Merge branch 'trade-bot'

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

@@ -43,6 +43,8 @@ import org.qortal.api.websocket.ActiveChatsWebSocket;
 import org.qortal.api.websocket.AdminStatusWebSocket;
 import org.qortal.api.websocket.BlocksWebSocket;
 import org.qortal.api.websocket.ChatMessagesWebSocket;
+import org.qortal.api.websocket.TradeBotWebSocket;
+import org.qortal.api.websocket.TradeOffersWebSocket;
 import org.qortal.settings.Settings;
 
 public class ApiService {
@@ -196,6 +198,8 @@ public class ApiService {
 			context.addServlet(BlocksWebSocket.class, "/websockets/blocks");
 			context.addServlet(ActiveChatsWebSocket.class, "/websockets/chat/active/*");
 			context.addServlet(ChatMessagesWebSocket.class, "/websockets/chat/messages");
+			context.addServlet(TradeOffersWebSocket.class, "/websockets/crosschain/tradeoffers");
+			context.addServlet(TradeBotWebSocket.class, "/websockets/crosschain/tradebot");
 
 			// Start server
 			this.server.start();

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

@@ -25,6 +25,9 @@ public class CrossChainBitcoinRedeemRequest {
 	@Schema(description = "32-byte secret", example = "6gVbAXCVzJXAWwtAVGAfgAkkXpeXvPUwSciPmCfSfXJG")
 	public byte[] secret;
 
+	@Schema(description = "Bitcoin HASH160(public key) for receiving funds, or omit to derive from private key", example = "u17kBVKkKSp12oUzaxFwNnq1JZf")
+	public byte[] receivingAccountInfo;
+
 	public CrossChainBitcoinRedeemRequest() {
 	}
 

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

@@ -12,20 +12,19 @@ public class CrossChainBuildRequest {
 	@Schema(description = "AT creator's public key", example = "C6wuddsBV3HzRrXUtezE7P5MoRXp5m3mEDokRDGZB6ry")
 	public byte[] creatorPublicKey;
 
-	@Schema(description = "Initial QORT amount paid when trade agreed", example = "0.00100000")
-	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
-	public long initialQortAmount;
-
 	@Schema(description = "Final QORT amount paid out on successful trade", example = "80.40200000")
 	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
-	public long finalQortAmount;
+	public long qortAmount;
 
 	@Schema(description = "QORT amount funding AT, including covering AT execution fees", example = "123.45670000")
 	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
 	public long fundingQortAmount;
 
+	@Schema(description = "HASH160 of creator's Bitcoin public key", example = "2daMveGc5pdjRyFacbxBzMksCbyC")
+	public byte[] bitcoinPublicKeyHash;
+
 	@Schema(description = "HASH160 of secret", example = "43vnftqkjxrhb5kJdkU1ZFQLEnWV")
-	public byte[] secretHash;
+	public byte[] hashOfSecretB;
 
 	@Schema(description = "Bitcoin P2SH BTC balance for release of secret", example = "0.00864200")
 	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)

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

@@ -8,10 +8,10 @@ import io.swagger.v3.oas.annotations.media.Schema;
 @XmlAccessorType(XmlAccessType.FIELD)
 public class CrossChainCancelRequest {
 
-	@Schema(description = "AT creator's public key", example = "C6wuddsBV3HzRrXUtezE7P5MoRXp5m3mEDokRDGZB6ry")
+	@Schema(description = "AT creator's public key", example = "K6wuddsBV3HzRrXFFezE7P5MoRXp5m3mEDokRDGZB6ry")
 	public byte[] creatorPublicKey;
 
-	@Schema(description = "Qortal AT address")
+	@Schema(description = "Qortal trade AT address")
 	public String atAddress;
 
 	public CrossChainCancelRequest() {

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

@@ -0,0 +1,86 @@
+package org.qortal.api.model;
+
+import javax.xml.bind.annotation.XmlAccessType;
+import javax.xml.bind.annotation.XmlAccessorType;
+import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
+
+import org.qortal.crosschain.BTCACCT;
+import org.qortal.data.crosschain.CrossChainTradeData;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+
+// All properties to be converted to JSON via JAXB
+@XmlAccessorType(XmlAccessType.FIELD)
+public class CrossChainOfferSummary {
+
+	// Properties
+
+	@Schema(description = "AT's Qortal address")
+	public String qortalAtAddress;
+
+	@Schema(description = "AT creator's Qortal address")
+	public String qortalCreator;
+
+	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
+	private long qortAmount;
+
+	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
+	private long btcAmount;
+
+	@Schema(description = "Suggested trade timeout (minutes)", example = "10080")
+	private int tradeTimeout;
+
+	private BTCACCT.Mode mode;
+
+	private long timestamp;
+
+	private String partnerQortalReceivingAddress;
+
+	protected CrossChainOfferSummary() {
+		/* For JAXB */
+	}
+
+	public CrossChainOfferSummary(CrossChainTradeData crossChainTradeData, long timestamp) {
+		this.qortalAtAddress = crossChainTradeData.qortalAtAddress;
+		this.qortalCreator = crossChainTradeData.qortalCreator;
+		this.qortAmount = crossChainTradeData.qortAmount;
+		this.btcAmount = crossChainTradeData.expectedBitcoin;
+		this.tradeTimeout = crossChainTradeData.tradeTimeout;
+		this.mode = crossChainTradeData.mode;
+		this.timestamp = timestamp;
+		this.partnerQortalReceivingAddress = crossChainTradeData.qortalPartnerReceivingAddress;
+	}
+
+	public String getQortalAtAddress() {
+		return this.qortalAtAddress;
+	}
+
+	public String getQortalCreator() {
+		return this.qortalCreator;
+	}
+
+	public long getQortAmount() {
+		return this.qortAmount;
+	}
+
+	public long getBtcAmount() {
+		return this.btcAmount;
+	}
+
+	public int getTradeTimeout() {
+		return this.tradeTimeout;
+	}
+
+	public BTCACCT.Mode getMode() {
+		return this.mode;
+	}
+
+	public long getTimestamp() {
+		return this.timestamp;
+	}
+
+	public String getPartnerQortalReceivingAddress() {
+		return this.partnerQortalReceivingAddress;
+	}
+
+}

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

@@ -8,14 +8,20 @@ import io.swagger.v3.oas.annotations.media.Schema;
 @XmlAccessorType(XmlAccessType.FIELD)
 public class CrossChainSecretRequest {
 
-	@Schema(description = "Public key to match AT's 'recipient'", example = "C6wuddsBV3HzRrXUtezE7P5MoRXp5m3mEDokRDGZB6ry")
-	public byte[] recipientPublicKey;
+	@Schema(description = "Public key to match AT's trade 'partner'", example = "C6wuddsBV3HzRrXUtezE7P5MoRXp5m3mEDokRDGZB6ry")
+	public byte[] partnerPublicKey;
 
 	@Schema(description = "Qortal AT address")
 	public String atAddress;
 
-	@Schema(description = "32-byte secret", example = "6gVbAXCVzJXAWwtAVGAfgAkkXpeXvPUwSciPmCfSfXJG")
-	public byte[] secret;
+	@Schema(description = "secret-A (32 bytes)", example = "FHMzten4he9jZ4HGb4297Utj6F5g2w7serjq2EnAg2s1")
+	public byte[] secretA;
+
+	@Schema(description = "secret-B (32 bytes)", example = "EN2Bgx3BcEMtxFCewmCVSMkfZjVKYhx3KEXC5A21KBGx")
+	public byte[] secretB;
+
+	@Schema(description = "Qortal address for receiving QORT from AT")
+	public String receivingAddress;
 
 	public CrossChainSecretRequest() {
 	}

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

@@ -8,14 +8,14 @@ import io.swagger.v3.oas.annotations.media.Schema;
 @XmlAccessorType(XmlAccessType.FIELD)
 public class CrossChainTradeRequest {
 
-	@Schema(description = "AT creator's public key", example = "C6wuddsBV3HzRrXUtezE7P5MoRXp5m3mEDokRDGZB6ry")
-	public byte[] creatorPublicKey;
+	@Schema(description = "AT creator's 'trade' public key", example = "C6wuddsBV3HzRrXUtezE7P5MoRXp5m3mEDokRDGZB6ry")
+	public byte[] tradePublicKey;
 
 	@Schema(description = "Qortal AT address")
 	public String atAddress;
 
-	@Schema(description = "Qortal address for trade partner/recipient")
-	public String recipient;
+	@Schema(description = "Signature of trading partner's 'offer' MESSAGE transaction")
+	public byte[] messageTransactionSignature;
 
 	public CrossChainTradeRequest() {
 	}

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

@@ -0,0 +1,43 @@
+package org.qortal.api.model;
+
+import javax.xml.bind.annotation.XmlAccessType;
+import javax.xml.bind.annotation.XmlAccessorType;
+import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
+
+import org.qortal.data.crosschain.CrossChainTradeData;
+
+// All properties to be converted to JSON via JAXB
+@XmlAccessorType(XmlAccessType.FIELD)
+public class CrossChainTradeSummary {
+
+	private long tradeTimestamp;
+
+	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
+	private long qortAmount;
+
+	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
+	private long btcAmount;
+
+	protected CrossChainTradeSummary() {
+		/* For JAXB */
+	}
+
+	public CrossChainTradeSummary(CrossChainTradeData crossChainTradeData, long timestamp) {
+		this.tradeTimestamp = timestamp;
+		this.qortAmount = crossChainTradeData.qortAmount;
+		this.btcAmount = crossChainTradeData.expectedBitcoin;
+	}
+
+	public long getTradeTimestamp() {
+		return this.tradeTimestamp;
+	}
+
+	public long getQortAmount() {
+		return this.qortAmount;
+	}
+
+	public long getBtcAmount() {
+		return this.btcAmount;
+	}
+
+}

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

@@ -0,0 +1,36 @@
+package org.qortal.api.model;
+
+import javax.xml.bind.annotation.XmlAccessType;
+import javax.xml.bind.annotation.XmlAccessorType;
+import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+
+@XmlAccessorType(XmlAccessType.FIELD)
+public class TradeBotCreateRequest {
+
+	@Schema(description = "Trade creator's public key", example = "2zR1WFsbM7akHghqSCYKBPk6LDP8aKiQSRS1FrwoLvoB")
+	public byte[] creatorPublicKey;
+
+	@Schema(description = "QORT amount paid out on successful trade", example = "80.40200000")
+	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
+	public long qortAmount;
+
+	@Schema(description = "QORT amount funding AT, including covering AT execution fees", example = "81")
+	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
+	public long fundingQortAmount;
+
+	@Schema(description = "Bitcoin amount wanted in return", example = "0.00864200")
+	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
+	public long bitcoinAmount;
+
+	@Schema(description = "Suggested trade timeout (minutes)", example = "10080")
+	public int tradeTimeout;
+
+	@Schema(description = "Bitcoin address for receiving", example = "1NCTG9oLk41bU6pcehLNo9DVJup77EHAVx")
+	public String receivingAddress;
+
+	public TradeBotCreateRequest() {
+	}
+
+}

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

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

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

@@ -12,7 +12,6 @@ import org.eclipse.jetty.websocket.api.annotations.OnWebSocketConnect;
 import org.eclipse.jetty.websocket.api.annotations.OnWebSocketError;
 import org.eclipse.jetty.websocket.api.annotations.OnWebSocketMessage;
 import org.eclipse.jetty.websocket.api.annotations.WebSocket;
-import org.eclipse.jetty.websocket.servlet.WebSocketServlet;
 import org.eclipse.jetty.websocket.servlet.WebSocketServletFactory;
 import org.qortal.controller.ChatNotifier;
 import org.qortal.crypto.Crypto;
@@ -24,7 +23,7 @@ import org.qortal.repository.RepositoryManager;
 
 @WebSocket
 @SuppressWarnings("serial")
-public class ActiveChatsWebSocket extends WebSocketServlet implements ApiWebSocket {
+public class ActiveChatsWebSocket extends ApiWebSocket {
 
 	@Override
 	public void configure(WebSocketServletFactory factory) {
@@ -33,7 +32,7 @@ public class ActiveChatsWebSocket extends WebSocketServlet implements ApiWebSock
 
 	@OnWebSocketConnect
 	public void onWebSocketConnect(Session session) {
-		Map<String, String> pathParams = this.getPathParams(session, "/{address}");
+		Map<String, String> pathParams = getPathParams(session, "/{address}");
 
 		String address = pathParams.get("address");
 		if (address == null || !Crypto.isValidAddress(address)) {
@@ -76,7 +75,7 @@ public class ActiveChatsWebSocket extends WebSocketServlet implements ApiWebSock
 
 			StringWriter stringWriter = new StringWriter();
 
-			this.marshall(stringWriter, activeChats);
+			marshall(stringWriter, activeChats);
 
 			// Only output if something has changed
 			String output = stringWriter.toString();

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

@@ -11,7 +11,6 @@ import org.eclipse.jetty.websocket.api.annotations.OnWebSocketConnect;
 import org.eclipse.jetty.websocket.api.annotations.OnWebSocketError;
 import org.eclipse.jetty.websocket.api.annotations.OnWebSocketMessage;
 import org.eclipse.jetty.websocket.api.annotations.WebSocket;
-import org.eclipse.jetty.websocket.servlet.WebSocketServlet;
 import org.eclipse.jetty.websocket.servlet.WebSocketServletFactory;
 import org.qortal.api.model.NodeStatus;
 import org.qortal.controller.StatusNotifier;
@@ -21,7 +20,7 @@ import org.qortal.repository.RepositoryManager;
 
 @WebSocket
 @SuppressWarnings("serial")
-public class AdminStatusWebSocket extends WebSocketServlet implements ApiWebSocket {
+public class AdminStatusWebSocket extends ApiWebSocket {
 
 	@Override
 	public void configure(WebSocketServletFactory factory) {
@@ -57,7 +56,7 @@ public class AdminStatusWebSocket extends WebSocketServlet implements ApiWebSock
 
 			StringWriter stringWriter = new StringWriter();
 
-			this.marshall(stringWriter, nodeStatus);
+			marshall(stringWriter, nodeStatus);
 
 			// Only output if something has changed
 			String output = stringWriter.toString();

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

@@ -3,7 +3,10 @@ package org.qortal.api.websocket;
 import java.io.IOException;
 import java.io.StringWriter;
 import java.io.Writer;
+import java.util.ArrayList;
 import java.util.Collection;
+import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 import javax.xml.bind.JAXBContext;
@@ -13,24 +16,28 @@ import javax.xml.bind.Marshaller;
 import org.eclipse.jetty.http.pathmap.UriTemplatePathSpec;
 import org.eclipse.jetty.websocket.api.Session;
 import org.eclipse.jetty.websocket.servlet.ServletUpgradeRequest;
+import org.eclipse.jetty.websocket.servlet.WebSocketServlet;
 import org.eclipse.persistence.jaxb.JAXBContextFactory;
 import org.eclipse.persistence.jaxb.MarshallerProperties;
 import org.qortal.api.ApiError;
 import org.qortal.api.ApiErrorRoot;
 
-interface ApiWebSocket {
+@SuppressWarnings("serial")
+abstract class ApiWebSocket extends WebSocketServlet {
 
-	default String getPathInfo(Session session) {
+	private static final Map<Class<? extends ApiWebSocket>, List<Session>> SESSIONS_BY_CLASS = new HashMap<>();
+
+	protected static String getPathInfo(Session session) {
 		ServletUpgradeRequest upgradeRequest = (ServletUpgradeRequest) session.getUpgradeRequest();
 		return upgradeRequest.getHttpServletRequest().getPathInfo();
 	}
 
-	default Map<String, String> getPathParams(Session session, String pathSpec) {
+	protected static Map<String, String> getPathParams(Session session, String pathSpec) {
 		UriTemplatePathSpec uriTemplatePathSpec = new UriTemplatePathSpec(pathSpec);
-		return uriTemplatePathSpec.getPathParams(this.getPathInfo(session));
+		return uriTemplatePathSpec.getPathParams(getPathInfo(session));
 	}
 
-	default void sendError(Session session, ApiError apiError) {
+	protected static void sendError(Session session, ApiError apiError) {
 		ApiErrorRoot apiErrorRoot = new ApiErrorRoot();
 		apiErrorRoot.setApiError(apiError);
 
@@ -43,7 +50,7 @@ interface ApiWebSocket {
 		}
 	}
 
-	default void marshall(Writer writer, Object object) throws IOException {
+	protected static void marshall(Writer writer, Object object) throws IOException {
 		Marshaller marshaller = createMarshaller(object.getClass());
 
 		try {
@@ -53,7 +60,7 @@ interface ApiWebSocket {
 		}
 	}
 
-	default void marshall(Writer writer, Collection<?> collection) throws IOException {
+	protected static void marshall(Writer writer, Collection<?> collection) throws IOException {
 		// If collection is empty then we're returning "[]" anyway
 		if (collection.isEmpty()) {
 			writer.append("[]");
@@ -92,4 +99,22 @@ interface ApiWebSocket {
 		}
 	}
 
+	public void onWebSocketConnect(Session session) {
+		synchronized (SESSIONS_BY_CLASS) {
+			SESSIONS_BY_CLASS.computeIfAbsent(this.getClass(), clazz -> new ArrayList<>()).add(session);
+		}
+	}
+
+	public void onWebSocketClose(Session session, int statusCode, String reason) {
+		synchronized (SESSIONS_BY_CLASS) {
+			SESSIONS_BY_CLASS.get(this.getClass()).remove(session);
+		}
+	}
+
+	protected List<Session> getSessions() {
+		synchronized (SESSIONS_BY_CLASS) {
+			return new ArrayList<>(SESSIONS_BY_CLASS.get(this.getClass()));
+		}
+	}
+
 }

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

@@ -11,7 +11,6 @@ import org.eclipse.jetty.websocket.api.annotations.OnWebSocketConnect;
 import org.eclipse.jetty.websocket.api.annotations.OnWebSocketError;
 import org.eclipse.jetty.websocket.api.annotations.OnWebSocketMessage;
 import org.eclipse.jetty.websocket.api.annotations.WebSocket;
-import org.eclipse.jetty.websocket.servlet.WebSocketServlet;
 import org.eclipse.jetty.websocket.servlet.WebSocketServletFactory;
 import org.qortal.api.ApiError;
 import org.qortal.api.model.BlockInfo;
@@ -23,7 +22,7 @@ import org.qortal.utils.Base58;
 
 @WebSocket
 @SuppressWarnings("serial")
-public class BlocksWebSocket extends WebSocketServlet implements ApiWebSocket {
+public class BlocksWebSocket extends ApiWebSocket {
 
 	@Override
 	public void configure(WebSocketServletFactory factory) {
@@ -111,7 +110,7 @@ public class BlocksWebSocket extends WebSocketServlet implements ApiWebSocket {
 		StringWriter stringWriter = new StringWriter();
 
 		try {
-			this.marshall(stringWriter, blockInfo);
+			marshall(stringWriter, blockInfo);
 
 			session.getRemote().sendStringByFuture(stringWriter.toString());
 		} catch (IOException | WebSocketException e) {

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

@@ -14,7 +14,6 @@ import org.eclipse.jetty.websocket.api.annotations.OnWebSocketConnect;
 import org.eclipse.jetty.websocket.api.annotations.OnWebSocketError;
 import org.eclipse.jetty.websocket.api.annotations.OnWebSocketMessage;
 import org.eclipse.jetty.websocket.api.annotations.WebSocket;
-import org.eclipse.jetty.websocket.servlet.WebSocketServlet;
 import org.eclipse.jetty.websocket.servlet.WebSocketServletFactory;
 import org.qortal.controller.ChatNotifier;
 import org.qortal.data.chat.ChatMessage;
@@ -25,7 +24,7 @@ import org.qortal.repository.RepositoryManager;
 
 @WebSocket
 @SuppressWarnings("serial")
-public class ChatMessagesWebSocket extends WebSocketServlet implements ApiWebSocket {
+public class ChatMessagesWebSocket extends ApiWebSocket {
 
 	@Override
 	public void configure(WebSocketServletFactory factory) {
@@ -129,7 +128,7 @@ public class ChatMessagesWebSocket extends WebSocketServlet implements ApiWebSoc
 		StringWriter stringWriter = new StringWriter();
 
 		try {
-			this.marshall(stringWriter, chatMessages);
+			marshall(stringWriter, chatMessages);
 
 			session.getRemote().sendStringByFuture(stringWriter.toString());
 		} catch (IOException | WebSocketException e) {

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

@@ -0,0 +1,119 @@
+package org.qortal.api.websocket;
+
+import java.io.IOException;
+import java.io.StringWriter;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+import org.eclipse.jetty.websocket.api.Session;
+import org.eclipse.jetty.websocket.api.annotations.OnWebSocketClose;
+import org.eclipse.jetty.websocket.api.annotations.OnWebSocketConnect;
+import org.eclipse.jetty.websocket.api.annotations.OnWebSocketMessage;
+import org.eclipse.jetty.websocket.api.annotations.WebSocket;
+import org.eclipse.jetty.websocket.servlet.WebSocketServletFactory;
+import org.qortal.controller.TradeBot;
+import org.qortal.data.crosschain.TradeBotData;
+import org.qortal.event.Event;
+import org.qortal.event.EventBus;
+import org.qortal.event.Listener;
+import org.qortal.repository.DataException;
+import org.qortal.repository.Repository;
+import org.qortal.repository.RepositoryManager;
+import org.qortal.utils.Base58;
+
+@WebSocket
+@SuppressWarnings("serial")
+public class TradeBotWebSocket extends ApiWebSocket implements Listener {
+
+	/** Cache of trade-bot entry states, keyed by trade-bot entry's "trade private key" (base58) */
+	private static final Map<String, TradeBotData.State> PREVIOUS_STATES = new HashMap<>();
+
+	@Override
+	public void configure(WebSocketServletFactory factory) {
+		factory.register(TradeBotWebSocket.class);
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			List<TradeBotData> tradeBotEntries = repository.getCrossChainRepository().getAllTradeBotData();
+			if (tradeBotEntries == null)
+				// How do we properly fail here?
+				return;
+
+			PREVIOUS_STATES.putAll(tradeBotEntries.stream().collect(Collectors.toMap(entry -> Base58.encode(entry.getTradePrivateKey()), TradeBotData::getState)));
+		} catch (DataException e) {
+			// No output this time
+		}
+
+		EventBus.INSTANCE.addListener(this::listen);
+	}
+
+	@Override
+	public void listen(Event event) {
+		if (!(event instanceof TradeBot.StateChangeEvent))
+			return;
+
+		TradeBotData tradeBotData = ((TradeBot.StateChangeEvent) event).getTradeBotData();
+		String tradePrivateKey58 = Base58.encode(tradeBotData.getTradePrivateKey());
+
+		synchronized (PREVIOUS_STATES) {
+			if (PREVIOUS_STATES.get(tradePrivateKey58) == tradeBotData.getState())
+				// Not changed
+				return;
+
+			PREVIOUS_STATES.put(tradePrivateKey58, tradeBotData.getState());
+		}
+
+		List<TradeBotData> tradeBotEntries = Collections.singletonList(tradeBotData);
+		for (Session session : getSessions())
+			sendEntries(session, tradeBotEntries);
+	}
+
+	@OnWebSocketConnect
+	public void onWebSocketConnect(Session session) {
+		// Send all known trade-bot entries
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			List<TradeBotData> tradeBotEntries = repository.getCrossChainRepository().getAllTradeBotData();
+			if (tradeBotEntries == null) {
+				session.close(4001, "repository issue fetching trade-bot entries");
+				return;
+			}
+
+			if (!sendEntries(session, tradeBotEntries)) {
+				session.close(4002, "websocket issue");
+				return;
+			}
+		} catch (DataException e) {
+			// No output this time
+		}
+
+		super.onWebSocketConnect(session);
+	}
+
+	@OnWebSocketClose
+	public void onWebSocketClose(Session session, int statusCode, String reason) {
+		super.onWebSocketClose(session, statusCode, reason);
+	}
+
+	@OnWebSocketMessage
+	public void onWebSocketMessage(Session session, String message) {
+		/* ignored */
+	}
+
+	private boolean sendEntries(Session session, List<TradeBotData> tradeBotEntries) {
+		try {
+			StringWriter stringWriter = new StringWriter();
+			marshall(stringWriter, tradeBotEntries);
+
+			String output = stringWriter.toString();
+			session.getRemote().sendStringByFuture(output);
+		} catch (IOException e) {
+			// No output this time?
+			return false;
+		}
+
+		return true;
+	}
+
+}

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

@@ -0,0 +1,212 @@
+package org.qortal.api.websocket;
+
+import java.io.IOException;
+import java.io.StringWriter;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+import org.eclipse.jetty.websocket.api.Session;
+import org.eclipse.jetty.websocket.api.annotations.OnWebSocketClose;
+import org.eclipse.jetty.websocket.api.annotations.OnWebSocketConnect;
+import org.eclipse.jetty.websocket.api.annotations.OnWebSocketMessage;
+import org.eclipse.jetty.websocket.api.annotations.WebSocket;
+import org.eclipse.jetty.websocket.servlet.WebSocketServletFactory;
+import org.qortal.api.model.CrossChainOfferSummary;
+import org.qortal.controller.BlockNotifier;
+import org.qortal.crosschain.BTCACCT;
+import org.qortal.data.at.ATStateData;
+import org.qortal.data.block.BlockData;
+import org.qortal.data.crosschain.CrossChainTradeData;
+import org.qortal.repository.DataException;
+import org.qortal.repository.Repository;
+import org.qortal.repository.RepositoryManager;
+import org.qortal.utils.NTP;
+
+@WebSocket
+@SuppressWarnings("serial")
+public class TradeOffersWebSocket extends ApiWebSocket {
+
+	@Override
+	public void configure(WebSocketServletFactory factory) {
+		factory.register(TradeOffersWebSocket.class);
+	}
+
+	@OnWebSocketConnect
+	public void onWebSocketConnect(Session session) {
+		Map<String, List<String>> queryParams = session.getUpgradeRequest().getParameterMap();
+
+		final boolean includeHistoric = queryParams.get("includeHistoric") != null;
+		final Map<String, BTCACCT.Mode> previousAtModes = new HashMap<>();
+		List<CrossChainOfferSummary> crossChainOfferSummaries;
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			List<ATStateData> initialAtStates;
+
+			// We want ALL OFFERING trades
+			Boolean isFinished = Boolean.FALSE;
+			Integer dataByteOffset = BTCACCT.MODE_BYTE_OFFSET;
+			Long expectedValue = (long) BTCACCT.Mode.OFFERING.value;
+			Integer minimumFinalHeight = null;
+
+			initialAtStates = repository.getATRepository().getMatchingFinalATStates(BTCACCT.CODE_BYTES_HASH,
+					isFinished, dataByteOffset, expectedValue, minimumFinalHeight,
+					null, null, null);
+
+			if (initialAtStates == null) {
+				session.close(4001, "repository issue fetching OFFERING trades");
+				return;
+			}
+
+			// Save initial AT modes
+			previousAtModes.putAll(initialAtStates.stream().collect(Collectors.toMap(ATStateData::getATAddress, atState -> BTCACCT.Mode.OFFERING)));
+
+			// Convert to offer summaries
+			crossChainOfferSummaries = produceSummaries(repository, initialAtStates, null);
+
+			if (includeHistoric) {
+				// We also want REDEEMED/REFUNDED/CANCELLED trades over the last 24 hours
+				long timestamp = NTP.getTime() - 24 * 60 * 60 * 1000L;
+				minimumFinalHeight = repository.getBlockRepository().getHeightFromTimestamp(timestamp);
+
+				if (minimumFinalHeight != 0) {
+					isFinished = Boolean.TRUE;
+					dataByteOffset = null;
+					expectedValue = null;
+					++minimumFinalHeight; // because height is just *before* timestamp
+
+					List<ATStateData> historicAtStates = repository.getATRepository().getMatchingFinalATStates(BTCACCT.CODE_BYTES_HASH,
+							isFinished, dataByteOffset, expectedValue, minimumFinalHeight,
+							null, null, null);
+
+					if (historicAtStates == null) {
+						session.close(4002, "repository issue fetching historic trades");
+						return;
+					}
+
+					for (ATStateData historicAtState : historicAtStates) {
+						CrossChainOfferSummary historicOfferSummary = produceSummary(repository, historicAtState, null);
+
+						switch (historicOfferSummary.getMode()) {
+							case REDEEMED:
+							case REFUNDED:
+							case CANCELLED:
+								break;
+
+							default:
+								continue;
+						}
+
+						// Add summary to initial burst
+						crossChainOfferSummaries.add(historicOfferSummary);
+
+						// Save initial AT mode
+						previousAtModes.put(historicAtState.getATAddress(), historicOfferSummary.getMode());
+					}
+				}
+			}
+
+		} catch (DataException e) {
+			session.close(4003, "generic repository issue");
+			return;
+		}
+
+		if (!sendOfferSummaries(session, crossChainOfferSummaries)) {
+			session.close(4004, "websocket issue");
+			return;
+		}
+
+		BlockNotifier.Listener listener = blockData -> onNotify(session, blockData, previousAtModes);
+		BlockNotifier.getInstance().register(session, listener);
+	}
+
+	@OnWebSocketClose
+	public void onWebSocketClose(Session session, int statusCode, String reason) {
+		BlockNotifier.getInstance().deregister(session);
+	}
+
+	@OnWebSocketMessage
+	public void onWebSocketMessage(Session session, String message) {
+		/* ignored */
+	}
+
+	private void onNotify(Session session, BlockData blockData, final Map<String, BTCACCT.Mode> previousAtModes) {
+		List<CrossChainOfferSummary> crossChainOfferSummaries = null;
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			// Find any new trade ATs since this block
+			final Boolean isFinished = null;
+			final Integer dataByteOffset = null;
+			final Long expectedValue = null;
+			final Integer minimumFinalHeight = blockData.getHeight();
+
+			List<ATStateData> atStates = repository.getATRepository().getMatchingFinalATStates(BTCACCT.CODE_BYTES_HASH,
+					isFinished, dataByteOffset, expectedValue, minimumFinalHeight,
+					null, null, null);
+
+			if (atStates == null)
+				return;
+
+			crossChainOfferSummaries = produceSummaries(repository, atStates, blockData.getTimestamp());
+		} catch (DataException e) {
+			// No output this time
+		}
+
+		synchronized (previousAtModes) { //NOSONAR squid:S2445 suppressed because previousAtModes is final and curried in lambda
+			// Remove any entries unchanged from last time
+			crossChainOfferSummaries.removeIf(offerSummary -> previousAtModes.get(offerSummary.getQortalAtAddress()) == offerSummary.getMode());
+
+			// Don't send anything if no results
+			if (crossChainOfferSummaries.isEmpty())
+				return;
+
+			final boolean wasSent = sendOfferSummaries(session, crossChainOfferSummaries);
+
+			if (!wasSent)
+				return;
+
+			previousAtModes.putAll(crossChainOfferSummaries.stream().collect(Collectors.toMap(CrossChainOfferSummary::getQortalAtAddress, CrossChainOfferSummary::getMode)));
+		}
+	}
+
+	private boolean sendOfferSummaries(Session session, List<CrossChainOfferSummary> crossChainOfferSummaries) {
+		try {
+			StringWriter stringWriter = new StringWriter();
+			marshall(stringWriter, crossChainOfferSummaries);
+
+			String output = stringWriter.toString();
+			session.getRemote().sendStringByFuture(output);
+		} catch (IOException e) {
+			// No output this time?
+			return false;
+		}
+
+		return true;
+	}
+
+	private static CrossChainOfferSummary produceSummary(Repository repository, ATStateData atState, Long timestamp) throws DataException {
+		CrossChainTradeData crossChainTradeData = BTCACCT.populateTradeData(repository, atState);
+
+		long atStateTimestamp;
+
+		if (crossChainTradeData.mode == BTCACCT.Mode.OFFERING)
+			// We want when trade was created, not when it was last updated
+			atStateTimestamp = atState.getCreation();
+		else
+			atStateTimestamp = timestamp != null ? timestamp : repository.getBlockRepository().getTimestampFromHeight(atState.getHeight());
+
+		return new CrossChainOfferSummary(crossChainTradeData, atStateTimestamp);
+	}
+
+	private static List<CrossChainOfferSummary> produceSummaries(Repository repository, List<ATStateData> atStates, Long timestamp) throws DataException {
+		List<CrossChainOfferSummary> offerSummaries = new ArrayList<>();
+
+		for (ATStateData atState : atStates)
+			offerSummaries.add(produceSummary(repository, atState, timestamp));
+
+		return offerSummaries;
+	}
+
+}

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

@@ -17,7 +17,6 @@ import org.qortal.account.Account;
 import org.qortal.account.NullAccount;
 import org.qortal.account.PublicKeyAccount;
 import org.qortal.asset.Asset;
-import org.qortal.block.Block;
 import org.qortal.block.BlockChain;
 import org.qortal.block.BlockChain.CiyamAtSettings;
 import org.qortal.crypto.Crypto;
@@ -30,13 +29,13 @@ import org.qortal.data.transaction.MessageTransactionData;
 import org.qortal.data.transaction.PaymentTransactionData;
 import org.qortal.data.transaction.TransactionData;
 import org.qortal.group.Group;
-import org.qortal.repository.BlockRepository;
+import org.qortal.repository.ATRepository;
 import org.qortal.repository.DataException;
 import org.qortal.repository.Repository;
 import org.qortal.transaction.AtTransaction;
-import org.qortal.transaction.Transaction;
 import org.qortal.transaction.Transaction.TransactionType;
 import org.qortal.utils.Base58;
+import org.qortal.utils.BitTwiddling;
 
 import com.google.common.primitives.Bytes;
 
@@ -133,9 +132,9 @@ public class QortalATAPI extends API {
 
 			byte[] signature = blockSummaries.get(0).getSignature();
 			// Save some of minter's signature and transactions signature, so middle 24 bytes of the full 128 byte signature.
-			this.setA2(state, fromBytes(signature, 52));
-			this.setA3(state, fromBytes(signature, 60));
-			this.setA4(state, fromBytes(signature, 68));
+			this.setA2(state, BitTwiddling.longFromBEBytes(signature, 52));
+			this.setA3(state, BitTwiddling.longFromBEBytes(signature, 60));
+			this.setA4(state, BitTwiddling.longFromBEBytes(signature, 68));
 		} catch (DataException e) {
 			throw new RuntimeException("AT API unable to fetch previous block?", e);
 		}
@@ -149,59 +148,27 @@ public class QortalATAPI extends API {
 		int height = timestamp.blockHeight;
 		int sequence = timestamp.transactionSequence + 1;
 
-		BlockRepository blockRepository = this.getRepository().getBlockRepository();
-
+		ATRepository.NextTransactionInfo nextTransactionInfo;
 		try {
-			int currentHeight = blockRepository.getBlockchainHeight();
-			List<Transaction> blockTransactions = null;
-
-			while (height <= currentHeight) {
-				if (blockTransactions == null) {
-					BlockData blockData = blockRepository.fromHeight(height);
-
-					if (blockData == null)
-						throw new DataException("Unable to fetch block " + height + " from repository?");
-
-					Block block = new Block(this.getRepository(), blockData);
-
-					blockTransactions = block.getTransactions();
-				}
-
-				// No more transactions in this block? Try next block
-				if (sequence >= blockTransactions.size()) {
-					++height;
-					sequence = 0;
-					blockTransactions = null;
-					continue;
-				}
-
-				Transaction transaction = blockTransactions.get(sequence);
-
-				// Transaction needs to be sent to specified recipient
-				List<String> recipientAddresses = transaction.getRecipientAddresses();
-				if (recipientAddresses.contains(atAddress)) {
-					// Found a transaction
-
-					this.setA1(state, new Timestamp(height, timestamp.blockchainId, sequence).longValue());
-
-					// Copy transaction's partial signature into the other three A fields for future verification that it's the same transaction
-					byte[] signature = transaction.getTransactionData().getSignature();
-					this.setA2(state, fromBytes(signature, 8));
-					this.setA3(state, fromBytes(signature, 16));
-					this.setA4(state, fromBytes(signature, 24));
-
-					return;
-				}
-
-				// Transaction wasn't for us - keep going
-				++sequence;
-			}
-
-			// No more transactions - zero A and exit
-			this.zeroA(state);
+			nextTransactionInfo = this.getRepository().getATRepository().findNextTransaction(atAddress, height, sequence);
 		} catch (DataException e) {
 			throw new RuntimeException("AT API unable to fetch next transaction?", e);
 		}
+
+		if (nextTransactionInfo == null) {
+			// No more transactions for AT at this time - zero A and exit
+			this.zeroA(state);
+			return;
+		}
+
+		// Found a transaction
+
+		this.setA1(state, new Timestamp(nextTransactionInfo.height, timestamp.blockchainId, nextTransactionInfo.sequence).longValue());
+
+		// Copy transaction's partial signature into the other three A fields for future verification that it's the same transaction
+		this.setA2(state, BitTwiddling.longFromBEBytes(nextTransactionInfo.signature, 8));
+		this.setA3(state, BitTwiddling.longFromBEBytes(nextTransactionInfo.signature, 16));
+		this.setA4(state, BitTwiddling.longFromBEBytes(nextTransactionInfo.signature, 24));
 	}
 
 	@Override
@@ -282,7 +249,7 @@ public class QortalATAPI extends API {
 
 				byte[] hash = Crypto.digest(input);
 
-				return fromBytes(hash, 0);
+				return BitTwiddling.longFromBEBytes(hash, 0);
 			} catch (DataException e) {
 				throw new RuntimeException("AT API unable to fetch latest block from repository?", e);
 			}
@@ -296,30 +263,14 @@ public class QortalATAPI extends API {
 
 		TransactionData transactionData = this.getTransactionFromA(state);
 
-		byte[] messageData = null;
-
-		switch (transactionData.getType()) {
-			case MESSAGE:
-				messageData = ((MessageTransactionData) transactionData).getData();
-				break;
-
-			case AT:
-				messageData = ((ATTransactionData) transactionData).getMessage();
-				break;
-
-			default:
-				return;
-		}
-
-		// Check data length is appropriate, i.e. not larger than B
-		if (messageData.length > 4 * 8)
-			return;
+		byte[] messageData = this.getMessageFromTransaction(transactionData);
 
 		// Pad messageData to fit B
-		byte[] paddedMessageData = Bytes.ensureCapacity(messageData, 4 * 8, 0);
+		if (messageData.length < 4 * 8)
+			messageData = Bytes.ensureCapacity(messageData, 4 * 8, 0);
 
 		// Endian must be correct here so that (for example) a SHA256 message can be compared to one generated locally
-		this.setB(state, paddedMessageData);
+		this.setB(state, messageData);
 	}
 
 	@Override
@@ -457,12 +408,6 @@ public class QortalATAPI extends API {
 
 	// Utility methods
 
-	/** Convert part of little-endian byte[] to long */
-	/* package */ static long fromBytes(byte[] bytes, int start) {
-		return (bytes[start] & 0xffL) | (bytes[start + 1] & 0xffL) << 8 | (bytes[start + 2] & 0xffL) << 16 | (bytes[start + 3] & 0xffL) << 24
-				| (bytes[start + 4] & 0xffL) << 32 | (bytes[start + 5] & 0xffL) << 40 | (bytes[start + 6] & 0xffL) << 48 | (bytes[start + 7] & 0xffL) << 56;
-	}
-
 	/** Returns partial transaction signature, used to verify we're operating on the same transaction and not naively using block height & sequence. */
 	public static byte[] partialSignature(byte[] fullSignature) {
 		return Arrays.copyOfRange(fullSignature, 8, 32);
@@ -473,7 +418,7 @@ public class QortalATAPI extends API {
 		// Compare end of transaction's signature against A2 thru A4
 		byte[] sig = transactionData.getSignature();
 
-		if (this.getA2(state) != fromBytes(sig, 8) || this.getA3(state) != fromBytes(sig, 16) || this.getA4(state) != fromBytes(sig, 24))
+		if (this.getA2(state) != BitTwiddling.longFromBEBytes(sig, 8) || this.getA3(state) != BitTwiddling.longFromBEBytes(sig, 16) || this.getA4(state) != BitTwiddling.longFromBEBytes(sig, 24))
 			throw new IllegalStateException("Transaction signature in A no longer matches signature from repository");
 	}
 
@@ -497,6 +442,20 @@ public class QortalATAPI extends API {
 		}
 	}
 
+	/** Returns message data from transaction. */
+	/*package*/ byte[] getMessageFromTransaction(TransactionData transactionData) {
+		switch (transactionData.getType()) {
+			case MESSAGE:
+				return ((MessageTransactionData) transactionData).getData();
+
+			case AT:
+				return ((ATTransactionData) transactionData).getMessage();
+
+			default:
+				return null;
+		}
+	}
+
 	/** Returns AT's account */
 	/* package */ Account getATAccount() {
 		return new Account(this.repository, this.atData.getATAddress());
@@ -563,4 +522,8 @@ public class QortalATAPI extends API {
 		super.setB(state, bBytes);
 	}
 
+	protected void zeroB(MachineState state) {
+		super.zeroB(state);
+	}
+
 }

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

@@ -12,6 +12,7 @@ import org.ciyam.at.IllegalFunctionCodeException;
 import org.ciyam.at.MachineState;
 import org.qortal.crosschain.BTC;
 import org.qortal.crypto.Crypto;
+import org.qortal.data.transaction.TransactionData;
 import org.qortal.settings.Settings;
 
 /**
@@ -22,8 +23,70 @@ import org.qortal.settings.Settings;
  */
 public enum QortalFunctionCode {
 	/**
-	 * <tt>0x0510</tt><br>
-	 * Convert address in B to 20-byte value in LSB of B1, and all of B2 & B3.
+	 * Returns length of message data from transaction in A.<br>
+	 * <tt>0x0501</tt><br>
+	 * If transaction has no 'message', returns -1.
+	 */
+	GET_MESSAGE_LENGTH_FROM_TX_IN_A(0x0501, 0, true) {
+		@Override
+		protected void postCheckExecute(FunctionData functionData, MachineState state, short rawFunctionCode) throws ExecutionException {
+			QortalATAPI api = (QortalATAPI) state.getAPI();
+
+			TransactionData transactionData = api.getTransactionFromA(state);
+
+			byte[] messageData = api.getMessageFromTransaction(transactionData);
+
+			if (messageData == null)
+				functionData.returnValue = -1L;
+			else
+				functionData.returnValue = (long) messageData.length;
+		}
+	},
+	/**
+	 * Put offset 'message' from transaction in A into B<br>
+	 * <tt>0x0502 start-offset</tt><br>
+	 * Copies up to 32 bytes of message data, starting at <tt>start-offset</tt> into B.<br>
+	 * If transaction has no 'message', or <tt>start-offset</tt> out of bounds, then zero B<br>
+	 * Example 'message' could be 256-bit shared secret
+	 */
+	PUT_PARTIAL_MESSAGE_FROM_TX_IN_A_INTO_B(0x0502, 1, false) {
+		@Override
+		protected void postCheckExecute(FunctionData functionData, MachineState state, short rawFunctionCode) throws ExecutionException {
+			QortalATAPI api = (QortalATAPI) state.getAPI();
+
+			// In case something goes wrong, or we don't have enough message data.
+			api.zeroB(state);
+
+			if (functionData.value1 < 0 || functionData.value1 > Integer.MAX_VALUE)
+				return;
+
+			int startOffset = functionData.value1.intValue();
+
+			TransactionData transactionData = api.getTransactionFromA(state);
+
+			byte[] messageData = api.getMessageFromTransaction(transactionData);
+
+			if (messageData == null || startOffset > messageData.length)
+				return;
+
+			/*
+			 * Copy up to 32 bytes of message data into B,
+			 * retain order but pad with zeros in lower bytes.
+			 * 
+			 * So a 4-byte message "a b c d" would copy thusly:
+			 * a b c d 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
+			 */
+			int byteCount = Math.min(32, messageData.length - startOffset);
+			byte[] bBytes = new byte[32];
+
+			System.arraycopy(messageData, startOffset, bBytes, 0, byteCount);
+
+			api.setB(state, bBytes);
+		}
+	},
+	/**
+	 * Convert address in B to 20-byte value in LSB of B1, and all of B2 & B3.<br>
+	 * <tt>0x0510</tt>
 	 */
 	CONVERT_B_TO_PKH(0x0510, 0, false) {
 		@Override
@@ -38,8 +101,8 @@ public enum QortalFunctionCode {
 		}
 	},
 	/**
-	 * <tt>0x0511</tt><br>
 	 * Convert 20-byte value in LSB of B1, and all of B2 & B3 to P2SH.<br>
+	 * <tt>0x0511</tt><br>
 	 * P2SH stored in lower 25 bytes of B.
 	 */
 	CONVERT_B_TO_P2SH(0x0511, 0, false) {
@@ -51,8 +114,8 @@ public enum QortalFunctionCode {
 		}
 	},
 	/**
-	 * <tt>0x0512</tt><br>
 	 * Convert 20-byte value in LSB of B1, and all of B2 & B3 to Qortal address.<br>
+	 * <tt>0x0512</tt><br>
 	 * Qortal address stored in lower 25 bytes of B.
 	 */
 	CONVERT_B_TO_QORTAL(0x0512, 0, false) {

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

@@ -792,6 +792,9 @@ public class Controller extends Thread {
 				this.notifyGroupMembershipChange = false;
 				ChatNotifier.getInstance().onGroupMembershipChange();
 			}
+
+			// Trade-bot might want to perform some actions too
+			TradeBot.getInstance().onChainTipChange();
 		});
 	}
 

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

@@ -1,28 +1,45 @@
 package org.qortal.crosschain;
 
 import java.util.ArrayList;
+import java.util.HashSet;
 import java.util.List;
+import java.util.Set;
 import java.util.stream.Collectors;
 
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.bitcoinj.core.Address;
 import org.bitcoinj.core.Coin;
+import org.bitcoinj.core.ECKey;
+import org.bitcoinj.core.InsufficientMoneyException;
+import org.bitcoinj.core.LegacyAddress;
 import org.bitcoinj.core.NetworkParameters;
+import org.bitcoinj.core.Sha256Hash;
 import org.bitcoinj.core.Transaction;
 import org.bitcoinj.core.TransactionOutput;
+import org.bitcoinj.core.UTXO;
+import org.bitcoinj.core.UTXOProvider;
+import org.bitcoinj.core.UTXOProviderException;
+import org.bitcoinj.crypto.DeterministicHierarchy;
+import org.bitcoinj.crypto.DeterministicKey;
 import org.bitcoinj.params.MainNetParams;
 import org.bitcoinj.params.RegTestParams;
 import org.bitcoinj.params.TestNet3Params;
+import org.bitcoinj.script.Script.ScriptType;
 import org.bitcoinj.script.ScriptBuilder;
 import org.bitcoinj.utils.MonetaryFormat;
+import org.bitcoinj.wallet.DeterministicKeyChain;
+import org.bitcoinj.wallet.SendRequest;
+import org.bitcoinj.wallet.Wallet;
+import org.qortal.crosschain.ElectrumX.UnspentOutput;
+import org.qortal.crypto.Crypto;
 import org.qortal.settings.Settings;
 import org.qortal.utils.BitTwiddling;
-import org.qortal.utils.Pair;
+
+import com.google.common.hash.HashCode;
 
 public class BTC {
 
-	public static final MonetaryFormat FORMAT = new MonetaryFormat().minDecimals(8).postfixCode();
 	public static final long NO_LOCKTIME_NO_RBF_SEQUENCE = 0xFFFFFFFFL;
 	public static final long LOCKTIME_NO_RBF_SEQUENCE = NO_LOCKTIME_NO_RBF_SEQUENCE - 1;
 	public static final int HASH160_LENGTH = 20;
@@ -30,6 +47,7 @@ public class BTC {
 	protected static final Logger LOGGER = LogManager.getLogger(BTC.class);
 
 	private static final int TIMESTAMP_OFFSET = 4 + 32 + 32;
+	private static final MonetaryFormat FORMAT = new MonetaryFormat().minDecimals(8).postfixCode();
 
 	public enum BitcoinNet {
 		MAIN {
@@ -58,6 +76,9 @@ public class BTC {
 	private final NetworkParameters params;
 	private final ElectrumX electrumX;
 
+	// Let ECKey.equals() do the hard work
+	private final Set<ECKey> spentKeys = new HashSet<>();
+
 	// Constructors and instance
 
 	private BTC() {
@@ -88,6 +109,34 @@ public class BTC {
 
 	// Actual useful methods for use by other classes
 
+	public static String format(Coin amount) {
+		return BTC.FORMAT.format(amount).toString();
+	}
+
+	public static String format(long amount) {
+		return format(Coin.valueOf(amount));
+	}
+
+	public boolean isValidXprv(String xprv58) {
+		try {
+			DeterministicKey.deserializeB58(null, xprv58, this.params);
+			return true;
+		} catch (IllegalArgumentException e) {
+			return false;
+		}
+	}
+
+	/** Returns P2PKH Bitcoin address using passed public key hash. */
+	public String pkhToAddress(byte[] publicKeyHash) {
+		return LegacyAddress.fromPubKeyHash(this.params, publicKeyHash).toString();
+	}
+
+	public String deriveP2shAddress(byte[] redeemScriptBytes) {
+		byte[] redeemScriptHash = Crypto.hash160(redeemScriptBytes);
+		Address p2shAddress = LegacyAddress.fromScriptHash(params, redeemScriptHash);
+		return p2shAddress.toString();
+	}
+
 	/** Returns median timestamp from latest 11 blocks, in seconds. */
 	public Integer getMedianBlockTime() {
 		Integer height = this.electrumX.getCurrentHeight();
@@ -99,34 +148,31 @@ public class BTC {
 		if (blockHeaders == null || blockHeaders.size() < 11)
 			return null;
 
-		List<Integer> blockTimestamps = blockHeaders.stream().map(blockHeader -> BitTwiddling.fromLEBytes(blockHeader, TIMESTAMP_OFFSET)).collect(Collectors.toList());
+		List<Integer> blockTimestamps = blockHeaders.stream().map(blockHeader -> BitTwiddling.intFromLEBytes(blockHeader, TIMESTAMP_OFFSET)).collect(Collectors.toList());
 
-		// Descending, but order shouldn't matter as we're picking median...
+		// Descending order
 		blockTimestamps.sort((a, b) -> Integer.compare(b, a));
 
+		// Pick median
 		return blockTimestamps.get(5);
 	}
 
-	public Coin getBalance(String base58Address) {
-		Long balance = this.electrumX.getBalance(addressToScript(base58Address));
-		if (balance == null)
-			return null;
-
-		return Coin.valueOf(balance);
+	public Long getBalance(String base58Address) {
+		return this.electrumX.getBalance(addressToScript(base58Address));
 	}
 
 	public List<TransactionOutput> getUnspentOutputs(String base58Address) {
-		List<Pair<byte[], Integer>> unspentOutputs = this.electrumX.getUnspentOutputs(addressToScript(base58Address));
+		List<UnspentOutput> unspentOutputs = this.electrumX.getUnspentOutputs(addressToScript(base58Address));
 		if (unspentOutputs == null)
 			return null;
 
 		List<TransactionOutput> unspentTransactionOutputs = new ArrayList<>();
-		for (Pair<byte[], Integer> unspentOutput : unspentOutputs) {
-			List<TransactionOutput> transactionOutputs = getOutputs(unspentOutput.getA());
+		for (UnspentOutput unspentOutput : unspentOutputs) {
+			List<TransactionOutput> transactionOutputs = getOutputs(unspentOutput.hash);
 			if (transactionOutputs == null)
 				return null;
 
-			unspentTransactionOutputs.add(transactionOutputs.get(unspentOutput.getB()));
+			unspentTransactionOutputs.add(transactionOutputs.get(unspentOutput.index));
 		}
 
 		return unspentTransactionOutputs;
@@ -141,6 +187,7 @@ public class BTC {
 		return transaction.getOutputs();
 	}
 
+	/** Returns list of raw transactions spending passed address. */
 	public List<byte[]> getAddressTransactions(String base58Address) {
 		return this.electrumX.getAddressTransactions(addressToScript(base58Address));
 	}
@@ -149,6 +196,181 @@ public class BTC {
 		return this.electrumX.broadcastTransaction(transaction.bitcoinSerialize());
 	}
 
+	/**
+	 * Returns bitcoinj transaction sending <tt>amount</tt> to <tt>recipient</tt>.
+	 * 
+	 * @param xprv58 BIP32 extended Bitcoin private key
+	 * @param recipient P2PKH address
+	 * @param amount unscaled amount
+	 * @return transaction, or null if insufficient funds
+	 */
+	public Transaction buildSpend(String xprv58, String recipient, long amount) {
+		Wallet wallet = Wallet.fromSpendingKeyB58(this.params, xprv58, DeterministicHierarchy.BIP32_STANDARDISATION_TIME_SECS);
+		wallet.setUTXOProvider(new WalletAwareUTXOProvider(this, wallet, WalletAwareUTXOProvider.KeySearchMode.REQUEST_MORE_IF_ALL_SPENT));
+
+		Address destination = Address.fromString(this.params, recipient);
+		SendRequest sendRequest = SendRequest.to(destination, Coin.valueOf(amount));
+
+		if (this.params == TestNet3Params.get())
+			// Much smaller fee for TestNet3
+			sendRequest.feePerKb = Coin.valueOf(2000L);
+
+		try {
+			wallet.completeTx(sendRequest);
+			return sendRequest.tx;
+		} catch (InsufficientMoneyException e) {
+			return null;
+		}
+	}
+
+	/**
+	 * Returns unspent Bitcoin balance given 'm' BIP32 key.
+	 *
+	 * @param xprv58 BIP32 extended Bitcoin private key
+	 * @return unspent BTC balance, or null if unable to determine balance
+	 */
+	public Long getWalletBalance(String xprv58) {
+		Wallet wallet = Wallet.fromSpendingKeyB58(this.params, xprv58, DeterministicHierarchy.BIP32_STANDARDISATION_TIME_SECS);
+		wallet.setUTXOProvider(new WalletAwareUTXOProvider(this, wallet, WalletAwareUTXOProvider.KeySearchMode.REQUEST_MORE_IF_ANY_SPENT));
+
+		Coin balance = wallet.getBalance();
+		if (balance == null)
+			return null;
+
+		return balance.value;
+	}
+
+	// UTXOProvider support
+
+	static class WalletAwareUTXOProvider implements UTXOProvider {
+		private static final int LOOKAHEAD_INCREMENT = 3;
+
+		private final BTC btc;
+		private final Wallet wallet;
+
+		enum KeySearchMode {
+			REQUEST_MORE_IF_ALL_SPENT, REQUEST_MORE_IF_ANY_SPENT;
+		}
+		private final KeySearchMode keySearchMode;
+		private final DeterministicKeyChain keyChain;
+
+		public WalletAwareUTXOProvider(BTC btc, Wallet wallet, KeySearchMode keySearchMode) {
+			this.btc = btc;
+			this.wallet = wallet;
+			this.keySearchMode = keySearchMode;
+			this.keyChain = this.wallet.getActiveKeyChain();
+
+			// Set up wallet's key chain
+			this.keyChain.setLookaheadSize(LOOKAHEAD_INCREMENT);
+			this.keyChain.maybeLookAhead();
+		}
+
+		public List<UTXO> getOpenTransactionOutputs(List<ECKey> keys) throws UTXOProviderException {
+			List<UTXO> allUnspentOutputs = new ArrayList<>();
+			final boolean coinbase = false;
+
+			int ki = 0;
+			do {
+				boolean areAllKeysUnspent = true;
+				boolean areAllKeysSpent = true;
+
+				for (; ki < keys.size(); ++ki) {
+					ECKey key = keys.get(ki);
+
+					Address address = Address.fromKey(btc.params, key, ScriptType.P2PKH);
+					byte[] script = ScriptBuilder.createOutputScript(address).getProgram();
+
+					List<UnspentOutput> unspentOutputs = btc.electrumX.getUnspentOutputs(script);
+					if (unspentOutputs == null)
+						throw new UTXOProviderException(String.format("Unable to fetch unspent outputs for %s", address));
+
+					/*
+					 * If there are no unspent outputs then either:
+					 * a) all the outputs have been spent
+					 * b) address has never been used
+					 * 
+					 * For case (a) we want to remember not to check this address (key) again.
+					 */
+
+					if (unspentOutputs.isEmpty()) {
+						// If this is a known key that has been spent before, then we can skip asking for transaction history
+						if (btc.spentKeys.contains(key)) {
+							wallet.getActiveKeyChain().markKeyAsUsed((DeterministicKey) key);
+							areAllKeysUnspent = false;
+							continue;
+						}
+
+						// Ask for transaction history - if it's empty then key has never been used
+						List<byte[]> historicTransactionHashes = btc.electrumX.getAddressTransactions(script);
+						if (historicTransactionHashes == null)
+							throw new UTXOProviderException(
+									String.format("Unable to fetch transaction history for %s", address));
+
+						if (!historicTransactionHashes.isEmpty()) {
+							// Fully spent key - case (a)
+							btc.spentKeys.add(key);
+							wallet.getActiveKeyChain().markKeyAsUsed((DeterministicKey) key);
+							areAllKeysUnspent = false;
+						} else {
+							// Key never been used - case (b)
+							areAllKeysSpent = false;
+						}
+
+						continue;
+					}
+
+					// If we reach here, then there's definitely at least one unspent key
+					areAllKeysSpent = false;
+
+					for (UnspentOutput unspentOutput : unspentOutputs) {
+						List<TransactionOutput> transactionOutputs = btc.getOutputs(unspentOutput.hash);
+						if (transactionOutputs == null)
+							throw new UTXOProviderException(String.format("Unable to fetch outputs for TX %s",
+									HashCode.fromBytes(unspentOutput.hash)));
+
+						TransactionOutput transactionOutput = transactionOutputs.get(unspentOutput.index);
+
+						UTXO utxo = new UTXO(Sha256Hash.wrap(unspentOutput.hash), unspentOutput.index,
+								Coin.valueOf(unspentOutput.value), unspentOutput.height, coinbase,
+								transactionOutput.getScriptPubKey());
+
+						allUnspentOutputs.add(utxo);
+					}
+				}
+
+				if ((this.keySearchMode == KeySearchMode.REQUEST_MORE_IF_ALL_SPENT && areAllKeysSpent)
+						|| (this.keySearchMode == KeySearchMode.REQUEST_MORE_IF_ANY_SPENT && !areAllKeysUnspent)) {
+					// Generate some more keys
+					this.keyChain.setLookaheadSize(this.keyChain.getLookaheadSize() + LOOKAHEAD_INCREMENT);
+					this.keyChain.maybeLookAhead();
+
+					// This returns all keys, including those already in 'keys'
+					List<DeterministicKey> allLeafKeys = this.keyChain.getLeafKeys();
+					// Add only new keys onto our list of keys to search
+					List<DeterministicKey> newKeys = allLeafKeys.subList(ki, allLeafKeys.size());
+					keys.addAll(newKeys);
+					// Fall-through to checking more keys as now 'ki' is smaller than 'keys.size()' again
+				}
+
+				// If we have processed all keys, then we're done
+			} while (ki < keys.size());
+
+			return allUnspentOutputs;
+		}
+
+		public int getChainHeadHeight() throws UTXOProviderException {
+			Integer height = btc.electrumX.getCurrentHeight();
+			if (height == null)
+				throw new UTXOProviderException("Unable to determine Bitcoin chain height");
+
+			return height.intValue();
+		}
+
+		public NetworkParameters getParams() {
+			return btc.params;
+		}
+	}
+
 	// Utility methods for us
 
 	private byte[] addressToScript(String base58Address) {

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

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

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

@@ -25,11 +25,11 @@ import org.json.simple.JSONObject;
 import org.json.simple.JSONValue;
 import org.qortal.crypto.Crypto;
 import org.qortal.crypto.TrustlessSSLSocketFactory;
-import org.qortal.utils.Pair;
 
 import com.google.common.hash.HashCode;
 import com.google.common.primitives.Bytes;
 
+/** ElectrumX network support for querying Bitcoin-related info like block headers, transaction outputs, etc. */
 public class ElectrumX {
 
 	private static final Logger LOGGER = LogManager.getLogger(ElectrumX.class);
@@ -93,7 +93,21 @@ public class ElectrumX {
 	private ElectrumX(String bitcoinNetwork) {
 		switch (bitcoinNetwork) {
 			case "MAIN":
-				servers.addAll(Arrays.asList());
+				servers.addAll(Arrays.asList(
+						// Servers chosen on NO BASIS WHATSOEVER from various sources!
+						new Server("tardis.bauerj.eu", Server.ConnectionType.SSL, 50002),
+						new Server("rbx.curalle.ovh", Server.ConnectionType.SSL, 50002),
+						new Server("quick.electumx.live", Server.ConnectionType.SSL, 50002),
+						new Server("enode.duckdns.org", Server.ConnectionType.SSL, 50002),
+						new Server("electrumx.ddns.net", Server.ConnectionType.SSL, 50002),
+						new Server("electrumx.ml", Server.ConnectionType.SSL, 50002),
+						new Server("electrum.eff.ro", Server.ConnectionType.SSL, 50002),
+						new Server("electrum.bitkoins.nl", Server.ConnectionType.SSL, 50512),
+						new Server("E-X.not.fyi", Server.ConnectionType.SSL, 50002),
+						new Server("btc.electroncash.dk", Server.ConnectionType.SSL, 60002),
+						new Server("electrum.blockstream.info", Server.ConnectionType.TCP, 50001),
+						new Server("electrum.blockstream.info", Server.ConnectionType.SSL, 50002),
+						new Server("bitcoin.aranguren.org", Server.ConnectionType.TCP, 50001)));
 				break;
 
 			case "TEST3":
@@ -119,6 +133,7 @@ public class ElectrumX {
 		rpc("server.banner");
 	}
 
+	/** Returns ElectrumX instance linked to passed Bitcoin network, one of "MAIN", "TEST3" or "REGTEST". */
 	public static synchronized ElectrumX getInstance(String bitcoinNetwork) {
 		if (!instances.containsKey(bitcoinNetwork))
 			instances.put(bitcoinNetwork, new ElectrumX(bitcoinNetwork));
@@ -129,16 +144,26 @@ public class ElectrumX {
 	// Methods for use by other classes
 
 	public Integer getCurrentHeight() {
-		JSONObject blockJson = (JSONObject) this.rpc("blockchain.headers.subscribe");
-		if (blockJson == null || !blockJson.containsKey("height"))
+		Object blockObj = this.rpc("blockchain.headers.subscribe");
+		if (!(blockObj instanceof JSONObject))
+			return null;
+
+		JSONObject blockJson = (JSONObject) blockObj;
+
+		if (!blockJson.containsKey("height"))
 			return null;
 
 		return ((Long) blockJson.get("height")).intValue();
 	}
 
 	public List<byte[]> getBlockHeaders(int startHeight, long count) {
-		JSONObject blockJson = (JSONObject) this.rpc("blockchain.block.headers", startHeight, count);
-		if (blockJson == null || !blockJson.containsKey("count") || !blockJson.containsKey("hex"))
+		Object blockObj = this.rpc("blockchain.block.headers", startHeight, count);
+		if (!(blockObj instanceof JSONObject))
+			return null;
+
+		JSONObject blockJson = (JSONObject) blockObj;
+
+		if (!blockJson.containsKey("count") || !blockJson.containsKey("hex"))
 			return null;
 
 		Long returnedCount = (Long) blockJson.get("count");
@@ -155,57 +180,87 @@ public class ElectrumX {
 		return rawBlockHeaders;
 	}
 
+	/** Returns confirmed balance, based on passed payment script, or null if there was an error or no known balance. */
 	public Long getBalance(byte[] script) {
 		byte[] scriptHash = Crypto.digest(script);
 		Bytes.reverse(scriptHash);
 
-		JSONObject balanceJson = (JSONObject) this.rpc("blockchain.scripthash.get_balance", HashCode.fromBytes(scriptHash).toString());
-		if (balanceJson == null || !balanceJson.containsKey("confirmed"))
+		Object balanceObj = this.rpc("blockchain.scripthash.get_balance", HashCode.fromBytes(scriptHash).toString());
+		if (!(balanceObj instanceof JSONObject))
+			return null;
+
+		JSONObject balanceJson = (JSONObject) balanceObj;
+
+		if (!balanceJson.containsKey("confirmed"))
 			return null;
 
 		return (Long) balanceJson.get("confirmed");
 	}
 
-	public List<Pair<byte[], Integer>> getUnspentOutputs(byte[] script) {
+	/** Unspent output info as returned by ElectrumX network. */
+	public static class UnspentOutput {
+		public final byte[] hash;
+		public final int index;
+		public final int height;
+		public final long value;
+
+		public UnspentOutput(byte[] hash, int index, int height, long value) {
+			this.hash = hash;
+			this.index = index;
+			this.height = height;
+			this.value = value;
+		}
+	}
+
+	/** Returns list of unspent outputs pertaining to passed payment script, or null if there was an error. */
+	public List<UnspentOutput> getUnspentOutputs(byte[] script) {
 		byte[] scriptHash = Crypto.digest(script);
 		Bytes.reverse(scriptHash);
 
-		JSONArray unspentJson = (JSONArray) this.rpc("blockchain.scripthash.listunspent", HashCode.fromBytes(scriptHash).toString());
-		if (unspentJson == null)
+		Object unspentJson = this.rpc("blockchain.scripthash.listunspent", HashCode.fromBytes(scriptHash).toString());
+		if (!(unspentJson instanceof JSONArray))
 			return null;
 
-		List<Pair<byte[], Integer>> unspentOutputs = new ArrayList<>();
-		for (Object rawUnspent : unspentJson) {
+		List<UnspentOutput> unspentOutputs = new ArrayList<>();
+		for (Object rawUnspent : (JSONArray) unspentJson) {
 			JSONObject unspent = (JSONObject) rawUnspent;
 
+			int height = ((Long) unspent.get("height")).intValue();
+			// We only want unspent outputs from confirmed transactions (and definitely not mempool duplicates with height 0)
+			if (height <= 0)
+				continue;
+
 			byte[] txHash = HashCode.fromString((String) unspent.get("tx_hash")).asBytes();
 			int outputIndex = ((Long) unspent.get("tx_pos")).intValue();
+			long value = (Long) unspent.get("value");
 
-			unspentOutputs.add(new Pair<>(txHash, outputIndex));
+			unspentOutputs.add(new UnspentOutput(txHash, outputIndex, height, value));
 		}
 
 		return unspentOutputs;
 	}
 
+	/** Returns raw transaction for passed transaction hash, or null if not found. */
 	public byte[] getRawTransaction(byte[] txHash) {
-		String rawTransactionHex = (String) this.rpc("blockchain.transaction.get", HashCode.fromBytes(txHash).toString());
-		if (rawTransactionHex == null)
+		Object rawTransactionHex = this.rpc("blockchain.transaction.get", HashCode.fromBytes(txHash).toString());
+		if (!(rawTransactionHex instanceof String))
 			return null;
 
-		return HashCode.fromString(rawTransactionHex).asBytes();
+		return HashCode.fromString((String) rawTransactionHex).asBytes();
 	}
 
+	/** Returns list of raw transactions, relating to passed payment script, if null if there's an error. */
 	public List<byte[]> getAddressTransactions(byte[] script) {
 		byte[] scriptHash = Crypto.digest(script);
 		Bytes.reverse(scriptHash);
 
-		JSONArray transactionsJson = (JSONArray) this.rpc("blockchain.scripthash.get_history", HashCode.fromBytes(scriptHash).toString());
-		if (transactionsJson == null)
+		Object transactionsJson = this.rpc("blockchain.scripthash.get_history", HashCode.fromBytes(scriptHash).toString());
+		if (!(transactionsJson instanceof JSONArray))
 			return null;
 
 		List<byte[]> rawTransactions = new ArrayList<>();
 
-		for (Object rawTransactionInfo : transactionsJson) {
+		for (Object rawTransactionInfo : (JSONArray) transactionsJson) {
 			JSONObject transactionInfo = (JSONObject) rawTransactionInfo;
 
 			// We only want confirmed transactions
@@ -223,6 +278,7 @@ public class ElectrumX {
 		return rawTransactions;
 	}
 
+	/** Returns true if raw transaction successfully broadcast. */
 	public boolean broadcastTransaction(byte[] transactionBytes) {
 		Object rawBroadcastResult = this.rpc("blockchain.transaction.broadcast", HashCode.fromBytes(transactionBytes).toString());
 		if (rawBroadcastResult == null)
@@ -235,14 +291,15 @@ public class ElectrumX {
 
 	// Class-private utility methods
 
+	/** Query current server for its list of peer servers, and return those we can parse. */
 	private Set<Server> serverPeersSubscribe() {
 		Set<Server> newServers = new HashSet<>();
 
-		JSONArray peers = (JSONArray) this.connectedRpc("server.peers.subscribe");
-		if (peers == null)
+		Object peers = this.connectedRpc("server.peers.subscribe");
+		if (!(peers instanceof JSONArray))
 			return newServers;
 
-		for (Object rawPeer : peers) {
+		for (Object rawPeer : (JSONArray) peers) {
 			JSONArray peer = (JSONArray) rawPeer;
 			if (peer.size() < 3)
 				continue;
@@ -287,6 +344,7 @@ public class ElectrumX {
 		return newServers;
 	}
 
+	/** Return output from RPC call, with automatic reconnection to different server if needed. */
 	private synchronized Object rpc(String method, Object...params) {
 		while (haveConnection()) {
 			Object response = connectedRpc(method, params);
@@ -305,6 +363,7 @@ public class ElectrumX {
 		return null;
 	}
 
+	/** Returns true if we have, or create, a connection to an ElectrumX server. */
 	private boolean haveConnection() {
 		if (this.currentServer != null)
 			return true;
@@ -377,10 +436,12 @@ public class ElectrumX {
 		if (response.isEmpty())
 			return null;
 
-		JSONObject responseJson = (JSONObject) JSONValue.parse(response);
-		if (responseJson == null)
+		Object responseObj = JSONValue.parse(response);
+		if (!(responseObj instanceof JSONObject))
 			return null;
 
+		JSONObject responseJson = (JSONObject) responseObj;
+
 		return responseJson.get("result");
 	}
 

src/main/java/org/qortal/data/crosschain/CrossChainTradeData.java

@@ -4,14 +4,14 @@ import javax.xml.bind.annotation.XmlAccessType;
 import javax.xml.bind.annotation.XmlAccessorType;
 import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
 
+import org.qortal.crosschain.BTCACCT;
+
 import io.swagger.v3.oas.annotations.media.Schema;
 
 // All properties to be converted to JSON via JAXB
 @XmlAccessorType(XmlAccessType.FIELD)
 public class CrossChainTradeData {
 
-	public enum Mode { OFFER, TRADE };
-
 	// Properties
 
 	@Schema(description = "AT's Qortal address")
@@ -20,32 +20,40 @@ public class CrossChainTradeData {
 	@Schema(description = "AT creator's Qortal address")
 	public String qortalCreator;
 
+	@Schema(description = "AT creator's Qortal trade address")
+	public String qortalCreatorTradeAddress;
+
+	@Schema(description = "AT creator's Bitcoin trade public-key-hash (PKH)")
+	public byte[] creatorBitcoinPKH;
+
 	@Schema(description = "Timestamp when AT was created (milliseconds since epoch)")
 	public long creationTimestamp;
 
+	@Schema(description = "Suggested trade timeout (minutes)", example = "10080")
+	public int tradeTimeout;
+
 	@Schema(description = "AT's current QORT balance")
 	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
 	public long qortBalance;
 
-	@Schema(description = "HASH160 of 32-byte secret")
-	public byte[] secretHash;
+	@Schema(description = "HASH160 of 32-byte secret-A")
+	public byte[] hashOfSecretA;
 
-	@Schema(description = "Initial QORT payment that will be sent to Qortal trade partner")
-	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
-	public long initialPayout;
+	@Schema(description = "HASH160 of 32-byte secret-B")
+	public byte[] hashOfSecretB;
 
 	@Schema(description = "Final QORT payment that will be sent to Qortal trade partner")
 	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
-	public long redeemPayout;
+	public long qortAmount;
 
 	@Schema(description = "Trade partner's Qortal address (trade begins when this is set)")
-	public String qortalRecipient;
+	public String qortalPartnerAddress;
 
 	@Schema(description = "Timestamp when AT switched to trade mode")
 	public Long tradeModeTimestamp;
 
-	@Schema(description = "How long from beginning trade until AT triggers automatic refund to AT creator (minutes)")
-	public long tradeRefundTimeout;
+	@Schema(description = "How long from AT creation until AT triggers automatic refund to AT creator (minutes)")
+	public Integer refundTimeout;
 
 	@Schema(description = "Actual Qortal block height when AT will automatically refund to AT creator (after trade begins)")
 	public Integer tradeRefundHeight;
@@ -54,10 +62,19 @@ public class CrossChainTradeData {
 	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
 	public long expectedBitcoin;
 
-	public Mode mode;
+	public BTCACCT.Mode mode;
 
-	@Schema(description = "Suggested Bitcoin P2SH nLockTime based on trade timeout")
-	public Integer lockTime;
+	@Schema(description = "Suggested Bitcoin P2SH-A nLockTime based on trade timeout")
+	public Integer lockTimeA;
+
+	@Schema(description = "Suggested Bitcoin P2SH-B nLockTime based on trade timeout")
+	public Integer lockTimeB;
+
+	@Schema(description = "Trade partner's Bitcoin public-key-hash (PKH)")
+	public byte[] partnerBitcoinPKH;
+
+	@Schema(description = "Trade partner's Qortal receiving address")
+	public String qortalPartnerReceivingAddress;
 
 	// Constructors
 

src/main/java/org/qortal/data/crosschain/TradeBotData.java

@@ -0,0 +1,193 @@
+package org.qortal.data.crosschain;
+
+import static java.util.Arrays.stream;
+import static java.util.stream.Collectors.toMap;
+
+import java.util.Map;
+
+import javax.xml.bind.annotation.XmlAccessType;
+import javax.xml.bind.annotation.XmlAccessorType;
+import javax.xml.bind.annotation.XmlTransient;
+import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+
+// All properties to be converted to JSON via JAXB
+@XmlAccessorType(XmlAccessType.FIELD)
+public class TradeBotData {
+
+	private byte[] tradePrivateKey;
+
+	public enum State {
+		BOB_WAITING_FOR_AT_CONFIRM(10), BOB_WAITING_FOR_MESSAGE(15), BOB_WAITING_FOR_P2SH_B(20), BOB_WAITING_FOR_AT_REDEEM(25), BOB_DONE(30), BOB_REFUNDED(35),
+		ALICE_WAITING_FOR_P2SH_A(80), ALICE_WAITING_FOR_AT_LOCK(85), ALICE_WATCH_P2SH_B(90), ALICE_DONE(95), ALICE_REFUNDING_B(100), ALICE_REFUNDING_A(105), ALICE_REFUNDED(110);
+
+		public final int value;
+		private static final Map<Integer, State> map = stream(State.values()).collect(toMap(state -> state.value, state -> state));
+
+		State(int value) {
+			this.value = value;
+		}
+
+		public static State valueOf(int value) {
+			return map.get(value);
+		}
+	}
+	private State tradeState;
+
+	private String creatorAddress;
+	private String atAddress;
+
+	private long timestamp;
+
+	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
+	private long qortAmount;
+
+	private byte[] tradeNativePublicKey;
+	private byte[] tradeNativePublicKeyHash;
+	String tradeNativeAddress;
+
+	private byte[] secret;
+	private byte[] hashOfSecret;
+
+	private byte[] tradeForeignPublicKey;
+	private byte[] tradeForeignPublicKeyHash;
+
+	@XmlJavaTypeAdapter(value = org.qortal.api.AmountTypeAdapter.class)
+	private long bitcoinAmount;
+
+	// Never expose this via API
+	@XmlTransient
+	@Schema(hidden = true)
+	private String xprv58;
+
+	private byte[] lastTransactionSignature;
+
+	private Integer lockTimeA;
+
+	// Could be Bitcoin or Qortal...
+	private byte[] receivingAccountInfo;
+
+	protected TradeBotData() {
+		/* JAXB */
+	}
+
+	public TradeBotData(byte[] tradePrivateKey, State tradeState, String creatorAddress, String atAddress,
+			long timestamp, long qortAmount,
+			byte[] tradeNativePublicKey, byte[] tradeNativePublicKeyHash, String tradeNativeAddress,
+			byte[] secret, byte[] hashOfSecret,
+			byte[] tradeForeignPublicKey, byte[] tradeForeignPublicKeyHash,
+			long bitcoinAmount, String xprv58, byte[] lastTransactionSignature, Integer lockTimeA, byte[] receivingAccountInfo) {
+		this.tradePrivateKey = tradePrivateKey;
+		this.tradeState = tradeState;
+		this.creatorAddress = creatorAddress;
+		this.atAddress = atAddress;
+		this.timestamp = timestamp;
+		this.qortAmount = qortAmount;
+		this.tradeNativePublicKey = tradeNativePublicKey;
+		this.tradeNativePublicKeyHash = tradeNativePublicKeyHash;
+		this.tradeNativeAddress = tradeNativeAddress;
+		this.secret = secret;
+		this.hashOfSecret = hashOfSecret;
+		this.tradeForeignPublicKey = tradeForeignPublicKey;
+		this.tradeForeignPublicKeyHash = tradeForeignPublicKeyHash;
+		this.bitcoinAmount = bitcoinAmount;
+		this.xprv58 = xprv58;
+		this.lastTransactionSignature = lastTransactionSignature;
+		this.lockTimeA = lockTimeA;
+		this.receivingAccountInfo = receivingAccountInfo;
+	}
+
+	public byte[] getTradePrivateKey() {
+		return this.tradePrivateKey;
+	}
+
+	public State getState() {
+		return this.tradeState;
+	}
+
+	public void setState(State state) {
+		this.tradeState = state;
+	}
+
+	public String getCreatorAddress() {
+		return this.creatorAddress;
+	}
+
+	public String getAtAddress() {
+		return this.atAddress;
+	}
+
+	public void setAtAddress(String atAddress) {
+		this.atAddress = atAddress;
+	}
+
+	public long getTimestamp() {
+		return this.timestamp;
+	}
+
+	public void setTimestamp(long timestamp) {
+		this.timestamp = timestamp;
+	}
+
+	public long getQortAmount() {
+		return this.qortAmount;
+	}
+
+	public byte[] getTradeNativePublicKey() {
+		return this.tradeNativePublicKey;
+	}
+
+	public byte[] getTradeNativePublicKeyHash() {
+		return this.tradeNativePublicKeyHash;
+	}
+
+	public String getTradeNativeAddress() {
+		return this.tradeNativeAddress;
+	}
+
+	public byte[] getSecret() {
+		return this.secret;
+	}
+
+	public byte[] getHashOfSecret() {
+		return this.hashOfSecret;
+	}
+
+	public byte[] getTradeForeignPublicKey() {
+		return this.tradeForeignPublicKey;
+	}
+
+	public byte[] getTradeForeignPublicKeyHash() {
+		return this.tradeForeignPublicKeyHash;
+	}
+
+	public long getBitcoinAmount() {
+		return this.bitcoinAmount;
+	}
+
+	public String getXprv58() {
+		return this.xprv58;
+	}
+
+	public byte[] getLastTransactionSignature() {
+		return this.lastTransactionSignature;
+	}
+
+	public void setLastTransactionSignature(byte[] lastTransactionSignature) {
+		this.lastTransactionSignature = lastTransactionSignature;
+	}
+
+	public Integer getLockTimeA() {
+		return this.lockTimeA;
+	}
+
+	public void setLockTimeA(Integer lockTimeA) {
+		this.lockTimeA = lockTimeA;
+	}
+
+	public byte[] getReceivingAccountInfo() {
+		return this.receivingAccountInfo;
+	}
+
+}

src/main/java/org/qortal/event/Event.java

@@ -0,0 +1,5 @@
+package org.qortal.event;
+
+public interface Event {
+
+}

src/main/java/org/qortal/event/EventBus.java

@@ -0,0 +1,33 @@
+package org.qortal.event;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public enum EventBus {
+	INSTANCE;
+
+	private static final List<Listener> LISTENERS = new ArrayList<>();
+
+	public void addListener(Listener newListener) {
+		synchronized (LISTENERS) {
+			LISTENERS.add(newListener);
+		}
+	}
+
+	public void removeListener(Listener listener) {
+		synchronized (LISTENERS) {
+			LISTENERS.remove(listener);
+		}
+	}
+
+	public void notify(Event event) {
+		List<Listener> clonedListeners;
+
+		synchronized (LISTENERS) {
+			clonedListeners = new ArrayList<>(LISTENERS);
+		}
+
+		for (Listener listener : clonedListeners)
+			listener.listen(event);
+	}
+}

src/main/java/org/qortal/event/Listener.java

@@ -0,0 +1,6 @@
+package org.qortal.event;
+
+@FunctionalInterface
+public interface Listener {
+	void listen(Event event);
+}

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

@@ -15,6 +15,9 @@ public interface ATRepository {
 	/** Returns where AT with passed address exists in repository */
 	public boolean exists(String atAddress) throws DataException;
 
+	/** Returns AT creator's public key, or null if not found */
+	public byte[] getCreatorPublicKey(String atAddress) throws DataException;
+
 	/** Returns list of executable ATs, empty if none found */
 	public List<ATData> getAllExecutableATs() throws DataException;
 
@@ -54,6 +57,24 @@ public interface ATRepository {
 	 */
 	public ATStateData getLatestATState(String atAddress) throws DataException;
 
+	/**
+	 * Returns final ATStateData for ATs matching codeHash (required)
+	 * and specific data segment value (optional).
+	 * <p>
+	 * If searching for specific data segment value, both <tt>dataByteOffset</tt>
+	 * and <tt>expectedValue</tt> need to be non-null.
+	 * <p>
+	 * Note that <tt>dataByteOffset</tt> starts from 0 and will typically be
+	 * a multiple of <tt>MachineState.VALUE_SIZE</tt>, which is usually 8:
+	 * width of a long.
+	 * <p>
+	 * Although <tt>expectedValue</tt>, if provided, is natively an unsigned long,
+	 * the data segment comparison is done via unsigned hex string.
+	 */
+	public List<ATStateData> getMatchingFinalATStates(byte[] codeHash, Boolean isFinished,
+			Integer dataByteOffset, Long expectedValue, Integer minimumFinalHeight,
+			Integer limit, Integer offset, Boolean reverse) throws DataException;
+
 	/**
 	 * Returns all ATStateData for a given block height.
 	 * <p>
@@ -88,4 +109,28 @@ public interface ATRepository {
 	/** Delete state data for all ATs at this height */
 	public void deleteATStates(int height) throws DataException;
 
+	// Finding transactions for ATs to process
+
+	static class NextTransactionInfo {
+		public final int height;
+		public final int sequence;
+		public final byte[] signature;
+
+		public NextTransactionInfo(int height, int sequence, byte[] signature) {
+			this.height = height;
+			this.sequence = sequence;
+			this.signature = signature;
+		}
+	}
+
+	/**
+	 * Find next transaction for AT to process.
+	 * <p>
+	 * @param recipient AT address
+	 * @param height starting height
+	 * @param sequence starting sequence
+	 * @return next transaction info, or null if none found
+	 */
+	public NextTransactionInfo findNextTransaction(String recipient, int height, int sequence) throws DataException;
+
 }

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

@@ -61,6 +61,15 @@ public interface BlockRepository {
 	 */
 	public int getHeightFromTimestamp(long timestamp) throws DataException;
 
+	/**
+	 * Returns block timestamp for a given height.
+	 *
+	 * @param height
+	 * @return timestamp, or 0 if height is out of bounds.
+	 * @throws DataException
+	 */
+	public long getTimestampFromHeight(int height) throws DataException;
+
 	/**
 	 * Return highest block height from repository.
 	 * 

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

@@ -0,0 +1,18 @@
+package org.qortal.repository;
+
+import java.util.List;
+
+import org.qortal.data.crosschain.TradeBotData;
+
+public interface CrossChainRepository {
+
+	public TradeBotData getTradeBotData(byte[] tradePrivateKey) throws DataException;
+
+	public List<TradeBotData> getAllTradeBotData() throws DataException;
+
+	public void save(TradeBotData tradeBotData) throws DataException;
+
+	/** Delete trade-bot states using passed private key. */
+	public int delete(byte[] tradePrivateKey) throws DataException;
+
+}

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

@@ -14,6 +14,8 @@ public interface Repository extends AutoCloseable {
 
 	public ChatRepository getChatRepository();
 
+	public CrossChainRepository getCrossChainRepository();
+
 	public GroupRepository getGroupRepository();
 
 	public NameRepository getNameRepository();

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

@@ -6,6 +6,7 @@ import java.util.Map;
 import org.qortal.api.resource.TransactionsResource.ConfirmationStatus;
 import org.qortal.data.group.GroupApprovalData;
 import org.qortal.data.transaction.GroupApprovalTransactionData;
+import org.qortal.data.transaction.MessageTransactionData;
 import org.qortal.data.transaction.TransactionData;
 import org.qortal.data.transaction.TransferAssetTransactionData;
 import org.qortal.transaction.Transaction.TransactionType;
@@ -107,6 +108,18 @@ public interface TransactionRepository {
 	 */
 	public byte[] getLatestAutoUpdateTransaction(TransactionType txType, int txGroupId, Integer service) throws DataException;
 
+	/**
+	 * Returns list of MESSAGE transaction data matching recipient.
+	 * @param recipient
+	 * @param limit
+	 * @param offset
+	 * @param reverse
+	 * @return
+	 * @throws DataException
+	 */
+	public List<MessageTransactionData> getMessagesByRecipient(String recipient,
+			Integer limit, Integer offset, Boolean reverse) throws DataException;
+
 	/**
 	 * Returns list of transactions relating to specific asset ID.
 	 * 

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

@@ -68,6 +68,20 @@ public class HSQLDBATRepository implements ATRepository {
 		}
 	}
 
+	@Override
+	public byte[] getCreatorPublicKey(String atAddress) throws DataException {
+		String sql = "SELECT creator FROM ATs WHERE AT_address = ?";
+
+		try (ResultSet resultSet = this.repository.checkedExecute(sql, atAddress)) {
+			if (resultSet == null)
+				return null;
+
+			return resultSet.getBytes(1);
+		} catch (SQLException e) {
+			throw new DataException("Unable to fetch AT creator's public key from repository", e);
+		}
+	}
+
 	@Override
 	public List<ATData> getAllExecutableATs() throws DataException {
 		String sql = "SELECT AT_address, creator, created_when, version, asset_id, code_bytes, code_hash, "
@@ -273,6 +287,78 @@ public class HSQLDBATRepository implements ATRepository {
 		}
 	}
 
+	@Override
+	public List<ATStateData> getMatchingFinalATStates(byte[] codeHash, Boolean isFinished,
+			Integer dataByteOffset, Long expectedValue, Integer minimumFinalHeight,
+			Integer limit, Integer offset, Boolean reverse) throws DataException {
+		StringBuilder sql = new StringBuilder(1024);
+		sql.append("SELECT AT_address, height, created_when, state_data, state_hash, fees, is_initial "
+				+ "FROM ATs "
+				+ "CROSS JOIN LATERAL("
+					+ "SELECT height, created_when, state_data, state_hash, fees, is_initial "
+					+ "FROM ATStates "
+					+ "WHERE ATStates.AT_address = ATs.AT_address "
+					+ "ORDER BY height DESC "
+					+ "LIMIT 1"
+				+ ") AS FinalATStates "
+				+ "WHERE code_hash = ? ");
+
+		List<Object> bindParams = new ArrayList<>();
+		bindParams.add(codeHash);
+
+		if (isFinished != null) {
+			sql.append("AND is_finished = ?");
+			bindParams.add(isFinished);
+		}
+
+		if (dataByteOffset != null && expectedValue != null) {
+			sql.append("AND RAWTOHEX(SUBSTRING(state_data FROM ? FOR 8)) = ? ");
+
+			// We convert our long to hex Java-side to control endian
+			String expectedHexValue = String.format("%016x", expectedValue); // left-zero-padding and conversion
+
+			// SQL binary data offsets start at 1
+			bindParams.add(dataByteOffset + 1);
+			bindParams.add(expectedHexValue);
+		}
+
+		if (minimumFinalHeight != null) {
+			sql.append("AND height >= ");
+			sql.append(minimumFinalHeight);
+		}
+
+		sql.append(" ORDER BY height ");
+		if (reverse != null && reverse)
+			sql.append("DESC");
+
+		HSQLDBRepository.limitOffsetSql(sql, limit, offset);
+
+		List<ATStateData> atStates = new ArrayList<>();
+
+		try (ResultSet resultSet = this.repository.checkedExecute(sql.toString(), bindParams.toArray())) {
+			if (resultSet == null)
+				return atStates;
+
+			do {
+				String atAddress = resultSet.getString(1);
+				int height = resultSet.getInt(2);
+				long created = resultSet.getLong(3);
+				byte[] stateData = resultSet.getBytes(4); // Actually BLOB
+				byte[] stateHash = resultSet.getBytes(5);
+				long fees = resultSet.getLong(6);
+				boolean isInitial = resultSet.getBoolean(7);
+
+				ATStateData atStateData = new ATStateData(atAddress, height, created, stateData, stateHash, fees, isInitial);
+
+				atStates.add(atStateData);
+			} while (resultSet.next());
+
+			return atStates;
+		} catch (SQLException e) {
+			throw new DataException("Unable to fetch matching AT states from repository", e);
+		}
+	}
+
 	@Override
 	public List<ATStateData> getBlockATStatesAtHeight(int height) throws DataException {
 		String sql = "SELECT AT_address, state_hash, fees, is_initial "
@@ -341,4 +427,40 @@ public class HSQLDBATRepository implements ATRepository {
 		}
 	}
 
+	// Finding transactions for ATs to process
+
+	public NextTransactionInfo findNextTransaction(String recipient, int height, int sequence) throws DataException {
+		// We only need to search for a subset of transaction types: MESSAGE, PAYMENT or AT
+
+		String sql = "SELECT height, sequence, Transactions.signature "
+				+ "FROM ("
+					+ "SELECT signature FROM PaymentTransactions WHERE recipient = ? "
+					+ "UNION "
+					+ "SELECT signature FROM MessageTransactions WHERE recipient = ? "
+					+ "UNION "
+					+ "SELECT signature FROM ATTransactions WHERE recipient = ?"
+				+ ") AS Transactions "
+				+ "JOIN BlockTransactions ON BlockTransactions.transaction_signature = Transactions.signature "
+				+ "JOIN Blocks ON Blocks.signature = BlockTransactions.block_signature "
+				+ "WHERE (height > ? OR (height = ? AND sequence > ?)) "
+				+ "ORDER BY height ASC, sequence ASC "
+				+ "LIMIT 1";
+
+		Object[] bindParams = new Object[] { recipient, recipient, recipient, height, height, sequence };
+
+		try (ResultSet resultSet = this.repository.checkedExecute(sql, bindParams)) {
+			if (resultSet == null)
+				return null;
+
+			int nextHeight = resultSet.getInt(1);
+			int nextSequence = resultSet.getInt(2);
+			byte[] nextSignature = resultSet.getBytes(3);
+
+			return new NextTransactionInfo(nextHeight, nextSequence, nextSignature);
+		} catch (SQLException e) {
+			throw new DataException("Unable to find next transaction to AT from repository", e);
+		}
+
+	}
+
 }

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

@@ -132,6 +132,20 @@ public class HSQLDBBlockRepository implements BlockRepository {
 		}
 	}
 
+	@Override
+	public long getTimestampFromHeight(int height) throws DataException {
+		String sql = "SELECT minted_when FROM Blocks WHERE height = ?";
+
+		try (ResultSet resultSet = this.repository.checkedExecute(sql, height)) {
+			if (resultSet == null)
+				return 0;
+
+			return resultSet.getLong(1);
+		} catch (SQLException e) {
+			throw new DataException("Error obtaining block timestamp by height from repository", e);
+		}
+	}
+
 	@Override
 	public int getBlockchainHeight() throws DataException {
 		String sql = "SELECT height FROM Blocks ORDER BY height DESC LIMIT 1";

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

@@ -0,0 +1,165 @@
+package org.qortal.repository.hsqldb;
+
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.util.ArrayList;
+import java.util.List;
+
+import org.qortal.data.crosschain.TradeBotData;
+import org.qortal.repository.CrossChainRepository;
+import org.qortal.repository.DataException;
+
+public class HSQLDBCrossChainRepository implements CrossChainRepository {
+
+	protected HSQLDBRepository repository;
+
+	public HSQLDBCrossChainRepository(HSQLDBRepository repository) {
+		this.repository = repository;
+	}
+
+	@Override
+	public TradeBotData getTradeBotData(byte[] tradePrivateKey) throws DataException {
+		String sql = "SELECT trade_state, creator_address, at_address, "
+				+ "updated_when, qort_amount, "
+				+ "trade_native_public_key, trade_native_public_key_hash, "
+				+ "trade_native_address, secret, hash_of_secret, "
+				+ "trade_foreign_public_key, trade_foreign_public_key_hash, "
+				+ "bitcoin_amount, xprv58, last_transaction_signature, locktime_a, receiving_account_info "
+				+ "FROM TradeBotStates "
+				+ "WHERE trade_private_key = ?";
+
+		try (ResultSet resultSet = this.repository.checkedExecute(sql, tradePrivateKey)) {
+			if (resultSet == null)
+				return null;
+
+			int tradeStateValue = resultSet.getInt(1);
+			TradeBotData.State tradeState = TradeBotData.State.valueOf(tradeStateValue);
+			if (tradeState == null)
+				throw new DataException("Illegal trade-bot trade-state fetched from repository");
+
+			String creatorAddress = resultSet.getString(2);
+			String atAddress = resultSet.getString(3);
+			long timestamp = resultSet.getLong(4);
+			long qortAmount = resultSet.getLong(5);
+			byte[] tradeNativePublicKey = resultSet.getBytes(6);
+			byte[] tradeNativePublicKeyHash = resultSet.getBytes(7);
+			String tradeNativeAddress = resultSet.getString(8);
+			byte[] secret = resultSet.getBytes(9);
+			byte[] hashOfSecret = resultSet.getBytes(10);
+			byte[] tradeForeignPublicKey = resultSet.getBytes(11);
+			byte[] tradeForeignPublicKeyHash = resultSet.getBytes(12);
+			long bitcoinAmount = resultSet.getLong(13);
+			String xprv58 = resultSet.getString(14);
+			byte[] lastTransactionSignature = resultSet.getBytes(15);
+			Integer lockTimeA = resultSet.getInt(16);
+			if (lockTimeA == 0 && resultSet.wasNull())
+				lockTimeA = null;
+			byte[] receivingAccountInfo = resultSet.getBytes(17);
+
+			return new TradeBotData(tradePrivateKey, tradeState,
+					creatorAddress, atAddress, timestamp, qortAmount,
+					tradeNativePublicKey, tradeNativePublicKeyHash, tradeNativeAddress,
+					secret, hashOfSecret,
+					tradeForeignPublicKey, tradeForeignPublicKeyHash,
+					bitcoinAmount, xprv58, lastTransactionSignature, lockTimeA, receivingAccountInfo);
+		} catch (SQLException e) {
+			throw new DataException("Unable to fetch trade-bot trading state from repository", e);
+		}
+	}
+
+	@Override
+	public List<TradeBotData> getAllTradeBotData() throws DataException {
+		String sql = "SELECT trade_private_key, trade_state, creator_address, at_address, "
+				+ "updated_when, qort_amount, "
+				+ "trade_native_public_key, trade_native_public_key_hash, "
+				+ "trade_native_address, secret, hash_of_secret, "
+				+ "trade_foreign_public_key, trade_foreign_public_key_hash, "
+				+ "bitcoin_amount, xprv58, last_transaction_signature, locktime_a, receiving_account_info "
+				+ "FROM TradeBotStates";
+
+		List<TradeBotData> allTradeBotData = new ArrayList<>();
+
+		try (ResultSet resultSet = this.repository.checkedExecute(sql)) {
+			if (resultSet == null)
+				return allTradeBotData;
+
+			do {
+				byte[] tradePrivateKey = resultSet.getBytes(1);
+				int tradeStateValue = resultSet.getInt(2);
+				TradeBotData.State tradeState = TradeBotData.State.valueOf(tradeStateValue);
+				if (tradeState == null)
+					throw new DataException("Illegal trade-bot trade-state fetched from repository");
+
+				String creatorAddress = resultSet.getString(3);
+				String atAddress = resultSet.getString(4);
+				long timestamp = resultSet.getLong(5);
+				long qortAmount = resultSet.getLong(6);
+				byte[] tradeNativePublicKey = resultSet.getBytes(7);
+				byte[] tradeNativePublicKeyHash = resultSet.getBytes(8);
+				String tradeNativeAddress = resultSet.getString(9);
+				byte[] secret = resultSet.getBytes(10);
+				byte[] hashOfSecret = resultSet.getBytes(11);
+				byte[] tradeForeignPublicKey = resultSet.getBytes(12);
+				byte[] tradeForeignPublicKeyHash = resultSet.getBytes(13);
+				long bitcoinAmount = resultSet.getLong(14);
+				String xprv58 = resultSet.getString(15);
+				byte[] lastTransactionSignature = resultSet.getBytes(16);
+				Integer lockTimeA = resultSet.getInt(17);
+				if (lockTimeA == 0 && resultSet.wasNull())
+					lockTimeA = null;
+				byte[] receivingAccountInfo = resultSet.getBytes(18);
+
+				TradeBotData tradeBotData = new TradeBotData(tradePrivateKey, tradeState,
+						creatorAddress, atAddress, timestamp, qortAmount,
+						tradeNativePublicKey, tradeNativePublicKeyHash, tradeNativeAddress,
+						secret, hashOfSecret,
+						tradeForeignPublicKey, tradeForeignPublicKeyHash,
+						bitcoinAmount, xprv58, lastTransactionSignature, lockTimeA, receivingAccountInfo);
+				allTradeBotData.add(tradeBotData);
+			} while (resultSet.next());
+
+			return allTradeBotData;
+		} catch (SQLException e) {
+			throw new DataException("Unable to fetch trade-bot trading states from repository", e);
+		}
+	}
+
+	@Override
+	public void save(TradeBotData tradeBotData) throws DataException {
+		HSQLDBSaver saveHelper = new HSQLDBSaver("TradeBotStates");
+
+		saveHelper.bind("trade_private_key", tradeBotData.getTradePrivateKey())
+				.bind("trade_state", tradeBotData.getState().value)
+				.bind("creator_address", tradeBotData.getCreatorAddress())
+				.bind("at_address", tradeBotData.getAtAddress())
+				.bind("updated_when", tradeBotData.getTimestamp())
+				.bind("qort_amount", tradeBotData.getQortAmount())
+				.bind("trade_native_public_key", tradeBotData.getTradeNativePublicKey())
+				.bind("trade_native_public_key_hash", tradeBotData.getTradeNativePublicKeyHash())
+				.bind("trade_native_address", tradeBotData.getTradeNativeAddress())
+				.bind("secret", tradeBotData.getSecret()).bind("hash_of_secret", tradeBotData.getHashOfSecret())
+				.bind("trade_foreign_public_key", tradeBotData.getTradeForeignPublicKey())
+				.bind("trade_foreign_public_key_hash", tradeBotData.getTradeForeignPublicKeyHash())
+				.bind("bitcoin_amount", tradeBotData.getBitcoinAmount())
+				.bind("xprv58", tradeBotData.getXprv58())
+				.bind("last_transaction_signature", tradeBotData.getLastTransactionSignature())
+				.bind("locktime_a", tradeBotData.getLockTimeA())
+				.bind("receiving_account_info", tradeBotData.getReceivingAccountInfo());
+
+		try {
+			saveHelper.execute(this.repository);
+		} catch (SQLException e) {
+			throw new DataException("Unable to save trade bot data into repository", e);
+		}
+	}
+
+	@Override
+	public int delete(byte[] tradePrivateKey) throws DataException {
+		try {
+			return this.repository.delete("TradeBotStates", "trade_private_key = ?", tradePrivateKey);
+		} catch (SQLException e) {
+			throw new DataException("Unable to delete trade-bot states from repository", e);
+		}
+	}
+
+}

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

@@ -4,9 +4,14 @@ import java.sql.Connection;
 import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.sql.Statement;
+import java.util.HashMap;
+import java.util.Map;
 
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
+import org.qortal.utils.Base58;
+
+import com.google.common.hash.HashCode;
 
 public class HSQLDBDatabaseUpdates {
 
@@ -618,6 +623,22 @@ public class HSQLDBDatabaseUpdates {
 					stmt.execute("CREATE TABLE PublicizeTransactions (signature Signature, nonce INT NOT NULL, " + TRANSACTION_KEYS + ")");
 					break;
 
+				case 20:
+					// Trade bot
+					stmt.execute("CREATE TABLE TradeBotStates (trade_private_key QortalKeySeed NOT NULL, trade_state TINYINT NOT NULL, "
+							+ "creator_address QortalAddress NOT NULL, at_address QortalAddress, updated_when BIGINT NOT NULL, qort_amount QortalAmount NOT NULL, "
+							+ "trade_native_public_key QortalPublicKey NOT NULL, trade_native_public_key_hash VARBINARY(32) NOT NULL, "
+							+ "trade_native_address QortalAddress NOT NULL, secret VARBINARY(32) NOT NULL, hash_of_secret VARBINARY(32) NOT NULL, "
+							+ "trade_foreign_public_key VARBINARY(33) NOT NULL, trade_foreign_public_key_hash VARBINARY(32) NOT NULL, "
+							+ "bitcoin_amount BIGINT NOT NULL, xprv58 VARCHAR(200), last_transaction_signature Signature, locktime_a BIGINT, "
+							+ "receiving_account_info VARBINARY(32) NOT NULL, PRIMARY KEY (trade_private_key))");
+					break;
+
+				case 21:
+					// AT functionality index
+					stmt.execute("CREATE INDEX IF NOT EXISTS ATCodeHashIndex ON ATs (code_hash, is_finished)");
+					break;
+
 				default:
 					// nothing to do
 					return false;

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

@@ -32,6 +32,7 @@ import org.qortal.repository.ArbitraryRepository;
 import org.qortal.repository.AssetRepository;
 import org.qortal.repository.BlockRepository;
 import org.qortal.repository.ChatRepository;
+import org.qortal.repository.CrossChainRepository;
 import org.qortal.repository.DataException;
 import org.qortal.repository.GroupRepository;
 import org.qortal.repository.NameRepository;
@@ -115,6 +116,11 @@ public class HSQLDBRepository implements Repository {
 		return new HSQLDBChatRepository(this);
 	}
 
+	@Override
+	public CrossChainRepository getCrossChainRepository() {
+		return new HSQLDBCrossChainRepository(this);
+	}
+
 	@Override
 	public GroupRepository getGroupRepository() {
 		return new HSQLDBGroupRepository(this);

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

@@ -19,6 +19,7 @@ import org.qortal.data.PaymentData;
 import org.qortal.data.group.GroupApprovalData;
 import org.qortal.data.transaction.BaseTransactionData;
 import org.qortal.data.transaction.GroupApprovalTransactionData;
+import org.qortal.data.transaction.MessageTransactionData;
 import org.qortal.data.transaction.TransactionData;
 import org.qortal.data.transaction.TransferAssetTransactionData;
 import org.qortal.repository.DataException;
@@ -630,6 +631,43 @@ public class HSQLDBTransactionRepository implements TransactionRepository {
 		}
 	}
 
+	@Override
+	public List<MessageTransactionData> getMessagesByRecipient(String recipient,
+			Integer limit, Integer offset, Boolean reverse) throws DataException {
+		StringBuilder sql = new StringBuilder(1024);
+		sql.append("SELECT signature from MessageTransactions "
+				+ "JOIN Transactions USING (signature) "
+				+ "JOIN BlockTransactions ON transaction_signature = signature "
+				+ "WHERE recipient = ?");
+
+		sql.append("ORDER BY Transactions.created_when");
+		sql.append((reverse == null || !reverse) ? " ASC" : " DESC");
+
+		HSQLDBRepository.limitOffsetSql(sql, limit, offset);
+
+		List<MessageTransactionData> messageTransactionsData = new ArrayList<>();
+
+		try (ResultSet resultSet = this.repository.checkedExecute(sql.toString(), recipient)) {
+			if (resultSet == null)
+				return messageTransactionsData;
+
+			do {
+				byte[] signature = resultSet.getBytes(1);
+
+				TransactionData transactionData = this.fromSignature(signature);
+				if (transactionData == null || transactionData.getType() != TransactionType.MESSAGE)
+					return null;
+
+				messageTransactionsData.add((MessageTransactionData) transactionData);
+			} while (resultSet.next());
+
+			return messageTransactionsData;
+		} catch (SQLException e) {
+			throw new DataException("Unable to fetch trade-bot messages from repository", e);
+		}
+	}
+
+
 	@Override
 	public List<TransactionData> getAssetTransactions(long assetId, ConfirmationStatus confirmationStatus, Integer limit, Integer offset, Boolean reverse)
 			throws DataException {

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

@@ -26,7 +26,7 @@ import com.google.common.base.Utf8;
 public class DeployAtTransaction extends Transaction {
 
 	// Properties
-	private DeployAtTransactionData deployATTransactionData;
+	private DeployAtTransactionData deployAtTransactionData;
 
 	// Other useful constants
 	public static final int MAX_NAME_SIZE = 200;
@@ -40,31 +40,31 @@ public class DeployAtTransaction extends Transaction {
 	public DeployAtTransaction(Repository repository, TransactionData transactionData) {
 		super(repository, transactionData);
 
-		this.deployATTransactionData = (DeployAtTransactionData) this.transactionData;
+		this.deployAtTransactionData = (DeployAtTransactionData) this.transactionData;
 	}
 
 	// More information
 
 	@Override
 	public List<String> getRecipientAddresses() throws DataException {
-		return Collections.singletonList(this.deployATTransactionData.getAtAddress());
+		return Collections.singletonList(this.deployAtTransactionData.getAtAddress());
 	}
 
 	/** Returns AT version from the header bytes */
 	private short getVersion() {
-		byte[] creationBytes = deployATTransactionData.getCreationBytes();
+		byte[] creationBytes = deployAtTransactionData.getCreationBytes();
 		return (short) ((creationBytes[0] << 8) | (creationBytes[1] & 0xff)); // Big-endian
 	}
 
 	/** Make sure deployATTransactionData has an ATAddress */
-	private void ensureATAddress() throws DataException {
-		if (this.deployATTransactionData.getAtAddress() != null)
+	public static void ensureATAddress(DeployAtTransactionData deployAtTransactionData) throws DataException {
+		if (deployAtTransactionData.getAtAddress() != null)
 			return;
 
 		// Use transaction transformer
 		try {
-			String atAddress = Crypto.toATAddress(TransactionTransformer.toBytesForSigning(this.deployATTransactionData));
-			this.deployATTransactionData.setAtAddress(atAddress);
+			String atAddress = Crypto.toATAddress(TransactionTransformer.toBytesForSigning(deployAtTransactionData));
+			deployAtTransactionData.setAtAddress(atAddress);
 		} catch (TransformationException e) {
 			throw new DataException("Unable to generate AT address");
 		}
@@ -73,9 +73,9 @@ public class DeployAtTransaction extends Transaction {
 	// Navigation
 
 	public Account getATAccount() throws DataException {
-		ensureATAddress();
+		ensureATAddress(this.deployAtTransactionData);
 
-		return new Account(this.repository, this.deployATTransactionData.getAtAddress());
+		return new Account(this.repository, this.deployAtTransactionData.getAtAddress());
 	}
 
 	// Processing
@@ -83,30 +83,30 @@ public class DeployAtTransaction extends Transaction {
 	@Override
 	public ValidationResult isValid() throws DataException {
 		// Check name size bounds
-		int nameLength = Utf8.encodedLength(this.deployATTransactionData.getName());
+		int nameLength = Utf8.encodedLength(this.deployAtTransactionData.getName());
 		if (nameLength < 1 || nameLength > MAX_NAME_SIZE)
 			return ValidationResult.INVALID_NAME_LENGTH;
 
 		// Check description size bounds
-		int descriptionlength = Utf8.encodedLength(this.deployATTransactionData.getDescription());
+		int descriptionlength = Utf8.encodedLength(this.deployAtTransactionData.getDescription());
 		if (descriptionlength < 1 || descriptionlength > MAX_DESCRIPTION_SIZE)
 			return ValidationResult.INVALID_DESCRIPTION_LENGTH;
 
 		// Check AT-type size bounds
-		int atTypeLength = Utf8.encodedLength(this.deployATTransactionData.getAtType());
+		int atTypeLength = Utf8.encodedLength(this.deployAtTransactionData.getAtType());
 		if (atTypeLength < 1 || atTypeLength > MAX_AT_TYPE_SIZE)
 			return ValidationResult.INVALID_AT_TYPE_LENGTH;
 
 		// Check tags size bounds
-		int tagsLength = Utf8.encodedLength(this.deployATTransactionData.getTags());
+		int tagsLength = Utf8.encodedLength(this.deployAtTransactionData.getTags());
 		if (tagsLength < 1 || tagsLength > MAX_TAGS_SIZE)
 			return ValidationResult.INVALID_TAGS_LENGTH;
 
 		// Check amount is positive
-		if (this.deployATTransactionData.getAmount() <= 0)
+		if (this.deployAtTransactionData.getAmount() <= 0)
 			return ValidationResult.NEGATIVE_AMOUNT;
 
-		long assetId = this.deployATTransactionData.getAssetId();
+		long assetId = this.deployAtTransactionData.getAssetId();
 		AssetData assetData = this.repository.getAssetRepository().fromAssetId(assetId);
 		// Check asset even exists
 		if (assetData == null)
@@ -117,7 +117,7 @@ public class DeployAtTransaction extends Transaction {
 			return ValidationResult.ASSET_NOT_SPENDABLE;
 
 		// Check asset amount is integer if asset is not divisible
-		if (!assetData.isDivisible() && this.deployATTransactionData.getAmount() % Amounts.MULTIPLIER != 0)
+		if (!assetData.isDivisible() && this.deployAtTransactionData.getAmount() % Amounts.MULTIPLIER != 0)
 			return ValidationResult.INVALID_AMOUNT;
 
 		Account creator = this.getCreator();
@@ -125,15 +125,15 @@ public class DeployAtTransaction extends Transaction {
 		// Check creator has enough funds
 		if (assetId == Asset.QORT) {
 			// Simple case: amount and fee both in QORT
-			long minimumBalance = this.deployATTransactionData.getFee() + this.deployATTransactionData.getAmount();
+			long minimumBalance = this.deployAtTransactionData.getFee() + this.deployAtTransactionData.getAmount();
 
 			if (creator.getConfirmedBalance(Asset.QORT) < minimumBalance)
 				return ValidationResult.NO_BALANCE;
 		} else {
-			if (creator.getConfirmedBalance(Asset.QORT) < this.deployATTransactionData.getFee())
+			if (creator.getConfirmedBalance(Asset.QORT) < this.deployAtTransactionData.getFee())
 				return ValidationResult.NO_BALANCE;
 
-			if (creator.getConfirmedBalance(assetId) < this.deployATTransactionData.getAmount())
+			if (creator.getConfirmedBalance(assetId) < this.deployAtTransactionData.getAmount())
 				return ValidationResult.NO_BALANCE;
 		}
 
@@ -142,12 +142,12 @@ public class DeployAtTransaction extends Transaction {
 			return ValidationResult.INVALID_CREATION_BYTES;
 
 		// Check creation bytes are valid (for v2+)
-		this.ensureATAddress();
+		ensureATAddress(this.deployAtTransactionData);
 
 		// Just enough AT data to allow API to query initial balances, etc.
-		String atAddress = this.deployATTransactionData.getAtAddress();
-		byte[] creatorPublicKey = this.deployATTransactionData.getCreatorPublicKey();
-		long creation = this.deployATTransactionData.getTimestamp();
+		String atAddress = this.deployAtTransactionData.getAtAddress();
+		byte[] creatorPublicKey = this.deployAtTransactionData.getCreatorPublicKey();
+		long creation = this.deployAtTransactionData.getTimestamp();
 		ATData skeletonAtData = new ATData(atAddress, creatorPublicKey, creation, assetId);
 
 		int height = this.repository.getBlockRepository().getBlockchainHeight() + 1;
@@ -157,7 +157,7 @@ public class DeployAtTransaction extends Transaction {
 		QortalAtLoggerFactory loggerFactory = QortalAtLoggerFactory.getInstance();
 
 		try {
-			new MachineState(api, loggerFactory, this.deployATTransactionData.getCreationBytes());
+			new MachineState(api, loggerFactory, this.deployAtTransactionData.getCreationBytes());
 		} catch (IllegalArgumentException e) {
 			// Not valid
 			return ValidationResult.INVALID_CREATION_BYTES;
@@ -169,25 +169,25 @@ public class DeployAtTransaction extends Transaction {
 	@Override
 	public ValidationResult isProcessable() throws DataException {
 		Account creator = getCreator();
-		long assetId = this.deployATTransactionData.getAssetId();
+		long assetId = this.deployAtTransactionData.getAssetId();
 
 		// Check creator has enough funds
 		if (assetId == Asset.QORT) {
 			// Simple case: amount and fee both in QORT
-			long minimumBalance = this.deployATTransactionData.getFee() + this.deployATTransactionData.getAmount();
+			long minimumBalance = this.deployAtTransactionData.getFee() + this.deployAtTransactionData.getAmount();
 
 			if (creator.getConfirmedBalance(Asset.QORT) < minimumBalance)
 				return ValidationResult.NO_BALANCE;
 		} else {
-			if (creator.getConfirmedBalance(Asset.QORT) < this.deployATTransactionData.getFee())
+			if (creator.getConfirmedBalance(Asset.QORT) < this.deployAtTransactionData.getFee())
 				return ValidationResult.NO_BALANCE;
 
-			if (creator.getConfirmedBalance(assetId) < this.deployATTransactionData.getAmount())
+			if (creator.getConfirmedBalance(assetId) < this.deployAtTransactionData.getAmount())
 				return ValidationResult.NO_BALANCE;
 		}
 
 		// Check AT doesn't already exist
-		if (this.repository.getATRepository().exists(this.deployATTransactionData.getAtAddress()))
+		if (this.repository.getATRepository().exists(this.deployAtTransactionData.getAtAddress()))
 			return ValidationResult.AT_ALREADY_EXISTS;
 
 		return ValidationResult.OK;
@@ -195,40 +195,40 @@ public class DeployAtTransaction extends Transaction {
 
 	@Override
 	public void process() throws DataException {
-		this.ensureATAddress();
+		ensureATAddress(this.deployAtTransactionData);
 
 		// Deploy AT, saving into repository
-		AT at = new AT(this.repository, this.deployATTransactionData);
+		AT at = new AT(this.repository, this.deployAtTransactionData);
 		at.deploy();
 
-		long assetId = this.deployATTransactionData.getAssetId();
+		long assetId = this.deployAtTransactionData.getAssetId();
 
 		// Update creator's balance regarding initial payment to AT
 		Account creator = getCreator();
-		creator.modifyAssetBalance(assetId, - this.deployATTransactionData.getAmount());
+		creator.modifyAssetBalance(assetId, - this.deployAtTransactionData.getAmount());
 
 		// Update AT's reference, which also creates AT account
 		Account atAccount = this.getATAccount();
-		atAccount.setLastReference(this.deployATTransactionData.getSignature());
+		atAccount.setLastReference(this.deployAtTransactionData.getSignature());
 
 		// Update AT's balance
-		atAccount.setConfirmedBalance(assetId, this.deployATTransactionData.getAmount());
+		atAccount.setConfirmedBalance(assetId, this.deployAtTransactionData.getAmount());
 	}
 
 	@Override
 	public void orphan() throws DataException {
 		// Delete AT from repository
-		AT at = new AT(this.repository, this.deployATTransactionData);
+		AT at = new AT(this.repository, this.deployAtTransactionData);
 		at.undeploy();
 
-		long assetId = this.deployATTransactionData.getAssetId();
+		long assetId = this.deployAtTransactionData.getAssetId();
 
 		// Update creator's balance regarding initial payment to AT
 		Account creator = getCreator();
-		creator.modifyAssetBalance(assetId, this.deployATTransactionData.getAmount());
+		creator.modifyAssetBalance(assetId, this.deployAtTransactionData.getAmount());
 
 		// Delete AT's account (and hence its balance)
-		this.repository.getAccountRepository().delete(this.deployATTransactionData.getAtAddress());
+		this.repository.getAccountRepository().delete(this.deployAtTransactionData.getAtAddress());
 	}
 
 }

src/main/java/org/qortal/utils/BitTwiddling.java

@@ -26,9 +26,26 @@ public class BitTwiddling {
 		return new byte[] { (byte) (value), (byte) (value >> 8), (byte) (value >> 16), (byte) (value >> 24) };
 	}
 
+	/** Convert int to big-endian byte array */
+	public static byte[] toBEByteArray(int value) {
+		return new byte[] { (byte) (value >> 24), (byte) (value >> 16), (byte) (value >> 8), (byte) (value) };
+	}
+
+	/** Convert long to big-endian byte array */
+	public static byte[] toBEByteArray(long value) {
+		return new byte[] { (byte) (value >> 56), (byte) (value >> 48), (byte) (value >> 40), (byte) (value >> 32),
+				(byte) (value >> 24), (byte) (value >> 16), (byte) (value >> 8), (byte) (value) };
+	}
+
 	/** Convert little-endian bytes to int */
-	public static int fromLEBytes(byte[] bytes, int offset) {
+	public static int intFromLEBytes(byte[] bytes, int offset) {
 		return (bytes[offset] & 0xff) | (bytes[offset + 1] & 0xff) << 8 | (bytes[offset + 2] & 0xff) << 16 | (bytes[offset + 3] & 0xff) << 24;
 	}
 
+	/** Convert big-endian bytes to long */
+	public static long longFromBEBytes(byte[] bytes, int start) {
+		return (bytes[start] & 0xffL) << 56 | (bytes[start + 1] & 0xffL) << 48 | (bytes[start + 2] & 0xffL) << 40 | (bytes[start + 3] & 0xffL) << 32
+				| (bytes[start + 4] & 0xffL) << 24 | (bytes[start + 5] & 0xffL) << 16 | (bytes[start + 6] & 0xffL) << 8 | (bytes[start + 7] & 0xffL);
+	}
+
 }