Merge branch 'lite-node'

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

@@ -8,11 +8,13 @@ import javax.xml.bind.annotation.XmlAccessorType;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.qortal.block.BlockChain;
+import org.qortal.controller.LiteNode;
 import org.qortal.data.account.AccountBalanceData;
 import org.qortal.data.account.AccountData;
 import org.qortal.data.account.RewardShareData;
 import org.qortal.repository.DataException;
 import org.qortal.repository.Repository;
+import org.qortal.settings.Settings;
 import org.qortal.utils.Base58;
 
 @XmlAccessorType(XmlAccessType.NONE) // Stops JAX-RS errors when unmarshalling blockchain config
@@ -59,7 +61,17 @@ public class Account {
 	// Balance manipulations - assetId is 0 for QORT
 
 	public long getConfirmedBalance(long assetId) throws DataException {
-		AccountBalanceData accountBalanceData = this.repository.getAccountRepository().getBalance(this.address, assetId);
+		AccountBalanceData accountBalanceData;
+
+		if (Settings.getInstance().isLite()) {
+			// Lite nodes request data from peers instead of the local db
+			accountBalanceData = LiteNode.getInstance().fetchAccountBalance(this.address, assetId);
+		}
+		else {
+			// All other node types fetch from the local db
+			accountBalanceData = this.repository.getAccountRepository().getBalance(this.address, assetId);
+		}
+
 		if (accountBalanceData == null)
 			return 0;
 

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

@@ -12,6 +12,7 @@ public class NodeInfo {
 	public long buildTimestamp;
 	public String nodeId;
 	public boolean isTestNet;
+	public String type;
 
 	public NodeInfo() {
 	}

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

@@ -30,6 +30,7 @@ import org.qortal.api.Security;
 import org.qortal.api.model.ApiOnlineAccount;
 import org.qortal.api.model.RewardShareKeyRequest;
 import org.qortal.asset.Asset;
+import org.qortal.controller.LiteNode;
 import org.qortal.controller.OnlineAccountsManager;
 import org.qortal.crypto.Crypto;
 import org.qortal.data.account.AccountData;
@@ -109,18 +110,26 @@ public class AddressesResource {
 		if (!Crypto.isValidAddress(address))
 			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_ADDRESS);
 
-		byte[] lastReference = null;
+		AccountData accountData;
 
-		try (final Repository repository = RepositoryManager.getRepository()) {
+		if (Settings.getInstance().isLite()) {
-			AccountData accountData = repository.getAccountRepository().getAccount(address);
+			// Lite nodes request data from peers instead of the local db
-			// Not found?
+			accountData = LiteNode.getInstance().fetchAccountData(address);
-			if (accountData == null)
-				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.ADDRESS_UNKNOWN);
-
-			lastReference = accountData.getReference();
-		} catch (DataException e) {
-			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.REPOSITORY_ISSUE, e);
 		}
+		else {
+			// All other node types request data from local db
+			try (final Repository repository = RepositoryManager.getRepository()) {
+				accountData = repository.getAccountRepository().getAccount(address);
+			} catch (DataException e) {
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.REPOSITORY_ISSUE, e);
+			}
+		}
+
+		// Not found?
+		if (accountData == null)
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.ADDRESS_UNKNOWN);
+
+		byte[] lastReference = accountData.getReference();
 
 		if (lastReference == null || lastReference.length == 0)
 			return "false";

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

@@ -119,10 +119,23 @@ public class AdminResource {
 		nodeInfo.buildTimestamp = Controller.getInstance().getBuildTimestamp();
 		nodeInfo.nodeId = Network.getInstance().getOurNodeId();
 		nodeInfo.isTestNet = Settings.getInstance().isTestNet();
+		nodeInfo.type = getNodeType();
 
 		return nodeInfo;
 	}
 
+	private String getNodeType() {
+		if (Settings.getInstance().isTopOnly()) {
+			return "topOnly";
+		}
+		else if (Settings.getInstance().isLite()) {
+			return "lite";
+		}
+		else {
+			return "full";
+		}
+	}
+
 	@GET
 	@Path("/status")
 	@Operation(

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

@@ -26,6 +26,7 @@ import org.qortal.api.ApiErrors;
 import org.qortal.api.ApiException;
 import org.qortal.api.ApiExceptionFactory;
 import org.qortal.api.model.NameSummary;
+import org.qortal.controller.LiteNode;
 import org.qortal.crypto.Crypto;
 import org.qortal.data.naming.NameData;
 import org.qortal.data.transaction.BuyNameTransactionData;
@@ -101,7 +102,14 @@ public class NamesResource {
 			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_ADDRESS);
 
 		try (final Repository repository = RepositoryManager.getRepository()) {
-			List<NameData> names = repository.getNameRepository().getNamesByOwner(address, limit, offset, reverse);
+			List<NameData> names;
+
+			if (Settings.getInstance().isLite()) {
+				names = LiteNode.getInstance().fetchAccountNames(address);
+			}
+			else {
+				names = repository.getNameRepository().getNamesByOwner(address, limit, offset, reverse);
+			}
 
 			return names.stream().map(NameSummary::new).collect(Collectors.toList());
 		} catch (DataException e) {
@@ -126,10 +134,18 @@ public class NamesResource {
 	@ApiErrors({ApiError.NAME_UNKNOWN, ApiError.REPOSITORY_ISSUE})
 	public NameData getName(@PathParam("name") String name) {
 		try (final Repository repository = RepositoryManager.getRepository()) {
-			NameData nameData = repository.getNameRepository().fromName(name);
+			NameData nameData;
 
-			if (nameData == null)
+			if (Settings.getInstance().isLite()) {
+				nameData = LiteNode.getInstance().fetchNameData(name);
+			}
+			else {
+				nameData = repository.getNameRepository().fromName(name);
+			}
+
+			if (nameData == null) {
 				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.NAME_UNKNOWN);
+			}
 
 			return nameData;
 		} catch (ApiException e) {

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

@@ -12,6 +12,7 @@ import io.swagger.v3.oas.annotations.tags.Tag;
 import java.lang.reflect.Constructor;
 import java.lang.reflect.InvocationTargetException;
 import java.util.ArrayList;
+import java.util.Comparator;
 import java.util.List;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.locks.ReentrantLock;
@@ -32,6 +33,8 @@ import org.qortal.api.ApiException;
 import org.qortal.api.ApiExceptionFactory;
 import org.qortal.api.model.SimpleTransactionSignRequest;
 import org.qortal.controller.Controller;
+import org.qortal.controller.LiteNode;
+import org.qortal.crypto.Crypto;
 import org.qortal.data.transaction.TransactionData;
 import org.qortal.globalization.Translator;
 import org.qortal.repository.DataException;
@@ -366,6 +369,73 @@ public class TransactionsResource {
 		}
 	}
 
+	@GET
+	@Path("/address/{address}")
+	@Operation(
+			summary = "Returns transactions for given address",
+			responses = {
+					@ApiResponse(
+							description = "transactions",
+							content = @Content(
+									array = @ArraySchema(
+											schema = @Schema(
+													implementation = TransactionData.class
+											)
+									)
+							)
+					)
+			}
+	)
+	@ApiErrors({ApiError.INVALID_ADDRESS,  ApiError.REPOSITORY_ISSUE})
+	public List<TransactionData> getAddressTransactions(@PathParam("address") String address,
+												 		@Parameter(ref = "limit") @QueryParam("limit") Integer limit,
+												 		@Parameter(ref = "offset") @QueryParam("offset") Integer offset,
+														@Parameter(ref = "reverse") @QueryParam("reverse") Boolean reverse) {
+		if (!Crypto.isValidAddress(address)) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_ADDRESS);
+		}
+
+		if (limit == null) {
+			limit = 0;
+		}
+		if (offset == null) {
+			offset = 0;
+		}
+
+		List<TransactionData> transactions;
+
+		if (Settings.getInstance().isLite()) {
+			// Fetch from network
+			transactions = LiteNode.getInstance().fetchAccountTransactions(address, limit, offset);
+
+			// Sort the data, since we can't guarantee the order that a peer sent it in
+			if (reverse) {
+				transactions.sort(Comparator.comparingLong(TransactionData::getTimestamp).reversed());
+			} else {
+				transactions.sort(Comparator.comparingLong(TransactionData::getTimestamp));
+			}
+		}
+		else {
+			// Fetch from local db
+			try (final Repository repository = RepositoryManager.getRepository()) {
+				List<byte[]> signatures = repository.getTransactionRepository().getSignaturesMatchingCriteria(null, null, null,
+						null, null, null, address, TransactionsResource.ConfirmationStatus.CONFIRMED, limit, offset, reverse);
+
+				// Expand signatures to transactions
+				transactions = new ArrayList<>(signatures.size());
+				for (byte[] signature : signatures) {
+					transactions.add(repository.getTransactionRepository().fromSignature(signature));
+				}
+			} catch (ApiException e) {
+				throw e;
+			} catch (DataException e) {
+				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.REPOSITORY_ISSUE, e);
+			}
+		}
+
+		return transactions;
+	}
+
 	@GET
 	@Path("/unitfee")
 	@Operation(

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

@@ -69,7 +69,8 @@ public class BlockChain {
 		newBlockSigHeight,
 		shareBinFix,
 		calcChainWeightTimestamp,
-		transactionV5Timestamp;
+		transactionV5Timestamp,
+		transactionV6Timestamp;
 	}
 
 	// Custom transaction fees
@@ -405,6 +406,10 @@ public class BlockChain {
 		return this.featureTriggers.get(FeatureTrigger.transactionV5Timestamp.name()).longValue();
 	}
 
+	public long getTransactionV6Timestamp() {
+		return this.featureTriggers.get(FeatureTrigger.transactionV6Timestamp.name()).longValue();
+	}
+
 	// More complex getters for aspects that change by height or timestamp
 
 	public long getRewardAtHeight(int ourHeight) {

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

@@ -61,6 +61,11 @@ public class BlockMinter extends Thread {
 	public void run() {
 		Thread.currentThread().setName("BlockMinter");
 
+		if (Settings.getInstance().isLite()) {
+			// Lite nodes do not mint
+			return;
+		}
+
 		try (final Repository repository = RepositoryManager.getRepository()) {
 			if (Settings.getInstance().getWipeUnconfirmedOnStart()) {
 				// Wipe existing unconfirmed transactions

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

@@ -32,6 +32,7 @@ import org.bouncycastle.jsse.provider.BouncyCastleJsseProvider;
 import org.qortal.api.ApiService;
 import org.qortal.api.DomainMapService;
 import org.qortal.api.GatewayService;
+import org.qortal.api.resource.TransactionsResource;
 import org.qortal.block.Block;
 import org.qortal.block.BlockChain;
 import org.qortal.block.BlockChain.BlockTimingByHeight;
@@ -39,8 +40,11 @@ import org.qortal.controller.arbitrary.*;
 import org.qortal.controller.repository.PruneManager;
 import org.qortal.controller.repository.NamesDatabaseIntegrityCheck;
 import org.qortal.controller.tradebot.TradeBot;
+import org.qortal.data.account.AccountBalanceData;
+import org.qortal.data.account.AccountData;
 import org.qortal.data.block.BlockData;
 import org.qortal.data.block.BlockSummaryData;
+import org.qortal.data.naming.NameData;
 import org.qortal.data.network.PeerChainTipData;
 import org.qortal.data.network.PeerData;
 import org.qortal.data.transaction.ChatTransactionData;
@@ -179,6 +183,52 @@ public class Controller extends Thread {
 		}
 		public GetArbitraryMetadataMessageStats getArbitraryMetadataMessageStats = new GetArbitraryMetadataMessageStats();
 
+		public static class GetAccountMessageStats {
+			public AtomicLong requests = new AtomicLong();
+			public AtomicLong cacheHits = new AtomicLong();
+			public AtomicLong unknownAccounts = new AtomicLong();
+
+			public GetAccountMessageStats() {
+			}
+		}
+		public GetAccountMessageStats getAccountMessageStats = new GetAccountMessageStats();
+
+		public static class GetAccountBalanceMessageStats {
+			public AtomicLong requests = new AtomicLong();
+			public AtomicLong unknownAccounts = new AtomicLong();
+
+			public GetAccountBalanceMessageStats() {
+			}
+		}
+		public GetAccountBalanceMessageStats getAccountBalanceMessageStats = new GetAccountBalanceMessageStats();
+
+		public static class GetAccountTransactionsMessageStats {
+			public AtomicLong requests = new AtomicLong();
+			public AtomicLong unknownAccounts = new AtomicLong();
+
+			public GetAccountTransactionsMessageStats() {
+			}
+		}
+		public GetAccountTransactionsMessageStats getAccountTransactionsMessageStats = new GetAccountTransactionsMessageStats();
+
+		public static class GetAccountNamesMessageStats {
+			public AtomicLong requests = new AtomicLong();
+			public AtomicLong unknownAccounts = new AtomicLong();
+
+			public GetAccountNamesMessageStats() {
+			}
+		}
+		public GetAccountNamesMessageStats getAccountNamesMessageStats = new GetAccountNamesMessageStats();
+
+		public static class GetNameMessageStats {
+			public AtomicLong requests = new AtomicLong();
+			public AtomicLong unknownAccounts = new AtomicLong();
+
+			public GetNameMessageStats() {
+			}
+		}
+		public GetNameMessageStats getNameMessageStats = new GetNameMessageStats();
+
 		public AtomicLong latestBlocksCacheRefills = new AtomicLong();
 
 		public StatsSnapshot() {
@@ -363,23 +413,27 @@ public class Controller extends Thread {
 			return; // Not System.exit() so that GUI can display error
 		}
 
-		// Rebuild Names table and check database integrity (if enabled)
+		// If we have a non-lite node, we need to perform some startup actions
-		NamesDatabaseIntegrityCheck namesDatabaseIntegrityCheck = new NamesDatabaseIntegrityCheck();
+		if (!Settings.getInstance().isLite()) {
-		namesDatabaseIntegrityCheck.rebuildAllNames();
-		if (Settings.getInstance().isNamesIntegrityCheckEnabled()) {
-			namesDatabaseIntegrityCheck.runIntegrityCheck();
-		}
 
-		LOGGER.info("Validating blockchain");
+			// Rebuild Names table and check database integrity (if enabled)
-		try {
+			NamesDatabaseIntegrityCheck namesDatabaseIntegrityCheck = new NamesDatabaseIntegrityCheck();
-			BlockChain.validate();
+			namesDatabaseIntegrityCheck.rebuildAllNames();
+			if (Settings.getInstance().isNamesIntegrityCheckEnabled()) {
+				namesDatabaseIntegrityCheck.runIntegrityCheck();
+			}
 
-			Controller.getInstance().refillLatestBlocksCache();
+			LOGGER.info("Validating blockchain");
-			LOGGER.info(String.format("Our chain height at start-up: %d", Controller.getInstance().getChainHeight()));
+			try {
-		} catch (DataException e) {
+				BlockChain.validate();
-			LOGGER.error("Couldn't validate blockchain", e);
+
-			Gui.getInstance().fatalError("Blockchain validation issue", e);
+				Controller.getInstance().refillLatestBlocksCache();
-			return; // Not System.exit() so that GUI can display error
+				LOGGER.info(String.format("Our chain height at start-up: %d", Controller.getInstance().getChainHeight()));
+			} catch (DataException e) {
+				LOGGER.error("Couldn't validate blockchain", e);
+				Gui.getInstance().fatalError("Blockchain validation issue", e);
+				return; // Not System.exit() so that GUI can display error
+			}
 		}
 
 		// Import current trade bot states and minting accounts if they exist
@@ -737,7 +791,11 @@ public class Controller extends Thread {
 		final Long minLatestBlockTimestamp = NTP.getTime() - (30 * 60 * 1000L);
 
 		synchronized (Synchronizer.getInstance().syncLock) {
-			if (this.isMintingPossible) {
+			if (Settings.getInstance().isLite()) {
+				actionText = Translator.INSTANCE.translate("SysTray", "LITE_NODE");
+				SysTray.getInstance().setTrayIcon(4);
+			}
+			else if (this.isMintingPossible) {
 				actionText = Translator.INSTANCE.translate("SysTray", "MINTING_ENABLED");
 				SysTray.getInstance().setTrayIcon(2);
 			}
@@ -759,7 +817,11 @@ public class Controller extends Thread {
 			}
 		}
 
-		String tooltip = String.format("%s - %d %s - %s %d", actionText, numberOfPeers, connectionsText, heightText, height) + "\n" + String.format("%s: %s", Translator.INSTANCE.translate("SysTray", "BUILD_VERSION"), this.buildVersion);
+		String tooltip = String.format("%s - %d %s", actionText, numberOfPeers, connectionsText);
+		if (!Settings.getInstance().isLite()) {
+			tooltip.concat(String.format(" - %s %d", heightText, height));
+		}
+		tooltip.concat(String.format("\n%s: %s", Translator.INSTANCE.translate("SysTray", "BUILD_VERSION"), this.buildVersion));
 		SysTray.getInstance().setToolTipText(tooltip);
 
 		this.callbackExecutor.execute(() -> {
@@ -916,6 +978,11 @@ public class Controller extends Thread {
 	// Callbacks for/from network
 
 	public void doNetworkBroadcast() {
+		if (Settings.getInstance().isLite()) {
+			// Lite nodes have nothing to broadcast
+			return;
+		}
+
 		Network network = Network.getInstance();
 
 		// Send (if outbound) / Request peer lists
@@ -1198,6 +1265,26 @@ public class Controller extends Thread {
 				TradeBot.getInstance().onTradePresencesMessage(peer, message);
 				break;
 
+			case GET_ACCOUNT:
+				onNetworkGetAccountMessage(peer, message);
+				break;
+
+			case GET_ACCOUNT_BALANCE:
+				onNetworkGetAccountBalanceMessage(peer, message);
+				break;
+
+			case GET_ACCOUNT_TRANSACTIONS:
+				onNetworkGetAccountTransactionsMessage(peer, message);
+				break;
+
+			case GET_ACCOUNT_NAMES:
+				onNetworkGetAccountNamesMessage(peer, message);
+				break;
+
+			case GET_NAME:
+				onNetworkGetNameMessage(peer, message);
+				break;
+
 			default:
 				LOGGER.debug(() -> String.format("Unhandled %s message [ID %d] from peer %s", message.getType().name(), message.getId(), peer));
 				break;
@@ -1434,11 +1521,13 @@ public class Controller extends Thread {
 	private void onNetworkHeightV2Message(Peer peer, Message message) {
 		HeightV2Message heightV2Message = (HeightV2Message) message;
 
-		// If peer is inbound and we've not updated their height
+		if (!Settings.getInstance().isLite()) {
-		// then this is probably their initial HEIGHT_V2 message
+			// If peer is inbound and we've not updated their height
-		// so they need a corresponding HEIGHT_V2 message from us
+			// then this is probably their initial HEIGHT_V2 message
-		if (!peer.isOutbound() && (peer.getChainTipData() == null || peer.getChainTipData().getLastHeight() == null))
+			// so they need a corresponding HEIGHT_V2 message from us
-			peer.sendMessage(Network.getInstance().buildHeightMessage(peer, getChainTip()));
+			if (!peer.isOutbound() && (peer.getChainTipData() == null || peer.getChainTipData().getLastHeight() == null))
+				peer.sendMessage(Network.getInstance().buildHeightMessage(peer, getChainTip()));
+		}
 
 		// Update peer chain tip data
 		PeerChainTipData newChainTipData = new PeerChainTipData(heightV2Message.getHeight(), heightV2Message.getSignature(), heightV2Message.getTimestamp(), heightV2Message.getMinterPublicKey());
@@ -1448,6 +1537,193 @@ public class Controller extends Thread {
 		Synchronizer.getInstance().requestSync();
 	}
 
+	private void onNetworkGetAccountMessage(Peer peer, Message message) {
+		GetAccountMessage getAccountMessage = (GetAccountMessage) message;
+		String address = getAccountMessage.getAddress();
+		this.stats.getAccountMessageStats.requests.incrementAndGet();
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			AccountData accountData = repository.getAccountRepository().getAccount(address);
+
+			if (accountData == null) {
+				// We don't have this account
+				this.stats.getAccountMessageStats.unknownAccounts.getAndIncrement();
+
+				// Send valid, yet unexpected message type in response, so peer doesn't have to wait for timeout
+				LOGGER.debug(() -> String.format("Sending 'account unknown' response to peer %s for GET_ACCOUNT request for unknown account %s", peer, address));
+
+				// We'll send empty block summaries message as it's very short
+				Message accountUnknownMessage = new BlockSummariesMessage(Collections.emptyList());
+				accountUnknownMessage.setId(message.getId());
+				if (!peer.sendMessage(accountUnknownMessage))
+					peer.disconnect("failed to send account-unknown response");
+				return;
+			}
+
+			AccountMessage accountMessage = new AccountMessage(accountData);
+			accountMessage.setId(message.getId());
+
+			if (!peer.sendMessage(accountMessage)) {
+				peer.disconnect("failed to send account");
+			}
+
+		} catch (DataException e) {
+			LOGGER.error(String.format("Repository issue while send account %s to peer %s", address, peer), e);
+		}
+	}
+
+	private void onNetworkGetAccountBalanceMessage(Peer peer, Message message) {
+		GetAccountBalanceMessage getAccountBalanceMessage = (GetAccountBalanceMessage) message;
+		String address = getAccountBalanceMessage.getAddress();
+		long assetId = getAccountBalanceMessage.getAssetId();
+		this.stats.getAccountBalanceMessageStats.requests.incrementAndGet();
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			AccountBalanceData accountBalanceData = repository.getAccountRepository().getBalance(address, assetId);
+
+			if (accountBalanceData == null) {
+				// We don't have this account
+				this.stats.getAccountBalanceMessageStats.unknownAccounts.getAndIncrement();
+
+				// Send valid, yet unexpected message type in response, so peer doesn't have to wait for timeout
+				LOGGER.debug(() -> String.format("Sending 'account unknown' response to peer %s for GET_ACCOUNT_BALANCE request for unknown account %s and asset ID %d", peer, address, assetId));
+
+				// We'll send empty block summaries message as it's very short
+				Message accountUnknownMessage = new BlockSummariesMessage(Collections.emptyList());
+				accountUnknownMessage.setId(message.getId());
+				if (!peer.sendMessage(accountUnknownMessage))
+					peer.disconnect("failed to send account-unknown response");
+				return;
+			}
+
+			AccountBalanceMessage accountMessage = new AccountBalanceMessage(accountBalanceData);
+			accountMessage.setId(message.getId());
+
+			if (!peer.sendMessage(accountMessage)) {
+				peer.disconnect("failed to send account balance");
+			}
+
+		} catch (DataException e) {
+			LOGGER.error(String.format("Repository issue while send balance for account %s and asset ID %d to peer %s", address, assetId, peer), e);
+		}
+	}
+
+	private void onNetworkGetAccountTransactionsMessage(Peer peer, Message message) {
+		GetAccountTransactionsMessage getAccountTransactionsMessage = (GetAccountTransactionsMessage) message;
+		String address = getAccountTransactionsMessage.getAddress();
+		int limit = Math.min(getAccountTransactionsMessage.getLimit(), 100);
+		int offset = getAccountTransactionsMessage.getOffset();
+		this.stats.getAccountTransactionsMessageStats.requests.incrementAndGet();
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			List<byte[]> signatures = repository.getTransactionRepository().getSignaturesMatchingCriteria(null, null, null,
+					null, null, null, address, TransactionsResource.ConfirmationStatus.CONFIRMED, limit, offset, false);
+
+			// Expand signatures to transactions
+			List<TransactionData> transactions = new ArrayList<>(signatures.size());
+			for (byte[] signature : signatures) {
+				transactions.add(repository.getTransactionRepository().fromSignature(signature));
+			}
+
+			if (transactions == null) {
+				// We don't have this account
+				this.stats.getAccountTransactionsMessageStats.unknownAccounts.getAndIncrement();
+
+				// Send valid, yet unexpected message type in response, so peer doesn't have to wait for timeout
+				LOGGER.debug(() -> String.format("Sending 'account unknown' response to peer %s for GET_ACCOUNT_TRANSACTIONS request for unknown account %s", peer, address));
+
+				// We'll send empty block summaries message as it's very short
+				Message accountUnknownMessage = new BlockSummariesMessage(Collections.emptyList());
+				accountUnknownMessage.setId(message.getId());
+				if (!peer.sendMessage(accountUnknownMessage))
+					peer.disconnect("failed to send account-unknown response");
+				return;
+			}
+
+			TransactionsMessage transactionsMessage = new TransactionsMessage(transactions);
+			transactionsMessage.setId(message.getId());
+
+			if (!peer.sendMessage(transactionsMessage)) {
+				peer.disconnect("failed to send account transactions");
+			}
+
+		} catch (DataException e) {
+			LOGGER.error(String.format("Repository issue while sending transactions for account %s %d to peer %s", address, peer), e);
+		} catch (MessageException e) {
+			LOGGER.error(String.format("Message serialization issue while sending transactions for account %s %d to peer %s", address, peer), e);
+		}
+	}
+
+	private void onNetworkGetAccountNamesMessage(Peer peer, Message message) {
+		GetAccountNamesMessage getAccountNamesMessage = (GetAccountNamesMessage) message;
+		String address = getAccountNamesMessage.getAddress();
+		this.stats.getAccountNamesMessageStats.requests.incrementAndGet();
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			List<NameData> namesDataList = repository.getNameRepository().getNamesByOwner(address);
+
+			if (namesDataList == null) {
+				// We don't have this account
+				this.stats.getAccountNamesMessageStats.unknownAccounts.getAndIncrement();
+
+				// Send valid, yet unexpected message type in response, so peer doesn't have to wait for timeout
+				LOGGER.debug(() -> String.format("Sending 'account unknown' response to peer %s for GET_ACCOUNT_NAMES request for unknown account %s", peer, address));
+
+				// We'll send empty block summaries message as it's very short
+				Message accountUnknownMessage = new BlockSummariesMessage(Collections.emptyList());
+				accountUnknownMessage.setId(message.getId());
+				if (!peer.sendMessage(accountUnknownMessage))
+					peer.disconnect("failed to send account-unknown response");
+				return;
+			}
+
+			NamesMessage namesMessage = new NamesMessage(namesDataList);
+			namesMessage.setId(message.getId());
+
+			if (!peer.sendMessage(namesMessage)) {
+				peer.disconnect("failed to send account names");
+			}
+
+		} catch (DataException e) {
+			LOGGER.error(String.format("Repository issue while send names for account %s to peer %s", address, peer), e);
+		}
+	}
+
+	private void onNetworkGetNameMessage(Peer peer, Message message) {
+		GetNameMessage getNameMessage = (GetNameMessage) message;
+		String name = getNameMessage.getName();
+		this.stats.getNameMessageStats.requests.incrementAndGet();
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			NameData nameData = repository.getNameRepository().fromName(name);
+
+			if (nameData == null) {
+				// We don't have this account
+				this.stats.getNameMessageStats.unknownAccounts.getAndIncrement();
+
+				// Send valid, yet unexpected message type in response, so peer doesn't have to wait for timeout
+				LOGGER.debug(() -> String.format("Sending 'name unknown' response to peer %s for GET_NAME request for unknown name %s", peer, name));
+
+				// We'll send empty block summaries message as it's very short
+				Message nameUnknownMessage = new BlockSummariesMessage(Collections.emptyList());
+				nameUnknownMessage.setId(message.getId());
+				if (!peer.sendMessage(nameUnknownMessage))
+					peer.disconnect("failed to send name-unknown response");
+				return;
+			}
+
+			NamesMessage namesMessage = new NamesMessage(Arrays.asList(nameData));
+			namesMessage.setId(message.getId());
+
+			if (!peer.sendMessage(namesMessage)) {
+				peer.disconnect("failed to send name data");
+			}
+
+		} catch (DataException e) {
+			LOGGER.error(String.format("Repository issue while send name %s to peer %s", name, peer), e);
+		}
+	}
+
 
 	// Utilities
 
@@ -1499,6 +1775,11 @@ public class Controller extends Thread {
 	 * @return boolean - whether our node's blockchain is up to date or not
 	 */
 	public boolean isUpToDate(Long minLatestBlockTimestamp) {
+		if (Settings.getInstance().isLite()) {
+			// Lite nodes are always "up to date"
+			return true;
+		}
+
 		// Do we even have a vaguely recent block?
 		if (minLatestBlockTimestamp == null)
 			return false;

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

@@ -0,0 +1,189 @@
+package org.qortal.controller;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.qortal.data.account.AccountBalanceData;
+import org.qortal.data.account.AccountData;
+import org.qortal.data.naming.NameData;
+import org.qortal.data.transaction.TransactionData;
+import org.qortal.network.Network;
+import org.qortal.network.Peer;
+import org.qortal.network.message.*;
+
+import java.security.SecureRandom;
+import java.util.*;
+
+import static org.qortal.network.message.MessageType.*;
+
+public class LiteNode {
+
+    private static final Logger LOGGER = LogManager.getLogger(LiteNode.class);
+
+    private static LiteNode instance;
+
+
+    public Map<Integer, Long> pendingRequests = Collections.synchronizedMap(new HashMap<>());
+
+    public int MAX_TRANSACTIONS_PER_MESSAGE = 100;
+
+
+    public LiteNode() {
+
+    }
+
+    public static synchronized LiteNode getInstance() {
+        if (instance == null) {
+            instance = new LiteNode();
+        }
+
+        return instance;
+    }
+
+
+    /**
+     * Fetch account data from peers for given QORT address
+     * @param address - the QORT address to query
+     * @return accountData - the account data for this address, or null if not retrieved
+     */
+    public AccountData fetchAccountData(String address) {
+        GetAccountMessage getAccountMessage = new GetAccountMessage(address);
+        AccountMessage accountMessage = (AccountMessage) this.sendMessage(getAccountMessage, ACCOUNT);
+        if (accountMessage == null) {
+            return null;
+        }
+        return accountMessage.getAccountData();
+    }
+
+    /**
+     * Fetch account balance data from peers for given QORT address and asset ID
+     * @param address - the QORT address to query
+     * @return balance - the balance for this address and assetId, or null if not retrieved
+     */
+    public AccountBalanceData fetchAccountBalance(String address, long assetId) {
+        GetAccountBalanceMessage getAccountMessage = new GetAccountBalanceMessage(address, assetId);
+        AccountBalanceMessage accountMessage = (AccountBalanceMessage) this.sendMessage(getAccountMessage, ACCOUNT_BALANCE);
+        if (accountMessage == null) {
+            return null;
+        }
+        return accountMessage.getAccountBalanceData();
+    }
+
+    /**
+     * Fetch list of transactions for given QORT address
+     * @param address - the QORT address to query
+     * @param limit - the maximum number of results to return
+     * @param offset - the starting index
+     * @return a list of TransactionData objects, or null if not retrieved
+     */
+    public List<TransactionData> fetchAccountTransactions(String address, int limit, int offset) {
+        List<TransactionData> allTransactions = new ArrayList<>();
+        if (limit == 0) {
+            limit = Integer.MAX_VALUE;
+        }
+        int batchSize = Math.min(limit, MAX_TRANSACTIONS_PER_MESSAGE);
+
+        while (allTransactions.size() < limit) {
+            GetAccountTransactionsMessage getAccountTransactionsMessage = new GetAccountTransactionsMessage(address, batchSize, offset);
+            TransactionsMessage transactionsMessage = (TransactionsMessage) this.sendMessage(getAccountTransactionsMessage, TRANSACTIONS);
+            if (transactionsMessage == null) {
+                // An error occurred, so give up instead of returning partial results
+                return null;
+            }
+            allTransactions.addAll(transactionsMessage.getTransactions());
+            if (transactionsMessage.getTransactions().size() < batchSize) {
+                // No more transactions to fetch
+                break;
+            }
+            offset += batchSize;
+        }
+        return allTransactions;
+    }
+
+    /**
+     * Fetch list of names for given QORT address
+     * @param address - the QORT address to query
+     * @return a list of NameData objects, or null if not retrieved
+     */
+    public List<NameData> fetchAccountNames(String address) {
+        GetAccountNamesMessage getAccountNamesMessage = new GetAccountNamesMessage(address);
+        NamesMessage namesMessage = (NamesMessage) this.sendMessage(getAccountNamesMessage, NAMES);
+        if (namesMessage == null) {
+            return null;
+        }
+        return namesMessage.getNameDataList();
+    }
+
+    /**
+     * Fetch info about a registered name
+     * @param name - the name to query
+     * @return a NameData object, or null if not retrieved
+     */
+    public NameData fetchNameData(String name) {
+        GetNameMessage getNameMessage = new GetNameMessage(name);
+        NamesMessage namesMessage = (NamesMessage) this.sendMessage(getNameMessage, NAMES);
+        if (namesMessage == null) {
+            return null;
+        }
+        List<NameData> nameDataList = namesMessage.getNameDataList();
+        if (nameDataList == null || nameDataList.size() != 1) {
+            return null;
+        }
+        // We are only expecting a single item in the list
+        return nameDataList.get(0);
+    }
+
+
+    private Message sendMessage(Message message, MessageType expectedResponseMessageType) {
+        // This asks a random peer for the data
+        // TODO: ask multiple peers, and disregard everything if there are any significant differences in the responses
+
+        // Needs a mutable copy of the unmodifiableList
+        List<Peer> peers = new ArrayList<>(Network.getInstance().getImmutableHandshakedPeers());
+
+        // Disregard peers that have "misbehaved" recently
+        peers.removeIf(Controller.hasMisbehaved);
+
+        // Disregard peers that only have genesis block
+        // TODO: peers.removeIf(Controller.hasOnlyGenesisBlock);
+
+        // Disregard peers that are on an old version
+        peers.removeIf(Controller.hasOldVersion);
+
+        // Disregard peers that are on a known inferior chain tip
+        // TODO: peers.removeIf(Controller.hasInferiorChainTip);
+
+        if (peers.isEmpty()) {
+            LOGGER.info("No peers available to send {} message to", message.getType());
+            return null;
+        }
+
+        // Pick random peer
+        int index = new SecureRandom().nextInt(peers.size());
+        Peer peer = peers.get(index);
+
+        LOGGER.info("Sending {} message to peer {}...", message.getType(), peer);
+
+        Message responseMessage;
+
+        try {
+            responseMessage = peer.getResponse(message);
+
+        } catch (InterruptedException e) {
+            return null;
+        }
+
+        if (responseMessage == null) {
+            LOGGER.info("Peer didn't respond to {} message", peer, message.getType());
+            return null;
+        }
+        else if (responseMessage.getType() != expectedResponseMessageType) {
+            LOGGER.info("Peer responded with unexpected message type {} (should be {})", peer, responseMessage.getType(), expectedResponseMessageType);
+            return null;
+        }
+
+        LOGGER.info("Peer {} responded with {} message", peer, responseMessage.getType());
+
+        return responseMessage;
+    }
+
+}

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

@@ -134,6 +134,11 @@ public class Synchronizer extends Thread {
 	public void run() {
 		Thread.currentThread().setName("Synchronizer");
 
+		if (Settings.getInstance().isLite()) {
+			// Lite nodes don't need to sync
+			return;
+		}
+
 		try {
 			while (running && !Controller.isStopping()) {
 				Thread.sleep(1000);

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

@@ -11,6 +11,7 @@ import org.qortal.network.message.TransactionSignaturesMessage;
 import org.qortal.repository.DataException;
 import org.qortal.repository.Repository;
 import org.qortal.repository.RepositoryManager;
+import org.qortal.settings.Settings;
 import org.qortal.transaction.Transaction;
 import org.qortal.transform.TransformationException;
 import org.qortal.utils.Base58;
@@ -55,6 +56,8 @@ public class TransactionImporter extends Thread {
 
     @Override
     public void run() {
+        Thread.currentThread().setName("Transaction Importer");
+
         try {
             while (!Controller.isStopping()) {
                 Thread.sleep(1000L);
@@ -106,6 +109,8 @@ public class TransactionImporter extends Thread {
 
             List<Transaction> sigValidTransactions = new ArrayList<>();
 
+            boolean isLiteNode = Settings.getInstance().isLite();
+
             // Signature validation round - does not require blockchain lock
             for (Map.Entry<TransactionData, Boolean> transactionEntry : incomingTransactionsCopy.entrySet()) {
                 // Quick exit?
@@ -119,6 +124,12 @@ public class TransactionImporter extends Thread {
                 // Only validate signature if we haven't already done so
                 Boolean isSigValid = transactionEntry.getValue();
                 if (!Boolean.TRUE.equals(isSigValid)) {
+                    if (isLiteNode) {
+                        // Lite nodes can't easily validate transactions, so for now we will have to assume that everything is valid
+                        sigValidTransactions.add(transaction);
+                        continue;
+                    }
+
                     if (!transaction.isSignatureValid()) {
                         String signature58 = Base58.encode(transactionData.getSignature());
 

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

@@ -19,6 +19,11 @@ public class AtStatesPruner implements Runnable {
 	public void run() {
 		Thread.currentThread().setName("AT States pruner");
 
+		if (Settings.getInstance().isLite()) {
+			// Nothing to prune in lite mode
+			return;
+		}
+
 		boolean archiveMode = false;
 		if (!Settings.getInstance().isTopOnly()) {
 			// Top-only mode isn't enabled, but we might want to prune for the purposes of archiving

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

@@ -19,6 +19,11 @@ public class AtStatesTrimmer implements Runnable {
 	public void run() {
 		Thread.currentThread().setName("AT States trimmer");
 
+		if (Settings.getInstance().isLite()) {
+			// Nothing to trim in lite mode
+			return;
+		}
+
 		try (final Repository repository = RepositoryManager.getRepository()) {
 			int trimStartHeight = repository.getATRepository().getAtTrimHeight();
 

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

@@ -21,7 +21,7 @@ public class BlockArchiver implements Runnable {
 	public void run() {
 		Thread.currentThread().setName("Block archiver");
 
-		if (!Settings.getInstance().isArchiveEnabled()) {
+		if (!Settings.getInstance().isArchiveEnabled() || Settings.getInstance().isLite()) {
 			return;
 		}
 

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

@@ -19,6 +19,11 @@ public class BlockPruner implements Runnable {
 	public void run() {
 		Thread.currentThread().setName("Block pruner");
 
+		if (Settings.getInstance().isLite()) {
+			// Nothing to prune in lite mode
+			return;
+		}
+
 		boolean archiveMode = false;
 		if (!Settings.getInstance().isTopOnly()) {
 			// Top-only mode isn't enabled, but we might want to prune for the purposes of archiving

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

@@ -21,6 +21,11 @@ public class OnlineAccountsSignaturesTrimmer implements Runnable {
 	public void run() {
 		Thread.currentThread().setName("Online Accounts trimmer");
 
+		if (Settings.getInstance().isLite()) {
+			// Nothing to trim in lite mode
+			return;
+		}
+
 		try (final Repository repository = RepositoryManager.getRepository()) {
 			// Don't even start trimming until initial rush has ended
 			Thread.sleep(INITIAL_SLEEP_PERIOD);

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

@@ -1084,11 +1084,13 @@ public class Network {
         // (If inbound sent anything here, it's possible it could be processed out-of-order with handshake message).
 
         if (peer.isOutbound()) {
-            // Send our height
+            if (!Settings.getInstance().isLite()) {
-            Message heightMessage = buildHeightMessage(peer, Controller.getInstance().getChainTip());
+                // Send our height
-            if (!peer.sendMessage(heightMessage)) {
+                Message heightMessage = buildHeightMessage(peer, Controller.getInstance().getChainTip());
-                peer.disconnect("failed to send height/info");
+                if (!peer.sendMessage(heightMessage)) {
-                return;
+                    peer.disconnect("failed to send height/info");
+                    return;
+                }
             }
 
             // Send our peers list

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

@@ -0,0 +1,70 @@
+package org.qortal.network.message;
+
+import com.google.common.primitives.Longs;
+import org.qortal.data.account.AccountBalanceData;
+import org.qortal.transform.Transformer;
+import org.qortal.utils.Base58;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.nio.ByteBuffer;
+
+public class AccountBalanceMessage extends Message {
+
+	private static final int ADDRESS_LENGTH = Transformer.ADDRESS_LENGTH;
+
+	private AccountBalanceData accountBalanceData;
+
+	public AccountBalanceMessage(AccountBalanceData accountBalanceData) {
+		super(MessageType.ACCOUNT_BALANCE);
+
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+
+		try {
+			// Send raw address instead of base58 encoded
+			byte[] address = Base58.decode(accountBalanceData.getAddress());
+			bytes.write(address);
+
+			bytes.write(Longs.toByteArray(accountBalanceData.getAssetId()));
+
+			bytes.write(Longs.toByteArray(accountBalanceData.getBalance()));
+
+		} catch (IOException e) {
+			throw new AssertionError("IOException shouldn't occur with ByteArrayOutputStream");
+		}
+
+		this.dataBytes = bytes.toByteArray();
+		this.checksumBytes = Message.generateChecksum(this.dataBytes);
+	}
+
+	public AccountBalanceMessage(int id, AccountBalanceData accountBalanceData) {
+		super(id, MessageType.ACCOUNT_BALANCE);
+
+		this.accountBalanceData = accountBalanceData;
+	}
+
+	public AccountBalanceData getAccountBalanceData() {
+		return this.accountBalanceData;
+	}
+
+
+	public static Message fromByteBuffer(int id, ByteBuffer byteBuffer) {
+		byte[] addressBytes = new byte[ADDRESS_LENGTH];
+		byteBuffer.get(addressBytes);
+		String address = Base58.encode(addressBytes);
+
+		long assetId = byteBuffer.getLong();
+
+		long balance = byteBuffer.getLong();
+
+		AccountBalanceData accountBalanceData = new AccountBalanceData(address, assetId, balance);
+		return new AccountBalanceMessage(id, accountBalanceData);
+	}
+
+	public AccountBalanceMessage cloneWithNewId(int newId) {
+		AccountBalanceMessage clone = new AccountBalanceMessage(this.accountBalanceData);
+		clone.setId(newId);
+		return clone;
+	}
+
+}

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

@@ -0,0 +1,93 @@
+package org.qortal.network.message;
+
+import com.google.common.primitives.Ints;
+import org.qortal.data.account.AccountData;
+import org.qortal.transform.Transformer;
+import org.qortal.utils.Base58;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.nio.ByteBuffer;
+
+public class AccountMessage extends Message {
+
+	private static final int ADDRESS_LENGTH = Transformer.ADDRESS_LENGTH;
+	private static final int REFERENCE_LENGTH = Transformer.SIGNATURE_LENGTH;
+	private static final int PUBLIC_KEY_LENGTH = Transformer.PUBLIC_KEY_LENGTH;
+
+	private AccountData accountData;
+
+	public AccountMessage(AccountData accountData) {
+		super(MessageType.ACCOUNT);
+
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+
+		try {
+			// Send raw address instead of base58 encoded
+			byte[] address = Base58.decode(accountData.getAddress());
+			bytes.write(address);
+
+			bytes.write(accountData.getReference());
+
+			bytes.write(accountData.getPublicKey());
+
+			bytes.write(Ints.toByteArray(accountData.getDefaultGroupId()));
+
+			bytes.write(Ints.toByteArray(accountData.getFlags()));
+
+			bytes.write(Ints.toByteArray(accountData.getLevel()));
+
+			bytes.write(Ints.toByteArray(accountData.getBlocksMinted()));
+
+			bytes.write(Ints.toByteArray(accountData.getBlocksMintedAdjustment()));
+
+		} catch (IOException e) {
+			throw new AssertionError("IOException shouldn't occur with ByteArrayOutputStream");
+		}
+
+		this.dataBytes = bytes.toByteArray();
+		this.checksumBytes = Message.generateChecksum(this.dataBytes);
+	}
+
+	public AccountMessage(int id, AccountData accountData) {
+		super(id, MessageType.ACCOUNT);
+
+		this.accountData = accountData;
+	}
+
+	public AccountData getAccountData() {
+		return this.accountData;
+	}
+
+	public static Message fromByteBuffer(int id, ByteBuffer byteBuffer) {
+		byte[] addressBytes = new byte[ADDRESS_LENGTH];
+		byteBuffer.get(addressBytes);
+		String address = Base58.encode(addressBytes);
+
+		byte[] reference = new byte[REFERENCE_LENGTH];
+		byteBuffer.get(reference);
+
+		byte[] publicKey = new byte[PUBLIC_KEY_LENGTH];
+		byteBuffer.get(publicKey);
+
+		int defaultGroupId = byteBuffer.getInt();
+
+		int flags = byteBuffer.getInt();
+
+		int level = byteBuffer.getInt();
+
+		int blocksMinted = byteBuffer.getInt();
+
+		int blocksMintedAdjustment = byteBuffer.getInt();
+
+		AccountData accountData = new AccountData(address, reference, publicKey, defaultGroupId, flags, level, blocksMinted, blocksMintedAdjustment);
+		return new AccountMessage(id, accountData);
+	}
+
+	public AccountMessage cloneWithNewId(int newId) {
+		AccountMessage clone = new AccountMessage(this.accountData);
+		clone.setId(newId);
+		return clone;
+	}
+
+}

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

@@ -0,0 +1,63 @@
+package org.qortal.network.message;
+
+import com.google.common.primitives.Longs;
+import org.qortal.transform.Transformer;
+import org.qortal.utils.Base58;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.nio.ByteBuffer;
+
+public class GetAccountBalanceMessage extends Message {
+
+	private static final int ADDRESS_LENGTH = Transformer.ADDRESS_LENGTH;
+
+	private String address;
+	private long assetId;
+
+	public GetAccountBalanceMessage(String address, long assetId) {
+		super(MessageType.GET_ACCOUNT_BALANCE);
+
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+
+		try {
+			// Send raw address instead of base58 encoded
+			byte[] addressBytes = Base58.decode(address);
+			bytes.write(addressBytes);
+
+			bytes.write(Longs.toByteArray(assetId));
+
+		} catch (IOException e) {
+			throw new AssertionError("IOException shouldn't occur with ByteArrayOutputStream");
+		}
+
+		this.dataBytes = bytes.toByteArray();
+		this.checksumBytes = Message.generateChecksum(this.dataBytes);
+	}
+
+	private GetAccountBalanceMessage(int id, String address, long assetId) {
+		super(id, MessageType.GET_ACCOUNT_BALANCE);
+
+		this.address = address;
+		this.assetId = assetId;
+	}
+
+	public String getAddress() {
+		return this.address;
+	}
+
+	public long getAssetId() {
+		return this.assetId;
+	}
+
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) {
+		byte[] addressBytes = new byte[ADDRESS_LENGTH];
+		bytes.get(addressBytes);
+		String address = Base58.encode(addressBytes);
+
+		long assetId = bytes.getLong();
+
+		return new GetAccountBalanceMessage(id, address, assetId);
+	}
+
+}

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

@@ -0,0 +1,56 @@
+package org.qortal.network.message;
+
+import org.qortal.transform.Transformer;
+import org.qortal.utils.Base58;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.nio.BufferUnderflowException;
+import java.nio.ByteBuffer;
+
+public class GetAccountMessage extends Message {
+
+	private static final int ADDRESS_LENGTH = Transformer.ADDRESS_LENGTH;
+
+	private String address;
+
+	public GetAccountMessage(String address) {
+		super(MessageType.GET_ACCOUNT);
+
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+
+		try {
+			// Send raw address instead of base58 encoded
+			byte[] addressBytes = Base58.decode(address);
+			bytes.write(addressBytes);
+
+		} catch (IOException e) {
+			throw new AssertionError("IOException shouldn't occur with ByteArrayOutputStream");
+		}
+
+		this.dataBytes = bytes.toByteArray();
+		this.checksumBytes = Message.generateChecksum(this.dataBytes);
+	}
+
+	private GetAccountMessage(int id, String address) {
+		super(id, MessageType.GET_ACCOUNT);
+
+		this.address = address;
+	}
+
+	public String getAddress() {
+		return this.address;
+	}
+
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) {
+		if (bytes.remaining() != ADDRESS_LENGTH)
+			throw new BufferUnderflowException();
+
+		byte[] addressBytes = new byte[ADDRESS_LENGTH];
+		bytes.get(addressBytes);
+		String address = Base58.encode(addressBytes);
+
+		return new GetAccountMessage(id, address);
+	}
+
+}

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

@@ -0,0 +1,53 @@
+package org.qortal.network.message;
+
+import org.qortal.transform.Transformer;
+import org.qortal.utils.Base58;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.nio.ByteBuffer;
+
+public class GetAccountNamesMessage extends Message {
+
+	private static final int ADDRESS_LENGTH = Transformer.ADDRESS_LENGTH;
+
+	private String address;
+
+	public GetAccountNamesMessage(String address) {
+		super(MessageType.GET_ACCOUNT_NAMES);
+
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+
+		try {
+			// Send raw address instead of base58 encoded
+			byte[] addressBytes = Base58.decode(address);
+			bytes.write(addressBytes);
+
+		} catch (IOException e) {
+			throw new AssertionError("IOException shouldn't occur with ByteArrayOutputStream");
+		}
+
+		this.dataBytes = bytes.toByteArray();
+		this.checksumBytes = Message.generateChecksum(this.dataBytes);
+	}
+
+	private GetAccountNamesMessage(int id, String address) {
+		super(id, MessageType.GET_ACCOUNT_NAMES);
+
+		this.address = address;
+	}
+
+	public String getAddress() {
+		return this.address;
+	}
+
+
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) {
+		byte[] addressBytes = new byte[ADDRESS_LENGTH];
+		bytes.get(addressBytes);
+		String address = Base58.encode(addressBytes);
+
+		return new GetAccountNamesMessage(id, address);
+	}
+
+}

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

@@ -0,0 +1,69 @@
+package org.qortal.network.message;
+
+import com.google.common.primitives.Ints;
+import org.qortal.transform.Transformer;
+import org.qortal.utils.Base58;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.nio.ByteBuffer;
+
+public class GetAccountTransactionsMessage extends Message {
+
+	private static final int ADDRESS_LENGTH = Transformer.ADDRESS_LENGTH;
+
+	private String address;
+	private int limit;
+	private int offset;
+
+	public GetAccountTransactionsMessage(String address, int limit, int offset) {
+		super(MessageType.GET_ACCOUNT_TRANSACTIONS);
+
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+
+		try {
+			// Send raw address instead of base58 encoded
+			byte[] addressBytes = Base58.decode(address);
+			bytes.write(addressBytes);
+
+			bytes.write(Ints.toByteArray(limit));
+
+			bytes.write(Ints.toByteArray(offset));
+
+		} catch (IOException e) {
+			throw new AssertionError("IOException shouldn't occur with ByteArrayOutputStream");
+		}
+
+		this.dataBytes = bytes.toByteArray();
+		this.checksumBytes = Message.generateChecksum(this.dataBytes);
+	}
+
+	private GetAccountTransactionsMessage(int id, String address, int limit, int offset) {
+		super(id, MessageType.GET_ACCOUNT_TRANSACTIONS);
+
+		this.address = address;
+		this.limit = limit;
+		this.offset = offset;
+	}
+
+	public String getAddress() {
+		return this.address;
+	}
+
+	public int getLimit() { return this.limit; }
+
+	public int getOffset() { return this.offset; }
+
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) {
+		byte[] addressBytes = new byte[ADDRESS_LENGTH];
+		bytes.get(addressBytes);
+		String address = Base58.encode(addressBytes);
+
+		int limit = bytes.getInt();
+
+		int offset = bytes.getInt();
+
+		return new GetAccountTransactionsMessage(id, address, limit, offset);
+	}
+
+}

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

@@ -0,0 +1,53 @@
+package org.qortal.network.message;
+
+import org.qortal.naming.Name;
+import org.qortal.transform.TransformationException;
+import org.qortal.utils.Serialization;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.nio.ByteBuffer;
+
+public class GetNameMessage extends Message {
+
+	private String name;
+
+	public GetNameMessage(String address) {
+		super(MessageType.GET_NAME);
+
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+
+		try {
+			Serialization.serializeSizedStringV2(bytes, name);
+
+		} catch (IOException e) {
+			throw new AssertionError("IOException shouldn't occur with ByteArrayOutputStream");
+		}
+
+		this.dataBytes = bytes.toByteArray();
+		this.checksumBytes = Message.generateChecksum(this.dataBytes);
+	}
+
+	private GetNameMessage(int id, String name) {
+		super(id, MessageType.GET_NAME);
+
+		this.name = name;
+	}
+
+	public String getName() {
+		return this.name;
+	}
+
+
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws MessageException {
+		try {
+			String name = Serialization.deserializeSizedStringV2(bytes, Name.MAX_NAME_SIZE);
+
+			return new GetNameMessage(id, name);
+
+		} catch (TransformationException e) {
+			throw new MessageException(e.getMessage(), e);
+		}
+	}
+
+}

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

@@ -61,7 +61,21 @@ public enum MessageType {
     GET_TRADE_PRESENCES(141, GetTradePresencesMessage::fromByteBuffer),
 
     ARBITRARY_METADATA(150, ArbitraryMetadataMessage::fromByteBuffer),
-    GET_ARBITRARY_METADATA(151, GetArbitraryMetadataMessage::fromByteBuffer);
+    GET_ARBITRARY_METADATA(151, GetArbitraryMetadataMessage::fromByteBuffer),
+
+    // Lite node support
+    ACCOUNT(160, AccountMessage::fromByteBuffer),
+    GET_ACCOUNT(161, GetAccountMessage::fromByteBuffer),
+
+    ACCOUNT_BALANCE(170, AccountBalanceMessage::fromByteBuffer),
+    GET_ACCOUNT_BALANCE(171, GetAccountBalanceMessage::fromByteBuffer),
+
+    NAMES(180, NamesMessage::fromByteBuffer),
+    GET_ACCOUNT_NAMES(181, GetAccountNamesMessage::fromByteBuffer),
+    GET_NAME(182, GetNameMessage::fromByteBuffer),
+
+    TRANSACTIONS(190, TransactionsMessage::fromByteBuffer),
+    GET_ACCOUNT_TRANSACTIONS(191, GetAccountTransactionsMessage::fromByteBuffer);
 
     public final int value;
     public final MessageProducer fromByteBufferMethod;

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

@@ -0,0 +1,142 @@
+package org.qortal.network.message;
+
+import com.google.common.primitives.Ints;
+import com.google.common.primitives.Longs;
+import org.qortal.data.naming.NameData;
+import org.qortal.naming.Name;
+import org.qortal.transform.TransformationException;
+import org.qortal.transform.Transformer;
+import org.qortal.utils.Serialization;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.nio.BufferUnderflowException;
+import java.nio.ByteBuffer;
+import java.util.ArrayList;
+import java.util.List;
+
+public class NamesMessage extends Message {
+
+	private static final int SIGNATURE_LENGTH = Transformer.SIGNATURE_LENGTH;
+
+	private List<NameData> nameDataList;
+
+	public NamesMessage(List<NameData> nameDataList) {
+		super(MessageType.NAMES);
+
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+
+		try {
+			bytes.write(Ints.toByteArray(nameDataList.size()));
+
+			for (int i = 0; i < nameDataList.size(); ++i) {
+				NameData nameData = nameDataList.get(i);
+
+				Serialization.serializeSizedStringV2(bytes, nameData.getName());
+
+				Serialization.serializeSizedStringV2(bytes, nameData.getReducedName());
+
+				Serialization.serializeAddress(bytes, nameData.getOwner());
+
+				Serialization.serializeSizedStringV2(bytes, nameData.getData());
+
+				bytes.write(Longs.toByteArray(nameData.getRegistered()));
+
+				Long updated = nameData.getUpdated();
+				int wasUpdated = (updated != null) ? 1 : 0;
+				bytes.write(Ints.toByteArray(wasUpdated));
+
+				if (updated != null) {
+					bytes.write(Longs.toByteArray(nameData.getUpdated()));
+				}
+
+				int isForSale = nameData.isForSale() ? 1 : 0;
+				bytes.write(Ints.toByteArray(isForSale));
+
+				if (nameData.isForSale()) {
+					bytes.write(Longs.toByteArray(nameData.getSalePrice()));
+				}
+
+				bytes.write(nameData.getReference());
+
+				bytes.write(Ints.toByteArray(nameData.getCreationGroupId()));
+			}
+
+		} catch (IOException e) {
+			throw new AssertionError("IOException shouldn't occur with ByteArrayOutputStream");
+		}
+
+		this.dataBytes = bytes.toByteArray();
+		this.checksumBytes = Message.generateChecksum(this.dataBytes);
+	}
+
+	public NamesMessage(int id, List<NameData> nameDataList) {
+		super(id, MessageType.NAMES);
+
+		this.nameDataList = nameDataList;
+	}
+
+	public List<NameData> getNameDataList() {
+		return this.nameDataList;
+	}
+
+
+	public static Message fromByteBuffer(int id, ByteBuffer bytes) throws MessageException {
+		try {
+			final int nameCount = bytes.getInt();
+
+			List<NameData> nameDataList = new ArrayList<>(nameCount);
+
+			for (int i = 0; i < nameCount; ++i) {
+				String name = Serialization.deserializeSizedStringV2(bytes, Name.MAX_NAME_SIZE);
+
+				String reducedName = Serialization.deserializeSizedStringV2(bytes, Name.MAX_NAME_SIZE);
+
+				String owner = Serialization.deserializeAddress(bytes);
+
+				String data = Serialization.deserializeSizedStringV2(bytes, Name.MAX_DATA_SIZE);
+
+				long registered = bytes.getLong();
+
+				int wasUpdated = bytes.getInt();
+
+				Long updated = null;
+				if (wasUpdated == 1) {
+					updated = bytes.getLong();
+				}
+
+				boolean isForSale = (bytes.getInt() == 1);
+
+				Long salePrice = null;
+				if (isForSale) {
+					salePrice = bytes.getLong();
+				}
+
+				byte[] reference = new byte[SIGNATURE_LENGTH];
+				bytes.get(reference);
+
+				int creationGroupId = bytes.getInt();
+
+				NameData nameData = new NameData(name, reducedName, owner, data, registered, updated,
+						isForSale, salePrice, reference, creationGroupId);
+				nameDataList.add(nameData);
+			}
+
+			if (bytes.hasRemaining()) {
+				throw new BufferUnderflowException();
+			}
+
+			return new NamesMessage(id, nameDataList);
+
+		} catch (TransformationException e) {
+			throw new MessageException(e.getMessage(), e);
+		}
+	}
+
+	public NamesMessage cloneWithNewId(int newId) {
+		NamesMessage clone = new NamesMessage(this.nameDataList);
+		clone.setId(newId);
+		return clone;
+	}
+
+}

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

@@ -0,0 +1,76 @@
+package org.qortal.network.message;
+
+import com.google.common.primitives.Ints;
+import org.qortal.data.transaction.TransactionData;
+import org.qortal.transform.TransformationException;
+import org.qortal.transform.transaction.TransactionTransformer;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.nio.BufferUnderflowException;
+import java.nio.ByteBuffer;
+import java.util.ArrayList;
+import java.util.List;
+
+public class TransactionsMessage extends Message {
+
+	private List<TransactionData> transactions;
+
+	public TransactionsMessage(List<TransactionData> transactions) throws MessageException {
+		super(MessageType.TRANSACTIONS);
+
+		ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+
+		try {
+			bytes.write(Ints.toByteArray(transactions.size()));
+
+			for (int i = 0; i < transactions.size(); ++i) {
+				TransactionData transactionData = transactions.get(i);
+
+				byte[] serializedTransactionData = TransactionTransformer.toBytes(transactionData);
+				bytes.write(serializedTransactionData);
+			}
+
+		} catch (IOException e) {
+			throw new AssertionError("IOException shouldn't occur with ByteArrayOutputStream");
+		} catch (TransformationException e) {
+			throw new MessageException(e.getMessage(), e);
+		}
+
+		this.dataBytes = bytes.toByteArray();
+		this.checksumBytes = Message.generateChecksum(this.dataBytes);
+	}
+
+	private TransactionsMessage(int id, List<TransactionData> transactions) {
+		super(id, MessageType.TRANSACTIONS);
+
+		this.transactions = transactions;
+	}
+
+	public List<TransactionData> getTransactions() {
+		return this.transactions;
+	}
+
+	public static Message fromByteBuffer(int id, ByteBuffer byteBuffer) throws MessageException {
+		try {
+			final int transactionCount = byteBuffer.getInt();
+
+			List<TransactionData> transactions = new ArrayList<>();
+
+			for (int i = 0; i < transactionCount; ++i) {
+				TransactionData transactionData = TransactionTransformer.fromByteBuffer(byteBuffer);
+				transactions.add(transactionData);
+			}
+
+			if (byteBuffer.hasRemaining()) {
+				throw new BufferUnderflowException();
+			}
+
+			return new TransactionsMessage(id, transactions);
+
+		} catch (TransformationException e) {
+			throw new MessageException(e.getMessage(), e);
+		}
+	}
+
+}

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

@@ -62,6 +62,11 @@ public abstract class RepositoryManager {
 	}
 
 	public static boolean archive(Repository repository) {
+		if (Settings.getInstance().isLite()) {
+			// Lite nodes have no blockchain
+			return false;
+		}
+
 		// Bulk archive the database the first time we use archive mode
 		if (Settings.getInstance().isArchiveEnabled()) {
 			if (RepositoryManager.canArchiveOrPrune()) {
@@ -82,6 +87,11 @@ public abstract class RepositoryManager {
 	}
 
 	public static boolean prune(Repository repository) {
+		if (Settings.getInstance().isLite()) {
+			// Lite nodes have no blockchain
+			return false;
+		}
+
 		// Bulk prune the database the first time we use top-only or block archive mode
 		if (Settings.getInstance().isTopOnly() ||
 			Settings.getInstance().isArchiveEnabled()) {

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

@@ -145,6 +145,8 @@ public class Settings {
 	 * This has a significant effect on execution time. */
 	private int onlineSignaturesTrimBatchSize = 100; // blocks
 
+	/** Lite nodes don't sync blocks, and instead request "derived data" from peers */
+	private boolean lite = false;
 
 	/** Whether we should prune old data to reduce database size
 	 * This prevents the node from being able to serve older blocks */
@@ -820,6 +822,10 @@ public class Settings {
 		return this.onlineSignaturesTrimBatchSize;
 	}
 
+	public boolean isLite() {
+		return this.lite;
+	}
+
 	public boolean isTopOnly() {
 		return this.topOnly;
 	}

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

@@ -393,7 +393,10 @@ public abstract class Transaction {
 	 * @return transaction version number
 	 */
 	public static int getVersionByTimestamp(long timestamp) {
-		if (timestamp >= BlockChain.getInstance().getTransactionV5Timestamp()) {
+		if (timestamp >= BlockChain.getInstance().getTransactionV6Timestamp()) {
+			return 6;
+		}
+		else if (timestamp >= BlockChain.getInstance().getTransactionV5Timestamp()) {
 			return 5;
 		}
 		return 4;
@@ -530,11 +533,6 @@ public abstract class Transaction {
 		if (now >= this.getDeadline())
 			return ValidationResult.TIMESTAMP_TOO_OLD;
 
-		// Transactions with a expiry prior to latest block's timestamp are too old
-		BlockData latestBlock = repository.getBlockRepository().getLastBlock();
-		if (this.getDeadline() <= latestBlock.getTimestamp())
-			return ValidationResult.TIMESTAMP_TOO_OLD;
-
 		// Transactions with a timestamp too far into future are too new
 		long maxTimestamp = now + Settings.getInstance().getMaxTransactionTimestampFuture();
 		if (this.transactionData.getTimestamp() > maxTimestamp)
@@ -545,6 +543,15 @@ public abstract class Transaction {
 		if (feeValidationResult != ValidationResult.OK)
 			return feeValidationResult;
 
+		if (Settings.getInstance().isLite()) {
+			// Everything from this point is difficult to validate for a lite node, since it has no blocks.
+			// For now, we will assume it is valid, to allow it to move around the network easily.
+			// If it turns out to be invalid, other full/top-only nodes will reject it on receipt.
+			// Lite nodes would never mint a block, so there's not much risk of holding invalid transactions.
+			// TODO: implement lite-only validation for each transaction type
+			return ValidationResult.OK;
+		}
+
 		PublicKeyAccount creator = this.getCreator();
 		if (creator == null)
 			return ValidationResult.MISSING_CREATOR;
@@ -553,6 +560,12 @@ public abstract class Transaction {
 		if (countUnconfirmedByCreator(creator) >= Settings.getInstance().getMaxUnconfirmedPerAccount())
 			return ValidationResult.TOO_MANY_UNCONFIRMED;
 
+		// Transactions with a expiry prior to latest block's timestamp are too old
+		// Not relevant for lite nodes, as they don't have any blocks
+		BlockData latestBlock = repository.getBlockRepository().getLastBlock();
+		if (this.getDeadline() <= latestBlock.getTimestamp())
+			return ValidationResult.TIMESTAMP_TOO_OLD;
+
 		// Check transaction's txGroupId
 		if (!this.isValidTxGroupId())
 			return ValidationResult.INVALID_TX_GROUP_ID;

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

@@ -4,8 +4,12 @@ import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.nio.ByteBuffer;
 
+import org.qortal.account.NullAccount;
 import org.qortal.data.transaction.ATTransactionData;
+import org.qortal.data.transaction.BaseTransactionData;
 import org.qortal.data.transaction.TransactionData;
+import org.qortal.group.Group;
+import org.qortal.transaction.Transaction;
 import org.qortal.transform.TransformationException;
 import org.qortal.utils.Serialization;
 
@@ -17,12 +21,97 @@ public class AtTransactionTransformer extends TransactionTransformer {
 	protected static final TransactionLayout layout = null;
 
 	// Property lengths
+
+	private static final int MESSAGE_SIZE_LENGTH = INT_LENGTH;
+	private static final int TYPE_LENGTH = INT_LENGTH;
+
+
 	public static TransactionData fromByteBuffer(ByteBuffer byteBuffer) throws TransformationException {
-		throw new TransformationException("Serialized AT transactions should not exist!");
+		long timestamp = byteBuffer.getLong();
+
+		int version = Transaction.getVersionByTimestamp(timestamp);
+
+		byte[] reference = new byte[REFERENCE_LENGTH];
+		byteBuffer.get(reference);
+
+		String atAddress = Serialization.deserializeAddress(byteBuffer);
+
+		String recipient = Serialization.deserializeAddress(byteBuffer);
+
+		// Default to PAYMENT-type, as there were no MESSAGE-type transactions before transaction v6
+		boolean isMessageType = false;
+
+		if (version >= 6) {
+			// Version 6 supports both PAYMENT-type and MESSAGE-type, specified using an integer.
+			// This could be extended to support additional types at a later date, simply by adding
+			// additional integer values.
+			int type = byteBuffer.getInt();
+			isMessageType = (type == 1);
+		}
+
+		int messageLength = 0;
+		byte[] message = null;
+		long assetId = 0L;
+		long amount = 0L;
+
+		if (isMessageType) {
+			messageLength = byteBuffer.getInt();
+
+			message = new byte[messageLength];
+			byteBuffer.get(message);
+		}
+		else {
+			// Assume PAYMENT-type, as there were no MESSAGE-type transactions until this time
+			assetId = byteBuffer.getLong();
+
+			amount = byteBuffer.getLong();
+		}
+
+		long fee = byteBuffer.getLong();
+
+		byte[] signature = new byte[SIGNATURE_LENGTH];
+		byteBuffer.get(signature);
+
+		BaseTransactionData baseTransactionData = new BaseTransactionData(timestamp, Group.NO_GROUP, reference, NullAccount.PUBLIC_KEY, fee, signature);
+
+		if (isMessageType) {
+			// MESSAGE-type
+			return new ATTransactionData(baseTransactionData, atAddress, recipient, message);
+		}
+		else {
+			// PAYMENT-type
+			return new ATTransactionData(baseTransactionData, atAddress, recipient, amount, assetId);
+		}
+
 	}
 
 	public static int getDataLength(TransactionData transactionData) throws TransformationException {
-		throw new TransformationException("Serialized AT transactions should not exist!");
+		ATTransactionData atTransactionData = (ATTransactionData) transactionData;
+		int version = Transaction.getVersionByTimestamp(transactionData.getTimestamp());
+
+		final int baseLength = TYPE_LENGTH + TIMESTAMP_LENGTH + REFERENCE_LENGTH + ADDRESS_LENGTH + ADDRESS_LENGTH +
+				FEE_LENGTH + SIGNATURE_LENGTH;
+
+		int typeSpecificLength = 0;
+
+		byte[] message = atTransactionData.getMessage();
+		boolean isMessageType = (message != null);
+
+		// MESSAGE-type and PAYMENT-type transactions will have differing lengths
+		if (isMessageType) {
+			typeSpecificLength = MESSAGE_SIZE_LENGTH + message.length;
+		}
+		else {
+			typeSpecificLength = ASSET_ID_LENGTH + AMOUNT_LENGTH;
+		}
+
+		// V6 transactions include an extra integer to denote the type
+		int versionSpecificLength = 0;
+		if (version >= 6) {
+			versionSpecificLength = TYPE_LENGTH;
+		}
+
+		return baseLength + typeSpecificLength + versionSpecificLength;
 	}
 
 	// Used for generating fake transaction signatures
@@ -30,6 +119,8 @@ public class AtTransactionTransformer extends TransactionTransformer {
 		try {
 			ATTransactionData atTransactionData = (ATTransactionData) transactionData;
 
+			int version = Transaction.getVersionByTimestamp(atTransactionData.getTimestamp());
+
 			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
 
 			bytes.write(Ints.toByteArray(atTransactionData.getType().value));
@@ -42,7 +133,17 @@ public class AtTransactionTransformer extends TransactionTransformer {
 
 			byte[] message = atTransactionData.getMessage();
 
-			if (message != null) {
+			boolean isMessageType = (message != null);
+			int type = isMessageType ? 1 : 0;
+
+			if (version >= 6) {
+				// Version 6 supports both PAYMENT-type and MESSAGE-type, specified using an integer.
+				// This could be extended to support additional types at a later date, simply by adding
+				// additional integer values.
+				bytes.write(Ints.toByteArray(type));
+			}
+
+			if (isMessageType) {
 				// MESSAGE-type
 				bytes.write(Ints.toByteArray(message.length));
 				bytes.write(message);

src/main/resources/blockchain.json

@@ -58,7 +58,8 @@
 		"newBlockSigHeight": 320000,
 		"shareBinFix": 399000,
 		"calcChainWeightTimestamp": 1620579600000,
-		"transactionV5Timestamp": 1642176000000
+		"transactionV5Timestamp": 1642176000000,
+		"transactionV6Timestamp": 9999999999999
 	},
 	"genesisInfo": {
 		"version": 4,

src/main/resources/i18n/SysTray_de.properties

@@ -27,6 +27,8 @@ DB_MAINTENANCE = Datenbank Instandhaltung
 
 EXIT = Verlassen
 
+LITE_NODE = Lite node
+
 MINTING_DISABLED = NOT minting
 
 MINTING_ENABLED = \u2714 Minting

src/main/resources/i18n/SysTray_en.properties

@@ -27,6 +27,8 @@ DB_MAINTENANCE = Database Maintenance
 
 EXIT = Exit
 
+LITE_NODE = Lite node
+
 MINTING_DISABLED = NOT minting
 
 MINTING_ENABLED = \u2714 Minting

src/main/resources/i18n/SysTray_fi.properties

@@ -27,6 +27,8 @@ DB_MAINTENANCE = Tietokannan ylläpito
 
 EXIT = Pois
 
+LITE_NODE = Lite node
+
 MINTING_DISABLED = EI lyö rahaa
 
 MINTING_ENABLED = \u2714 Lyö rahaa

src/main/resources/i18n/SysTray_fr.properties

@@ -27,6 +27,8 @@ DB_MAINTENANCE = Maintenance de la base de données
 
 EXIT = Quitter
 
+LITE_NODE = Lite node
+
 MINTING_DISABLED = NE mint PAS
 
 MINTING_ENABLED = \u2714 Minting

src/main/resources/i18n/SysTray_hu.properties

@@ -27,6 +27,8 @@ DB_MAINTENANCE = Adatbázis karbantartás
 
 EXIT = Kilépés
 
+LITE_NODE = Lite node
+
 MINTING_DISABLED = QORT-érmeverés jelenleg nincs folyamatban
 
 MINTING_ENABLED = \u2714 QORT-érmeverés folyamatban

src/main/resources/i18n/SysTray_it.properties

@@ -27,6 +27,8 @@ DB_MAINTENANCE = Manutenzione del database
 
 EXIT = Uscita
 
+LITE_NODE = Lite node
+
 MINTING_DISABLED = Conio disabilitato
 
 MINTING_ENABLED = \u2714 Conio abilitato

src/main/resources/i18n/SysTray_nl.properties

@@ -27,6 +27,8 @@ DB_MAINTENANCE = Database Onderhoud
 
 EXIT = Verlaten
 
+LITE_NODE = Lite node
+
 MINTING_DISABLED = Minten is uitgeschakeld
 
 MINTING_ENABLED = \u2714 Minten is ingeschakeld

src/main/resources/i18n/SysTray_ru.properties

@@ -27,6 +27,8 @@ DB_MAINTENANCE = Обслуживание базы данных
 
 EXIT = Выход
 
+LITE_NODE = Lite node
+
 MINTING_DISABLED = Чеканка отключена
 
 MINTING_ENABLED = \u2714 Чеканка активна

src/main/resources/i18n/SysTray_zh_CN.properties

@@ -27,6 +27,8 @@ DB_MAINTENANCE = 数据库维护
 
 EXIT = 退出核心
 
+LITE_NODE = Lite node
+
 MINTING_DISABLED = 没有铸币
 
 MINTING_ENABLED = \u2714 铸币

src/main/resources/i18n/SysTray_zh_TW.properties

@@ -27,6 +27,8 @@ DB_MAINTENANCE = 數據庫維護
 
 EXIT = 退出核心
 
+LITE_NODE = Lite node
+
 MINTING_DISABLED = 沒有鑄幣
 
 MINTING_ENABLED = \u2714 鑄幣

src/test/java/org/qortal/test/SerializationTests.java

@@ -47,7 +47,6 @@ public class SerializationTests extends Common {
 				switch (txType) {
 					case GENESIS:
 					case ACCOUNT_FLAGS:
-					case AT:
 					case CHAT:
 					case PUBLICIZE:
 					case AIRDROP:

src/test/java/org/qortal/test/apps/CheckTranslations.java

@@ -15,7 +15,7 @@ public class CheckTranslations {
 	private static final String[] SUPPORTED_LANGS = new String[] { "en", "de", "zh", "ru" };
 	private static final Set<String> SYSTRAY_KEYS = Set.of("AUTO_UPDATE", "APPLYING_UPDATE_AND_RESTARTING", "BLOCK_HEIGHT",
 			"BUILD_VERSION", "CHECK_TIME_ACCURACY", "CONNECTING", "CONNECTION", "CONNECTIONS", "CREATING_BACKUP_OF_DB_FILES",
-			"DB_BACKUP", "DB_CHECKPOINT", "EXIT", "MINTING_DISABLED", "MINTING_ENABLED", "OPEN_UI", "PERFORMING_DB_CHECKPOINT",
+			"DB_BACKUP", "DB_CHECKPOINT", "EXIT", "LITE_NODE", "MINTING_DISABLED", "MINTING_ENABLED", "OPEN_UI", "PERFORMING_DB_CHECKPOINT",
 			"SYNCHRONIZE_CLOCK", "SYNCHRONIZING_BLOCKCHAIN", "SYNCHRONIZING_CLOCK");
 
 	private static String failurePrefix;

src/test/java/org/qortal/test/at/AtSerializationTests.java

@@ -0,0 +1,96 @@
+package org.qortal.test.at;
+
+import com.google.common.hash.HashCode;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.qortal.account.PrivateKeyAccount;
+import org.qortal.data.transaction.ATTransactionData;
+import org.qortal.data.transaction.TransactionData;
+import org.qortal.repository.DataException;
+import org.qortal.repository.Repository;
+import org.qortal.repository.RepositoryManager;
+import org.qortal.test.common.Common;
+import org.qortal.test.common.transaction.AtTestTransaction;
+import org.qortal.transaction.Transaction;
+import org.qortal.transform.TransformationException;
+import org.qortal.transform.transaction.TransactionTransformer;
+import org.qortal.utils.Base58;
+
+import static org.junit.Assert.assertEquals;
+
+public class AtSerializationTests extends Common {
+
+    @Before
+    public void beforeTest() throws DataException {
+        Common.useDefaultSettings();
+    }
+
+    @After
+    public void afterTest() throws DataException {
+        Common.orphanCheck();
+    }
+
+
+    @Test
+    public void testPaymentTypeAtSerialization() throws DataException, TransformationException {
+        try (final Repository repository = RepositoryManager.getRepository()) {
+
+            // Build PAYMENT-type AT transaction
+            PrivateKeyAccount signingAccount = Common.getTestAccount(repository, "alice");
+            ATTransactionData transactionData = (ATTransactionData) AtTestTransaction.paymentType(repository, signingAccount, true);
+            Transaction transaction = Transaction.fromData(repository, transactionData);
+            transaction.sign(signingAccount);
+
+            final int claimedLength = TransactionTransformer.getDataLength(transactionData);
+            byte[] serializedTransaction = TransactionTransformer.toBytes(transactionData);
+            assertEquals("Serialized PAYMENT-type AT transaction length differs from declared length", claimedLength, serializedTransaction.length);
+
+            TransactionData deserializedTransactionData = TransactionTransformer.fromBytes(serializedTransaction);
+            // Re-sign
+            Transaction deserializedTransaction = Transaction.fromData(repository, deserializedTransactionData);
+            deserializedTransaction.sign(signingAccount);
+            assertEquals("Deserialized PAYMENT-type AT transaction signature differs", Base58.encode(transactionData.getSignature()), Base58.encode(deserializedTransactionData.getSignature()));
+
+            // Re-serialize to check new length and bytes
+            final int reclaimedLength = TransactionTransformer.getDataLength(deserializedTransactionData);
+            assertEquals("Reserialized PAYMENT-type AT transaction declared length differs", claimedLength, reclaimedLength);
+
+            byte[] reserializedTransaction = TransactionTransformer.toBytes(deserializedTransactionData);
+            assertEquals("Reserialized PAYMENT-type AT transaction bytes differ", HashCode.fromBytes(serializedTransaction).toString(), HashCode.fromBytes(reserializedTransaction).toString());
+        }
+    }
+
+    @Test
+    public void testMessageTypeAtSerialization() throws DataException, TransformationException {
+        try (final Repository repository = RepositoryManager.getRepository()) {
+
+            // Build MESSAGE-type AT transaction
+            PrivateKeyAccount signingAccount = Common.getTestAccount(repository, "alice");
+            ATTransactionData transactionData = (ATTransactionData) AtTestTransaction.messageType(repository, signingAccount, true);
+            Transaction transaction = Transaction.fromData(repository, transactionData);
+            transaction.sign(signingAccount);
+
+            // MESSAGE-type AT transactions are only fully supported since transaction V6
+            assertEquals(6, Transaction.getVersionByTimestamp(transactionData.getTimestamp()));
+
+            final int claimedLength = TransactionTransformer.getDataLength(transactionData);
+            byte[] serializedTransaction = TransactionTransformer.toBytes(transactionData);
+            assertEquals("Serialized MESSAGE-type AT transaction length differs from declared length", claimedLength, serializedTransaction.length);
+
+            TransactionData deserializedTransactionData = TransactionTransformer.fromBytes(serializedTransaction);
+            // Re-sign
+            Transaction deserializedTransaction = Transaction.fromData(repository, deserializedTransactionData);
+            deserializedTransaction.sign(signingAccount);
+            assertEquals("Deserialized MESSAGE-type AT transaction signature differs", Base58.encode(transactionData.getSignature()), Base58.encode(deserializedTransactionData.getSignature()));
+
+            // Re-serialize to check new length and bytes
+            final int reclaimedLength = TransactionTransformer.getDataLength(deserializedTransactionData);
+            assertEquals("Reserialized MESSAGE-type AT transaction declared length differs", claimedLength, reclaimedLength);
+
+            byte[] reserializedTransaction = TransactionTransformer.toBytes(deserializedTransactionData);
+            assertEquals("Reserialized MESSAGE-type AT transaction bytes differ", HashCode.fromBytes(serializedTransaction).toString(), HashCode.fromBytes(reserializedTransaction).toString());
+        }
+    }
+
+}

src/test/java/org/qortal/test/common/transaction/AtTestTransaction.java

@@ -12,16 +12,33 @@ import org.qortal.utils.Amounts;
 public class AtTestTransaction extends TestTransaction {
 
 	public static TransactionData randomTransaction(Repository repository, PrivateKeyAccount account, boolean wantValid) throws DataException {
+		return AtTestTransaction.paymentType(repository, account, wantValid);
+	}
+
+	public static TransactionData paymentType(Repository repository, PrivateKeyAccount account, boolean wantValid) throws DataException {
 		byte[] signature = new byte[64];
 		random.nextBytes(signature);
 		String atAddress = Crypto.toATAddress(signature);
 		String recipient = account.getAddress();
+
+		// Use PAYMENT-type
 		long amount = 123L * Amounts.MULTIPLIER;
 		final long assetId = Asset.QORT;
+
+		return new ATTransactionData(generateBase(account), atAddress, recipient, amount, assetId);
+	}
+
+	public static TransactionData messageType(Repository repository, PrivateKeyAccount account, boolean wantValid) throws DataException {
+		byte[] signature = new byte[64];
+		random.nextBytes(signature);
+		String atAddress = Crypto.toATAddress(signature);
+		String recipient = account.getAddress();
+
+		// Use MESSAGE-type
 		byte[] message = new byte[32];
 		random.nextBytes(message);
 
-		return new ATTransactionData(generateBase(account), atAddress, recipient, amount, assetId, message);
+		return new ATTransactionData(generateBase(account), atAddress, recipient, message);
 	}
 
 }

src/test/resources/test-chain-v2-founder-rewards.json

@@ -52,7 +52,8 @@
 		"newBlockSigHeight": 999999,
 		"shareBinFix": 999999,
 		"calcChainWeightTimestamp": 0,
-		"transactionV5Timestamp": 0
+		"transactionV5Timestamp": 0,
+		"transactionV6Timestamp": 0
 	},
 	"genesisInfo": {
 		"version": 4,

src/test/resources/test-chain-v2-leftover-reward.json

@@ -52,7 +52,8 @@
 		"newBlockSigHeight": 999999,
 		"shareBinFix": 999999,
 		"calcChainWeightTimestamp": 0,
-		"transactionV5Timestamp": 0
+		"transactionV5Timestamp": 0,
+		"transactionV6Timestamp": 0
 	},
 	"genesisInfo": {
 		"version": 4,

src/test/resources/test-chain-v2-minting.json

@@ -52,7 +52,8 @@
 		"newBlockSigHeight": 999999,
 		"shareBinFix": 999999,
 		"calcChainWeightTimestamp": 0,
-		"transactionV5Timestamp": 0
+		"transactionV5Timestamp": 0,
+		"transactionV6Timestamp": 0
 	},
 	"genesisInfo": {
 		"version": 4,

src/test/resources/test-chain-v2-qora-holder-extremes.json

@@ -52,7 +52,8 @@
 		"newBlockSigHeight": 999999,
 		"shareBinFix": 999999,
 		"calcChainWeightTimestamp": 0,
-		"transactionV5Timestamp": 0
+		"transactionV5Timestamp": 0,
+		"transactionV6Timestamp": 0
 	},
 	"genesisInfo": {
 		"version": 4,

src/test/resources/test-chain-v2-qora-holder.json

@@ -52,7 +52,8 @@
 		"newBlockSigHeight": 999999,
 		"shareBinFix": 999999,
 		"calcChainWeightTimestamp": 0,
-		"transactionV5Timestamp": 0
+		"transactionV5Timestamp": 0,
+		"transactionV6Timestamp": 0
 	},
 	"genesisInfo": {
 		"version": 4,

src/test/resources/test-chain-v2-reward-levels.json

@@ -52,7 +52,8 @@
 		"newBlockSigHeight": 999999,
 		"shareBinFix": 6,
 		"calcChainWeightTimestamp": 0,
-		"transactionV5Timestamp": 0
+		"transactionV5Timestamp": 0,
+		"transactionV6Timestamp": 0
 	},
 	"genesisInfo": {
 		"version": 4,

src/test/resources/test-chain-v2-reward-scaling.json

@@ -52,7 +52,8 @@
 		"newBlockSigHeight": 999999,
 		"shareBinFix": 999999,
 		"calcChainWeightTimestamp": 0,
-		"transactionV5Timestamp": 0
+		"transactionV5Timestamp": 0,
+		"transactionV6Timestamp": 0
 	},
 	"genesisInfo": {
 		"version": 4,

src/test/resources/test-chain-v2.json

@@ -52,7 +52,8 @@
 		"newBlockSigHeight": 999999,
 		"shareBinFix": 999999,
 		"calcChainWeightTimestamp": 0,
-		"transactionV5Timestamp": 0
+		"transactionV5Timestamp": 0,
+		"transactionV6Timestamp": 0
 	},
 	"genesisInfo": {
 		"version": 4,