split(&apos;\\&apos;).join(&apos;\\\\&apos;) + &quot;data\&quot;,&quot; );&#13;&#10;&#13;&#10;// copy rest of settings&#13;&#10;while( !fin.AtEndOfStream ) {&#13;&#10;&#9;fout.WriteLine( fin.ReadLine() );&#13;&#10;}&#13;&#10;&#13;&#10;fin.Close();&#13;&#10;fout.Close();&#13;&#10;" AdditionalSeq="AI_DATA_SETTER_3"/>
+    <ROW Action="CustomizeSettingsJsonScript" Type="3109" Target="Script Text" TargetUnformatted="var actionData = Session.Property(&quot;CustomActionData&quot;);&#13;&#10;var actionDataArray = actionData.split(&quot;|&quot;);&#13;&#10;var appDir = actionDataArray[0];&#13;&#10;var dataFolder = actionDataArray[1] + actionDataArray[2] + &quot;\\&quot;;&#13;&#10;&#13;&#10;var ForReading = 1, ForWriting = 2, ForAppending = 8;&#13;&#10;var fso = new ActiveXObject(&quot;Scripting.FileSystemObject&quot;);&#13;&#10;&#13;&#10;// Create basic %APPDIR%\settings.json with path to real settings.json in dataFolder&#13;&#10;var fts = fso.OpenTextFile(appDir + &quot;settings.json&quot;, ForWriting, true);&#13;&#10;&#13;&#10;fts.WriteLine( &quot;{&quot; );&#13;&#10;// We need to escape Windows path backslashes to keep JSON valid&#13;&#10;fts.WriteLine( &quot;  \&quot;userPath\&quot;: \&quot;&quot; + dataFolder.split(&apos;\\&apos;).join(&apos;\\\\&apos;) + &quot;\&quot;&quot; );&#13;&#10;fts.WriteLine( &quot;}&quot; );&#13;&#10;&#13;&#10;fts.Close();&#13;&#10;&#13;&#10;// Make copy&#13;&#10;fso.CopyFile(dataFolder + &quot;settings.json&quot;, dataFolder + &quot;settings-orig.json&quot;, true); // overwrite&#13;&#10;&#13;&#10;// Rewrite settings.json to update repository path&#13;&#10;var fin = fso.OpenTextFile(dataFolder + &quot;settings-orig.json&quot;, ForReading, false);&#13;&#10;var fout = fso.OpenTextFile(dataFolder + &quot;settings.json&quot;, ForWriting, true);&#13;&#10;&#13;&#10;// First line should contain opening brace&#13;&#10;fout.WriteLine( fin.ReadLine() );&#13;&#10;&#13;&#10;// Append our entries&#13;&#10;fout.WriteLine( &quot;  \&quot;repositoryPath\&quot;: \&quot;&quot; + dataFolder.split(&apos;\\&apos;).join(&apos;\\\\&apos;) + &quot;db\&quot;,&quot; );&#13;&#10;fout.WriteLine( &quot;  \&quot;dataPath\&quot;: \&quot;&quot; + dataFolder.split(&apos;\\&apos;).join(&apos;\\\\&apos;) + &quot;data\&quot;,&quot; );&#13;&#10;fout.WriteLine( &quot;  \&quot;walletsPath\&quot;: \&quot;&quot; + dataFolder.split(&apos;\\&apos;).join(&apos;\\\\&apos;) + &quot;wallets\&quot;,&quot; );&#13;&#10;fout.WriteLine( &quot;  \&quot;listsPath\&quot;: \&quot;&quot; + dataFolder.split(&apos;\\&apos;).join(&apos;\\\\&apos;) + &quot;lists\&quot;,&quot; );&#13;&#10;&#13;&#10;// copy rest of settings&#13;&#10;while( !fin.AtEndOfStream ) {&#13;&#10;&#9;fout.WriteLine( fin.ReadLine() );&#13;&#10;}&#13;&#10;&#13;&#10;fin.Close();&#13;&#10;fout.Close();&#13;&#10;" AdditionalSeq="AI_DATA_SETTER_3"/>
     <ROW Action="DetectRunningProcess" Type="1" Source="aicustact.dll" Target="DetectProcess" Options="3" AdditionalSeq="AI_DATA_SETTER_8"/>
     <ROW Action="DetectW32Time" Type="1" Source="aicustact.dll" Target="DetectService" Options="3" AdditionalSeq="AI_DATA_SETTER_11"/>
     <ROW Action="NTP_config" Type="3090" Source="ntpcfg.bat"/>

lib/org/ciyam/AT/1.4.0/AT-1.4.0.pom

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://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>1.4.0</version>
+  <description>POM was created from install:install-file</description>
+</project>

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

@@ -3,14 +3,15 @@
   <groupId>org.ciyam</groupId>
   <artifactId>AT</artifactId>
   <versioning>
-    <release>1.3.8</release>
+    <release>1.4.0</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>
+      <version>1.4.0</version>
     </versions>
-    <lastUpdated>20200925114415</lastUpdated>
+    <lastUpdated>20221105114346</lastUpdated>
   </versioning>
 </metadata>

pom.xml

@@ -3,7 +3,7 @@
 	<modelVersion>4.0.0</modelVersion>
 	<groupId>org.qortal</groupId>
 	<artifactId>qortal</artifactId>
-	<version>3.6.1</version>
+	<version>3.8.4</version>
 	<packaging>jar</packaging>
 	<properties>
 		<skipTests>true</skipTests>
@@ -11,7 +11,7 @@
 		<bitcoinj.version>0.15.10</bitcoinj.version>
 		<bouncycastle.version>1.69</bouncycastle.version>
 		<build.timestamp>${maven.build.timestamp}</build.timestamp>
-		<ciyam-at.version>1.3.8</ciyam-at.version>
+		<ciyam-at.version>1.4.0</ciyam-at.version>
 		<commons-net.version>3.6</commons-net.version>
 		<commons-text.version>1.8</commons-text.version>
 		<commons-io.version>2.6</commons-io.version>

src/main/java/org/qortal/account/Account.java

@@ -211,7 +211,8 @@ public class Account {
 		if (level != null && level >= BlockChain.getInstance().getMinAccountLevelToMint())
 			return true;
 
-		if (Account.isFounder(accountData.getFlags()))
+		// Founders can always mint, unless they have a penalty
+		if (Account.isFounder(accountData.getFlags()) && accountData.getBlocksMintedPenalty() == 0)
 			return true;
 
 		return false;
@@ -222,6 +223,11 @@ public class Account {
 		return this.repository.getAccountRepository().getMintedBlockCount(this.address);
 	}
 
+	/** Returns account's blockMintedPenalty or null if account not found in repository. */
+	public Integer getBlocksMintedPenalty() throws DataException {
+		return this.repository.getAccountRepository().getBlocksMintedPenaltyCount(this.address);
+	}
+
 
 	/** Returns whether account can build reward-shares.
 	 * <p>
@@ -243,7 +249,7 @@ public class Account {
 		if (level != null && level >= BlockChain.getInstance().getMinAccountLevelToRewardShare())
 			return true;
 
-		if (Account.isFounder(accountData.getFlags()))
+		if (Account.isFounder(accountData.getFlags()) && accountData.getBlocksMintedPenalty() == 0)
 			return true;
 
 		return false;
@@ -271,7 +277,7 @@ public class Account {
 	/**
 	 * Returns 'effective' minting level, or zero if account does not exist/cannot mint.
 	 * <p>
-	 * For founder accounts, this returns "founderEffectiveMintingLevel" from blockchain config.
+	 * For founder accounts with no penalty, this returns "founderEffectiveMintingLevel" from blockchain config.
 	 * 
 	 * @return 0+
 	 * @throws DataException
@@ -281,7 +287,8 @@ public class Account {
 		if (accountData == null)
 			return 0;
 
-		if (Account.isFounder(accountData.getFlags()))
+		// Founders are assigned a different effective minting level, as long as they have no penalty
+		if (Account.isFounder(accountData.getFlags()) && accountData.getBlocksMintedPenalty() == 0)
 			return BlockChain.getInstance().getFounderEffectiveMintingLevel();
 
 		return accountData.getLevel();
@@ -289,8 +296,6 @@ public class Account {
 
 	/**
 	 * Returns 'effective' minting level, or zero if reward-share does not exist.
-	 * <p>
-	 * this is being used on src/main/java/org/qortal/api/resource/AddressesResource.java to fulfil the online accounts api call
 	 * 
 	 * @param repository
 	 * @param rewardSharePublicKey
@@ -309,7 +314,7 @@ public class Account {
 	/**
 	 * Returns 'effective' minting level, with a fix for the zero level.
 	 * <p>
-	 * For founder accounts, this returns "founderEffectiveMintingLevel" from blockchain config.
+	 * For founder accounts with no penalty, this returns "founderEffectiveMintingLevel" from blockchain config.
 	 *
 	 * @param repository
 	 * @param rewardSharePublicKey
@@ -322,7 +327,7 @@ public class Account {
 		if (rewardShareData == null)
 			return 0;
 
-		else if(!rewardShareData.getMinter().equals(rewardShareData.getRecipient()))//the minter is different than the recipient this means sponsorship
+		else if (!rewardShareData.getMinter().equals(rewardShareData.getRecipient())) // Sponsorship reward share
 			return 0;
 
 		Account rewardShareMinter = new Account(repository, rewardShareData.getMinter());

src/main/java/org/qortal/account/SelfSponsorshipAlgoV1.java

@@ -0,0 +1,367 @@
+package org.qortal.account;
+
+import org.qortal.api.resource.TransactionsResource;
+import org.qortal.asset.Asset;
+import org.qortal.data.account.AccountData;
+import org.qortal.data.naming.NameData;
+import org.qortal.data.transaction.*;
+import org.qortal.repository.DataException;
+import org.qortal.repository.Repository;
+import org.qortal.transaction.Transaction.TransactionType;
+
+import java.util.*;
+import java.util.stream.Collectors;
+
+public class SelfSponsorshipAlgoV1 {
+
+    private final Repository repository;
+    private final String address;
+    private final AccountData accountData;
+    private final long snapshotTimestamp;
+    private final boolean override;
+
+    private int registeredNameCount = 0;
+    private int suspiciousCount = 0;
+    private int suspiciousPercent = 0;
+    private int consolidationCount = 0;
+    private int bulkIssuanceCount = 0;
+    private int recentSponsorshipCount = 0;
+
+    private List<RewardShareTransactionData> sponsorshipRewardShares = new ArrayList<>();
+    private final Map<String, List<TransactionData>> paymentsByAddress = new HashMap<>();
+    private final Set<String> sponsees = new LinkedHashSet<>();
+    private Set<String> consolidatedAddresses = new LinkedHashSet<>();
+    private final Set<String> zeroTransactionAddreses = new LinkedHashSet<>();
+    private final Set<String> penaltyAddresses = new LinkedHashSet<>();
+
+    public SelfSponsorshipAlgoV1(Repository repository, String address, long snapshotTimestamp, boolean override) throws DataException {
+        this.repository = repository;
+        this.address = address;
+        this.accountData = this.repository.getAccountRepository().getAccount(this.address);
+        this.snapshotTimestamp = snapshotTimestamp;
+        this.override = override;
+    }
+
+    public String getAddress() {
+        return this.address;
+    }
+
+    public Set<String> getPenaltyAddresses() {
+        return this.penaltyAddresses;
+    }
+
+
+    public void run() throws DataException {
+        if (this.accountData == null) {
+            // Nothing to do
+            return;
+        }
+
+        this.fetchSponsorshipRewardShares();
+        if (this.sponsorshipRewardShares.isEmpty()) {
+            // Nothing to do
+            return;
+        }
+
+        this.findConsolidatedRewards();
+        this.findBulkIssuance();
+        this.findRegisteredNameCount();
+        this.findRecentSponsorshipCount();
+
+        int score = this.calculateScore();
+        if (score <= 0 && !override) {
+            return;
+        }
+
+        String newAddress = this.getDestinationAccount(this.address);
+        while (newAddress != null) {
+            // Found destination account
+            this.penaltyAddresses.add(newAddress);
+
+            // Run algo for this address, but in "override" mode because it has already been flagged
+            SelfSponsorshipAlgoV1 algoV1 = new SelfSponsorshipAlgoV1(this.repository, newAddress, this.snapshotTimestamp, true);
+            algoV1.run();
+            this.penaltyAddresses.addAll(algoV1.getPenaltyAddresses());
+
+            newAddress = this.getDestinationAccount(newAddress);
+        }
+
+        this.penaltyAddresses.add(this.address);
+
+        if (this.override || this.recentSponsorshipCount < 20) {
+            this.penaltyAddresses.addAll(this.consolidatedAddresses);
+            this.penaltyAddresses.addAll(this.zeroTransactionAddreses);
+        }
+        else {
+            this.penaltyAddresses.addAll(this.sponsees);
+        }
+    }
+
+    private String getDestinationAccount(String address) throws DataException {
+        List<TransactionData> transferPrivsTransactions = fetchTransferPrivsForAddress(address);
+        if (transferPrivsTransactions.isEmpty()) {
+            // No TRANSFER_PRIVS transactions for this address
+            return null;
+        }
+
+        AccountData accountData = this.repository.getAccountRepository().getAccount(address);
+        if (accountData == null) {
+            return null;
+        }
+
+        for (TransactionData transactionData : transferPrivsTransactions) {
+            TransferPrivsTransactionData transferPrivsTransactionData = (TransferPrivsTransactionData) transactionData;
+            if (Arrays.equals(transferPrivsTransactionData.getSenderPublicKey(), accountData.getPublicKey())) {
+                return transferPrivsTransactionData.getRecipient();
+            }
+        }
+
+        return null;
+    }
+
+    private void findConsolidatedRewards() throws DataException {
+        List<String> sponseesThatSentRewards = new ArrayList<>();
+        Map<String, Integer> paymentRecipients = new HashMap<>();
+
+        // Collect outgoing payments of each sponsee
+        for (String sponseeAddress : this.sponsees) {
+
+            // Firstly fetch all payments for address, since the functions below depend on this data
+            this.fetchPaymentsForAddress(sponseeAddress);
+
+            // Check if the address has zero relevant transactions
+            if (this.hasZeroTransactions(sponseeAddress)) {
+                this.zeroTransactionAddreses.add(sponseeAddress);
+            }
+
+            // Get payment recipients
+            List<String> allPaymentRecipients = this.fetchOutgoingPaymentRecipientsForAddress(sponseeAddress);
+            if (allPaymentRecipients.isEmpty()) {
+                continue;
+            }
+            sponseesThatSentRewards.add(sponseeAddress);
+
+            List<String> addressesPaidByThisSponsee = new ArrayList<>();
+            for (String paymentRecipient : allPaymentRecipients) {
+                if (addressesPaidByThisSponsee.contains(paymentRecipient)) {
+                    // We already tracked this association - don't allow multiple to stack up
+                    continue;
+                }
+                addressesPaidByThisSponsee.add(paymentRecipient);
+
+                // Increment count for this recipient, or initialize to 1 if not present
+                if (paymentRecipients.computeIfPresent(paymentRecipient, (k, v) -> v + 1) == null) {
+                    paymentRecipients.put(paymentRecipient, 1);
+                }
+            }
+
+        }
+
+        // Exclude addresses with a low number of payments
+        Map<String, Integer> filteredPaymentRecipients = paymentRecipients.entrySet().stream()
+                .filter(p -> p.getValue() != null && p.getValue() >= 10)
+                .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));
+
+        // Now check how many sponsees have sent to this subset of addresses
+        Map<String, Integer> sponseesThatConsolidatedRewards = new HashMap<>();
+        for (String sponseeAddress : sponseesThatSentRewards) {
+            List<String> allPaymentRecipients = this.fetchOutgoingPaymentRecipientsForAddress(sponseeAddress);
+            // Remove any that aren't to one of the flagged recipients (i.e. consolidation)
+            allPaymentRecipients.removeIf(r -> !filteredPaymentRecipients.containsKey(r));
+
+            int count = allPaymentRecipients.size();
+            if (count == 0) {
+                continue;
+            }
+            if (sponseesThatConsolidatedRewards.computeIfPresent(sponseeAddress, (k, v) -> v + count) == null) {
+                sponseesThatConsolidatedRewards.put(sponseeAddress, count);
+            }
+        }
+
+        // Remove sponsees that have only sent a low number of payments to the filtered addresses
+        Map<String, Integer> filteredSponseesThatConsolidatedRewards = sponseesThatConsolidatedRewards.entrySet().stream()
+                .filter(p -> p.getValue() != null && p.getValue() >= 2)
+                .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));
+
+        this.consolidationCount = sponseesThatConsolidatedRewards.size();
+        this.consolidatedAddresses = new LinkedHashSet<>(filteredSponseesThatConsolidatedRewards.keySet());
+        this.suspiciousCount = this.consolidationCount + this.zeroTransactionAddreses.size();
+        this.suspiciousPercent = (int)(this.suspiciousCount / (float) this.sponsees.size() * 100);
+    }
+
+    private void findBulkIssuance() {
+        Long lastTimestamp = null;
+        for (RewardShareTransactionData rewardShareTransactionData : sponsorshipRewardShares) {
+            long timestamp = rewardShareTransactionData.getTimestamp();
+            if (timestamp >= this.snapshotTimestamp) {
+                continue;
+            }
+
+            if (lastTimestamp != null) {
+                if (timestamp - lastTimestamp < 3*60*1000L) {
+                    this.bulkIssuanceCount++;
+                }
+            }
+            lastTimestamp = timestamp;
+        }
+    }
+
+    private void findRegisteredNameCount() throws DataException {
+        int registeredNameCount = 0;
+        for (String sponseeAddress : sponsees) {
+            List<NameData> names = repository.getNameRepository().getNamesByOwner(sponseeAddress);
+            for (NameData name : names) {
+                if (name.getRegistered() < this.snapshotTimestamp) {
+                    registeredNameCount++;
+                    break;
+                }
+            }
+        }
+        this.registeredNameCount = registeredNameCount;
+    }
+
+    private void findRecentSponsorshipCount() {
+        final long referenceTimestamp = this.snapshotTimestamp - (365 * 24 * 60 * 60 * 1000L);
+        int recentSponsorshipCount = 0;
+        for (RewardShareTransactionData rewardShare : sponsorshipRewardShares) {
+            if (rewardShare.getTimestamp() >= referenceTimestamp) {
+                recentSponsorshipCount++;
+            }
+        }
+        this.recentSponsorshipCount = recentSponsorshipCount;
+    }
+
+    private int calculateScore() {
+        final int suspiciousMultiplier = (this.suspiciousCount >= 100) ? this.suspiciousPercent : 1;
+        final int nameMultiplier = (this.sponsees.size() >= 50 && this.registeredNameCount == 0) ? 2 : 1;
+        final int consolidationMultiplier = Math.max(this.consolidationCount, 1);
+        final int bulkIssuanceMultiplier = Math.max(this.bulkIssuanceCount / 2, 1);
+        final int offset = 9;
+        return suspiciousMultiplier * nameMultiplier * consolidationMultiplier * bulkIssuanceMultiplier - offset;
+    }
+
+    private void fetchSponsorshipRewardShares() throws DataException {
+        List<RewardShareTransactionData> sponsorshipRewardShares = new ArrayList<>();
+
+        // Define relevant transactions
+        List<TransactionType> txTypes = List.of(TransactionType.REWARD_SHARE);
+        List<TransactionData> transactionDataList = fetchTransactions(repository, txTypes, this.address, false);
+
+        for (TransactionData transactionData : transactionDataList) {
+            if (transactionData.getType() != TransactionType.REWARD_SHARE) {
+                continue;
+            }
+
+            RewardShareTransactionData rewardShareTransactionData = (RewardShareTransactionData) transactionData;
+
+            // Skip removals
+            if (rewardShareTransactionData.getSharePercent() < 0) {
+                continue;
+            }
+
+            // Skip if not sponsored by this account
+            if (!Arrays.equals(rewardShareTransactionData.getCreatorPublicKey(), accountData.getPublicKey())) {
+                continue;
+            }
+
+            // Skip self shares
+            if (Objects.equals(rewardShareTransactionData.getRecipient(), this.address)) {
+                continue;
+            }
+
+            boolean duplicateFound = false;
+            for (RewardShareTransactionData existingRewardShare : sponsorshipRewardShares) {
+                if (Objects.equals(existingRewardShare.getRecipient(), rewardShareTransactionData.getRecipient())) {
+                    // Duplicate
+                    duplicateFound = true;
+                    break;
+                }
+            }
+            if (!duplicateFound) {
+                sponsorshipRewardShares.add(rewardShareTransactionData);
+                this.sponsees.add(rewardShareTransactionData.getRecipient());
+            }
+        }
+
+        this.sponsorshipRewardShares = sponsorshipRewardShares;
+    }
+
+    private List<TransactionData> fetchTransferPrivsForAddress(String address) throws DataException {
+        return fetchTransactions(repository,
+                List.of(TransactionType.TRANSFER_PRIVS),
+                address, true);
+    }
+
+    private void fetchPaymentsForAddress(String address) throws DataException {
+        List<TransactionData> payments = fetchTransactions(repository,
+                Arrays.asList(TransactionType.PAYMENT, TransactionType.TRANSFER_ASSET),
+                address, false);
+        this.paymentsByAddress.put(address, payments);
+    }
+
+    private List<String> fetchOutgoingPaymentRecipientsForAddress(String address) {
+        List<String> outgoingPaymentRecipients = new ArrayList<>();
+
+        List<TransactionData> transactionDataList = this.paymentsByAddress.get(address);
+        if (transactionDataList == null) transactionDataList = new ArrayList<>();
+        transactionDataList.removeIf(t -> t.getTimestamp() >= this.snapshotTimestamp);
+        for (TransactionData transactionData : transactionDataList) {
+            switch (transactionData.getType()) {
+
+                case PAYMENT:
+                    PaymentTransactionData paymentTransactionData = (PaymentTransactionData) transactionData;
+                    if (!Objects.equals(paymentTransactionData.getRecipient(), address)) {
+                        // Outgoing payment from this account
+                        outgoingPaymentRecipients.add(paymentTransactionData.getRecipient());
+                    }
+                    break;
+
+                case TRANSFER_ASSET:
+                    TransferAssetTransactionData transferAssetTransactionData = (TransferAssetTransactionData) transactionData;
+                    if (transferAssetTransactionData.getAssetId() == Asset.QORT) {
+                        if (!Objects.equals(transferAssetTransactionData.getRecipient(), address)) {
+                            // Outgoing payment from this account
+                            outgoingPaymentRecipients.add(transferAssetTransactionData.getRecipient());
+                        }
+                    }
+                    break;
+
+                default:
+                    break;
+            }
+        }
+
+        return outgoingPaymentRecipients;
+    }
+
+    private boolean hasZeroTransactions(String address) {
+        List<TransactionData> transactionDataList = this.paymentsByAddress.get(address);
+        if (transactionDataList == null) {
+            return true;
+        }
+        transactionDataList.removeIf(t -> t.getTimestamp() >= this.snapshotTimestamp);
+        return transactionDataList.size() == 0;
+    }
+
+    private static List<TransactionData> fetchTransactions(Repository repository, List<TransactionType> txTypes, String address, boolean reverse) throws DataException {
+        // Fetch all relevant transactions for this account
+        List<byte[]> signatures = repository.getTransactionRepository()
+                .getSignaturesMatchingCriteria(null, null, null, txTypes,
+                        null, null, address, TransactionsResource.ConfirmationStatus.CONFIRMED,
+                        null, null, reverse);
+
+        List<TransactionData> transactionDataList = new ArrayList<>();
+
+        for (byte[] signature : signatures) {
+            // Fetch transaction data
+            TransactionData transactionData = repository.getTransactionRepository().fromSignature(signature);
+            if (transactionData == null) {
+                continue;
+            }
+            transactionDataList.add(transactionData);
+        }
+
+        return transactionDataList;
+    }
+
+}

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

@@ -0,0 +1,56 @@
+package org.qortal.api.model;
+
+import org.qortal.block.SelfSponsorshipAlgoV1Block;
+import org.qortal.data.account.AccountData;
+import org.qortal.data.naming.NameData;
+
+import javax.xml.bind.annotation.XmlAccessType;
+import javax.xml.bind.annotation.XmlAccessorType;
+import javax.xml.bind.annotation.XmlElement;
+import java.util.ArrayList;
+import java.util.List;
+
+@XmlAccessorType(XmlAccessType.FIELD)
+public class AccountPenaltyStats {
+
+	public Integer totalPenalties;
+	public Integer maxPenalty;
+	public Integer minPenalty;
+	public String penaltyHash;
+
+	protected AccountPenaltyStats() {
+	}
+
+	public AccountPenaltyStats(Integer totalPenalties, Integer maxPenalty, Integer minPenalty, String penaltyHash) {
+		this.totalPenalties = totalPenalties;
+		this.maxPenalty = maxPenalty;
+		this.minPenalty = minPenalty;
+		this.penaltyHash = penaltyHash;
+	}
+
+	public static AccountPenaltyStats fromAccounts(List<AccountData> accounts) {
+		int totalPenalties = 0;
+		Integer maxPenalty = null;
+		Integer minPenalty = null;
+
+		List<String> addresses = new ArrayList<>();
+		for (AccountData accountData : accounts) {
+			int penalty = accountData.getBlocksMintedPenalty();
+			addresses.add(accountData.getAddress());
+			totalPenalties++;
+
+			// Penalties are expressed as a negative number, so the min and the max are reversed here
+			if (maxPenalty == null || penalty < maxPenalty) maxPenalty = penalty;
+			if (minPenalty == null || penalty > minPenalty) minPenalty = penalty;
+		}
+
+		String penaltyHash = SelfSponsorshipAlgoV1Block.getHash(addresses);
+		return new AccountPenaltyStats(totalPenalties, maxPenalty, minPenalty, penaltyHash);
+	}
+
+
+	@Override
+	public String toString() {
+		return String.format("totalPenalties: %d, maxPenalty: %d, minPenalty: %d, penaltyHash: %s", totalPenalties, maxPenalty, minPenalty, penaltyHash == null ? "null" : penaltyHash);
+	}
+}

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

@@ -1,6 +1,7 @@
 package org.qortal.api.model;
 
 import io.swagger.v3.oas.annotations.media.Schema;
+import org.qortal.controller.Controller;
 import org.qortal.data.block.BlockSummaryData;
 import org.qortal.data.network.PeerData;
 import org.qortal.network.Handshake;
@@ -36,6 +37,7 @@ public class ConnectedPeer {
     public Long lastBlockTimestamp;
     public UUID connectionId;
     public String age;
+    public Boolean isTooDivergent;
 
     protected ConnectedPeer() {
     }
@@ -69,6 +71,11 @@ public class ConnectedPeer {
             this.lastBlockSignature = peerChainTipData.getSignature();
             this.lastBlockTimestamp = peerChainTipData.getTimestamp();
         }
+
+        // Only include isTooDivergent decision if we've had the opportunity to request block summaries this peer
+        if (peer.getLastTooDivergentTime() != null) {
+            this.isTooDivergent = Controller.wasRecentlyTooDivergent.test(peer);
+        }
     }
 
 }

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

@@ -14,6 +14,7 @@ import java.math.BigDecimal;
 import java.util.ArrayList;
 import java.util.Comparator;
 import java.util.List;
+import java.util.stream.Collectors;
 
 import javax.servlet.http.HttpServletRequest;
 import javax.ws.rs.*;
@@ -27,6 +28,7 @@ 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.AccountPenaltyStats;
 import org.qortal.api.model.ApiOnlineAccount;
 import org.qortal.api.model.RewardShareKeyRequest;
 import org.qortal.asset.Asset;
@@ -34,6 +36,7 @@ import org.qortal.controller.LiteNode;
 import org.qortal.controller.OnlineAccountsManager;
 import org.qortal.crypto.Crypto;
 import org.qortal.data.account.AccountData;
+import org.qortal.data.account.AccountPenaltyData;
 import org.qortal.data.account.RewardShareData;
 import org.qortal.data.network.OnlineAccountData;
 import org.qortal.data.network.OnlineAccountLevel;
@@ -471,6 +474,54 @@ public class AddressesResource {
 		}
 	}
 
+	@GET
+	@Path("/penalties")
+	@Operation(
+			summary = "Get addresses with penalties",
+			description = "Returns a list of accounts with a blocksMintedPenalty",
+			responses = {
+					@ApiResponse(
+							description = "accounts with penalties",
+							content = @Content(mediaType = MediaType.APPLICATION_JSON, array = @ArraySchema(schema = @Schema(implementation = AccountPenaltyData.class)))
+					)
+			}
+	)
+	@ApiErrors({ApiError.INVALID_ADDRESS, ApiError.REPOSITORY_ISSUE})
+	public List<AccountPenaltyData> getAccountsWithPenalties() {
+		try (final Repository repository = RepositoryManager.getRepository()) {
+
+			List<AccountData> accounts = repository.getAccountRepository().getPenaltyAccounts();
+			List<AccountPenaltyData> penalties = accounts.stream().map(a -> new AccountPenaltyData(a.getAddress(), a.getBlocksMintedPenalty())).collect(Collectors.toList());
+
+			return penalties;
+		} catch (DataException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.REPOSITORY_ISSUE, e);
+		}
+	}
+
+	@GET
+	@Path("/penalties/stats")
+	@Operation(
+			summary = "Get stats about current penalties",
+			responses = {
+					@ApiResponse(
+							description = "aggregated stats about accounts with penalties",
+							content = @Content(mediaType = MediaType.APPLICATION_JSON, array = @ArraySchema(schema = @Schema(implementation = AccountPenaltyStats.class)))
+					)
+			}
+	)
+	@ApiErrors({ApiError.INVALID_ADDRESS, ApiError.REPOSITORY_ISSUE})
+	public AccountPenaltyStats getPenaltyStats() {
+		try (final Repository repository = RepositoryManager.getRepository()) {
+
+			List<AccountData> accounts = repository.getAccountRepository().getPenaltyAccounts();
+			return AccountPenaltyStats.fromAccounts(accounts);
+
+		} catch (DataException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.REPOSITORY_ISSUE, e);
+		}
+	}
+
 	@POST
 	@Path("/publicize")
 	@Operation(

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

@@ -719,7 +719,7 @@ public class ArbitraryResource {
 		try {
 			ArbitraryDataTransactionMetadata transactionMetadata = ArbitraryMetadataManager.getInstance().fetchMetadata(resource, false);
 			if (transactionMetadata != null) {
-				ArbitraryResourceMetadata resourceMetadata = ArbitraryResourceMetadata.fromTransactionMetadata(transactionMetadata);
+				ArbitraryResourceMetadata resourceMetadata = ArbitraryResourceMetadata.fromTransactionMetadata(transactionMetadata, true);
 				if (resourceMetadata != null) {
 					return resourceMetadata;
 				}
@@ -1128,7 +1128,7 @@ public class ArbitraryResource {
 			if (path == null) {
 				// See if we have a string instead
 				if (string != null) {
-					File tempFile = File.createTempFile("qortal-", ".tmp");
+					File tempFile = File.createTempFile("qortal-", "");
 					tempFile.deleteOnExit();
 					BufferedWriter writer = new BufferedWriter(new FileWriter(tempFile.toPath().toString()));
 					writer.write(string);
@@ -1138,7 +1138,7 @@ public class ArbitraryResource {
 				}
 				// ... or base64 encoded raw data
 				else if (base64 != null) {
-					File tempFile = File.createTempFile("qortal-", ".tmp");
+					File tempFile = File.createTempFile("qortal-", "");
 					tempFile.deleteOnExit();
 					Files.write(tempFile.toPath(), Base64.decode(base64));
 					path = tempFile.toPath().toString();
@@ -1288,7 +1288,7 @@ public class ArbitraryResource {
 			ArbitraryDataResource resource = new ArbitraryDataResource(resourceInfo.name, ResourceIdType.NAME,
 					resourceInfo.service, resourceInfo.identifier);
 			ArbitraryDataTransactionMetadata transactionMetadata = resource.getLatestTransactionMetadata();
-			ArbitraryResourceMetadata resourceMetadata = ArbitraryResourceMetadata.fromTransactionMetadata(transactionMetadata);
+			ArbitraryResourceMetadata resourceMetadata = ArbitraryResourceMetadata.fromTransactionMetadata(transactionMetadata, false);
 			if (resourceMetadata != null) {
 				resourceInfo.metadata = resourceMetadata;
 			}

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

@@ -634,13 +634,16 @@ public class BlocksResource {
 	@ApiErrors({
 		ApiError.REPOSITORY_ISSUE
 	})
-	public List<BlockData> getBlockRange(@PathParam("height") int height, @Parameter(
-		ref = "count"
-	) @QueryParam("count") int count) {
+	public List<BlockData> getBlockRange(@PathParam("height") int height,
+										 @Parameter(ref = "count") @QueryParam("count") int count,
+										 @Parameter(ref = "reverse") @QueryParam("reverse") Boolean reverse,
+										 @QueryParam("includeOnlineSignatures") Boolean includeOnlineSignatures) {
 		try (final Repository repository = RepositoryManager.getRepository()) {
 			List<BlockData> blocks = new ArrayList<>();
+			boolean shouldReverse = (reverse != null && reverse == true);
 
-			for (/* count already set */; count > 0; --count, ++height) {
+			int i = 0;
+			while (i < count) {
 				BlockData blockData = repository.getBlockRepository().fromHeight(height);
 				if (blockData == null) {
 					// Not found - try the archive
@@ -650,8 +653,14 @@ public class BlocksResource {
 						break;
 					}
 				}
+				if (includeOnlineSignatures == null || includeOnlineSignatures == false) {
+					blockData.setOnlineAccountsSignatures(null);
+				}
 
 				blocks.add(blockData);
+
+				height = shouldReverse ? height - 1 : height + 1;
+				i++;
 			}
 
 			return blocks;

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

@@ -70,6 +70,8 @@ public class ChatResource {
 			@QueryParam("txGroupId") Integer txGroupId,
 			@QueryParam("involving") List<String> involvingAddresses,
 			@QueryParam("reference") String reference,
+			@QueryParam("chatreference") String chatReference,
+			@QueryParam("haschatreference") Boolean hasChatReference,
 			@Parameter(ref = "limit") @QueryParam("limit") Integer limit,
 			@Parameter(ref = "offset") @QueryParam("offset") Integer offset,
 			@Parameter(ref = "reverse") @QueryParam("reverse") Boolean reverse) {
@@ -92,12 +94,18 @@ public class ChatResource {
 		if (reference != null)
 			referenceBytes = Base58.decode(reference);
 
+		byte[] chatReferenceBytes = null;
+		if (chatReference != null)
+			chatReferenceBytes = Base58.decode(chatReference);
+
 		try (final Repository repository = RepositoryManager.getRepository()) {
 			return repository.getChatRepository().getMessagesMatchingCriteria(
 					before,
 					after,
 					txGroupId,
 					referenceBytes,
+					chatReferenceBytes,
+					hasChatReference,
 					involvingAddresses,
 					limit, offset, reverse);
 		} catch (DataException e) {

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

@@ -68,7 +68,7 @@ public class CrossChainBitcoinResource {
 			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_PRIVATE_KEY);
 
 		try {
-			Long balance = bitcoin.getWalletBalanceFromTransactions(key58);
+			Long balance = bitcoin.getWalletBalance(key58);
 			if (balance == null)
 				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.FOREIGN_BLOCKCHAIN_NETWORK_ISSUE);
 

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

@@ -68,7 +68,7 @@ public class CrossChainDigibyteResource {
 			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_PRIVATE_KEY);
 
 		try {
-			Long balance = digibyte.getWalletBalanceFromTransactions(key58);
+			Long balance = digibyte.getWalletBalance(key58);
 			if (balance == null)
 				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.FOREIGN_BLOCKCHAIN_NETWORK_ISSUE);
 

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

@@ -66,7 +66,7 @@ public class CrossChainDogecoinResource {
 			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_PRIVATE_KEY);
 
 		try {
-			Long balance = dogecoin.getWalletBalanceFromTransactions(key58);
+			Long balance = dogecoin.getWalletBalance(key58);
 			if (balance == null)
 				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.FOREIGN_BLOCKCHAIN_NETWORK_ISSUE);
 

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

@@ -8,11 +8,10 @@ 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;
 import java.math.BigDecimal;
 import java.util.List;
 import java.util.Objects;
-import java.util.concurrent.locks.ReentrantLock;
+import java.util.stream.Collectors;
 
 import javax.servlet.http.HttpServletRequest;
 import javax.ws.rs.*;
@@ -25,7 +24,6 @@ import org.bitcoinj.core.*;
 import org.bitcoinj.script.Script;
 import org.qortal.api.*;
 import org.qortal.api.model.CrossChainBitcoinyHTLCStatus;
-import org.qortal.controller.Controller;
 import org.qortal.crosschain.*;
 import org.qortal.crypto.Crypto;
 import org.qortal.data.at.ATData;
@@ -586,98 +584,103 @@ public class CrossChainHtlcResource {
 			}
 
 			List<TradeBotData> allTradeBotData = repository.getCrossChainRepository().getAllTradeBotData();
-			TradeBotData tradeBotData = allTradeBotData.stream().filter(tradeBotDataItem -> tradeBotDataItem.getAtAddress().equals(atAddress)).findFirst().orElse(null);
-			if (tradeBotData == null)
+			List<TradeBotData> tradeBotDataList = allTradeBotData.stream().filter(tradeBotDataItem -> tradeBotDataItem.getAtAddress().equals(atAddress)).collect(Collectors.toList());
+			if (tradeBotDataList == null || tradeBotDataList.isEmpty())
 				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
 
-			Bitcoiny bitcoiny = (Bitcoiny) acct.getBlockchain();
-			int lockTime = tradeBotData.getLockTimeA();
+			// Loop through all matching entries for this AT address, as there might be more than one
+			for (TradeBotData tradeBotData : tradeBotDataList) {
 
-			// 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);
+				if (tradeBotData == null)
+					throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
 
-			// We can't refund P2SH-A until median block time has passed lockTime-A (see BIP113)
-			int medianBlockTime = bitcoiny.getMedianBlockTime();
-			if (medianBlockTime <= lockTime)
-				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.FOREIGN_BLOCKCHAIN_TOO_SOON);
+				Bitcoiny bitcoiny = (Bitcoiny) acct.getBlockchain();
+				int lockTime = tradeBotData.getLockTimeA();
 
-			// Fee for redeem/refund is subtracted from P2SH-A balance.
-			long feeTimestamp = calcFeeTimestamp(lockTime, crossChainTradeData.tradeTimeout);
-			long p2shFee = bitcoiny.getP2shFee(feeTimestamp);
-			long minimumAmountA = crossChainTradeData.expectedForeignAmount + p2shFee;
+				// We can't refund P2SH-A until lockTime-A has passed
+				if (NTP.getTime() <= lockTime * 1000L)
+					continue;
 
-			// Create redeem script based on destination chain
-			byte[] redeemScriptA;
-			String p2shAddressA;
-			BitcoinyHTLC.Status htlcStatusA;
-			if (Objects.equals(bitcoiny.getCurrencyCode(), "ARRR")) {
-				redeemScriptA = PirateChainHTLC.buildScript(tradeBotData.getTradeForeignPublicKey(), lockTime, crossChainTradeData.creatorForeignPKH, tradeBotData.getHashOfSecret());
-				p2shAddressA = PirateChain.getInstance().deriveP2shAddressBPrefix(redeemScriptA);
-				htlcStatusA = PirateChainHTLC.determineHtlcStatus(bitcoiny.getBlockchainProvider(), p2shAddressA, minimumAmountA);
-			}
-			else {
-				redeemScriptA = BitcoinyHTLC.buildScript(tradeBotData.getTradeForeignPublicKeyHash(), lockTime, crossChainTradeData.creatorForeignPKH, tradeBotData.getHashOfSecret());
-				p2shAddressA = bitcoiny.deriveP2shAddress(redeemScriptA);
-				htlcStatusA = BitcoinyHTLC.determineHtlcStatus(bitcoiny.getBlockchainProvider(), p2shAddressA, minimumAmountA);
-			}
-			LOGGER.info(String.format("Refunding P2SH address: %s", p2shAddressA));
+				// We can't refund P2SH-A until median block time has passed lockTime-A (see BIP113)
+				int medianBlockTime = bitcoiny.getMedianBlockTime();
+				if (medianBlockTime <= lockTime)
+					continue;
 
-			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);
+				// Fee for redeem/refund is subtracted from P2SH-A balance.
+				long feeTimestamp = calcFeeTimestamp(lockTime, crossChainTradeData.tradeTimeout);
+				long p2shFee = bitcoiny.getP2shFee(feeTimestamp);
+				long minimumAmountA = crossChainTradeData.expectedForeignAmount + p2shFee;
 
-				case REDEEM_IN_PROGRESS:
-				case REDEEMED:
-				case REFUND_IN_PROGRESS:
-				case REFUNDED:
-					// Too late!
-					return false;
+				// Create redeem script based on destination chain
+				byte[] redeemScriptA;
+				String p2shAddressA;
+				BitcoinyHTLC.Status htlcStatusA;
+				if (Objects.equals(bitcoiny.getCurrencyCode(), "ARRR")) {
+					redeemScriptA = PirateChainHTLC.buildScript(tradeBotData.getTradeForeignPublicKey(), lockTime, crossChainTradeData.creatorForeignPKH, tradeBotData.getHashOfSecret());
+					p2shAddressA = PirateChain.getInstance().deriveP2shAddressBPrefix(redeemScriptA);
+					htlcStatusA = PirateChainHTLC.determineHtlcStatus(bitcoiny.getBlockchainProvider(), p2shAddressA, minimumAmountA);
+				} else {
+					redeemScriptA = BitcoinyHTLC.buildScript(tradeBotData.getTradeForeignPublicKeyHash(), lockTime, crossChainTradeData.creatorForeignPKH, tradeBotData.getHashOfSecret());
+					p2shAddressA = bitcoiny.deriveP2shAddress(redeemScriptA);
+					htlcStatusA = BitcoinyHTLC.determineHtlcStatus(bitcoiny.getBlockchainProvider(), p2shAddressA, minimumAmountA);
+				}
+				LOGGER.info(String.format("Refunding P2SH address: %s", p2shAddressA));
 
-				case FUNDED:{
-					Coin refundAmount = Coin.valueOf(crossChainTradeData.expectedForeignAmount);
+				switch (htlcStatusA) {
+					case UNFUNDED:
+					case FUNDING_IN_PROGRESS:
+						// Still waiting for P2SH-A to be funded...
+						continue;
 
-					if (Objects.equals(bitcoiny.getCurrencyCode(), "ARRR")) {
-						// Pirate Chain custom integration
+					case REDEEM_IN_PROGRESS:
+					case REDEEMED:
+					case REFUND_IN_PROGRESS:
+					case REFUNDED:
+						// Too late!
+						continue;
 
-						PirateChain pirateChain = PirateChain.getInstance();
-						String p2shAddressT3 = pirateChain.deriveP2shAddress(redeemScriptA);
+					case FUNDED: {
+						Coin refundAmount = Coin.valueOf(crossChainTradeData.expectedForeignAmount);
 
-						// Get funding txid
-						String fundingTxidHex = PirateChainHTLC.getUnspentFundingTxid(pirateChain.getBlockchainProvider(), p2shAddressA, minimumAmountA);
-						if (fundingTxidHex == null) {
-							throw new ForeignBlockchainException("Missing funding txid when refunding P2SH");
+						if (Objects.equals(bitcoiny.getCurrencyCode(), "ARRR")) {
+							// Pirate Chain custom integration
+
+							PirateChain pirateChain = PirateChain.getInstance();
+							String p2shAddressT3 = pirateChain.deriveP2shAddress(redeemScriptA);
+
+							// Get funding txid
+							String fundingTxidHex = PirateChainHTLC.getUnspentFundingTxid(pirateChain.getBlockchainProvider(), p2shAddressA, minimumAmountA);
+							if (fundingTxidHex == null) {
+								throw new ForeignBlockchainException("Missing funding txid when refunding P2SH");
+							}
+							String fundingTxid58 = Base58.encode(HashCode.fromString(fundingTxidHex).asBytes());
+
+							byte[] privateKey = tradeBotData.getTradePrivateKey();
+							String privateKey58 = Base58.encode(privateKey);
+							String redeemScript58 = Base58.encode(redeemScriptA);
+
+							String txid = PirateChain.getInstance().refundP2sh(p2shAddressT3,
+									receiveAddress, refundAmount.value, redeemScript58, fundingTxid58, lockTime, privateKey58);
+							LOGGER.info("Refund txid: {}", txid);
+						} else {
+							// ElectrumX coins
+
+							ECKey refundKey = ECKey.fromPrivate(tradeBotData.getTradePrivateKey());
+							List<TransactionOutput> fundingOutputs = bitcoiny.getUnspentOutputs(p2shAddressA);
+
+							// Validate the destination foreign blockchain address
+							Address receiving = Address.fromString(bitcoiny.getNetworkParameters(), receiveAddress);
+							if (receiving.getOutputScriptType() != Script.ScriptType.P2PKH)
+								throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
+
+							Transaction p2shRefundTransaction = BitcoinyHTLC.buildRefundTransaction(bitcoiny.getNetworkParameters(), refundAmount, refundKey,
+									fundingOutputs, redeemScriptA, lockTime, receiving.getHash());
+
+							bitcoiny.broadcastTransaction(p2shRefundTransaction);
 						}
-						String fundingTxid58 = Base58.encode(HashCode.fromString(fundingTxidHex).asBytes());
 
-						byte[] privateKey = tradeBotData.getTradePrivateKey();
-						String privateKey58 = Base58.encode(privateKey);
-						String redeemScript58 = Base58.encode(redeemScriptA);
-
-						String txid = PirateChain.getInstance().refundP2sh(p2shAddressT3,
-								receiveAddress, refundAmount.value, redeemScript58, fundingTxid58, lockTime, privateKey58);
-						LOGGER.info("Refund txid: {}", txid);
+						return true;
 					}
-					else {
-						// ElectrumX coins
-
-						ECKey refundKey = ECKey.fromPrivate(tradeBotData.getTradePrivateKey());
-						List<TransactionOutput> fundingOutputs = bitcoiny.getUnspentOutputs(p2shAddressA);
-
-						// Validate the destination foreign blockchain address
-						Address receiving = Address.fromString(bitcoiny.getNetworkParameters(), receiveAddress);
-						if (receiving.getOutputScriptType() != Script.ScriptType.P2PKH)
-							throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
-
-						Transaction p2shRefundTransaction = BitcoinyHTLC.buildRefundTransaction(bitcoiny.getNetworkParameters(), refundAmount, refundKey,
-								fundingOutputs, redeemScriptA, lockTime, receiving.getHash());
-
-						bitcoiny.broadcastTransaction(p2shRefundTransaction);
-					}
-
-					return true;
 				}
 			}
 

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

@@ -68,7 +68,7 @@ public class CrossChainLitecoinResource {
 			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_PRIVATE_KEY);
 
 		try {
-			Long balance = litecoin.getWalletBalanceFromTransactions(key58);
+			Long balance = litecoin.getWalletBalance(key58);
 			if (balance == null)
 				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.FOREIGN_BLOCKCHAIN_NETWORK_ISSUE);
 

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

@@ -68,7 +68,7 @@ public class CrossChainRavencoinResource {
 			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_PRIVATE_KEY);
 
 		try {
-			Long balance = ravencoin.getWalletBalanceFromTransactions(key58);
+			Long balance = ravencoin.getWalletBalance(key58);
 			if (balance == null)
 				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.FOREIGN_BLOCKCHAIN_NETWORK_ISSUE);
 

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

@@ -47,6 +47,8 @@ public class ChatMessagesWebSocket extends ApiWebSocket {
 						txGroupId,
 						null,
 						null,
+						null,
+						null,
 						null, null, null);
 
 				sendMessages(session, chatMessages);
@@ -74,6 +76,8 @@ public class ChatMessagesWebSocket extends ApiWebSocket {
 					null,
 					null,
 					null,
+					null,
+					null,
 					involvingAddresses,
 					null, null, null);
 

src/main/java/org/qortal/arbitrary/ArbitraryDataBuilder.java

@@ -2,6 +2,7 @@ package org.qortal.arbitrary;
 
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
+import org.qortal.arbitrary.exception.DataNotPublishedException;
 import org.qortal.arbitrary.exception.MissingDataException;
 import org.qortal.arbitrary.metadata.ArbitraryDataMetadataCache;
 import org.qortal.arbitrary.misc.Service;
@@ -88,7 +89,7 @@ public class ArbitraryDataBuilder {
             if (latestPut == null) {
                 String message = String.format("Couldn't find PUT transaction for name %s, service %s and identifier %s",
                         this.name, this.service, this.identifierString());
-                throw new DataException(message);
+                throw new DataNotPublishedException(message);
             }
             this.latestPutTransaction = latestPut;
 

src/main/java/org/qortal/arbitrary/ArbitraryDataReader.java

@@ -4,6 +4,7 @@ import org.apache.commons.io.FileUtils;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 
+import org.qortal.arbitrary.exception.DataNotPublishedException;
 import org.qortal.arbitrary.exception.MissingDataException;
 import org.qortal.arbitrary.misc.Service;
 import org.qortal.controller.arbitrary.ArbitraryDataBuildManager;
@@ -169,10 +170,18 @@ public class ArbitraryDataReader {
             this.uncompress();
             this.validate();
 
+        } catch (DataNotPublishedException e) {
+            if (e.getMessage() != null) {
+                // Log the message only, to avoid spamming the logs with a full stack trace
+                LOGGER.debug("DataNotPublishedException when trying to load QDN resource: {}", e.getMessage());
+            }
+            this.deleteWorkingDirectory();
+            throw e;
+
         } catch (DataException e) {
             LOGGER.info("DataException when trying to load QDN resource", e);
             this.deleteWorkingDirectory();
-            throw new DataException(e.getMessage());
+            throw e;
 
         } finally {
             this.postExecute();

src/main/java/org/qortal/arbitrary/ArbitraryDataResource.java

@@ -3,6 +3,7 @@ package org.qortal.arbitrary;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.qortal.arbitrary.ArbitraryDataFile.ResourceIdType;
+import org.qortal.arbitrary.exception.DataNotPublishedException;
 import org.qortal.arbitrary.metadata.ArbitraryDataTransactionMetadata;
 import org.qortal.arbitrary.misc.Service;
 import org.qortal.controller.arbitrary.ArbitraryDataBuildManager;
@@ -325,7 +326,7 @@ public class ArbitraryDataResource {
             if (latestPut == null) {
                 String message = String.format("Couldn't find PUT transaction for name %s, service %s and identifier %s",
                         this.resourceId, this.service, this.identifierString());
-                throw new DataException(message);
+                throw new DataNotPublishedException(message);
             }
             this.latestPutTransaction = latestPut;
 

src/main/java/org/qortal/arbitrary/ArbitraryDataWriter.java

@@ -23,16 +23,13 @@ import javax.crypto.NoSuchPaddingException;
 import javax.crypto.SecretKey;
 import java.io.File;
 import java.io.IOException;
-import java.nio.file.Files;
-import java.nio.file.Path;
-import java.nio.file.Paths;
+import java.nio.file.*;
 import java.security.InvalidAlgorithmParameterException;
 import java.security.InvalidKeyException;
 import java.security.NoSuchAlgorithmException;
-import java.util.ArrayList;
-import java.util.Iterator;
-import java.util.List;
-import java.util.Objects;
+import java.util.*;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 public class ArbitraryDataWriter {
 
@@ -50,6 +47,7 @@ public class ArbitraryDataWriter {
     private final String description;
     private final List<String> tags;
     private final Category category;
+    private List<String> files;
 
     private int chunkSize = ArbitraryDataFile.CHUNK_SIZE;
 
@@ -80,12 +78,14 @@ public class ArbitraryDataWriter {
         this.description = ArbitraryDataTransactionMetadata.limitDescription(description);
         this.tags = ArbitraryDataTransactionMetadata.limitTags(tags);
         this.category = category;
+        this.files = new ArrayList<>(); // Populated in buildFileList()
     }
 
     public void save() throws IOException, DataException, InterruptedException, MissingDataException {
         try {
             this.preExecute();
             this.validateService();
+            this.buildFileList();
             this.process();
             this.compress();
             this.encrypt();
@@ -143,6 +143,24 @@ public class ArbitraryDataWriter {
         }
     }
 
+    private void buildFileList() throws IOException {
+        // Single file resources consist of a single element in the file list
+        boolean isSingleFile = this.filePath.toFile().isFile();
+        if (isSingleFile) {
+            this.files.add(this.filePath.getFileName().toString());
+            return;
+        }
+
+        // Multi file resources require a walk through the directory tree
+        try (Stream<Path> stream = Files.walk(this.filePath)) {
+            this.files = stream
+                    .filter(Files::isRegularFile)
+                    .map(p -> this.filePath.relativize(p).toString())
+                    .filter(s -> !s.isEmpty())
+                    .collect(Collectors.toList());
+        }
+    }
+
     private void process() throws DataException, IOException, MissingDataException {
         switch (this.method) {
 
@@ -285,6 +303,7 @@ public class ArbitraryDataWriter {
             metadata.setTags(this.tags);
             metadata.setCategory(this.category);
             metadata.setChunks(this.arbitraryDataFile.chunkHashList());
+            metadata.setFiles(this.files);
             metadata.write();
 
             // Create an ArbitraryDataFile from the JSON file (we don't have a signature yet)

src/main/java/org/qortal/arbitrary/exception/DataNotPublishedException.java

@@ -0,0 +1,22 @@
+package org.qortal.arbitrary.exception;
+
+import org.qortal.repository.DataException;
+
+public class DataNotPublishedException extends DataException {
+
+	public DataNotPublishedException() {
+	}
+
+	public DataNotPublishedException(String message) {
+		super(message);
+	}
+
+	public DataNotPublishedException(String message, Throwable cause) {
+		super(message, cause);
+	}
+
+	public DataNotPublishedException(Throwable cause) {
+		super(cause);
+	}
+
+}

src/main/java/org/qortal/arbitrary/metadata/ArbitraryDataTransactionMetadata.java

@@ -19,6 +19,7 @@ public class ArbitraryDataTransactionMetadata extends ArbitraryDataMetadata {
     private String description;
     private List<String> tags;
     private Category category;
+    private List<String> files;
 
     private static int MAX_TITLE_LENGTH = 80;
     private static int MAX_DESCRIPTION_LENGTH = 500;
@@ -77,6 +78,20 @@ public class ArbitraryDataTransactionMetadata extends ArbitraryDataMetadata {
             }
             this.chunks = chunksList;
         }
+
+        List<String> filesList = new ArrayList<>();
+        if (metadata.has("files")) {
+            JSONArray files = metadata.getJSONArray("files");
+            if (files != null) {
+                for (int i=0; i<files.length(); i++) {
+                    String tag = files.getString(i);
+                    if (tag != null) {
+                        filesList.add(tag);
+                    }
+                }
+            }
+            this.files = filesList;
+        }
     }
 
     @Override
@@ -111,6 +126,14 @@ public class ArbitraryDataTransactionMetadata extends ArbitraryDataMetadata {
         }
         outer.put("chunks", chunks);
 
+        JSONArray files = new JSONArray();
+        if (this.files != null) {
+            for (String file : this.files) {
+                files.put(file);
+            }
+        }
+        outer.put("files", files);
+
         this.jsonString = outer.toString(2);
         LOGGER.trace("Transaction metadata: {}", this.jsonString);
     }
@@ -156,6 +179,14 @@ public class ArbitraryDataTransactionMetadata extends ArbitraryDataMetadata {
         return this.category;
     }
 
+    public void setFiles(List<String> files) {
+        this.files = files;
+    }
+
+    public List<String> getFiles() {
+        return this.files;
+    }
+
     public boolean containsChunk(byte[] chunk) {
         for (byte[] c : this.chunks) {
             if (Arrays.equals(c, chunk)) {

src/main/java/org/qortal/arbitrary/misc/Service.java

@@ -1,16 +1,16 @@
 package org.qortal.arbitrary.misc;
 
+import org.apache.commons.io.FilenameUtils;
 import org.json.JSONObject;
 import org.qortal.arbitrary.ArbitraryDataRenderer;
 import org.qortal.transaction.Transaction;
 import org.qortal.utils.FilesystemUtils;
 
+import java.io.File;
 import java.io.IOException;
 import java.nio.file.Path;
 import java.nio.file.Paths;
-import java.util.Arrays;
-import java.util.List;
-import java.util.Map;
+import java.util.*;
 
 import static java.util.Arrays.stream;
 import static java.util.stream.Collectors.toMap;
@@ -18,9 +18,52 @@ import static java.util.stream.Collectors.toMap;
 public enum Service {
     AUTO_UPDATE(1, false, null, null),
     ARBITRARY_DATA(100, false, null, null),
+    QCHAT_ATTACHMENT(120, true, 1024*1024L, null) {
+        @Override
+        public ValidationResult validate(Path path) throws IOException {
+            ValidationResult superclassResult = super.validate(path);
+            if (superclassResult != ValidationResult.OK) {
+                return superclassResult;
+            }
+
+            // Custom validation function to require a single file, with a whitelisted extension
+            int fileCount = 0;
+            File[] files = path.toFile().listFiles();
+            // If already a single file, replace the list with one that contains that file only
+            if (files == null && path.toFile().isFile()) {
+                files = new File[] { path.toFile() };
+            }
+            if (files != null) {
+                for (File file : files) {
+                    if (file.getName().equals(".qortal")) {
+                        continue;
+                    }
+                    if (file.isDirectory()) {
+                        return ValidationResult.DIRECTORIES_NOT_ALLOWED;
+                    }
+                    final String extension = FilenameUtils.getExtension(file.getName()).toLowerCase();
+                    // We must allow blank file extensions because these are used by data published from a plaintext or base64-encoded string
+                    final List<String> allowedExtensions = Arrays.asList("zip", "pdf", "txt", "odt", "ods", "doc", "docx", "xls", "xlsx", "ppt", "pptx", "");
+                    if (extension == null || !allowedExtensions.contains(extension)) {
+                        return ValidationResult.INVALID_FILE_EXTENSION;
+                    }
+                    fileCount++;
+                }
+            }
+            if (fileCount != 1) {
+                return ValidationResult.INVALID_FILE_COUNT;
+            }
+            return ValidationResult.OK;
+        }
+    },
     WEBSITE(200, true, null, null) {
         @Override
-        public ValidationResult validate(Path path) {
+        public ValidationResult validate(Path path) throws IOException {
+            ValidationResult superclassResult = super.validate(path);
+            if (superclassResult != ValidationResult.OK) {
+                return superclassResult;
+            }
+
             // Custom validation function to require an index HTML file in the root directory
             List<String> fileNames = ArbitraryDataRenderer.indexFiles();
             String[] files = path.toFile().list();
@@ -38,6 +81,7 @@ public enum Service {
     GIT_REPOSITORY(300, false, null, null),
     IMAGE(400, true, 10*1024*1024L, null),
     THUMBNAIL(410, true, 500*1024L, null),
+    QCHAT_IMAGE(420, true, 500*1024L, null),
     VIDEO(500, false, null, null),
     AUDIO(600, false, null, null),
     BLOG(700, false, null, null),
@@ -48,7 +92,42 @@ public enum Service {
     PLAYLIST(910, true, null, null),
     APP(1000, false, null, null),
     METADATA(1100, false, null, null),
-    QORTAL_METADATA(1111, true, 10*1024L, Arrays.asList("title", "description", "tags"));
+    GIF_REPOSITORY(1200, true, 25*1024*1024L, null) {
+        @Override
+        public ValidationResult validate(Path path) throws IOException {
+            ValidationResult superclassResult = super.validate(path);
+            if (superclassResult != ValidationResult.OK) {
+                return superclassResult;
+            }
+
+            // Custom validation function to require .gif files only, and at least 1
+            int gifCount = 0;
+            File[] files = path.toFile().listFiles();
+            // If already a single file, replace the list with one that contains that file only
+            if (files == null && path.toFile().isFile()) {
+                files = new File[] { path.toFile() };
+            }
+            if (files != null) {
+                for (File file : files) {
+                    if (file.getName().equals(".qortal")) {
+                        continue;
+                    }
+                    if (file.isDirectory()) {
+                        return ValidationResult.DIRECTORIES_NOT_ALLOWED;
+                    }
+                    String extension = FilenameUtils.getExtension(file.getName()).toLowerCase();
+                    if (!Objects.equals(extension, "gif")) {
+                        return ValidationResult.INVALID_FILE_EXTENSION;
+                    }
+                    gifCount++;
+                }
+            }
+            if (gifCount == 0) {
+                return ValidationResult.MISSING_DATA;
+            }
+            return ValidationResult.OK;
+        }
+    };
 
     public final int value;
     private final boolean requiresValidation;
@@ -114,7 +193,11 @@ public enum Service {
         OK(1),
         MISSING_KEYS(2),
         EXCEEDS_SIZE_LIMIT(3),
-        MISSING_INDEX_FILE(4);
+        MISSING_INDEX_FILE(4),
+        DIRECTORIES_NOT_ALLOWED(5),
+        INVALID_FILE_EXTENSION(6),
+        MISSING_DATA(7),
+        INVALID_FILE_COUNT(8);
 
         public final int value;
 

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

@@ -136,7 +136,7 @@ public class Block {
 	}
 
 	/** Lazy-instantiated expanded info on block's online accounts. */
-	private static class ExpandedAccount {
+	public static class ExpandedAccount {
 		private final RewardShareData rewardShareData;
 		private final int sharePercent;
 		private final boolean isRecipientAlsoMinter;
@@ -169,6 +169,13 @@ public class Block {
 			}
 		}
 
+		public Account getMintingAccount() {
+			return this.mintingAccount;
+		}
+		public Account getRecipientAccount() {
+			return this.recipientAccount;
+		}
+
 		/**
 		 * Returns share bin for expanded account.
 		 * <p>
@@ -363,15 +370,24 @@ public class Block {
 			return null;
 		}
 
+		int height = parentBlockData.getHeight() + 1;
 		long timestamp = calcTimestamp(parentBlockData, minter.getPublicKey(), minterLevel);
 		long onlineAccountsTimestamp = OnlineAccountsManager.getCurrentOnlineAccountTimestamp();
 
-		// Fetch our list of online accounts
+		// Fetch our list of online accounts, removing any that are missing a nonce
 		List<OnlineAccountData> onlineAccounts = OnlineAccountsManager.getInstance().getOnlineAccounts(onlineAccountsTimestamp);
+		onlineAccounts.removeIf(a -> a.getNonce() == null || a.getNonce() < 0);
 
-		// If mempow is active, remove any legacy accounts that are missing a nonce
-		if (timestamp >= BlockChain.getInstance().getOnlineAccountsMemoryPoWTimestamp()) {
-			onlineAccounts.removeIf(a -> a.getNonce() == null || a.getNonce() < 0);
+		// After feature trigger, remove any online accounts that are level 0
+		if (height >= BlockChain.getInstance().getOnlineAccountMinterLevelValidationHeight()) {
+			onlineAccounts.removeIf(a -> {
+				try {
+					return Account.getRewardShareEffectiveMintingLevel(repository, a.getPublicKey()) == 0;
+				} catch (DataException e) {
+					// Something went wrong, so remove the account
+					return true;
+				}
+			});
 		}
 
 		if (onlineAccounts.isEmpty()) {
@@ -412,29 +428,27 @@ public class Block {
 		// Aggregated, single signature
 		byte[] onlineAccountsSignatures = Qortal25519Extras.aggregateSignatures(signaturesToAggregate);
 
-		// Add nonces to the end of the online accounts signatures if mempow is active
-		if (timestamp >= BlockChain.getInstance().getOnlineAccountsMemoryPoWTimestamp()) {
-			try {
-				// Create ordered list of nonce values
-				List<Integer> nonces = new ArrayList<>();
-				for (int i = 0; i < onlineAccountsCount; ++i) {
-					Integer accountIndex = accountIndexes.get(i);
-					OnlineAccountData onlineAccountData = indexedOnlineAccounts.get(accountIndex);
-					nonces.add(onlineAccountData.getNonce());
-				}
-
-				// Encode the nonces to a byte array
-				byte[] encodedNonces = BlockTransformer.encodeOnlineAccountNonces(nonces);
-
-				// Append the encoded nonces to the encoded online account signatures
-				ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
-				outputStream.write(onlineAccountsSignatures);
-				outputStream.write(encodedNonces);
-				onlineAccountsSignatures = outputStream.toByteArray();
-			}
-			catch (TransformationException | IOException e) {
-				return null;
+		// Add nonces to the end of the online accounts signatures
+		try {
+			// Create ordered list of nonce values
+			List<Integer> nonces = new ArrayList<>();
+			for (int i = 0; i < onlineAccountsCount; ++i) {
+				Integer accountIndex = accountIndexes.get(i);
+				OnlineAccountData onlineAccountData = indexedOnlineAccounts.get(accountIndex);
+				nonces.add(onlineAccountData.getNonce());
 			}
+
+			// Encode the nonces to a byte array
+			byte[] encodedNonces = BlockTransformer.encodeOnlineAccountNonces(nonces);
+
+			// Append the encoded nonces to the encoded online account signatures
+			ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
+			outputStream.write(onlineAccountsSignatures);
+			outputStream.write(encodedNonces);
+			onlineAccountsSignatures = outputStream.toByteArray();
+		}
+		catch (TransformationException | IOException e) {
+			return null;
 		}
 
 		byte[] minterSignature = minter.sign(BlockTransformer.getBytesForMinterSignature(parentBlockData,
@@ -442,7 +456,6 @@ public class Block {
 
 		int transactionCount = 0;
 		byte[] transactionsSignature = null;
-		int height = parentBlockData.getHeight() + 1;
 
 		int atCount = 0;
 		long atFees = 0;
@@ -1036,6 +1049,15 @@ public class Block {
 		if (onlineRewardShares == null)
 			return ValidationResult.ONLINE_ACCOUNT_UNKNOWN;
 
+		// After feature trigger, require all online account minters to be greater than level 0
+		if (this.getBlockData().getHeight() >= BlockChain.getInstance().getOnlineAccountMinterLevelValidationHeight()) {
+			List<ExpandedAccount> expandedAccounts = this.getExpandedAccounts();
+			for (ExpandedAccount account : expandedAccounts) {
+				if (account.getMintingAccount().getEffectiveMintingLevel() == 0)
+					return ValidationResult.ONLINE_ACCOUNTS_INVALID;
+			}
+		}
+
 		// If block is past a certain age then we simply assume the signatures were correct
 		long signatureRequirementThreshold = NTP.getTime() - BlockChain.getInstance().getOnlineAccountSignaturesMinLifetime();
 		if (this.blockData.getTimestamp() < signatureRequirementThreshold)
@@ -1047,14 +1069,9 @@ public class Block {
 		final int signaturesLength = Transformer.SIGNATURE_LENGTH;
 		final int noncesLength = onlineRewardShares.size() * Transformer.INT_LENGTH;
 
-		if (this.blockData.getTimestamp() >= BlockChain.getInstance().getOnlineAccountsMemoryPoWTimestamp()) {
-			// We expect nonces to be appended to the online accounts signatures
-			if (this.blockData.getOnlineAccountsSignatures().length != signaturesLength + noncesLength)
-				return ValidationResult.ONLINE_ACCOUNT_SIGNATURES_MALFORMED;
-		} else {
-			if (this.blockData.getOnlineAccountsSignatures().length != signaturesLength)
-				return ValidationResult.ONLINE_ACCOUNT_SIGNATURES_MALFORMED;
-		}
+		// We expect nonces to be appended to the online accounts signatures
+		if (this.blockData.getOnlineAccountsSignatures().length != signaturesLength + noncesLength)
+			return ValidationResult.ONLINE_ACCOUNT_SIGNATURES_MALFORMED;
 
 		// Check signatures
 		long onlineTimestamp = this.blockData.getOnlineAccountsTimestamp();
@@ -1063,32 +1080,33 @@ public class Block {
 		byte[] encodedOnlineAccountSignatures = this.blockData.getOnlineAccountsSignatures();
 
 		// Split online account signatures into signature(s) + nonces, then validate the nonces
-		if (this.blockData.getTimestamp() >= BlockChain.getInstance().getOnlineAccountsMemoryPoWTimestamp()) {
-			byte[] extractedSignatures = BlockTransformer.extract(encodedOnlineAccountSignatures, 0, signaturesLength);
-			byte[] extractedNonces = BlockTransformer.extract(encodedOnlineAccountSignatures, signaturesLength, onlineRewardShares.size() * Transformer.INT_LENGTH);
-			encodedOnlineAccountSignatures = extractedSignatures;
+		byte[] extractedSignatures = BlockTransformer.extract(encodedOnlineAccountSignatures, 0, signaturesLength);
+		byte[] extractedNonces = BlockTransformer.extract(encodedOnlineAccountSignatures, signaturesLength, onlineRewardShares.size() * Transformer.INT_LENGTH);
+		encodedOnlineAccountSignatures = extractedSignatures;
 
-			List<Integer> nonces = BlockTransformer.decodeOnlineAccountNonces(extractedNonces);
+		List<Integer> nonces = BlockTransformer.decodeOnlineAccountNonces(extractedNonces);
 
-			// Build block's view of online accounts (without signatures, as we don't need them here)
-			Set<OnlineAccountData> onlineAccounts = new HashSet<>();
-			for (int i = 0; i < onlineRewardShares.size(); ++i) {
-				Integer nonce = nonces.get(i);
-				byte[] publicKey = onlineRewardShares.get(i).getRewardSharePublicKey();
+		// Build block's view of online accounts (without signatures, as we don't need them here)
+		Set<OnlineAccountData> onlineAccounts = new HashSet<>();
+		for (int i = 0; i < onlineRewardShares.size(); ++i) {
+			Integer nonce = nonces.get(i);
+			byte[] publicKey = onlineRewardShares.get(i).getRewardSharePublicKey();
 
-				OnlineAccountData onlineAccountData = new OnlineAccountData(onlineTimestamp, null, publicKey, nonce);
-				onlineAccounts.add(onlineAccountData);
-			}
-
-			// Remove those already validated & cached by online accounts manager - no need to re-validate them
-			OnlineAccountsManager.getInstance().removeKnown(onlineAccounts, onlineTimestamp);
-
-			// Validate the rest
-			for (OnlineAccountData onlineAccount : onlineAccounts)
-				if (!OnlineAccountsManager.getInstance().verifyMemoryPoW(onlineAccount, this.blockData.getTimestamp()))
-					return ValidationResult.ONLINE_ACCOUNT_NONCE_INCORRECT;
+			OnlineAccountData onlineAccountData = new OnlineAccountData(onlineTimestamp, null, publicKey, nonce);
+			onlineAccounts.add(onlineAccountData);
 		}
 
+		// Remove those already validated & cached by online accounts manager - no need to re-validate them
+		OnlineAccountsManager.getInstance().removeKnown(onlineAccounts, onlineTimestamp);
+
+		// Validate the rest
+		for (OnlineAccountData onlineAccount : onlineAccounts)
+			if (!OnlineAccountsManager.getInstance().verifyMemoryPoW(onlineAccount, null))
+				return ValidationResult.ONLINE_ACCOUNT_NONCE_INCORRECT;
+
+		// Cache the valid online accounts as they will likely be needed for the next block
+		OnlineAccountsManager.getInstance().addBlocksOnlineAccounts(onlineAccounts, onlineTimestamp);
+
 		// Extract online accounts' timestamp signatures from block data. Only one signature if aggregated.
 		List<byte[]> onlineAccountsSignatures = BlockTransformer.decodeTimestampSignatures(encodedOnlineAccountSignatures);
 
@@ -1445,6 +1463,9 @@ public class Block {
 			if (this.blockData.getHeight() == 212937)
 				// Apply fix for block 212937
 				Block212937.processFix(this);
+
+			else if (this.blockData.getHeight() == BlockChain.getInstance().getSelfSponsorshipAlgoV1Height())
+				SelfSponsorshipAlgoV1Block.processAccountPenalties(this);
 		}
 
 		// We're about to (test-)process a batch of transactions,
@@ -1501,19 +1522,23 @@ public class Block {
 		// Batch update in repository
 		repository.getAccountRepository().modifyMintedBlockCounts(allUniqueExpandedAccounts.stream().map(AccountData::getAddress).collect(Collectors.toList()), +1);
 
+		// Keep track of level bumps in case we need to apply to other entries
+		Map<String, Integer> bumpedAccounts = new HashMap<>();
+
 		// Local changes and also checks for level bump
 		for (AccountData accountData : allUniqueExpandedAccounts) {
 			// Adjust count locally (in Java)
 			accountData.setBlocksMinted(accountData.getBlocksMinted() + 1);
 			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();
+			final int effectiveBlocksMinted = accountData.getBlocksMinted() + accountData.getBlocksMintedAdjustment() + accountData.getBlocksMintedPenalty();
 
 			for (int newLevel = maximumLevel; newLevel >= 0; --newLevel)
 				if (effectiveBlocksMinted >= cumulativeBlocksByLevel.get(newLevel)) {
 					if (newLevel > accountData.getLevel()) {
 						// Account has increased in level!
 						accountData.setLevel(newLevel);
+						bumpedAccounts.put(accountData.getAddress(), newLevel);
 						repository.getAccountRepository().setLevel(accountData);
 						LOGGER.trace(() -> String.format("Block minter %s bumped to level %d", accountData.getAddress(), accountData.getLevel()));
 					}
@@ -1521,6 +1546,25 @@ public class Block {
 					break;
 				}
 		}
+
+		// Also bump other entries if need be
+		if (!bumpedAccounts.isEmpty()) {
+			for (ExpandedAccount expandedAccount : expandedAccounts) {
+				Integer newLevel = bumpedAccounts.get(expandedAccount.mintingAccountData.getAddress());
+				if (newLevel != null && expandedAccount.mintingAccountData.getLevel() != newLevel) {
+					expandedAccount.mintingAccountData.setLevel(newLevel);
+					LOGGER.trace("Also bumped {} to level {}", expandedAccount.mintingAccountData.getAddress(), newLevel);
+				}
+
+				if (!expandedAccount.isRecipientAlsoMinter) {
+					newLevel = bumpedAccounts.get(expandedAccount.recipientAccountData.getAddress());
+					if (newLevel != null && expandedAccount.recipientAccountData.getLevel() != newLevel) {
+						expandedAccount.recipientAccountData.setLevel(newLevel);
+						LOGGER.trace("Also bumped {} to level {}", expandedAccount.recipientAccountData.getAddress(), newLevel);
+					}
+				}
+			}
+		}
 	}
 
 	protected void processBlockRewards() throws DataException {
@@ -1680,6 +1724,9 @@ public class Block {
 				// Revert fix for block 212937
 				Block212937.orphanFix(this);
 
+			else if (this.blockData.getHeight() == BlockChain.getInstance().getSelfSponsorshipAlgoV1Height())
+				SelfSponsorshipAlgoV1Block.orphanAccountPenalties(this);
+
 			// Block rewards, including transaction fees, removed after transactions undone
 			orphanBlockRewards();
 
@@ -1808,7 +1855,7 @@ public class Block {
 			accountData.setBlocksMinted(accountData.getBlocksMinted() - 1);
 			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();
+			final int effectiveBlocksMinted = accountData.getBlocksMinted() + accountData.getBlocksMintedAdjustment() + accountData.getBlocksMintedPenalty();
 
 			for (int newLevel = maximumLevel; newLevel >= 0; --newLevel)
 				if (effectiveBlocksMinted >= cumulativeBlocksByLevel.get(newLevel)) {

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

@@ -73,7 +73,12 @@ public class BlockChain {
 		calcChainWeightTimestamp,
 		transactionV5Timestamp,
 		transactionV6Timestamp,
-		disableReferenceTimestamp;
+		disableReferenceTimestamp,
+		increaseOnlineAccountsDifficultyTimestamp,
+		onlineAccountMinterLevelValidationHeight,
+		selfSponsorshipAlgoV1Height,
+		feeValidationFixTimestamp,
+		chatReferenceTimestamp;
 	}
 
 	// Custom transaction fees
@@ -95,6 +100,13 @@ public class BlockChain {
 	/** Whether only one registered name is allowed per account. */
 	private boolean oneNamePerAccount = false;
 
+	/** Checkpoints */
+	public static class Checkpoint {
+		public int height;
+		public String signature;
+	}
+	private List<Checkpoint> checkpoints;
+
 	/** Block rewards by block height */
 	public static class RewardByHeight {
 		public int height;
@@ -195,9 +207,8 @@ public class BlockChain {
 	 * featureTriggers because unit tests need to set this value via Reflection. */
 	private long onlineAccountsModulusV2Timestamp;
 
-	/** Feature trigger timestamp for online accounts mempow verification. Can't use featureTriggers
-	 * because unit tests need to set this value via Reflection. */
-	private long onlineAccountsMemoryPoWTimestamp;
+	/** Snapshot timestamp for self sponsorship algo V1 */
+	private long selfSponsorshipAlgoV1SnapshotTimestamp;
 
 	/** Max reward shares by block height */
 	public static class MaxRewardSharesByTimestamp {
@@ -359,8 +370,9 @@ public class BlockChain {
 		return this.onlineAccountsModulusV2Timestamp;
 	}
 
-	public long getOnlineAccountsMemoryPoWTimestamp() {
-		return this.onlineAccountsMemoryPoWTimestamp;
+	// Self sponsorship algo
+	public long getSelfSponsorshipAlgoV1SnapshotTimestamp() {
+		return this.selfSponsorshipAlgoV1SnapshotTimestamp;
 	}
 
 	/** Returns true if approval-needing transaction types require a txGroupId other than NO_GROUP. */
@@ -376,6 +388,10 @@ public class BlockChain {
 		return this.oneNamePerAccount;
 	}
 
+	public List<Checkpoint> getCheckpoints() {
+		return this.checkpoints;
+	}
+
 	public List<RewardByHeight> getBlockRewardsByHeight() {
 		return this.rewardsByHeight;
 	}
@@ -486,6 +502,26 @@ public class BlockChain {
 		return this.featureTriggers.get(FeatureTrigger.disableReferenceTimestamp.name()).longValue();
 	}
 
+	public long getIncreaseOnlineAccountsDifficultyTimestamp() {
+		return this.featureTriggers.get(FeatureTrigger.increaseOnlineAccountsDifficultyTimestamp.name()).longValue();
+	}
+
+	public int getSelfSponsorshipAlgoV1Height() {
+		return this.featureTriggers.get(FeatureTrigger.selfSponsorshipAlgoV1Height.name()).intValue();
+	}
+
+	public long getOnlineAccountMinterLevelValidationHeight() {
+		return this.featureTriggers.get(FeatureTrigger.onlineAccountMinterLevelValidationHeight.name()).intValue();
+	}
+
+	public long getFeeValidationFixTimestamp() {
+		return this.featureTriggers.get(FeatureTrigger.feeValidationFixTimestamp.name()).longValue();
+	}
+
+	public long getChatReferenceTimestamp() {
+		return this.featureTriggers.get(FeatureTrigger.chatReferenceTimestamp.name()).longValue();
+	}
+
 
 	// More complex getters for aspects that change by height or timestamp
 
@@ -654,6 +690,7 @@ public class BlockChain {
 
 		boolean isTopOnly = Settings.getInstance().isTopOnly();
 		boolean archiveEnabled = Settings.getInstance().isArchiveEnabled();
+		boolean isLite = Settings.getInstance().isLite();
 		boolean canBootstrap = Settings.getInstance().getBootstrap();
 		boolean needsArchiveRebuild = false;
 		BlockData chainTip;
@@ -674,22 +711,44 @@ public class BlockChain {
 					}
 				}
 			}
+
+			// Validate checkpoints
+			// Limited to topOnly nodes for now, in order to reduce risk, and to solve a real-world problem with divergent topOnly nodes
+			// TODO: remove the isTopOnly conditional below once this feature has had more testing time
+			if (isTopOnly && !isLite) {
+				List<Checkpoint> checkpoints = BlockChain.getInstance().getCheckpoints();
+				for (Checkpoint checkpoint : checkpoints) {
+					BlockData blockData = repository.getBlockRepository().fromHeight(checkpoint.height);
+					if (blockData == null) {
+						// Try the archive
+						blockData = repository.getBlockArchiveRepository().fromHeight(checkpoint.height);
+					}
+					if (blockData == null) {
+						LOGGER.trace("Couldn't find block for height {}", checkpoint.height);
+						// This is likely due to the block being pruned, so is safe to ignore.
+						// Continue, as there might be other blocks we can check more definitively.
+						continue;
+					}
+
+					byte[] signature = Base58.decode(checkpoint.signature);
+					if (!Arrays.equals(signature, blockData.getSignature())) {
+						LOGGER.info("Error: block at height {} with signature {} doesn't match checkpoint sig: {}. Bootstrapping...", checkpoint.height, Base58.encode(blockData.getSignature()), checkpoint.signature);
+						needsArchiveRebuild = true;
+						break;
+					}
+					LOGGER.info("Block at height {} matches checkpoint signature", blockData.getHeight());
+				}
+			}
+
 		}
 
-		boolean hasBlocks = (chainTip != null && chainTip.getHeight() > 1);
+		// Check first block is Genesis Block
+		if (!isGenesisBlockValid() || needsArchiveRebuild) {
+			try {
+				rebuildBlockchain();
 
-		if (isTopOnly && hasBlocks) {
-			// Top-only mode is enabled and we have blocks, so it's possible that the genesis block has been pruned
-			// It's best not to validate it, and there's no real need to
-		} else {
-			// Check first block is Genesis Block
-			if (!isGenesisBlockValid() || needsArchiveRebuild) {
-				try {
-					rebuildBlockchain();
-
-				} catch (InterruptedException e) {
-					throw new DataException(String.format("Interrupted when trying to rebuild blockchain: %s", e.getMessage()));
-				}
+			} catch (InterruptedException e) {
+				throw new DataException(String.format("Interrupted when trying to rebuild blockchain: %s", e.getMessage()));
 			}
 		}
 
@@ -698,9 +757,7 @@ public class BlockChain {
 		try (final Repository repository = RepositoryManager.getRepository()) {
 			repository.checkConsistency();
 
-			// Set the number of blocks to validate based on the pruned state of the chain
-			// If pruned, subtract an extra 10 to allow room for error
-			int blocksToValidate = (isTopOnly || archiveEnabled) ? Settings.getInstance().getPruneBlockLimit() - 10 : 1440;
+			int blocksToValidate = Math.min(Settings.getInstance().getPruneBlockLimit() - 10, 1440);
 
 			int startHeight = Math.max(repository.getBlockRepository().getBlockchainHeight() - blocksToValidate, 1);
 			BlockData detachedBlockData = repository.getBlockRepository().getDetachedBlockSignature(startHeight);

src/main/java/org/qortal/block/SelfSponsorshipAlgoV1Block.java

@@ -0,0 +1,133 @@
+package org.qortal.block;
+
+import org.apache.commons.lang3.StringUtils;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.qortal.account.SelfSponsorshipAlgoV1;
+import org.qortal.api.model.AccountPenaltyStats;
+import org.qortal.crypto.Crypto;
+import org.qortal.data.account.AccountData;
+import org.qortal.data.account.AccountPenaltyData;
+import org.qortal.repository.DataException;
+import org.qortal.repository.Repository;
+import org.qortal.utils.Base58;
+
+import java.nio.charset.StandardCharsets;
+import java.util.*;
+import java.util.stream.Collectors;
+
+/**
+ * Self Sponsorship AlgoV1 Block
+ * <p>
+ * Selected block for the initial run on the "self sponsorship detection algorithm"
+ */
+public final class SelfSponsorshipAlgoV1Block {
+
+	private static final Logger LOGGER = LogManager.getLogger(SelfSponsorshipAlgoV1Block.class);
+
+
+	private SelfSponsorshipAlgoV1Block() {
+		/* Do not instantiate */
+	}
+
+	public static void processAccountPenalties(Block block) throws DataException {
+		LOGGER.info("Running algo for block processing - this will take a while...");
+		logPenaltyStats(block.repository);
+		long startTime = System.currentTimeMillis();
+		Set<AccountPenaltyData> penalties = getAccountPenalties(block.repository, -5000000);
+		block.repository.getAccountRepository().updateBlocksMintedPenalties(penalties);
+		long totalTime = System.currentTimeMillis() - startTime;
+		String hash = getHash(penalties.stream().map(p -> p.getAddress()).collect(Collectors.toList()));
+		LOGGER.info("{} penalty addresses processed (hash: {}). Total time taken: {} seconds", penalties.size(), hash, (int)(totalTime / 1000.0f));
+		logPenaltyStats(block.repository);
+
+		int updatedCount = updateAccountLevels(block.repository, penalties);
+		LOGGER.info("Account levels updated for {} penalty addresses", updatedCount);
+	}
+
+	public static void orphanAccountPenalties(Block block) throws DataException {
+		LOGGER.info("Running algo for block orphaning - this will take a while...");
+		logPenaltyStats(block.repository);
+		long startTime = System.currentTimeMillis();
+		Set<AccountPenaltyData> penalties = getAccountPenalties(block.repository, 5000000);
+		block.repository.getAccountRepository().updateBlocksMintedPenalties(penalties);
+		long totalTime = System.currentTimeMillis() - startTime;
+		String hash = getHash(penalties.stream().map(p -> p.getAddress()).collect(Collectors.toList()));
+		LOGGER.info("{} penalty addresses orphaned (hash: {}). Total time taken: {} seconds", penalties.size(), hash, (int)(totalTime / 1000.0f));
+		logPenaltyStats(block.repository);
+
+		int updatedCount = updateAccountLevels(block.repository, penalties);
+		LOGGER.info("Account levels updated for {} penalty addresses", updatedCount);
+	}
+
+	public static Set<AccountPenaltyData> getAccountPenalties(Repository repository, int penalty) throws DataException {
+		final long snapshotTimestamp = BlockChain.getInstance().getSelfSponsorshipAlgoV1SnapshotTimestamp();
+		Set<AccountPenaltyData> penalties = new LinkedHashSet<>();
+		List<String> addresses = repository.getTransactionRepository().getConfirmedRewardShareCreatorsExcludingSelfShares();
+		for (String address : addresses) {
+			//System.out.println(String.format("address: %s", address));
+			SelfSponsorshipAlgoV1 selfSponsorshipAlgoV1 = new SelfSponsorshipAlgoV1(repository, address, snapshotTimestamp, false);
+			selfSponsorshipAlgoV1.run();
+			//System.out.println(String.format("Penalty addresses: %d", selfSponsorshipAlgoV1.getPenaltyAddresses().size()));
+
+			for (String penaltyAddress : selfSponsorshipAlgoV1.getPenaltyAddresses()) {
+				penalties.add(new AccountPenaltyData(penaltyAddress, penalty));
+			}
+		}
+		return penalties;
+	}
+
+	private static int updateAccountLevels(Repository repository, Set<AccountPenaltyData> accountPenalties) throws DataException {
+		final List<Integer> cumulativeBlocksByLevel = BlockChain.getInstance().getCumulativeBlocksByLevel();
+		final int maximumLevel = cumulativeBlocksByLevel.size() - 1;
+
+		int updatedCount = 0;
+
+		for (AccountPenaltyData penaltyData : accountPenalties) {
+			AccountData accountData = repository.getAccountRepository().getAccount(penaltyData.getAddress());
+			final int effectiveBlocksMinted = accountData.getBlocksMinted() + accountData.getBlocksMintedAdjustment() + accountData.getBlocksMintedPenalty();
+
+			// Shortcut for penalties
+			if (effectiveBlocksMinted < 0) {
+				accountData.setLevel(0);
+				repository.getAccountRepository().setLevel(accountData);
+				updatedCount++;
+				LOGGER.trace(() -> String.format("Block minter %s dropped to level %d", accountData.getAddress(), accountData.getLevel()));
+				continue;
+			}
+
+			for (int newLevel = maximumLevel; newLevel >= 0; --newLevel) {
+				if (effectiveBlocksMinted >= cumulativeBlocksByLevel.get(newLevel)) {
+					accountData.setLevel(newLevel);
+					repository.getAccountRepository().setLevel(accountData);
+					updatedCount++;
+					LOGGER.trace(() -> String.format("Block minter %s increased to level %d", accountData.getAddress(), accountData.getLevel()));
+					break;
+				}
+			}
+		}
+
+		return updatedCount;
+	}
+
+	private static void logPenaltyStats(Repository repository) {
+		try {
+			LOGGER.info(getPenaltyStats(repository));
+
+		} catch (DataException e) {}
+	}
+
+	private static AccountPenaltyStats getPenaltyStats(Repository repository) throws DataException {
+		List<AccountData> accounts = repository.getAccountRepository().getPenaltyAccounts();
+		return AccountPenaltyStats.fromAccounts(accounts);
+	}
+
+	public static String getHash(List<String> penaltyAddresses) {
+		if (penaltyAddresses == null || penaltyAddresses.isEmpty()) {
+			return null;
+		}
+		Collections.sort(penaltyAddresses);
+		return Base58.encode(Crypto.digest(StringUtils.join(penaltyAddresses).getBytes(StandardCharsets.UTF_8)));
+	}
+
+}

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

@@ -26,9 +26,6 @@ import org.qortal.data.block.CommonBlockData;
 import org.qortal.data.transaction.TransactionData;
 import org.qortal.network.Network;
 import org.qortal.network.Peer;
-import org.qortal.network.message.BlockSummariesV2Message;
-import org.qortal.network.message.HeightV2Message;
-import org.qortal.network.message.Message;
 import org.qortal.repository.BlockRepository;
 import org.qortal.repository.DataException;
 import org.qortal.repository.Repository;
@@ -38,6 +35,8 @@ import org.qortal.transaction.Transaction;
 import org.qortal.utils.Base58;
 import org.qortal.utils.NTP;
 
+import static org.junit.Assert.assertNotNull;
+
 // Minting new blocks
 
 public class BlockMinter extends Thread {
@@ -64,8 +63,8 @@ public class BlockMinter extends Thread {
 	public void run() {
 		Thread.currentThread().setName("BlockMinter");
 
-		if (Settings.getInstance().isLite()) {
-			// Lite nodes do not mint
+		if (Settings.getInstance().isTopOnly() || Settings.getInstance().isLite()) {
+			// Top only and lite nodes do not sign blocks
 			return;
 		}
 		if (Settings.getInstance().getWipeUnconfirmedOnStart()) {
@@ -93,6 +92,8 @@ public class BlockMinter extends Thread {
 
 		List<Block> newBlocks = new ArrayList<>();
 
+		final boolean isSingleNodeTestnet = Settings.getInstance().isSingleNodeTestnet();
+
 		try (final Repository repository = RepositoryManager.getRepository()) {
 			// Going to need this a lot...
 			BlockRepository blockRepository = repository.getBlockRepository();
@@ -111,8 +112,9 @@ public class BlockMinter extends Thread {
 					// Free up any repository locks
 					repository.discardChanges();
 
-					// Sleep for a while
-					Thread.sleep(1000);
+					// Sleep for a while.
+					// It's faster on single node testnets, to allow lots of blocks to be minted quickly.
+					Thread.sleep(isSingleNodeTestnet ? 50 : 1000);
 
 					isMintingPossible = false;
 
@@ -223,9 +225,10 @@ public class BlockMinter extends Thread {
 					List<PrivateKeyAccount> newBlocksMintingAccounts = mintingAccountsData.stream().map(accountData -> new PrivateKeyAccount(repository, accountData.getPrivateKey())).collect(Collectors.toList());
 
 					// We might need to sit the next block out, if one of our minting accounts signed the previous one
+					// Skip this check for single node testnets, since they definitely need to mint every block
 					byte[] previousBlockMinter = previousBlockData.getMinterPublicKey();
 					boolean mintedLastBlock = mintingAccountsData.stream().anyMatch(mintingAccount -> Arrays.equals(mintingAccount.getPublicKey(), previousBlockMinter));
-					if (mintedLastBlock) {
+					if (mintedLastBlock && !isSingleNodeTestnet) {
 						LOGGER.trace(String.format("One of our keys signed the last block, so we won't sign the next one"));
 						continue;
 					}
@@ -244,7 +247,7 @@ public class BlockMinter extends Thread {
 							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"));
+								moderatedLog(() -> LOGGER.info("Couldn't build a to-be-minted block"));
 								continue;
 							}
 
@@ -507,6 +510,21 @@ public class BlockMinter extends Thread {
 
 		PrivateKeyAccount mintingAccount = mintingAndOnlineAccounts[0];
 
+		Block block = mintTestingBlockRetainingTimestamps(repository, mintingAccount);
+		assertNotNull("Minted block must not be null", block);
+
+		return block;
+	}
+
+	public static Block mintTestingBlockUnvalidated(Repository repository, PrivateKeyAccount... mintingAndOnlineAccounts) throws DataException {
+		if (!BlockChain.getInstance().isTestChain())
+			throw new DataException("Ignoring attempt to mint testing block for non-test chain!");
+
+		// Ensure mintingAccount is 'online' so blocks can be minted
+		OnlineAccountsManager.getInstance().ensureTestingAccountsOnline(mintingAndOnlineAccounts);
+
+		PrivateKeyAccount mintingAccount = mintingAndOnlineAccounts[0];
+
 		return mintTestingBlockRetainingTimestamps(repository, mintingAccount);
 	}
 
@@ -514,6 +532,8 @@ public class BlockMinter extends Thread {
 		BlockData previousBlockData = repository.getBlockRepository().getLastBlock();
 
 		Block newBlock = Block.mint(repository, previousBlockData, mintingAccount);
+		if (newBlock == null)
+			return null;
 
 		// Make sure we're the only thread modifying the blockchain
 		ReentrantLock blockchainLock = Controller.getInstance().getBlockchainLock();

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

@@ -29,6 +29,7 @@ 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.account.Account;
 import org.qortal.api.ApiService;
 import org.qortal.api.DomainMapService;
 import org.qortal.api.GatewayService;
@@ -756,6 +757,28 @@ public class Controller extends Thread {
 		return peer.isAtLeastVersion(minPeerVersion) == false;
 	};
 
+	public static final Predicate<Peer> hasInvalidSigner = peer -> {
+		final BlockSummaryData peerChainTipData = peer.getChainTipData();
+		if (peerChainTipData == null)
+			return true;
+
+		try (Repository repository = RepositoryManager.getRepository()) {
+			return Account.getRewardShareEffectiveMintingLevel(repository, peerChainTipData.getMinterPublicKey()) == 0;
+		} catch (DataException e) {
+			return true;
+		}
+	};
+
+	public static final Predicate<Peer> wasRecentlyTooDivergent = peer -> {
+		Long now = NTP.getTime();
+		Long peerLastTooDivergentTime = peer.getLastTooDivergentTime();
+		if (now == null || peerLastTooDivergentTime == null)
+			return false;
+
+		// Exclude any peers that were TOO_DIVERGENT in the last 5 mins
+		return (now - peerLastTooDivergentTime < 5 * 60 * 1000L);
+	};
+
 	private long getRandomRepositoryMaintenanceInterval() {
 		final long minInterval = Settings.getInstance().getRepositoryMaintenanceMinInterval();
 		final long maxInterval = Settings.getInstance().getRepositoryMaintenanceMaxInterval();
@@ -838,6 +861,12 @@ public class Controller extends Thread {
 		String tooltip = String.format("%s - %d %s", actionText, numberOfPeers, connectionsText);
 		if (!Settings.getInstance().isLite()) {
 			tooltip = tooltip.concat(String.format(" - %s %d", heightText, height));
+
+			final Integer blocksRemaining = Synchronizer.getInstance().getBlocksRemaining();
+			if (blocksRemaining != null && blocksRemaining > 0) {
+				String blocksRemainingText = Translator.INSTANCE.translate("SysTray", "BLOCKS_REMAINING");
+				tooltip = tooltip.concat(String.format(" - %d %s", blocksRemaining, blocksRemainingText));
+			}
 		}
 		tooltip = tooltip.concat(String.format("\n%s: %s", Translator.INSTANCE.translate("SysTray", "BUILD_VERSION"), this.buildVersion));
 		SysTray.getInstance().setToolTipText(tooltip);
@@ -1603,6 +1632,17 @@ public class Controller extends Thread {
 			}
 		}
 
+		if (message.hasId()) {
+			/*
+			 * Experimental proof-of-concept: discard messages with ID
+			 * These are 'late' reply messages received after timeout has expired,
+			 * having been passed upwards from Peer to Network to Controller.
+			 * Hence, these are NOT simple "here's my chain tip" broadcasts from other peers.
+			 */
+			LOGGER.debug("Discarding late {} message with ID {} from {}", message.getType().name(), message.getId(), peer);
+			return;
+		}
+
 		// Update peer chain tip data
 		peer.setChainTipSummaries(blockSummariesV2Message.getBlockSummaries());
 
@@ -1861,6 +1901,10 @@ public class Controller extends Thread {
 		if (latestBlockData == null || latestBlockData.getTimestamp() < minLatestBlockTimestamp)
 			return false;
 
+		if (Settings.getInstance().isSingleNodeTestnet())
+			// Single node testnets won't have peers, so we can assume up to date from this point
+			return true;
+
 		// Needs a mutable copy of the unmodifiableList
 		List<Peer> peers = new ArrayList<>(Network.getInstance().getImmutableHandshakedPeers());
 		if (peers == null)

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

@@ -64,9 +64,19 @@ public class OnlineAccountsManager {
 
     private static final long ONLINE_ACCOUNTS_COMPUTE_INITIAL_SLEEP_INTERVAL = 30 * 1000L; // ms
 
-    // MemoryPoW
-    public final int POW_BUFFER_SIZE = 1 * 1024 * 1024; // bytes
-    public int POW_DIFFICULTY = 18; // leading zero bits
+    // MemoryPoW - mainnet
+    public static final int POW_BUFFER_SIZE = 1 * 1024 * 1024; // bytes
+    public static final int POW_DIFFICULTY_V1 = 18; // leading zero bits
+    public static final int POW_DIFFICULTY_V2 = 19; // leading zero bits
+
+    // MemoryPoW - testnet
+    public static final int POW_BUFFER_SIZE_TESTNET = 1 * 1024 * 1024; // bytes
+    public static final int POW_DIFFICULTY_TESTNET = 5; // leading zero bits
+
+    // IMPORTANT: if we ever need to dynamically modify the buffer size using a feature trigger, the
+    // pre-allocated buffer below will NOT work, and we should instead use a dynamically allocated
+    // one for the transition period.
+    private static long[] POW_VERIFY_WORK_BUFFER = new long[getPoWBufferSize() / 8];
 
     private final ScheduledExecutorService executor = Executors.newScheduledThreadPool(4, new NamedThreadFactory("OnlineAccounts"));
     private volatile boolean isStopping = false;
@@ -112,6 +122,23 @@ public class OnlineAccountsManager {
         return (timestamp / getOnlineTimestampModulus()) * getOnlineTimestampModulus();
     }
 
+    private static int getPoWBufferSize() {
+        if (Settings.getInstance().isTestNet())
+            return POW_BUFFER_SIZE_TESTNET;
+
+        return POW_BUFFER_SIZE;
+    }
+
+    private static int getPoWDifficulty(long timestamp) {
+        if (Settings.getInstance().isTestNet())
+            return POW_DIFFICULTY_TESTNET;
+
+        if (timestamp >= BlockChain.getInstance().getIncreaseOnlineAccountsDifficultyTimestamp())
+            return POW_DIFFICULTY_V2;
+
+        return POW_DIFFICULTY_V1;
+    }
+
     private OnlineAccountsManager() {
     }
 
@@ -156,7 +183,6 @@ public class OnlineAccountsManager {
             return;
 
         byte[] timestampBytes = Longs.toByteArray(onlineAccountsTimestamp);
-        final boolean mempowActive = onlineAccountsTimestamp >= BlockChain.getInstance().getOnlineAccountsMemoryPoWTimestamp();
 
         Set<OnlineAccountData> replacementAccounts = new HashSet<>();
         for (PrivateKeyAccount onlineAccount : onlineAccounts) {
@@ -165,7 +191,7 @@ public class OnlineAccountsManager {
             byte[] signature = Qortal25519Extras.signForAggregation(onlineAccount.getPrivateKey(), timestampBytes);
             byte[] publicKey = onlineAccount.getPublicKey();
 
-            Integer nonce = mempowActive ? new Random().nextInt(500000) : null;
+            Integer nonce = new Random().nextInt(500000);
 
             OnlineAccountData ourOnlineAccountData = new OnlineAccountData(onlineAccountsTimestamp, signature, publicKey, nonce);
             replacementAccounts.add(ourOnlineAccountData);
@@ -192,8 +218,8 @@ public class OnlineAccountsManager {
                     return;
 
                 // Skip this account if it's already validated
-                Set<OnlineAccountData> onlineAccounts = this.currentOnlineAccounts.computeIfAbsent(onlineAccountData.getTimestamp(), k -> ConcurrentHashMap.newKeySet());
-                if (onlineAccounts.contains(onlineAccountData)) {
+                Set<OnlineAccountData> onlineAccounts = this.currentOnlineAccounts.get(onlineAccountData.getTimestamp());
+                if (onlineAccounts != null && onlineAccounts.contains(onlineAccountData)) {
                     // We have already validated this online account
                     onlineAccountsImportQueue.remove(onlineAccountData);
                     continue;
@@ -214,8 +240,8 @@ public class OnlineAccountsManager {
             if (!onlineAccountsToAdd.isEmpty()) {
                 LOGGER.debug("Merging {} validated online accounts from import queue", onlineAccountsToAdd.size());
                 addAccounts(onlineAccountsToAdd);
-                onlineAccountsImportQueue.removeAll(onlineAccountsToRemove);
             }
+            onlineAccountsImportQueue.removeAll(onlineAccountsToRemove);
         }
     }
 
@@ -321,13 +347,10 @@ public class OnlineAccountsManager {
             return false;
         }
 
-        // Validate mempow if feature trigger is active (or if online account's timestamp is past the trigger timestamp)
-        long memoryPoWStartTimestamp = BlockChain.getInstance().getOnlineAccountsMemoryPoWTimestamp();
-        if (now >= memoryPoWStartTimestamp || onlineAccountTimestamp >= memoryPoWStartTimestamp) {
-            if (!getInstance().verifyMemoryPoW(onlineAccountData, now)) {
-                LOGGER.trace(() -> String.format("Rejecting online reward-share for account %s due to invalid PoW nonce", mintingAccount.getAddress()));
-                return false;
-            }
+        // Validate mempow
+        if (!getInstance().verifyMemoryPoW(onlineAccountData, POW_VERIFY_WORK_BUFFER)) {
+            LOGGER.trace(() -> String.format("Rejecting online reward-share for account %s due to invalid PoW nonce", mintingAccount.getAddress()));
+            return false;
         }
 
         return true;
@@ -471,12 +494,10 @@ public class OnlineAccountsManager {
 
         // 'next' timestamp (prioritize this as it's the most important, if mempow active)
         final long nextOnlineAccountsTimestamp = toOnlineAccountTimestamp(now) + getOnlineTimestampModulus();
-        if (isMemoryPoWActive(now)) {
-            boolean success = computeOurAccountsForTimestamp(nextOnlineAccountsTimestamp);
-            if (!success) {
-                // We didn't compute the required nonce value(s), and so can't proceed until they have been retried
-                return;
-            }
+        boolean success = computeOurAccountsForTimestamp(nextOnlineAccountsTimestamp);
+        if (!success) {
+            // We didn't compute the required nonce value(s), and so can't proceed until they have been retried
+            return;
         }
 
         // 'current' timestamp
@@ -553,21 +574,15 @@ public class OnlineAccountsManager {
 
             // Compute nonce
             Integer nonce;
-            if (isMemoryPoWActive(NTP.getTime())) {
-                try {
-                    nonce = this.computeMemoryPoW(mempowBytes, publicKey, onlineAccountsTimestamp);
-                    if (nonce == null) {
-                        // A nonce is required
-                        return false;
-                    }
-                } catch (TimeoutException e) {
-                    LOGGER.info(String.format("Timed out computing nonce for account %.8s", Base58.encode(publicKey)));
+            try {
+                nonce = this.computeMemoryPoW(mempowBytes, publicKey, onlineAccountsTimestamp);
+                if (nonce == null) {
+                    // A nonce is required
                     return false;
                 }
-            }
-            else {
-                // Send -1 if we haven't computed a nonce due to feature trigger timestamp
-                nonce = -1;
+            } catch (TimeoutException e) {
+                LOGGER.info(String.format("Timed out computing nonce for account %.8s", Base58.encode(publicKey)));
+                return false;
             }
 
             byte[] signature = Qortal25519Extras.signForAggregation(privateKey, timestampBytes);
@@ -576,7 +591,7 @@ public class OnlineAccountsManager {
             OnlineAccountData ourOnlineAccountData = new OnlineAccountData(onlineAccountsTimestamp, signature, publicKey, nonce);
 
             // Make sure to verify before adding
-            if (verifyMemoryPoW(ourOnlineAccountData, NTP.getTime())) {
+            if (verifyMemoryPoW(ourOnlineAccountData, null)) {
                 ourOnlineAccounts.add(ourOnlineAccountData);
             }
         }
@@ -599,12 +614,6 @@ public class OnlineAccountsManager {
 
     // MemoryPoW
 
-    private boolean isMemoryPoWActive(Long timestamp) {
-        if (timestamp >= BlockChain.getInstance().getOnlineAccountsMemoryPoWTimestamp() || Settings.getInstance().isOnlineAccountsMemPoWEnabled()) {
-            return true;
-        }
-        return false;
-    }
     private byte[] getMemoryPoWBytes(byte[] publicKey, long onlineAccountsTimestamp) throws IOException {
         byte[] timestampBytes = Longs.toByteArray(onlineAccountsTimestamp);
 
@@ -616,11 +625,6 @@ public class OnlineAccountsManager {
     }
 
     private Integer computeMemoryPoW(byte[] bytes, byte[] publicKey, long onlineAccountsTimestamp) throws TimeoutException {
-        if (!isMemoryPoWActive(NTP.getTime())) {
-            LOGGER.info("Mempow start timestamp not yet reached, and onlineAccountsMemPoWEnabled not enabled in settings");
-            return null;
-        }
-
         LOGGER.info(String.format("Computing nonce for account %.8s and timestamp %d...", Base58.encode(publicKey), onlineAccountsTimestamp));
 
         // Calculate the time until the next online timestamp and use it as a timeout when computing the nonce
@@ -628,7 +632,8 @@ public class OnlineAccountsManager {
         final long nextOnlineAccountsTimestamp = toOnlineAccountTimestamp(startTime) + getOnlineTimestampModulus();
         long timeUntilNextTimestamp = nextOnlineAccountsTimestamp - startTime;
 
-        Integer nonce = MemoryPoW.compute2(bytes, POW_BUFFER_SIZE, POW_DIFFICULTY, timeUntilNextTimestamp);
+        int difficulty = getPoWDifficulty(onlineAccountsTimestamp);
+        Integer nonce = MemoryPoW.compute2(bytes, getPoWBufferSize(), difficulty, timeUntilNextTimestamp);
 
         double totalSeconds = (NTP.getTime() - startTime) / 1000.0f;
         int minutes = (int) ((totalSeconds % 3600) / 60);
@@ -637,16 +642,15 @@ public class OnlineAccountsManager {
 
         LOGGER.info(String.format("Computed nonce for timestamp %d and account %.8s: %d. Buffer size: %d. Difficulty: %d. " +
                         "Time taken: %02d:%02d. Hashrate: %f", onlineAccountsTimestamp, Base58.encode(publicKey),
-                nonce, POW_BUFFER_SIZE, POW_DIFFICULTY, minutes, seconds, hashRate));
+                nonce, getPoWBufferSize(), difficulty, minutes, seconds, hashRate));
 
         return nonce;
     }
 
-    public boolean verifyMemoryPoW(OnlineAccountData onlineAccountData, Long timestamp) {
-        long memoryPoWStartTimestamp = BlockChain.getInstance().getOnlineAccountsMemoryPoWTimestamp();
-        if (timestamp < memoryPoWStartTimestamp && onlineAccountData.getTimestamp() < memoryPoWStartTimestamp) {
-            // Not active yet, so treat it as valid
-            return true;
+    public boolean verifyMemoryPoW(OnlineAccountData onlineAccountData, long[] workBuffer) {
+        // Require a valid nonce value
+        if (onlineAccountData.getNonce() == null || onlineAccountData.getNonce() < 0) {
+            return false;
         }
 
         int nonce = onlineAccountData.getNonce();
@@ -659,7 +663,7 @@ public class OnlineAccountsManager {
         }
 
         // Verify the nonce
-        return MemoryPoW.verify2(mempowBytes, POW_BUFFER_SIZE, POW_DIFFICULTY, nonce);
+        return MemoryPoW.verify2(mempowBytes, workBuffer, getPoWBufferSize(), getPoWDifficulty(onlineAccountData.getTimestamp()), nonce);
     }
 
 
@@ -697,7 +701,7 @@ public class OnlineAccountsManager {
      */
     // Block::mint() - only wants online accounts with (online) timestamp that matches block's (online) timestamp so they can be added to new block
     public List<OnlineAccountData> getOnlineAccounts(long onlineTimestamp) {
-        LOGGER.info(String.format("caller's timestamp: %d, our timestamps: %s", onlineTimestamp, String.join(", ", this.currentOnlineAccounts.keySet().stream().map(l -> Long.toString(l)).collect(Collectors.joining(", ")))));
+        LOGGER.debug(String.format("caller's timestamp: %d, our timestamps: %s", onlineTimestamp, String.join(", ", this.currentOnlineAccounts.keySet().stream().map(l -> Long.toString(l)).collect(Collectors.joining(", ")))));
 
         return new ArrayList<>(Set.copyOf(this.currentOnlineAccounts.getOrDefault(onlineTimestamp, Collections.emptySet())));
     }
@@ -743,11 +747,12 @@ public class OnlineAccountsManager {
      * Typically called by {@link Block#areOnlineAccountsValid()}
      */
     public void addBlocksOnlineAccounts(Set<OnlineAccountData> blocksOnlineAccounts, Long timestamp) {
-        // We want to add to 'current' in preference if possible
-        if (this.currentOnlineAccounts.containsKey(timestamp)) {
-            addAccounts(blocksOnlineAccounts);
+        // If these are current accounts, then there is no need to cache them, and should instead rely
+        // on the more complete entries we already have in self.currentOnlineAccounts.
+        // Note: since sig-agg, we no longer have individual signatures included in blocks, so we
+        // mustn't add anything to currentOnlineAccounts from here.
+        if (this.currentOnlineAccounts.containsKey(timestamp))
             return;
-        }
 
         // Add to block cache instead
         this.latestBlocksOnlineAccounts.computeIfAbsent(timestamp, k -> ConcurrentHashMap.newKeySet())

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

@@ -4,6 +4,7 @@ import com.rust.litewalletjni.LiteWalletJni;
 import org.apache.commons.io.FileUtils;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
+import org.json.JSONException;
 import org.json.JSONObject;
 import org.qortal.arbitrary.ArbitraryDataFile;
 import org.qortal.arbitrary.ArbitraryDataReader;
@@ -99,14 +100,19 @@ public class PirateChainWalletController extends Thread {
                 LOGGER.debug("Syncing Pirate Chain wallet...");
                 String response = LiteWalletJni.execute("sync", "");
                 LOGGER.debug("sync response: {}", response);
-                JSONObject json = new JSONObject(response);
-                if (json.has("result")) {
-                    String result = json.getString("result");
 
-                    // We may have to set wallet to ready if this is the first ever successful sync
-                    if (Objects.equals(result, "success")) {
-                        this.currentWallet.setReady(true);
+                try {
+                    JSONObject json = new JSONObject(response);
+                    if (json.has("result")) {
+                        String result = json.getString("result");
+
+                        // We may have to set wallet to ready if this is the first ever successful sync
+                        if (Objects.equals(result, "success")) {
+                            this.currentWallet.setReady(true);
+                        }
                     }
+                } catch (JSONException e) {
+                    LOGGER.info("Unable to interpret JSON", e);
                 }
 
                 // Rate limit sync attempts

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

@@ -53,7 +53,8 @@ public class Synchronizer extends Thread {
 	/** Maximum number of block signatures we ask from peer in one go */
 	private static final int MAXIMUM_REQUEST_SIZE = 200; // XXX move to Settings?
 
-	private static final long RECOVERY_MODE_TIMEOUT = 10 * 60 * 1000L; // ms
+	/** Maximum number of consecutive failed sync attempts before marking peer as misbehaved */
+	private static final int MAX_CONSECUTIVE_FAILED_SYNC_ATTEMPTS = 3;
 
 
 	private boolean running;
@@ -75,6 +76,8 @@ public class Synchronizer extends Thread {
 	private volatile boolean isSynchronizing = false;
 	/** Temporary estimate of synchronization progress for SysTray use. */
 	private volatile int syncPercent = 0;
+	/** Temporary estimate of blocks remaining for SysTray use. */
+	private volatile int blocksRemaining = 0;
 
 	private static volatile boolean requestSync = false;
 	private boolean syncRequestPending = false;
@@ -180,6 +183,18 @@ public class Synchronizer extends Thread {
 		}
 	}
 
+	public Integer getBlocksRemaining() {
+		synchronized (this.syncLock) {
+			// Report as 0 blocks remaining if the latest block is within the last 60 mins
+			final Long minLatestBlockTimestamp = NTP.getTime() - (60 * 60 * 1000L);
+			if (Controller.getInstance().isUpToDate(minLatestBlockTimestamp)) {
+				return 0;
+			}
+
+			return this.isSynchronizing ? this.blocksRemaining : null;
+		}
+	}
+
 	public void requestSync() {
 		requestSync = true;
 	}
@@ -232,6 +247,9 @@ public class Synchronizer extends Thread {
 		// Disregard peers that are on the same block as last sync attempt and we didn't like their chain
 		peers.removeIf(Controller.hasInferiorChainTip);
 
+		// Disregard peers that have a block with an invalid signer
+		peers.removeIf(Controller.hasInvalidSigner);
+
 		final int peersBeforeComparison = peers.size();
 
 		// Request recent block summaries from the remaining peers, and locate our common block with each
@@ -396,9 +414,10 @@ public class Synchronizer extends Thread {
 					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) {
+				long recoveryModeTimeout = Settings.getInstance().getRecoveryModeTimeout();
+				if (NTP.getTime() - timePeersLastAvailable > recoveryModeTimeout) {
 					if (recoveryMode == false) {
-						LOGGER.info(String.format("Peers have been unavailable for %d minutes. Entering recovery mode...", RECOVERY_MODE_TIMEOUT/60/1000));
+						LOGGER.info(String.format("Peers have been unavailable for %d minutes. Entering recovery mode...", recoveryModeTimeout/60/1000));
 						recoveryMode = true;
 					}
 				}
@@ -1102,6 +1121,7 @@ public class Synchronizer extends Thread {
 			// If common block is too far behind us then we're on massively different forks so give up.
 			if (!force && testHeight < ourHeight - MAXIMUM_COMMON_DELTA) {
 				LOGGER.info(String.format("Blockchain too divergent with peer %s", peer));
+				peer.setLastTooDivergentTime(NTP.getTime());
 				return SynchronizationResult.TOO_DIVERGENT;
 			}
 
@@ -1111,6 +1131,9 @@ public class Synchronizer extends Thread {
 			testHeight = Math.max(testHeight - step, 1);
 		}
 
+		// Peer not considered too divergent
+		peer.setLastTooDivergentTime(0L);
+
 		// Prepend test block's summary as first block summary, as summaries returned are *after* test block
 		BlockSummaryData testBlockSummary = new BlockSummaryData(testBlockData);
 		blockSummariesFromCommon.add(0, testBlockSummary);
@@ -1246,7 +1269,14 @@ public class Synchronizer extends Thread {
 		int numberSignaturesRequired = additionalPeerBlocksAfterCommonBlock - peerBlockSignatures.size();
 
 		int retryCount = 0;
-		while (height < peerHeight) {
+
+		// Keep fetching blocks from peer until we reach their tip, or reach a count of MAXIMUM_COMMON_DELTA blocks.
+		// We need to limit the total number, otherwise too much can be loaded into memory, causing an
+		// OutOfMemoryException. This is common when syncing from 1000+ blocks behind the chain tip, after starting
+		// from a small fork that didn't become part of the main chain. This causes the entire sync process to
+		// use syncToPeerChain(), resulting in potentially thousands of blocks being held in memory if the limit
+		// below isn't applied.
+		while (height < peerHeight && peerBlocks.size() <= MAXIMUM_COMMON_DELTA) {
 			if (Controller.isStopping())
 				return SynchronizationResult.SHUTTING_DOWN;
 
@@ -1448,6 +1478,12 @@ public class Synchronizer extends Thread {
 
 			repository.saveChanges();
 
+			synchronized (this.syncLock) {
+				if (peer.getChainTipData() != null) {
+					this.blocksRemaining = peer.getChainTipData().getHeight() - newBlock.getBlockData().getHeight();
+				}
+			}
+
 			Controller.getInstance().onNewBlock(newBlock.getBlockData());
 		}
 
@@ -1543,6 +1579,12 @@ public class Synchronizer extends Thread {
 
 			repository.saveChanges();
 
+			synchronized (this.syncLock) {
+				if (peer.getChainTipData() != null) {
+					this.blocksRemaining = peer.getChainTipData().getHeight() - newBlock.getBlockData().getHeight();
+				}
+			}
+
 			Controller.getInstance().onNewBlock(newBlock.getBlockData());
 		}
 
@@ -1584,8 +1626,20 @@ public class Synchronizer extends Thread {
 		Message getBlockMessage = new GetBlockMessage(signature);
 
 		Message message = peer.getResponse(getBlockMessage);
-		if (message == null)
+		if (message == null) {
+			peer.getPeerData().incrementFailedSyncCount();
+			if (peer.getPeerData().getFailedSyncCount() >= MAX_CONSECUTIVE_FAILED_SYNC_ATTEMPTS) {
+				// Several failed attempts, so mark peer as misbehaved
+				LOGGER.info("Marking peer {} as misbehaved due to {} failed sync attempts", peer, peer.getPeerData().getFailedSyncCount());
+				Network.getInstance().peerMisbehaved(peer);
+			}
 			return null;
+		}
+
+		// Reset failed sync count now that we have a block response
+		// FUTURE: we could move this to the end of the sync process, but to reduce risk this can be done
+		// at a later stage. For now we are only defending against serialization errors or no responses.
+		peer.getPeerData().setFailedSyncCount(0);
 
 		switch (message.getType()) {
 			case BLOCK: {

src/main/java/org/qortal/controller/arbitrary/ArbitraryDataFileManager.java

@@ -82,7 +82,7 @@ public class ArbitraryDataFileManager extends Thread {
 
         try {
             // Use a fixed thread pool to execute the arbitrary data file requests
-            int threadCount = 10;
+            int threadCount = 5;
             ExecutorService arbitraryDataFileRequestExecutor = Executors.newFixedThreadPool(threadCount);
             for (int i = 0; i < threadCount; i++) {
                 arbitraryDataFileRequestExecutor.execute(new ArbitraryDataFileRequestThread());
@@ -288,7 +288,7 @@ public class ArbitraryDataFileManager extends Thread {
         // The ID needs to match that of the original request
         message.setId(originalMessage.getId());
 
-        if (!requestingPeer.sendMessage(message)) {
+        if (!requestingPeer.sendMessageWithTimeout(message, (int) ArbitraryDataManager.ARBITRARY_REQUEST_TIMEOUT)) {
             LOGGER.debug("Failed to forward arbitrary data file to peer {}", requestingPeer);
             requestingPeer.disconnect("failed to forward arbitrary data file");
         }
@@ -564,13 +564,16 @@ public class ArbitraryDataFileManager extends Thread {
                 LOGGER.trace("Hash {} exists", hash58);
 
                 // We can serve the file directly as we already have it
+                LOGGER.debug("Sending file {}...", arbitraryDataFile);
                 ArbitraryDataFileMessage arbitraryDataFileMessage = new ArbitraryDataFileMessage(signature, arbitraryDataFile);
                 arbitraryDataFileMessage.setId(message.getId());
-                if (!peer.sendMessage(arbitraryDataFileMessage)) {
-                    LOGGER.debug("Couldn't sent file");
+                if (!peer.sendMessageWithTimeout(arbitraryDataFileMessage, (int) ArbitraryDataManager.ARBITRARY_REQUEST_TIMEOUT)) {
+                    LOGGER.debug("Couldn't send file {}", arbitraryDataFile);
                     peer.disconnect("failed to send file");
                 }
-                LOGGER.debug("Sent file {}", arbitraryDataFile);
+                else {
+                    LOGGER.debug("Sent file {}", arbitraryDataFile);
+                }
             }
             else if (relayInfo != null) {
                 LOGGER.debug("We have relay info for hash {}", Base58.encode(hash));

src/main/java/org/qortal/controller/repository/AtStatesPruner.java

@@ -42,6 +42,7 @@ public class AtStatesPruner implements Runnable {
 
 			repository.discardChanges();
 			repository.getATRepository().rebuildLatestAtStates();
+			repository.saveChanges();
 
 			while (!Controller.isStopping()) {
 				repository.discardChanges();

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

@@ -29,6 +29,7 @@ public class AtStatesTrimmer implements Runnable {
 
 			repository.discardChanges();
 			repository.getATRepository().rebuildLatestAtStates();
+			repository.saveChanges();
 
 			while (!Controller.isStopping()) {
 				repository.discardChanges();

src/main/java/org/qortal/controller/tradebot/LitecoinACCTv3TradeBot.java

@@ -19,6 +19,7 @@ import org.qortal.data.transaction.MessageTransactionData;
 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.ValidationResult;
@@ -317,20 +318,27 @@ public class LitecoinACCTv3TradeBot implements AcctTradeBot {
 
 		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);
+			// Do this in a new thread so caller doesn't have to wait for computeNonce()
+			// In the unlikely event that the transaction doesn't validate then the buy won't happen and eventually Alice's AT will be refunded
+			new Thread(() -> {
+				try (final Repository threadsRepository = RepositoryManager.getRepository()) {
+					PrivateKeyAccount sender = new PrivateKeyAccount(threadsRepository, tradeBotData.getTradePrivateKey());
+					MessageTransaction messageTransaction = MessageTransaction.build(threadsRepository, sender, Group.NO_GROUP, messageRecipient, messageData, false, false);
 
-			messageTransaction.computeNonce();
-			messageTransaction.sign(sender);
+					messageTransaction.computeNonce();
+					messageTransaction.sign(sender);
 
-			// reset repository state to prevent deadlock
-			repository.discardChanges();
-			ValidationResult result = messageTransaction.importAsUnconfirmed();
+					// reset repository state to prevent deadlock
+					threadsRepository.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;
-			}
+					if (result != ValidationResult.OK) {
+						LOGGER.warn(() -> String.format("Unable to send MESSAGE to Bob's trade-bot %s: %s", messageRecipient, result.name()));
+					}
+				} catch (DataException e) {
+					LOGGER.warn(() -> String.format("Unable to send MESSAGE to Bob's trade-bot %s: %s", messageRecipient, e.getMessage()));
+				}
+			}, "TradeBot response").start();
 		}
 
 		TradeBot.updateTradeBotState(repository, tradeBotData, () -> String.format("Funding P2SH-A %s. Messaged Bob. Waiting for AT-lock", p2shAddress));

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

@@ -357,19 +357,33 @@ public abstract class Bitcoiny implements ForeignBlockchain {
 	 * @return unspent BTC balance, or null if unable to determine balance
 	 */
 	public Long getWalletBalance(String key58) throws ForeignBlockchainException {
-		// It's more accurate to calculate the balance from the transactions, rather than asking Bitcoinj
-		return this.getWalletBalanceFromTransactions(key58);
+		Long balance = 0L;
 
-//		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;
+		List<TransactionOutput> allUnspentOutputs = new ArrayList<>();
+		Set<String> walletAddresses = this.getWalletAddresses(key58);
+		for (String address : walletAddresses) {
+			allUnspentOutputs.addAll(this.getUnspentOutputs(address));
+		}
+		for (TransactionOutput output : allUnspentOutputs) {
+			if (!output.isAvailableForSpending()) {
+				continue;
+			}
+			balance += output.getValue().value;
+		}
+		return balance;
+	}
+
+	public Long getWalletBalanceFromBitcoinj(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 Long getWalletBalanceFromTransactions(String key58) throws ForeignBlockchainException {
@@ -464,6 +478,64 @@ public abstract class Bitcoiny implements ForeignBlockchain {
 		}
 	}
 
+	public Set<String> getWalletAddresses(String key58) throws ForeignBlockchainException {
+		synchronized (this) {
+			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<String> keySet = new HashSet<>();
+
+			int unusedCounter = 0;
+			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.getAddressTransactions(script, false);
+
+					if (!historicTransactionHashes.isEmpty()) {
+						areAllKeysUnused = false;
+					}
+				}
+
+				if (areAllKeysUnused) {
+					// No transactions
+					if (unusedCounter >= Settings.getInstance().getGapLimit()) {
+						// ... and we've hit our search limit
+						break;
+					}
+					// We haven't hit our search limit yet so increment the counter and keep looking
+					unusedCounter += WALLET_KEY_LOOKAHEAD_INCREMENT;
+				} else {
+					// Some keys in this batch were used, so reset the counter
+					unusedCounter = 0;
+				}
+
+				// Generate some more keys
+				keys.addAll(generateMoreKeys(keyChain));
+
+				// Process new keys
+			} while (true);
+
+			return keySet;
+		}
+	}
+
 	protected SimpleTransaction convertToSimpleTransaction(BitcoinyTransaction t, Set<String> keySet) {
 		long amount = 0;
 		long total = 0L;

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

@@ -134,6 +134,8 @@ public class Digibyte extends Bitcoiny {
 			Context bitcoinjContext = new Context(digibyteNet.getParams());
 
 			instance = new Digibyte(digibyteNet, electrumX, bitcoinjContext, CURRENCY_CODE);
+
+			electrumX.setBlockchain(instance);
 		}
 
 		return instance;

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

@@ -40,7 +40,7 @@ public class ElectrumX extends BitcoinyBlockchainProvider {
 	private static final String VERBOSE_TRANSACTIONS_UNSUPPORTED_MESSAGE = "verbose transactions are currently unsupported";
 
 	private static final int RESPONSE_TIME_READINGS = 5;
-	private static final long MAX_AVG_RESPONSE_TIME = 500L; // ms
+	private static final long MAX_AVG_RESPONSE_TIME = 1000L; // ms
 
 	public static class Server {
 		String hostname;

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

@@ -117,7 +117,7 @@ public class PirateWallet {
                 // Restore existing wallet
                 String response = LiteWalletJni.initfromb64(serverUri, params, wallet, saplingOutput64, saplingSpend64);
                 if (response != null && !response.contains("\"initalized\":true")) {
-                    LOGGER.info("Unable to initialize Pirate Chain wallet: {}", response);
+                    LOGGER.info("Unable to initialize Pirate Chain wallet at {}: {}", serverUri, response);
                     return false;
                 }
                 this.seedPhrase = inputSeedPhrase;

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

@@ -138,6 +138,8 @@ public class Ravencoin extends Bitcoiny {
 			Context bitcoinjContext = new Context(ravencoinNet.getParams());
 
 			instance = new Ravencoin(ravencoinNet, electrumX, bitcoinjContext, CURRENCY_CODE);
+
+			electrumX.setBlockchain(instance);
 		}
 
 		return instance;

src/main/java/org/qortal/crypto/MemoryPoW.java

@@ -99,6 +99,10 @@ public class MemoryPoW {
 	}
 
 	public static boolean verify2(byte[] data, int workBufferLength, long difficulty, int nonce) {
+		return verify2(data, null, workBufferLength, difficulty, nonce);
+	}
+
+	public static boolean verify2(byte[] data, long[] workBuffer, int workBufferLength, long difficulty, int nonce) {
 		// Hash data with SHA256
 		byte[] hash = Crypto.digest(data);
 
@@ -111,7 +115,10 @@ public class MemoryPoW {
 		byteBuffer = null;
 
 		int longBufferLength = workBufferLength / 8;
-		long[] workBuffer = new long[longBufferLength];
+
+		if (workBuffer == null)
+			workBuffer = new long[longBufferLength];
+
 		long[] state = new long[4];
 
 		long seed = 8682522807148012L;

src/main/java/org/qortal/data/account/AccountData.java

@@ -18,6 +18,7 @@ public class AccountData {
 	protected int level;
 	protected int blocksMinted;
 	protected int blocksMintedAdjustment;
+	protected int blocksMintedPenalty;
 
 	// Constructors
 
@@ -25,7 +26,7 @@ public class AccountData {
 	protected AccountData() {
 	}
 
-	public AccountData(String address, byte[] reference, byte[] publicKey, int defaultGroupId, int flags, int level, int blocksMinted, int blocksMintedAdjustment) {
+	public AccountData(String address, byte[] reference, byte[] publicKey, int defaultGroupId, int flags, int level, int blocksMinted, int blocksMintedAdjustment, int blocksMintedPenalty) {
 		this.address = address;
 		this.reference = reference;
 		this.publicKey = publicKey;
@@ -34,10 +35,11 @@ public class AccountData {
 		this.level = level;
 		this.blocksMinted = blocksMinted;
 		this.blocksMintedAdjustment = blocksMintedAdjustment;
+		this.blocksMintedPenalty = blocksMintedPenalty;
 	}
 
 	public AccountData(String address) {
-		this(address, null, null, Group.NO_GROUP, 0, 0, 0, 0);
+		this(address, null, null, Group.NO_GROUP, 0, 0, 0, 0, 0);
 	}
 
 	// Getters/Setters
@@ -102,6 +104,14 @@ public class AccountData {
 		this.blocksMintedAdjustment = blocksMintedAdjustment;
 	}
 
+	public int getBlocksMintedPenalty() {
+		return this.blocksMintedPenalty;
+	}
+
+	public void setBlocksMintedPenalty(int blocksMintedPenalty) {
+		this.blocksMintedPenalty = blocksMintedPenalty;
+	}
+
 	// Comparison
 
 	@Override

src/main/java/org/qortal/data/account/AccountPenaltyData.java

@@ -0,0 +1,52 @@
+package org.qortal.data.account;
+
+import javax.xml.bind.annotation.XmlAccessType;
+import javax.xml.bind.annotation.XmlAccessorType;
+
+// All properties to be converted to JSON via JAXB
+@XmlAccessorType(XmlAccessType.FIELD)
+public class AccountPenaltyData {
+
+	// Properties
+	private String address;
+	private int blocksMintedPenalty;
+
+	// Constructors
+
+	// necessary for JAXB
+	protected AccountPenaltyData() {
+	}
+
+	public AccountPenaltyData(String address, int blocksMintedPenalty) {
+		this.address = address;
+		this.blocksMintedPenalty = blocksMintedPenalty;
+	}
+
+	// Getters/Setters
+
+	public String getAddress() {
+		return this.address;
+	}
+
+	public int getBlocksMintedPenalty() {
+		return this.blocksMintedPenalty;
+	}
+
+	public String toString() {
+		return String.format("%s has penalty %d", this.address, this.blocksMintedPenalty);
+	}
+
+	@Override
+	public boolean equals(Object b) {
+		if (!(b instanceof AccountPenaltyData))
+			return false;
+
+		return this.getAddress().equals(((AccountPenaltyData) b).getAddress());
+	}
+
+	@Override
+	public int hashCode() {
+		return address.hashCode();
+	}
+
+}

src/main/java/org/qortal/data/arbitrary/ArbitraryResourceMetadata.java

@@ -15,22 +15,24 @@ public class ArbitraryResourceMetadata {
     private List<String> tags;
     private Category category;
     private String categoryName;
+    private List<String> files;
 
     public ArbitraryResourceMetadata() {
     }
 
-    public ArbitraryResourceMetadata(String title, String description, List<String> tags, Category category) {
+    public ArbitraryResourceMetadata(String title, String description, List<String> tags, Category category, List<String> files) {
         this.title = title;
         this.description = description;
         this.tags = tags;
         this.category = category;
+        this.files = files;
 
         if (category != null) {
             this.categoryName = category.getName();
         }
     }
 
-    public static ArbitraryResourceMetadata fromTransactionMetadata(ArbitraryDataTransactionMetadata transactionMetadata) {
+    public static ArbitraryResourceMetadata fromTransactionMetadata(ArbitraryDataTransactionMetadata transactionMetadata, boolean includeFileList) {
         if (transactionMetadata == null) {
             return null;
         }
@@ -39,10 +41,20 @@ public class ArbitraryResourceMetadata {
         List<String> tags = transactionMetadata.getTags();
         Category category = transactionMetadata.getCategory();
 
-        if (title == null && description == null && tags == null && category == null) {
+        // We don't always want to include the file list as it can be too verbose
+        List<String> files = null;
+        if (includeFileList) {
+            files = transactionMetadata.getFiles();
+        }
+
+        if (title == null && description == null && tags == null && category == null && files == null) {
             return null;
         }
 
-        return new ArbitraryResourceMetadata(title, description, tags, category);
+        return new ArbitraryResourceMetadata(title, description, tags, category, files);
+    }
+
+    public List<String> getFiles() {
+        return this.files;
     }
 }

src/main/java/org/qortal/data/chat/ChatMessage.java

@@ -27,6 +27,8 @@ public class ChatMessage {
 
 	private String recipientName;
 
+	private byte[] chatReference;
+
 	private byte[] data;
 
 	private boolean isText;
@@ -42,8 +44,8 @@ public class ChatMessage {
 
 	// For repository use
 	public ChatMessage(long timestamp, int txGroupId, byte[] reference, byte[] senderPublicKey, String sender,
-			String senderName, String recipient, String recipientName, byte[] data, boolean isText,
-			boolean isEncrypted, byte[] signature) {
+			String senderName, String recipient, String recipientName, byte[] chatReference, byte[] data,
+			boolean isText, boolean isEncrypted, byte[] signature) {
 		this.timestamp = timestamp;
 		this.txGroupId = txGroupId;
 		this.reference = reference;
@@ -52,6 +54,7 @@ public class ChatMessage {
 		this.senderName = senderName;
 		this.recipient = recipient;
 		this.recipientName = recipientName;
+		this.chatReference = chatReference;
 		this.data = data;
 		this.isText = isText;
 		this.isEncrypted = isEncrypted;
@@ -90,6 +93,10 @@ public class ChatMessage {
 		return this.recipientName;
 	}
 
+	public byte[] getChatReference() {
+		return this.chatReference;
+	}
+
 	public byte[] getData() {
 		return this.data;
 	}

src/main/java/org/qortal/data/network/PeerData.java

@@ -28,6 +28,9 @@ public class PeerData {
 	private Long addedWhen;
 	private String addedBy;
 
+	/** The number of consecutive times we failed to sync with this peer */
+	private int failedSyncCount = 0;
+
 	// Constructors
 
 	// necessary for JAXB serialization
@@ -92,6 +95,18 @@ public class PeerData {
 		return this.addedBy;
 	}
 
+	public int getFailedSyncCount() {
+		return this.failedSyncCount;
+	}
+
+	public void setFailedSyncCount(int failedSyncCount) {
+		this.failedSyncCount = failedSyncCount;
+	}
+
+	public void incrementFailedSyncCount() {
+		this.failedSyncCount++;
+	}
+
 	// Pretty peerAddress getter for JAXB
 	@XmlElement(name = "address")
 	protected String getPrettyAddress() {

src/main/java/org/qortal/data/transaction/ChatTransactionData.java

@@ -26,6 +26,8 @@ public class ChatTransactionData extends TransactionData {
 
 	private String recipient; // can be null
 
+	private byte[] chatReference; // can be null
+
 	@Schema(description = "raw message data, possibly UTF8 text", example = "2yGEbwRFyhPZZckKA")
 	private byte[] data;
 
@@ -44,13 +46,14 @@ public class ChatTransactionData extends TransactionData {
 	}
 
 	public ChatTransactionData(BaseTransactionData baseTransactionData,
-			String sender, int nonce, String recipient, byte[] data, boolean isText, boolean isEncrypted) {
+			String sender, int nonce, String recipient, byte[] chatReference, byte[] data, boolean isText, boolean isEncrypted) {
 		super(TransactionType.CHAT, baseTransactionData);
 
 		this.senderPublicKey = baseTransactionData.creatorPublicKey;
 		this.sender = sender;
 		this.nonce = nonce;
 		this.recipient = recipient;
+		this.chatReference = chatReference;
 		this.data = data;
 		this.isText = isText;
 		this.isEncrypted = isEncrypted;
@@ -78,6 +81,14 @@ public class ChatTransactionData extends TransactionData {
 		return this.recipient;
 	}
 
+	public byte[] getChatReference() {
+		return this.chatReference;
+	}
+
+	public void setChatReference(byte[] chatReference) {
+		this.chatReference = chatReference;
+	}
+
 	public byte[] getData() {
 		return this.data;
 	}

src/main/java/org/qortal/data/transaction/DeployAtTransactionData.java

@@ -2,6 +2,7 @@ package org.qortal.data.transaction;
 
 import javax.xml.bind.annotation.XmlAccessType;
 import javax.xml.bind.annotation.XmlAccessorType;
+import javax.xml.bind.annotation.XmlElement;
 import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
 
 import org.qortal.transaction.Transaction.TransactionType;
@@ -90,4 +91,17 @@ public class DeployAtTransactionData extends TransactionData {
 		this.aTAddress = AtAddress;
 	}
 
+	// Re-expose creatorPublicKey for this transaction type for JAXB
+	@XmlElement(name = "creatorPublicKey")
+	@Schema(name = "creatorPublicKey", description = "AT creator's public key", example = "2tiMr5LTpaWCgbRvkPK8TFd7k63DyHJMMFFsz9uBf1ZP")
+	public byte[] getAtCreatorPublicKey() {
+		return this.creatorPublicKey;
+	}
+
+	@XmlElement(name = "creatorPublicKey")
+	@Schema(name = "creatorPublicKey", description = "AT creator's public key", example = "2tiMr5LTpaWCgbRvkPK8TFd7k63DyHJMMFFsz9uBf1ZP")
+	public void setAtCreatorPublicKey(byte[] creatorPublicKey) {
+		this.creatorPublicKey = creatorPublicKey;
+	}
+
 }

src/main/java/org/qortal/data/transaction/TransactionData.java

@@ -128,6 +128,10 @@ public abstract class TransactionData {
 		return this.txGroupId;
 	}
 
+	public void setTxGroupId(int txGroupId) {
+		this.txGroupId = txGroupId;
+	}
+
 	public byte[] getReference() {
 		return this.reference;
 	}

src/main/java/org/qortal/group/Group.java

@@ -80,6 +80,9 @@ public class Group {
 	// Useful constants
 	public static final int NO_GROUP = 0;
 
+	// Null owner address corresponds with public key "11111111111111111111111111111111"
+	public static String NULL_OWNER_ADDRESS = "QdSnUy6sUiEnaN87dWmE92g1uQjrvPgrWG";
+
 	public static final int MIN_NAME_SIZE = 3;
 	public static final int MAX_NAME_SIZE = 32;
 	public static final int MAX_DESCRIPTION_SIZE = 128;

src/main/java/org/qortal/network/Handshake.java

@@ -265,7 +265,7 @@ public enum Handshake {
 	private static final long PEER_VERSION_131 = 0x0100030001L;
 
 	/** Minimum peer version that we are allowed to communicate with */
-	private static final String MIN_PEER_VERSION = "3.1.0";
+	private static final String MIN_PEER_VERSION = "3.8.2";
 
 	private static final int POW_BUFFER_SIZE_PRE_131 = 8 * 1024 * 1024; // bytes
 	private static final int POW_DIFFICULTY_PRE_131 = 8; // leading zero bits

src/main/java/org/qortal/network/Peer.java

@@ -155,6 +155,11 @@ public class Peer {
      */
     private CommonBlockData commonBlockData;
 
+    /**
+     * Last time we detected this peer as TOO_DIVERGENT
+     */
+    private Long lastTooDivergentTime;
+
     // Message stats
 
     private static class MessageStats {
@@ -383,6 +388,14 @@ public class Peer {
         this.commonBlockData = commonBlockData;
     }
 
+    public Long getLastTooDivergentTime() {
+        return this.lastTooDivergentTime;
+    }
+
+    public void setLastTooDivergentTime(Long lastTooDivergentTime) {
+        this.lastTooDivergentTime = lastTooDivergentTime;
+    }
+
     public boolean isSyncInProgress() {
         return this.syncInProgress;
     }

src/main/java/org/qortal/network/message/AccountMessage.java

@@ -41,6 +41,8 @@ public class AccountMessage extends Message {
 
 			bytes.write(Ints.toByteArray(accountData.getBlocksMintedAdjustment()));
 
+			bytes.write(Ints.toByteArray(accountData.getBlocksMintedPenalty()));
+
 		} catch (IOException e) {
 			throw new AssertionError("IOException shouldn't occur with ByteArrayOutputStream");
 		}
@@ -80,7 +82,9 @@ public class AccountMessage extends Message {
 
 		int blocksMintedAdjustment = byteBuffer.getInt();
 
-		AccountData accountData = new AccountData(address, reference, publicKey, defaultGroupId, flags, level, blocksMinted, blocksMintedAdjustment);
+		int blocksMintedPenalty = byteBuffer.getInt();
+
+		AccountData accountData = new AccountData(address, reference, publicKey, defaultGroupId, flags, level, blocksMinted, blocksMintedAdjustment, blocksMintedPenalty);
 		return new AccountMessage(id, accountData);
 	}
 

src/main/java/org/qortal/network/message/BlockSummariesV2Message.java

@@ -68,13 +68,18 @@ public class BlockSummariesV2Message extends Message {
 	}
 
 	public static Message fromByteBuffer(int id, ByteBuffer bytes) {
+		List<BlockSummaryData> blockSummaries = new ArrayList<>();
+
+		// If there are no bytes remaining then we can treat this as an empty array of summaries
+		if (bytes.remaining() == 0)
+			return new BlockSummariesV2Message(id, blockSummaries);
+
 		int height = bytes.getInt();
 
 		// Expecting bytes remaining to be exact multiples of BLOCK_SUMMARY_V2_LENGTH
 		if (bytes.remaining() % BLOCK_SUMMARY_V2_LENGTH != 0)
 			throw new BufferUnderflowException();
 
-		List<BlockSummaryData> blockSummaries = new ArrayList<>();
 		while (bytes.hasRemaining()) {
 			byte[] signature = new byte[BlockTransformer.BLOCK_SIGNATURE_LENGTH];
 			bytes.get(signature);

src/main/java/org/qortal/network/message/GenericUnknownMessage.java

@@ -4,7 +4,7 @@ import java.nio.ByteBuffer;
 
 public class GenericUnknownMessage extends Message {
 
-    public static final long MINIMUM_PEER_VERSION = 0x03000400cbL;
+    public static final long MINIMUM_PEER_VERSION = 0x0300060001L;
 
     public GenericUnknownMessage() {
         super(MessageType.GENERIC_UNKNOWN);

src/main/java/org/qortal/repository/AccountRepository.java

@@ -1,13 +1,9 @@
 package org.qortal.repository;
 
 import java.util.List;
+import java.util.Set;
 
-import org.qortal.data.account.AccountBalanceData;
-import org.qortal.data.account.AccountData;
-import org.qortal.data.account.EligibleQoraHolderData;
-import org.qortal.data.account.MintingAccountData;
-import org.qortal.data.account.QortFromQoraData;
-import org.qortal.data.account.RewardShareData;
+import org.qortal.data.account.*;
 
 public interface AccountRepository {
 
@@ -19,6 +15,9 @@ public interface AccountRepository {
 	/** Returns accounts with <b>any</b> bit set in given mask. */
 	public List<AccountData> getFlaggedAccounts(int mask) throws DataException;
 
+	/** Returns accounts with a blockedMintedPenalty */
+	public List<AccountData> getPenaltyAccounts() throws DataException;
+
 	/** Returns account's last reference or null if not set or account not found. */
 	public byte[] getLastReference(String address) throws DataException;
 
@@ -100,6 +99,18 @@ public interface AccountRepository {
 	 */
 	public void modifyMintedBlockCounts(List<String> addresses, int delta) throws DataException;
 
+	/** Returns account's block minted penalty count or null if account not found. */
+	public Integer getBlocksMintedPenaltyCount(String address) throws DataException;
+
+	/**
+	 * Sets blocks minted penalties for given list of accounts.
+	 * This replaces the existing values rather than modifying them by a delta.
+	 *
+	 * @param accountPenalties
+	 * @throws DataException
+	 */
+	public void updateBlocksMintedPenalties(Set<AccountPenaltyData> accountPenalties) throws DataException;
+
 	/** Delete account from repository. */
 	public void delete(String address) throws DataException;
 

src/main/java/org/qortal/repository/ChatRepository.java

@@ -14,8 +14,8 @@ public interface ChatRepository {
 	 * Expects EITHER non-null txGroupID OR non-null sender and recipient addresses.
 	 */
 	public List<ChatMessage> getMessagesMatchingCriteria(Long before, Long after,
-			Integer txGroupId, byte[] reference, List<String> involving,
-			Integer limit, Integer offset, Boolean reverse) throws DataException;
+			Integer txGroupId, byte[] reference, byte[] chatReferenceBytes, Boolean hasChatReference,
+			List<String> involving, Integer limit, Integer offset, Boolean reverse) throws DataException;
 
 	public ChatMessage toChatMessage(ChatTransactionData chatTransactionData) throws DataException;
 

src/main/java/org/qortal/repository/GroupRepository.java

@@ -131,7 +131,14 @@ public interface GroupRepository {
 
 	public GroupBanData getBan(int groupId, String member) throws DataException;
 
-	public boolean banExists(int groupId, String offender) throws DataException;
+	/**
+	 * IMPORTANT: when using banExists() as part of validation, the timestamp must be that of the transaction that
+	 * is calling banExists() as part of its validation. It must NOT be the current time, unless this is being
+	 * called outside of validation, as part of an on demand check for a ban existing (such as via an API call).
+	 * This is because we need to evaluate a ban's status based on the time of the subsequent transaction, as
+	 * validation will not occur at a fixed time for every node. For some, it could be months into the future.
+	 */
+	public boolean banExists(int groupId, String offender, long timestamp) throws DataException;
 
 	public List<GroupBanData> getGroupBans(int groupId, Integer limit, Integer offset, Boolean reverse) throws DataException;
 

src/main/java/org/qortal/repository/TransactionRepository.java

@@ -179,6 +179,15 @@ public interface TransactionRepository {
 	public List<TransferAssetTransactionData> getAssetTransfers(long assetId, String address, Integer limit, Integer offset, Boolean reverse)
 			throws DataException;
 
+	/**
+	 * Returns list of reward share transaction creators, excluding self shares.
+	 * This uses confirmed transactions only.
+	 *
+	 * @return
+	 * @throws DataException
+	 */
+	public List<String> getConfirmedRewardShareCreatorsExcludingSelfShares() throws DataException;
+
 	/**
 	 * Returns list of transactions pending approval, with optional txGgroupId filtering.
 	 * <p>

src/main/java/org/qortal/repository/hsqldb/HSQLDBAccountRepository.java

@@ -6,15 +6,11 @@ import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Set;
 import java.util.stream.Collectors;
 
 import org.qortal.asset.Asset;
-import org.qortal.data.account.AccountBalanceData;
-import org.qortal.data.account.AccountData;
-import org.qortal.data.account.EligibleQoraHolderData;
-import org.qortal.data.account.MintingAccountData;
-import org.qortal.data.account.QortFromQoraData;
-import org.qortal.data.account.RewardShareData;
+import org.qortal.data.account.*;
 import org.qortal.repository.AccountRepository;
 import org.qortal.repository.DataException;
 
@@ -30,7 +26,7 @@ public class HSQLDBAccountRepository implements AccountRepository {
 
 	@Override
 	public AccountData getAccount(String address) throws DataException {
-		String sql = "SELECT reference, public_key, default_group_id, flags, level, blocks_minted, blocks_minted_adjustment FROM Accounts WHERE account = ?";
+		String sql = "SELECT reference, public_key, default_group_id, flags, level, blocks_minted, blocks_minted_adjustment, blocks_minted_penalty FROM Accounts WHERE account = ?";
 
 		try (ResultSet resultSet = this.repository.checkedExecute(sql, address)) {
 			if (resultSet == null)
@@ -43,8 +39,9 @@ public class HSQLDBAccountRepository implements AccountRepository {
 			int level = resultSet.getInt(5);
 			int blocksMinted = resultSet.getInt(6);
 			int blocksMintedAdjustment = resultSet.getInt(7);
+			int blocksMintedPenalty = resultSet.getInt(8);
 
-			return new AccountData(address, reference, publicKey, defaultGroupId, flags, level, blocksMinted, blocksMintedAdjustment);
+			return new AccountData(address, reference, publicKey, defaultGroupId, flags, level, blocksMinted, blocksMintedAdjustment, blocksMintedPenalty);
 		} catch (SQLException e) {
 			throw new DataException("Unable to fetch account info from repository", e);
 		}
@@ -52,7 +49,7 @@ public class HSQLDBAccountRepository implements AccountRepository {
 
 	@Override
 	public List<AccountData> getFlaggedAccounts(int mask) throws DataException {
-		String sql = "SELECT reference, public_key, default_group_id, flags, level, blocks_minted, blocks_minted_adjustment, account FROM Accounts WHERE BITAND(flags, ?) != 0";
+		String sql = "SELECT reference, public_key, default_group_id, flags, level, blocks_minted, blocks_minted_adjustment, blocks_minted_penalty, account FROM Accounts WHERE BITAND(flags, ?) != 0";
 
 		List<AccountData> accounts = new ArrayList<>();
 
@@ -68,9 +65,10 @@ public class HSQLDBAccountRepository implements AccountRepository {
 				int level = resultSet.getInt(5);
 				int blocksMinted = resultSet.getInt(6);
 				int blocksMintedAdjustment = resultSet.getInt(7);
-				String address = resultSet.getString(8);
+				int blocksMintedPenalty = resultSet.getInt(8);
+				String address = resultSet.getString(9);
 
-				accounts.add(new AccountData(address, reference, publicKey, defaultGroupId, flags, level, blocksMinted, blocksMintedAdjustment));
+				accounts.add(new AccountData(address, reference, publicKey, defaultGroupId, flags, level, blocksMinted, blocksMintedAdjustment, blocksMintedPenalty));
 			} while (resultSet.next());
 
 			return accounts;
@@ -79,6 +77,36 @@ public class HSQLDBAccountRepository implements AccountRepository {
 		}
 	}
 
+	@Override
+	public List<AccountData> getPenaltyAccounts() throws DataException {
+		String sql = "SELECT reference, public_key, default_group_id, flags, level, blocks_minted, blocks_minted_adjustment, blocks_minted_penalty, account FROM Accounts WHERE blocks_minted_penalty != 0";
+
+		List<AccountData> accounts = new ArrayList<>();
+
+		try (ResultSet resultSet = this.repository.checkedExecute(sql)) {
+			if (resultSet == null)
+				return accounts;
+
+			do {
+				byte[] reference = resultSet.getBytes(1);
+				byte[] publicKey = resultSet.getBytes(2);
+				int defaultGroupId = resultSet.getInt(3);
+				int flags = resultSet.getInt(4);
+				int level = resultSet.getInt(5);
+				int blocksMinted = resultSet.getInt(6);
+				int blocksMintedAdjustment = resultSet.getInt(7);
+				int blocksMintedPenalty = resultSet.getInt(8);
+				String address = resultSet.getString(9);
+
+				accounts.add(new AccountData(address, reference, publicKey, defaultGroupId, flags, level, blocksMinted, blocksMintedAdjustment, blocksMintedPenalty));
+			} while (resultSet.next());
+
+			return accounts;
+		} catch (SQLException e) {
+			throw new DataException("Unable to fetch penalty accounts from repository", e);
+		}
+	}
+
 	@Override
 	public byte[] getLastReference(String address) throws DataException {
 		String sql = "SELECT reference FROM Accounts WHERE account = ?";
@@ -298,6 +326,39 @@ public class HSQLDBAccountRepository implements AccountRepository {
 		}
 	}
 
+	@Override
+	public Integer getBlocksMintedPenaltyCount(String address) throws DataException {
+		String sql = "SELECT blocks_minted_penalty FROM Accounts WHERE account = ?";
+
+		try (ResultSet resultSet = this.repository.checkedExecute(sql, address)) {
+			if (resultSet == null)
+				return null;
+
+			return resultSet.getInt(1);
+		} catch (SQLException e) {
+			throw new DataException("Unable to fetch account's block minted penalty count from repository", e);
+		}
+	}
+	public void updateBlocksMintedPenalties(Set<AccountPenaltyData> accountPenalties) throws DataException {
+		// Nothing to do?
+		if (accountPenalties == null || accountPenalties.isEmpty())
+			return;
+
+		// Map balance changes into SQL bind params, filtering out no-op changes
+		List<Object[]> updateBlocksMintedPenaltyParams = accountPenalties.stream()
+				.map(accountPenalty -> new Object[] { accountPenalty.getAddress(), accountPenalty.getBlocksMintedPenalty(), accountPenalty.getBlocksMintedPenalty() })
+				.collect(Collectors.toList());
+
+		// Perform actual balance changes
+		String sql = "INSERT INTO Accounts (account, blocks_minted_penalty) VALUES (?, ?) " +
+				"ON DUPLICATE KEY UPDATE blocks_minted_penalty = blocks_minted_penalty + ?";
+		try {
+			this.repository.executeCheckedBatchUpdate(sql, updateBlocksMintedPenaltyParams);
+		} catch (SQLException e) {
+			throw new DataException("Unable to set blocks minted penalties in repository", e);
+		}
+	}
+
 	@Override
 	public void delete(String address) throws DataException {
 		// NOTE: Account balances are deleted automatically by the database thanks to "ON DELETE CASCADE" in AccountBalances' FOREIGN KEY

src/main/java/org/qortal/repository/hsqldb/HSQLDBChatRepository.java

@@ -24,8 +24,8 @@ public class HSQLDBChatRepository implements ChatRepository {
 
 	@Override
 	public List<ChatMessage> getMessagesMatchingCriteria(Long before, Long after, Integer txGroupId, byte[] referenceBytes,
-			List<String> involving, Integer limit, Integer offset, Boolean reverse)
-			throws DataException {
+			byte[] chatReferenceBytes, Boolean hasChatReference, List<String> involving,
+			Integer limit, Integer offset, Boolean reverse) throws DataException {
 		// Check args meet expectations
 		if ((txGroupId != null && involving != null && !involving.isEmpty())
 				|| (txGroupId == null && (involving == null || involving.size() != 2)))
@@ -35,7 +35,7 @@ public class HSQLDBChatRepository implements ChatRepository {
 
 		sql.append("SELECT created_when, tx_group_id, Transactions.reference, creator, "
 				+ "sender, SenderNames.name, recipient, RecipientNames.name, "
-				+ "data, is_text, is_encrypted, signature "
+				+ "chat_reference, data, is_text, is_encrypted, signature "
 				+ "FROM ChatTransactions "
 				+ "JOIN Transactions USING (signature) "
 				+ "LEFT OUTER JOIN Names AS SenderNames ON SenderNames.owner = sender "
@@ -62,6 +62,18 @@ public class HSQLDBChatRepository implements ChatRepository {
 			bindParams.add(referenceBytes);
 		}
 
+		if (chatReferenceBytes != null) {
+			whereClauses.add("chat_reference = ?");
+			bindParams.add(chatReferenceBytes);
+		}
+
+		if (hasChatReference != null && hasChatReference == true) {
+			whereClauses.add("chat_reference IS NOT NULL");
+		}
+		else if (hasChatReference != null && hasChatReference == false) {
+			whereClauses.add("chat_reference IS NULL");
+		}
+
 		if (txGroupId != null) {
 			whereClauses.add("tx_group_id = " + txGroupId); // int safe to use literally
 			whereClauses.add("recipient IS NULL");
@@ -103,13 +115,14 @@ public class HSQLDBChatRepository implements ChatRepository {
 				String senderName = resultSet.getString(6);
 				String recipient = resultSet.getString(7);
 				String recipientName = resultSet.getString(8);
-				byte[] data = resultSet.getBytes(9);
-				boolean isText = resultSet.getBoolean(10);
-				boolean isEncrypted = resultSet.getBoolean(11);
-				byte[] signature = resultSet.getBytes(12);
+				byte[] chatReference = resultSet.getBytes(9);
+				byte[] data = resultSet.getBytes(10);
+				boolean isText = resultSet.getBoolean(11);
+				boolean isEncrypted = resultSet.getBoolean(12);
+				byte[] signature = resultSet.getBytes(13);
 
 				ChatMessage chatMessage = new ChatMessage(timestamp, groupId, reference, senderPublicKey, sender,
-						senderName, recipient, recipientName, data, isText, isEncrypted, signature);
+						senderName, recipient, recipientName, chatReference, data, isText, isEncrypted, signature);
 
 				chatMessages.add(chatMessage);
 			} while (resultSet.next());
@@ -141,13 +154,14 @@ public class HSQLDBChatRepository implements ChatRepository {
 			byte[] senderPublicKey = chatTransactionData.getSenderPublicKey();
 			String sender = chatTransactionData.getSender();
 			String recipient = chatTransactionData.getRecipient();
+			byte[] chatReference = chatTransactionData.getChatReference();
 			byte[] data = chatTransactionData.getData();
 			boolean isText = chatTransactionData.getIsText();
 			boolean isEncrypted = chatTransactionData.getIsEncrypted();
 			byte[] signature = chatTransactionData.getSignature();
 
 			return new ChatMessage(timestamp, groupId, reference, senderPublicKey, sender,
-					senderName, recipient, recipientName, data, isText, isEncrypted, signature);
+					senderName, recipient, recipientName, chatReference, data, isText, isEncrypted, signature);
 		} catch (SQLException e) {
 			throw new DataException("Unable to fetch convert chat transaction from repository", e);
 		}

src/main/java/org/qortal/repository/hsqldb/HSQLDBDatabaseUpdates.java

@@ -975,6 +975,19 @@ public class HSQLDBDatabaseUpdates {
 					stmt.execute("ALTER TABLE TradeBotStates ALTER COLUMN receiving_account_info SET DATA TYPE VARBINARY(128)");
 					break;
 
+				case 44:
+					// Add blocks minted penalty
+					stmt.execute("ALTER TABLE Accounts ADD blocks_minted_penalty INTEGER NOT NULL DEFAULT 0");
+					break;
+
+				case 45:
+					// Add a chat reference, to allow one message to reference another, and for this to be easily
+					// searchable. Null values are allowed as most transactions won't have a reference.
+					stmt.execute("ALTER TABLE ChatTransactions ADD chat_reference Signature");
+					// For finding chat messages by reference
+					stmt.execute("CREATE INDEX ChatTransactionsChatReferenceIndex ON ChatTransactions (chat_reference)");
+					break;
+
 				default:
 					// nothing to do
 					return false;

src/main/java/org/qortal/repository/hsqldb/HSQLDBGroupRepository.java

@@ -777,9 +777,9 @@ public class HSQLDBGroupRepository implements GroupRepository {
 	}
 
 	@Override
-	public boolean banExists(int groupId, String offender) throws DataException {
+	public boolean banExists(int groupId, String offender, long timestamp) throws DataException {
 		try {
-			return this.repository.exists("GroupBans", "group_id = ? AND offender = ?", groupId, offender);
+			return this.repository.exists("GroupBans", "group_id = ? AND offender = ? AND (expires_when IS NULL OR expires_when > ?)", groupId, offender, timestamp);
 		} catch (SQLException e) {
 			throw new DataException("Unable to check for group ban in repository", e);
 		}

src/main/java/org/qortal/repository/hsqldb/transaction/HSQLDBChatTransactionRepository.java

@@ -17,7 +17,7 @@ public class HSQLDBChatTransactionRepository extends HSQLDBTransactionRepository
 	}
 
 	TransactionData fromBase(BaseTransactionData baseTransactionData) throws DataException {
-		String sql = "SELECT sender, nonce, recipient, is_text, is_encrypted, data FROM ChatTransactions WHERE signature = ?";
+		String sql = "SELECT sender, nonce, recipient, is_text, is_encrypted, data, chat_reference FROM ChatTransactions WHERE signature = ?";
 
 		try (ResultSet resultSet = this.repository.checkedExecute(sql, baseTransactionData.getSignature())) {
 			if (resultSet == null)
@@ -29,8 +29,9 @@ public class HSQLDBChatTransactionRepository extends HSQLDBTransactionRepository
 			boolean isText = resultSet.getBoolean(4);
 			boolean isEncrypted = resultSet.getBoolean(5);
 			byte[] data = resultSet.getBytes(6);
+			byte[] chatReference = resultSet.getBytes(7);
 
-			return new ChatTransactionData(baseTransactionData, sender, nonce, recipient, data, isText, isEncrypted);
+			return new ChatTransactionData(baseTransactionData, sender, nonce, recipient, chatReference, data, isText, isEncrypted);
 		} catch (SQLException e) {
 			throw new DataException("Unable to fetch chat transaction from repository", e);
 		}
@@ -45,7 +46,7 @@ public class HSQLDBChatTransactionRepository extends HSQLDBTransactionRepository
 		saveHelper.bind("signature", chatTransactionData.getSignature()).bind("nonce", chatTransactionData.getNonce())
 				.bind("sender", chatTransactionData.getSender()).bind("recipient", chatTransactionData.getRecipient())
 				.bind("is_text", chatTransactionData.getIsText()).bind("is_encrypted", chatTransactionData.getIsEncrypted())
-				.bind("data", chatTransactionData.getData());
+				.bind("data", chatTransactionData.getData()).bind("chat_reference", chatTransactionData.getChatReference());
 
 		try {
 			saveHelper.execute(this.repository);

src/main/java/org/qortal/repository/hsqldb/transaction/HSQLDBTransactionRepository.java

@@ -7,11 +7,7 @@ import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.sql.ResultSet;
 import java.sql.SQLException;
-import java.util.ArrayList;
-import java.util.EnumMap;
-import java.util.EnumSet;
-import java.util.List;
-import java.util.Map;
+import java.util.*;
 
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
@@ -969,6 +965,33 @@ public class HSQLDBTransactionRepository implements TransactionRepository {
 		}
 	}
 
+	public List<String> getConfirmedRewardShareCreatorsExcludingSelfShares() throws DataException {
+		List<String> rewardShareCreators = new ArrayList<>();
+
+		String sql = "SELECT account "
+				+ "FROM RewardShareTransactions "
+				+ "JOIN Accounts ON Accounts.public_key = RewardShareTransactions.minter_public_key "
+				+ "JOIN Transactions ON Transactions.signature = RewardShareTransactions.signature "
+				+ "WHERE block_height IS NOT NULL AND RewardShareTransactions.recipient != Accounts.account "
+				+ "GROUP BY account "
+				+ "ORDER BY account";
+
+		try (ResultSet resultSet = this.repository.checkedExecute(sql)) {
+			if (resultSet == null)
+				return rewardShareCreators;
+
+			do {
+				String address = resultSet.getString(1);
+
+				rewardShareCreators.add(address);
+			} while (resultSet.next());
+
+			return rewardShareCreators;
+		} catch (SQLException e) {
+			throw new DataException("Unable to fetch reward share creators from repository", e);
+		}
+	}
+
 	@Override
 	public List<TransactionData> getApprovalPendingTransactions(Integer txGroupId, Integer limit, Integer offset, Boolean reverse) throws DataException {
 		StringBuilder sql = new StringBuilder(512);

src/main/java/org/qortal/settings/Settings.java

@@ -110,7 +110,13 @@ public class Settings {
 	/** Maximum number of unconfirmed transactions allowed per account */
 	private int maxUnconfirmedPerAccount = 25;
 	/** Max milliseconds into future for accepting new, unconfirmed transactions */
-	private int maxTransactionTimestampFuture = 24 * 60 * 60 * 1000; // milliseconds
+	private int maxTransactionTimestampFuture = 30 * 60 * 1000; // milliseconds
+
+	/** Maximum number of CHAT transactions allowed per account in recent timeframe */
+	private int maxRecentChatMessagesPerAccount = 250;
+	/** Maximum age of a CHAT transaction to be considered 'recent' */
+	private long recentChatMessagesMaxAge = 60 * 60 * 1000L; // milliseconds
+
 	/** Whether we check, fetch and install auto-updates */
 	private boolean autoUpdateEnabled = true;
 	/** How long between repository backups (ms), or 0 if disabled. */
@@ -153,7 +159,7 @@ public class Settings {
 	 * This prevents the node from being able to serve older blocks */
 	private boolean topOnly = false;
 	/** The amount of recent blocks we should keep when pruning */
-	private int pruneBlockLimit = 1450;
+	private int pruneBlockLimit = 6000;
 
 	/** How often to attempt AT state pruning (ms). */
 	private long atStatesPruneInterval = 3219L; // milliseconds
@@ -184,6 +190,8 @@ public class Settings {
 
 	// Peer-to-peer related
 	private boolean isTestNet = false;
+	/** Single node testnet mode */
+	private boolean singleNodeTestnet = false;
 	/** Port number for inbound peer-to-peer connections. */
 	private Integer listenPort;
 	/** Whether to attempt to open the listen port via UPnP */
@@ -203,8 +211,11 @@ public class Settings {
 	/** Maximum number of retry attempts if a peer fails to respond with the requested data */
 	private int maxRetries = 2;
 
+	/** The number of seconds of no activity before recovery mode begins */
+	public long recoveryModeTimeout = 10 * 60 * 1000L;
+
 	/** Minimum peer version number required in order to sync with them */
-	private String minPeerVersion = "3.3.7";
+	private String minPeerVersion = "3.8.2";
 	/** Whether to allow connections with peers below minPeerVersion
 	 * If true, we won't sync with them but they can still sync with us, and will show in the peers list
 	 * If false, sync will be blocked both ways, and they will not appear in the peers list */
@@ -262,7 +273,7 @@ public class Settings {
 	private String[] bootstrapHosts = new String[] {
 			"http://bootstrap.qortal.org",
 			"http://bootstrap2.qortal.org",
-			"http://62.171.190.193"
+			"http://bootstrap.qortal.online"
 	};
 
 	// Auto-update sources
@@ -290,10 +301,6 @@ public class Settings {
 	/** Additional offset added to values returned by NTP.getTime() */
 	private Long testNtpOffset = null;
 
-	// Online accounts
-
-	/** Whether to opt-in to mempow computations for online accounts, ahead of general release */
-	private boolean onlineAccountsMemPoWEnabled = false;
 
 
 	/* Foreign chains */
@@ -490,7 +497,7 @@ public class Settings {
 
 	private void validate() {
 		// Validation goes here
-		if (this.minBlockchainPeers < 1)
+		if (this.minBlockchainPeers < 1 && !singleNodeTestnet)
 			throwValidationError("minBlockchainPeers must be at least 1");
 
 		if (this.apiKey != null && this.apiKey.trim().length() < 8)
@@ -639,6 +646,14 @@ public class Settings {
 		return this.maxTransactionTimestampFuture;
 	}
 
+	public int getMaxRecentChatMessagesPerAccount() {
+		return this.maxRecentChatMessagesPerAccount;
+	}
+
+	public long getRecentChatMessagesMaxAge() {
+		return recentChatMessagesMaxAge;
+	}
+
 	public int getBlockCacheSize() {
 		return this.blockCacheSize;
 	}
@@ -647,6 +662,10 @@ public class Settings {
 		return this.isTestNet;
 	}
 
+	public boolean isSingleNodeTestnet() {
+		return this.singleNodeTestnet;
+	}
+
 	public int getListenPort() {
 		if (this.listenPort != null)
 			return this.listenPort;
@@ -667,6 +686,9 @@ public class Settings {
 	}
 
 	public int getMinBlockchainPeers() {
+		if (singleNodeTestnet)
+			return 0;
+
 		return this.minBlockchainPeers;
 	}
 
@@ -692,6 +714,10 @@ public class Settings {
 
 	public int getMaxRetries() { return this.maxRetries; }
 
+	public long getRecoveryModeTimeout() {
+		return recoveryModeTimeout;
+	}
+
 	public String getMinPeerVersion() { return this.minPeerVersion; }
 
 	public boolean getAllowConnectionsWithOlderPeerVersions() { return this.allowConnectionsWithOlderPeerVersions; }
@@ -800,10 +826,6 @@ public class Settings {
 		return this.testNtpOffset;
 	}
 
-	public boolean isOnlineAccountsMemPoWEnabled() {
-		return this.onlineAccountsMemPoWEnabled;
-	}
-
 	public long getRepositoryBackupInterval() {
 		return this.repositoryBackupInterval;
 	}

src/main/java/org/qortal/transaction/AddGroupAdminTransaction.java

@@ -2,6 +2,7 @@ package org.qortal.transaction;
 
 import java.util.Collections;
 import java.util.List;
+import java.util.Objects;
 
 import org.qortal.account.Account;
 import org.qortal.asset.Asset;
@@ -64,15 +65,24 @@ public class AddGroupAdminTransaction extends Transaction {
 
 		Account owner = getOwner();
 		String groupOwner = this.repository.getGroupRepository().getOwner(groupId);
+		boolean groupOwnedByNullAccount = Objects.equals(groupOwner, Group.NULL_OWNER_ADDRESS);
 
-		// Check transaction's public key matches group's current owner
-		if (!owner.getAddress().equals(groupOwner))
+		// Require approval if transaction relates to a group owned by the null account
+		if (groupOwnedByNullAccount && !this.needsGroupApproval())
+			return ValidationResult.GROUP_APPROVAL_REQUIRED;
+
+		// Check transaction's public key matches group's current owner (except for groups owned by the null account)
+		if (!groupOwnedByNullAccount && !owner.getAddress().equals(groupOwner))
 			return ValidationResult.INVALID_GROUP_OWNER;
 
 		// Check address is a group member
 		if (!this.repository.getGroupRepository().memberExists(groupId, memberAddress))
 			return ValidationResult.NOT_GROUP_MEMBER;
 
+		// Check transaction creator is a group member
+		if (!this.repository.getGroupRepository().memberExists(groupId, this.getCreator().getAddress()))
+			return ValidationResult.NOT_GROUP_MEMBER;
+
 		// Check group member is not already an admin
 		if (this.repository.getGroupRepository().adminExists(groupId, memberAddress))
 			return ValidationResult.ALREADY_GROUP_ADMIN;

src/main/java/org/qortal/transaction/ArbitraryTransaction.java

@@ -24,6 +24,7 @@ import org.qortal.transform.Transformer;
 import org.qortal.transform.transaction.ArbitraryTransactionTransformer;
 import org.qortal.transform.transaction.TransactionTransformer;
 import org.qortal.utils.ArbitraryTransactionUtils;
+import org.qortal.utils.NTP;
 
 public class ArbitraryTransaction extends Transaction {
 
@@ -34,9 +35,13 @@ public class ArbitraryTransaction extends Transaction {
 	public static final int MAX_DATA_SIZE = 4000;
 	public static final int MAX_METADATA_LENGTH = 32;
 	public static final int HASH_LENGTH = TransactionTransformer.SHA256_LENGTH;
-	public static final int POW_BUFFER_SIZE = 8 * 1024 * 1024; // bytes
 	public static final int MAX_IDENTIFIER_LENGTH = 64;
 
+	/** If time difference between transaction and now is greater than this then we don't verify proof-of-work. */
+	public static final long HISTORIC_THRESHOLD = 2 * 7 * 24 * 60 * 60 * 1000L;
+	public static final int POW_BUFFER_SIZE = 8 * 1024 * 1024; // bytes
+
+
 	// Constructors
 
 	public ArbitraryTransaction(Repository repository, TransactionData transactionData) {
@@ -202,9 +207,11 @@ public class ArbitraryTransaction extends Transaction {
 			// Clear nonce from transactionBytes
 			ArbitraryTransactionTransformer.clearNonce(transactionBytes);
 
-			// Check nonce
-			int difficulty = ArbitraryDataManager.getInstance().getPowDifficulty();
-			return MemoryPoW.verify2(transactionBytes, POW_BUFFER_SIZE, difficulty, nonce);
+			// We only need to check nonce for recent transactions due to PoW verification overhead
+			if (NTP.getTime() - this.arbitraryTransactionData.getTimestamp() < HISTORIC_THRESHOLD) {
+				int difficulty = ArbitraryDataManager.getInstance().getPowDifficulty();
+				return MemoryPoW.verify2(transactionBytes, POW_BUFFER_SIZE, difficulty, nonce);
+			}
 		}
 
 		return true;

src/main/java/org/qortal/transaction/CancelGroupBanTransaction.java

@@ -73,7 +73,7 @@ public class CancelGroupBanTransaction extends Transaction {
 		Account member = getMember();
 
 		// Check ban actually exists
-		if (!this.repository.getGroupRepository().banExists(groupId, member.getAddress()))
+		if (!this.repository.getGroupRepository().banExists(groupId, member.getAddress(), this.groupUnbanTransactionData.getTimestamp()))
 			return ValidationResult.BAN_UNKNOWN;
 
 		// Check admin has enough funds

src/main/java/org/qortal/transaction/ChatTransaction.java

@@ -1,7 +1,9 @@
 package org.qortal.transaction;
 
+import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
+import java.util.function.Predicate;
 
 import org.qortal.account.Account;
 import org.qortal.account.PublicKeyAccount;
@@ -16,9 +18,11 @@ import org.qortal.list.ResourceListManager;
 import org.qortal.repository.DataException;
 import org.qortal.repository.GroupRepository;
 import org.qortal.repository.Repository;
+import org.qortal.settings.Settings;
 import org.qortal.transform.TransformationException;
 import org.qortal.transform.transaction.ChatTransactionTransformer;
 import org.qortal.transform.transaction.TransactionTransformer;
+import org.qortal.utils.NTP;
 
 public class ChatTransaction extends Transaction {
 
@@ -26,10 +30,11 @@ public class ChatTransaction extends Transaction {
 	private ChatTransactionData chatTransactionData;
 
 	// Other useful constants
-	public static final int MAX_DATA_SIZE = 1024;
+	public static final int MAX_DATA_SIZE = 4000;
 	public static final int POW_BUFFER_SIZE = 8 * 1024 * 1024; // bytes
-	public static final int POW_DIFFICULTY_WITH_QORT = 8; // leading zero bits
-	public static final int POW_DIFFICULTY_NO_QORT = 12; // leading zero bits
+	public static final int POW_DIFFICULTY_ABOVE_QORT_THRESHOLD = 8; // leading zero bits
+	public static final int POW_DIFFICULTY_BELOW_QORT_THRESHOLD = 18; // leading zero bits
+	public static final long POW_QORT_THRESHOLD = 400000000L;
 
 	// Constructors
 
@@ -78,7 +83,7 @@ public class ChatTransaction extends Transaction {
 		// Clear nonce from transactionBytes
 		ChatTransactionTransformer.clearNonce(transactionBytes);
 
-		int difficulty = this.getSender().getConfirmedBalance(Asset.QORT) > 0 ? POW_DIFFICULTY_WITH_QORT : POW_DIFFICULTY_NO_QORT;
+		int difficulty = this.getSender().getConfirmedBalance(Asset.QORT) >= POW_QORT_THRESHOLD ? POW_DIFFICULTY_ABOVE_QORT_THRESHOLD : POW_DIFFICULTY_BELOW_QORT_THRESHOLD;
 
 		// Calculate nonce
 		this.chatTransactionData.setNonce(MemoryPoW.compute2(transactionBytes, POW_BUFFER_SIZE, difficulty));
@@ -145,6 +150,11 @@ public class ChatTransaction extends Transaction {
 	public ValidationResult isValid() throws DataException {
 		// Nonce checking is done via isSignatureValid() as that method is only called once per import
 
+		// Disregard messages with timestamp too far in the future (we have stricter limits for CHAT transactions)
+		if (this.chatTransactionData.getTimestamp() > NTP.getTime() + (5 * 60 * 1000L)) {
+			return ValidationResult.TIMESTAMP_TOO_NEW;
+		}
+
 		// Check for blocked author by address
 		ResourceListManager listManager = ResourceListManager.getInstance();
 		if (listManager.listContains("blockedAddresses", this.chatTransactionData.getSender(), true)) {
@@ -163,6 +173,14 @@ public class ChatTransaction extends Transaction {
 			}
 		}
 
+		PublicKeyAccount creator = this.getCreator();
+		if (creator == null)
+			return ValidationResult.MISSING_CREATOR;
+
+		// Reject if unconfirmed pile already has X recent CHAT transactions from same creator
+		if (countRecentChatTransactionsByCreator(creator) >= Settings.getInstance().getMaxRecentChatMessagesPerAccount())
+			return ValidationResult.TOO_MANY_UNCONFIRMED;
+
 		// If we exist in the repository then we've been imported as unconfirmed,
 		// but we don't want to make it into a block, so return fake non-OK result.
 		if (this.repository.getTransactionRepository().exists(this.chatTransactionData.getSignature()))
@@ -204,7 +222,7 @@ public class ChatTransaction extends Transaction {
 
 		int difficulty;
 		try {
-			difficulty = this.getSender().getConfirmedBalance(Asset.QORT) > 0 ? POW_DIFFICULTY_WITH_QORT : POW_DIFFICULTY_NO_QORT;
+			difficulty = this.getSender().getConfirmedBalance(Asset.QORT) >= POW_QORT_THRESHOLD ? POW_DIFFICULTY_ABOVE_QORT_THRESHOLD : POW_DIFFICULTY_BELOW_QORT_THRESHOLD;
 		} catch (DataException e) {
 			return false;
 		}
@@ -213,6 +231,26 @@ public class ChatTransaction extends Transaction {
 		return MemoryPoW.verify2(transactionBytes, POW_BUFFER_SIZE, difficulty, nonce);
 	}
 
+	private int countRecentChatTransactionsByCreator(PublicKeyAccount creator) throws DataException {
+		List<TransactionData> unconfirmedTransactions = repository.getTransactionRepository().getUnconfirmedTransactions();
+		final Long now = NTP.getTime();
+		long recentThreshold = Settings.getInstance().getRecentChatMessagesMaxAge();
+
+		// We only care about chat transactions, and only those that are considered 'recent'
+		Predicate<TransactionData> hasSameCreatorAndIsRecentChat = transactionData -> {
+			if (transactionData.getType() != TransactionType.CHAT)
+				return false;
+
+			if (transactionData.getTimestamp() < now - recentThreshold)
+				return false;
+
+			return Arrays.equals(creator.getPublicKey(), transactionData.getCreatorPublicKey());
+		};
+
+		return (int) unconfirmedTransactions.stream().filter(hasSameCreatorAndIsRecentChat).count();
+	}
+
+
 	/**
 	 * Ensure there's at least a skeleton account so people
 	 * can retrieve sender's public key using address, even if all their messages

src/main/java/org/qortal/transaction/GroupInviteTransaction.java

@@ -78,7 +78,7 @@ public class GroupInviteTransaction extends Transaction {
 			return ValidationResult.ALREADY_GROUP_MEMBER;
 
 		// Check invitee is not banned
-		if (this.repository.getGroupRepository().banExists(groupId, invitee.getAddress()))
+		if (this.repository.getGroupRepository().banExists(groupId, invitee.getAddress(), this.groupInviteTransactionData.getTimestamp()))
 			return ValidationResult.BANNED_FROM_GROUP;
 
 		// Check creator has enough funds

src/main/java/org/qortal/transaction/JoinGroupTransaction.java

@@ -53,7 +53,7 @@ public class JoinGroupTransaction extends Transaction {
 			return ValidationResult.ALREADY_GROUP_MEMBER;
 
 		// Check member is not banned
-		if (this.repository.getGroupRepository().banExists(groupId, joiner.getAddress()))
+		if (this.repository.getGroupRepository().banExists(groupId, joiner.getAddress(), this.joinGroupTransactionData.getTimestamp()))
 			return ValidationResult.BANNED_FROM_GROUP;
 
 		// Check join request doesn't already exist

src/main/java/org/qortal/transaction/PublicizeTransaction.java

@@ -4,7 +4,9 @@ import java.util.Collections;
 import java.util.List;
 
 import org.qortal.account.Account;
+import org.qortal.account.PublicKeyAccount;
 import org.qortal.api.resource.TransactionsResource.ConfirmationStatus;
+import org.qortal.asset.Asset;
 import org.qortal.crypto.MemoryPoW;
 import org.qortal.data.transaction.PublicizeTransactionData;
 import org.qortal.data.transaction.TransactionData;
@@ -26,7 +28,7 @@ public class PublicizeTransaction extends Transaction {
 	/** If time difference between transaction and now is greater than this then we don't verify proof-of-work. */
 	public static final long HISTORIC_THRESHOLD = 2 * 7 * 24 * 60 * 60 * 1000L;
 	public static final int POW_BUFFER_SIZE = 8 * 1024 * 1024; // bytes
-	public static final int POW_DIFFICULTY = 15; // leading zero bits
+	public static final int POW_DIFFICULTY = 14; // leading zero bits
 
 	// Constructors
 
@@ -102,6 +104,12 @@ public class PublicizeTransaction extends Transaction {
 			if (!verifyNonce())
 				return ValidationResult.INCORRECT_NONCE;
 
+		// Validate fee if one has been included
+		PublicKeyAccount creator = this.getCreator();
+		if (this.transactionData.getFee() > 0)
+			if (creator.getConfirmedBalance(Asset.QORT) < this.transactionData.getFee())
+				return ValidationResult.NO_BALANCE;
+
 		return ValidationResult.OK;
 	}
 

src/main/java/org/qortal/transaction/RemoveGroupAdminTransaction.java

@@ -2,6 +2,7 @@ package org.qortal.transaction;
 
 import java.util.Collections;
 import java.util.List;
+import java.util.Objects;
 
 import org.qortal.account.Account;
 import org.qortal.asset.Asset;
@@ -65,11 +66,21 @@ public class RemoveGroupAdminTransaction extends Transaction {
 			return ValidationResult.GROUP_DOES_NOT_EXIST;
 
 		Account owner = getOwner();
+		String groupOwner = this.repository.getGroupRepository().getOwner(groupId);
+		boolean groupOwnedByNullAccount = Objects.equals(groupOwner, Group.NULL_OWNER_ADDRESS);
 
-		// Check transaction's public key matches group's current owner
-		if (!owner.getAddress().equals(groupData.getOwner()))
+		// Require approval if transaction relates to a group owned by the null account
+		if (groupOwnedByNullAccount && !this.needsGroupApproval())
+			return ValidationResult.GROUP_APPROVAL_REQUIRED;
+
+		// Check transaction's public key matches group's current owner (except for groups owned by the null account)
+		if (!groupOwnedByNullAccount && !owner.getAddress().equals(groupOwner))
 			return ValidationResult.INVALID_GROUP_OWNER;
 
+		// Check transaction creator is a group member
+		if (!this.repository.getGroupRepository().memberExists(groupId, this.getCreator().getAddress()))
+			return ValidationResult.NOT_GROUP_MEMBER;
+
 		Account admin = getAdmin();
 
 		// Check member is an admin

src/main/java/org/qortal/transaction/RewardShareTransaction.java

@@ -163,9 +163,12 @@ public class RewardShareTransaction extends Transaction {
 				return ValidationResult.SELF_SHARE_EXISTS;
 		}
 
-		// Fee checking needed if not setting up new self-share
-		if (!(isRecipientAlsoMinter && existingRewardShareData == null))
-			// Check creator has enough funds
+		// Check creator has enough funds
+		if (this.rewardShareTransactionData.getTimestamp() >= BlockChain.getInstance().getFeeValidationFixTimestamp())
+			if (creator.getConfirmedBalance(Asset.QORT) < this.rewardShareTransactionData.getFee())
+				return ValidationResult.NO_BALANCE;
+
+		else if (!(isRecipientAlsoMinter && existingRewardShareData == null))
 			if (creator.getConfirmedBalance(Asset.QORT) < this.rewardShareTransactionData.getFee())
 				return ValidationResult.NO_BALANCE;
 

src/main/java/org/qortal/transaction/Transaction.java

@@ -1,13 +1,7 @@
 package org.qortal.transaction;
 
 import java.math.BigInteger;
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Comparator;
-import java.util.EnumSet;
-import java.util.Iterator;
-import java.util.List;
-import java.util.Map;
+import java.util.*;
 import java.util.concurrent.locks.ReentrantLock;
 import java.util.function.Predicate;
 
@@ -69,8 +63,8 @@ public abstract class Transaction {
 		AT(21, false),
 		CREATE_GROUP(22, true),
 		UPDATE_GROUP(23, true),
-		ADD_GROUP_ADMIN(24, false),
-		REMOVE_GROUP_ADMIN(25, false),
+		ADD_GROUP_ADMIN(24, true),
+		REMOVE_GROUP_ADMIN(25, true),
 		GROUP_BAN(26, false),
 		CANCEL_GROUP_BAN(27, false),
 		GROUP_KICK(28, false),
@@ -250,6 +244,8 @@ public abstract class Transaction {
 		INVALID_TIMESTAMP_SIGNATURE(95),
 		ADDRESS_BLOCKED(96),
 		NAME_BLOCKED(97),
+		GROUP_APPROVAL_REQUIRED(98),
+		ACCOUNT_NOT_TRANSFERABLE(99),
 		INVALID_BUT_OK(999),
 		NOT_YET_RELEASED(1000);
 
@@ -760,9 +756,13 @@ public abstract class Transaction {
 			// Group no longer exists? Possibly due to blockchain orphaning undoing group creation?
 			return true; // stops tx being included in block but it will eventually expire
 
+		String groupOwner = this.repository.getGroupRepository().getOwner(txGroupId);
+		boolean groupOwnedByNullAccount = Objects.equals(groupOwner, Group.NULL_OWNER_ADDRESS);
+
 		// If transaction's creator is group admin (of group with ID txGroupId) then auto-approve
+		// This is disabled for null-owned groups, since these require approval from other admins
 		PublicKeyAccount creator = this.getCreator();
-		if (groupRepository.adminExists(txGroupId, creator.getAddress()))
+		if (!groupOwnedByNullAccount && groupRepository.adminExists(txGroupId, creator.getAddress()))
 			return false;
 
 		return true;

src/main/java/org/qortal/transaction/TransferPrivsTransaction.java

@@ -67,6 +67,11 @@ public class TransferPrivsTransaction extends Transaction {
 		if (getSender().getConfirmedBalance(Asset.QORT) < this.transferPrivsTransactionData.getFee())
 			return ValidationResult.NO_BALANCE;
 
+		// Check sender doesn't have a blocksMintedPenalty, as these accounts cannot be transferred
+		AccountData senderAccountData = this.repository.getAccountRepository().getAccount(getSender().getAddress());
+		if (senderAccountData == null || senderAccountData.getBlocksMintedPenalty() != 0)
+			return ValidationResult.ACCOUNT_NOT_TRANSFERABLE;
+
 		return ValidationResult.OK;
 	}
 

src/main/java/org/qortal/transaction/UpdateGroupTransaction.java

@@ -103,7 +103,7 @@ public class UpdateGroupTransaction extends Transaction {
 		Account newOwner = getNewOwner();
 
 		// Check new owner is not banned
-		if (this.repository.getGroupRepository().banExists(this.updateGroupTransactionData.getGroupId(), newOwner.getAddress()))
+		if (this.repository.getGroupRepository().banExists(this.updateGroupTransactionData.getGroupId(), newOwner.getAddress(), this.updateGroupTransactionData.getTimestamp()))
 			return ValidationResult.BANNED_FROM_GROUP;
 
 		return ValidationResult.OK;

src/main/java/org/qortal/transform/block/BlockTransformer.java

@@ -235,7 +235,7 @@ public class BlockTransformer extends Transformer {
 			// Online accounts timestamp is only present if there are also signatures
 			onlineAccountsTimestamp = byteBuffer.getLong();
 
-			final int signaturesByteLength = getOnlineAccountSignaturesLength(onlineAccountsSignaturesCount, onlineAccountsCount, timestamp);
+			final int signaturesByteLength = (onlineAccountsSignaturesCount * Transformer.SIGNATURE_LENGTH) + (onlineAccountsCount * INT_LENGTH);
 			if (signaturesByteLength > BlockChain.getInstance().getMaxBlockSize())
 				throw new TransformationException("Byte data too long for online accounts signatures");
 
@@ -511,16 +511,6 @@ public class BlockTransformer extends Transformer {
 
 		return nonces;
 	}
-	public static int getOnlineAccountSignaturesLength(int onlineAccountsSignaturesCount, int onlineAccountCount, long blockTimestamp) {
-		if (blockTimestamp >= BlockChain.getInstance().getOnlineAccountsMemoryPoWTimestamp()) {
-			// Once mempow is active, we expect the online account signatures to be appended with the nonce values
-			return (onlineAccountsSignaturesCount * Transformer.SIGNATURE_LENGTH) + (onlineAccountCount * INT_LENGTH);
-		}
-		else {
-			// Before mempow, only the online account signatures were included (which will likely be a single signature)
-			return onlineAccountsSignaturesCount * Transformer.SIGNATURE_LENGTH;
-		}
-	}
 
 	public static byte[] extract(byte[] input, int pos, int length) {
 		byte[] output = new byte[length];

src/main/java/org/qortal/transform/transaction/ChatTransactionTransformer.java

@@ -4,6 +4,7 @@ import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.nio.ByteBuffer;
 
+import org.qortal.block.BlockChain;
 import org.qortal.crypto.Crypto;
 import org.qortal.data.transaction.BaseTransactionData;
 import org.qortal.data.transaction.ChatTransactionData;
@@ -22,11 +23,13 @@ public class ChatTransactionTransformer extends TransactionTransformer {
 	private static final int NONCE_LENGTH = INT_LENGTH;
 	private static final int HAS_RECIPIENT_LENGTH = BOOLEAN_LENGTH;
 	private static final int RECIPIENT_LENGTH = ADDRESS_LENGTH;
+	private static final int HAS_CHAT_REFERENCE_LENGTH = BOOLEAN_LENGTH;
+	private static final int CHAT_REFERENCE_LENGTH = SIGNATURE_LENGTH;
 	private static final int DATA_SIZE_LENGTH = INT_LENGTH;
 	private static final int IS_TEXT_LENGTH = BOOLEAN_LENGTH;
 	private static final int IS_ENCRYPTED_LENGTH = BOOLEAN_LENGTH;
 
-	private static final int EXTRAS_LENGTH = NONCE_LENGTH + HAS_RECIPIENT_LENGTH + DATA_SIZE_LENGTH + IS_ENCRYPTED_LENGTH + IS_TEXT_LENGTH;
+	private static final int EXTRAS_LENGTH = NONCE_LENGTH + HAS_RECIPIENT_LENGTH + DATA_SIZE_LENGTH + IS_ENCRYPTED_LENGTH + IS_TEXT_LENGTH + HAS_CHAT_REFERENCE_LENGTH;
 
 	protected static final TransactionLayout layout;
 
@@ -77,13 +80,24 @@ public class ChatTransactionTransformer extends TransactionTransformer {
 
 		long fee = byteBuffer.getLong();
 
+		byte[] chatReference = null;
+
+		if (timestamp >= BlockChain.getInstance().getChatReferenceTimestamp()) {
+			boolean hasChatReference = byteBuffer.get() != 0;
+
+			if (hasChatReference) {
+				chatReference = new byte[CHAT_REFERENCE_LENGTH];
+				byteBuffer.get(chatReference);
+			}
+		}
+
 		byte[] signature = new byte[SIGNATURE_LENGTH];
 		byteBuffer.get(signature);
 
 		BaseTransactionData baseTransactionData = new BaseTransactionData(timestamp, txGroupId, reference, senderPublicKey, fee, signature);
 
 		String sender = Crypto.toAddress(senderPublicKey);
-		return new ChatTransactionData(baseTransactionData, sender, nonce, recipient, data, isText, isEncrypted);
+		return new ChatTransactionData(baseTransactionData, sender, nonce, recipient, chatReference, data, isText, isEncrypted);
 	}
 
 	public static int getDataLength(TransactionData transactionData) {
@@ -94,6 +108,9 @@ public class ChatTransactionTransformer extends TransactionTransformer {
 		if (chatTransactionData.getRecipient() != null)
 			dataLength += RECIPIENT_LENGTH;
 
+		if (chatTransactionData.getChatReference() != null)
+			dataLength += CHAT_REFERENCE_LENGTH;
+
 		return dataLength;
 	}
 
@@ -124,6 +141,16 @@ public class ChatTransactionTransformer extends TransactionTransformer {
 
 			bytes.write(Longs.toByteArray(chatTransactionData.getFee()));
 
+			if (transactionData.getTimestamp() >= BlockChain.getInstance().getChatReferenceTimestamp()) {
+				// Include chat reference if it's not null
+				if (chatTransactionData.getChatReference() != null) {
+					bytes.write((byte) 1);
+					bytes.write(chatTransactionData.getChatReference());
+				} else {
+					bytes.write((byte) 0);
+				}
+			}
+
 			if (chatTransactionData.getSignature() != null)
 				bytes.write(chatTransactionData.getSignature());
 

src/main/resources/blockchain.json

@@ -24,7 +24,7 @@
 	"onlineAccountSignaturesMinLifetime": 43200000,
 	"onlineAccountSignaturesMaxLifetime": 86400000,
 	"onlineAccountsModulusV2Timestamp": 1659801600000,
-	"onlineAccountsMemoryPoWTimestamp": 9999999999999,
+	"selfSponsorshipAlgoV1SnapshotTimestamp": 1670230000000,
 	"rewardsByHeight": [
 		{ "height": 1, "reward": 5.00 },
 		{ "height": 259201, "reward": 4.75 },
@@ -80,8 +80,16 @@
 		"calcChainWeightTimestamp": 1620579600000,
 		"transactionV5Timestamp": 1642176000000,
 		"transactionV6Timestamp": 9999999999999,
-		"disableReferenceTimestamp": 1655222400000
+		"disableReferenceTimestamp": 1655222400000,
+		"increaseOnlineAccountsDifficultyTimestamp": 9999999999999,
+		"onlineAccountMinterLevelValidationHeight": 1092000,
+		"selfSponsorshipAlgoV1Height": 1092400,
+		"feeValidationFixTimestamp": 1671918000000,
+		"chatReferenceTimestamp": 1674316800000
 	},
+	"checkpoints": [
+		{ "height": 1136300, "signature": "3BbwawEF2uN8Ni5ofpJXkukoU8ctAPxYoFB7whq9pKfBnjfZcpfEJT4R95NvBDoTP8WDyWvsUvbfHbcr9qSZuYpSKZjUQTvdFf6eqznHGEwhZApWfvXu6zjGCxYCp65F4jsVYYJjkzbjmkCg5WAwN5voudngA23kMK6PpTNygapCzXt" }
+	],
 	"genesisInfo": {
 		"version": 4,
 		"timestamp": "1593450000000",

src/main/resources/i18n/SysTray_de.properties

@@ -7,6 +7,8 @@ AUTO_UPDATE = Automatisches Update
 
 BLOCK_HEIGHT = height
 
+BLOCKS_REMAINING = blocks remaining
+
 BUILD_VERSION = Build-Version
 
 CHECK_TIME_ACCURACY = Prüfe Zeitgenauigkeit

src/main/resources/i18n/SysTray_en.properties

@@ -7,6 +7,8 @@ AUTO_UPDATE = Auto Update
 
 BLOCK_HEIGHT = height
 
+BLOCKS_REMAINING = blocks remaining
+
 BUILD_VERSION = Build version
 
 CHECK_TIME_ACCURACY = Check time accuracy

src/main/resources/i18n/SysTray_es.properties

@@ -7,6 +7,8 @@ AUTO_UPDATE = Actualización automática
 
 BLOCK_HEIGHT = altura
 
+BLOCKS_REMAINING = blocks remaining
+
 BUILD_VERSION = Versión de compilación
 
 CHECK_TIME_ACCURACY = Comprobar la precisión del tiempo

src/main/resources/i18n/SysTray_fi.properties

@@ -7,6 +7,8 @@ AUTO_UPDATE = Automaattinen päivitys
 
 BLOCK_HEIGHT = korkeus
 
+BLOCKS_REMAINING = blocks remaining
+
 BUILD_VERSION = Versio
 
 CHECK_TIME_ACCURACY = Tarkista ajan tarkkuus

src/main/resources/i18n/SysTray_fr.properties

@@ -7,6 +7,8 @@ AUTO_UPDATE = Mise à jour automatique
 
 BLOCK_HEIGHT = hauteur
 
+BLOCKS_REMAINING = blocks remaining
+
 BUILD_VERSION = Numéro de version
 
 CHECK_TIME_ACCURACY = Vérifier l'heure

src/main/resources/i18n/SysTray_hu.properties

@@ -7,6 +7,8 @@ AUTO_UPDATE = Automatikus Frissítés
 
 BLOCK_HEIGHT = blokkmagasság
 
+BLOCKS_REMAINING = blocks remaining
+
 BUILD_VERSION = Verzió
 
 CHECK_TIME_ACCURACY = Óra pontosságának ellenőrzése

src/main/resources/i18n/SysTray_it.properties

@@ -7,6 +7,8 @@ AUTO_UPDATE = Aggiornamento automatico
 
 BLOCK_HEIGHT = altezza
 
+BLOCKS_REMAINING = blocks remaining
+
 BUILD_VERSION = Versione
 
 CHECK_TIME_ACCURACY = Controlla la precisione dell'ora

src/main/resources/i18n/SysTray_ko.properties

@@ -7,6 +7,8 @@ AUTO_UPDATE = 자동 업데이트
 
 BLOCK_HEIGHT = 높이
 
+BLOCKS_REMAINING = blocks remaining
+
 BUILD_VERSION = 빌드 버전
 
 CHECK_TIME_ACCURACY = 시간 정확도 점검

src/main/resources/i18n/SysTray_nl.properties

@@ -7,6 +7,8 @@ AUTO_UPDATE = Automatische Update
 
 BLOCK_HEIGHT = Block hoogte
 
+BLOCKS_REMAINING = blocks remaining
+
 BUILD_VERSION = Versie nummer
 
 CHECK_TIME_ACCURACY = Controleer accuraatheid van de tijd

src/main/resources/i18n/SysTray_ro.properties

@@ -7,6 +7,8 @@ AUTO_UPDATE = Actualizare automata
 
 BLOCK_HEIGHT = dimensiune
 
+BLOCKS_REMAINING = blocks remaining
+
 BUILD_VERSION = versiunea compilatiei
 
 CHECK_TIME_ACCURACY = verificare exactitate ora

src/main/resources/i18n/SysTray_ru.properties

@@ -7,6 +7,8 @@ AUTO_UPDATE = Автоматическое обновление
 
 BLOCK_HEIGHT = Высота блока
 
+BLOCKS_REMAINING = blocks remaining
+
 BUILD_VERSION = Версия сборки
 
 CHECK_TIME_ACCURACY = Проверка точного времени

src/main/resources/i18n/SysTray_sv.properties

@@ -7,6 +7,8 @@ AUTO_UPDATE = Automatisk uppdatering
 
 BLOCK_HEIGHT = höjd
 
+BLOCKS_REMAINING = blocks remaining
+
 BUILD_VERSION = Byggversion
 
 CHECK_TIME_ACCURACY = Kontrollera tidens noggrannhet

src/main/resources/i18n/SysTray_zh_CN.properties

@@ -7,6 +7,8 @@ AUTO_UPDATE = 自动更新
 
 BLOCK_HEIGHT = 区块高度
 
+BLOCKS_REMAINING = blocks remaining
+
 BUILD_VERSION = 版本
 
 CHECK_TIME_ACCURACY = 检查时间准确性

src/main/resources/i18n/SysTray_zh_TW.properties

@@ -7,6 +7,8 @@ AUTO_UPDATE = 自動更新
 
 BLOCK_HEIGHT = 區塊高度
 
+BLOCKS_REMAINING = blocks remaining
+
 BUILD_VERSION = 版本
 
 CHECK_TIME_ACCURACY = 檢查時間準確性