Added "allowConnectionsWithOlderPeerVersions" setting (default: true)

This controls whether to allow connections with peers below minPeerVersion.

If true, we won't sync with them but they can still sync with us, and will show in the peers list. This is the default, which allows older nodes to continue functioning, but prevents them from interfering with the sync behaviour of updated nodes.

If false, sync will be blocked both ways, and they will not appear in the peers list at all.

AutoUpdates.md

@@ -2,6 +2,7 @@
 
 ## TL;DR: how-to
 
+* Prepare new release version (see way below for details)
 * Assuming you are in git 'master' branch, at HEAD
 * Shutdown local node if running
 * Build auto-update download: `tools/build-auto-update.sh` - uploads auto-update file into new git branch
@@ -59,4 +60,12 @@ $ java -cp qortal.jar org.qortal.XorUpdate
 usage: XorUpdate <input-file> <output-file>
 $ java -cp qortal.jar org.qortal.XorUpdate qortal.jar qortal.update
 $
-```
+```
+
+## Preparing new release version
+
+* Shutdown local node
+* Modify `pom.xml` and increase version inside `<version>` tag
+* Commit new `pom.xml` and push to github, e.g. `git commit -m 'Bumped to v1.4.2' -- pom.xml; git push`
+* Tag this new commit with same version: `git tag v1.4.2`
+* Push tag up to github: `git push origin v1.4.2`

pom.xml

@@ -3,7 +3,7 @@
 	<modelVersion>4.0.0</modelVersion>
 	<groupId>org.qortal</groupId>
 	<artifactId>qortal</artifactId>
-	<version>1.4.1</version>
+	<version>1.5.1</version>
 	<packaging>jar</packaging>
 	<properties>
 		<skipTests>true</skipTests>

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

@@ -547,7 +547,7 @@ public class AdminResource {
 			blockchainLock.lockInterruptibly();
 
 			try {
-				repository.exportNodeLocalData();
+				repository.exportNodeLocalData(true);
 				return "true";
 			} finally {
 				blockchainLock.unlock();

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

@@ -262,6 +262,7 @@ public class CrossChainResource {
 
 		// We want both a minimum of 5 trades and enough trades to span at least 4 hours
 		int minimumCount = 5;
+		int maximumCount = 10;
 		long minimumPeriod = 4 * 60 * 60 * 1000L; // ms
 		Boolean isFinished = Boolean.TRUE;
 
@@ -276,7 +277,7 @@ public class CrossChainResource {
 				ACCT acct = acctInfo.getValue().get();
 
 				List<ATStateData> atStates = repository.getATRepository().getMatchingFinalATStatesQuorum(codeHash,
-						isFinished, acct.getModeByteOffset(), (long) AcctMode.REDEEMED.value, minimumCount, minimumPeriod);
+						isFinished, acct.getModeByteOffset(), (long) AcctMode.REDEEMED.value, minimumCount, maximumCount, minimumPeriod);
 
 				for (ATStateData atState : atStates) {
 					CrossChainTradeData crossChainTradeData = acct.populateTradeData(repository, atState);

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

@@ -176,19 +176,26 @@ public class Block {
 		 * 
 		 *  @return account-level share "bin" from blockchain config, or null if founder / none found
 		 */
-		public AccountLevelShareBin getShareBin() {
+		public AccountLevelShareBin getShareBin(int blockHeight) {
 			if (this.isMinterFounder)
 				return null;
 
 			final int accountLevel = this.mintingAccountData.getLevel();
 			if (accountLevel <= 0)
-					return null;
+				return null; // level 0 isn't included in any share bins
 
-			final AccountLevelShareBin[] shareBinsByLevel = BlockChain.getInstance().getShareBinsByAccountLevel();
+			final BlockChain blockChain = BlockChain.getInstance();
+			final AccountLevelShareBin[] shareBinsByLevel = blockChain.getShareBinsByAccountLevel();
 			if (accountLevel > shareBinsByLevel.length)
 				return null;
 
-			return shareBinsByLevel[accountLevel];
+			if (blockHeight < blockChain.getShareBinFixHeight())
+				// Off-by-one bug still in effect
+				return shareBinsByLevel[accountLevel];
+
+			// level 1 stored at index 0, level 2 stored at index 1, etc.
+			return shareBinsByLevel[accountLevel-1];
+
 		}
 
 		public long distribute(long accountAmount, Map<String, Long> balanceChanges) {
@@ -357,7 +364,7 @@ public class Block {
 			System.arraycopy(onlineAccountData.getSignature(), 0, onlineAccountsSignatures, i * Transformer.SIGNATURE_LENGTH, Transformer.SIGNATURE_LENGTH);
 		}
 
-		byte[] minterSignature = minter.sign(BlockTransformer.getBytesForMinterSignature(parentBlockData.getMinterSignature(),
+		byte[] minterSignature = minter.sign(BlockTransformer.getBytesForMinterSignature(parentBlockData,
 				minter.getPublicKey(), encodedOnlineAccounts));
 
 		// Qortal: minter is always a reward-share, so find actual minter and get their effective minting level
@@ -424,7 +431,7 @@ public class Block {
 		int version = this.blockData.getVersion();
 		byte[] reference = this.blockData.getReference();
 
-		byte[] minterSignature = minter.sign(BlockTransformer.getBytesForMinterSignature(parentBlockData.getMinterSignature(),
+		byte[] minterSignature = minter.sign(BlockTransformer.getBytesForMinterSignature(parentBlockData,
 				minter.getPublicKey(), this.blockData.getEncodedOnlineAccounts()));
 
 		// Qortal: minter is always a reward-share, so find actual minter and get their effective minting level
@@ -738,11 +745,7 @@ public class Block {
 		if (!(this.minter instanceof PrivateKeyAccount))
 			throw new IllegalStateException("Block's minter is not a PrivateKeyAccount - can't sign!");
 
-		try {
-			this.blockData.setMinterSignature(((PrivateKeyAccount) this.minter).sign(BlockTransformer.getBytesForMinterSignature(this.blockData)));
-		} catch (TransformationException e) {
-			throw new RuntimeException("Unable to calculate block's minter signature", e);
-		}
+		this.blockData.setMinterSignature(((PrivateKeyAccount) this.minter).sign(BlockTransformer.getBytesForMinterSignature(this.blockData)));
 	}
 
 	/**
@@ -793,7 +796,9 @@ public class Block {
 		NumberFormat formatter = new DecimalFormat("0.###E0");
 		boolean isLogging = LOGGER.getLevel().isLessSpecificThan(Level.TRACE);
 
+		int blockCount = 0;
 		for (BlockSummaryData blockSummaryData : blockSummaries) {
+			blockCount++;
 			StringBuilder stringBuilder = isLogging ? new StringBuilder(512) : null;
 
 			if (isLogging)
@@ -822,11 +827,11 @@ public class Block {
 			parentHeight = blockSummaryData.getHeight();
 			parentBlockSignature = blockSummaryData.getSignature();
 
-			/* Potential future consensus change: only comparing the same number of blocks.
-			if (parentHeight >= maxHeight)
+			// After this timestamp, we only compare the same number of blocks
+			if (NTP.getTime() >= BlockChain.getInstance().getCalcChainWeightTimestamp() && parentHeight >= maxHeight)
 				break;
-			*/
 		}
+		LOGGER.debug(String.format("Chain weight calculation was based on %d blocks", blockCount));
 
 		return cumulativeWeight;
 	}
@@ -1332,6 +1337,9 @@ public class Block {
 
 		// Give Controller our cached, valid online accounts data (if any) to help reduce CPU load for next block
 		Controller.getInstance().pushLatestBlocksOnlineAccounts(this.cachedValidOnlineAccounts);
+
+		// Log some debugging info relating to the block weight calculation
+		this.logDebugInfo();
 	}
 
 	protected void increaseAccountLevels() throws DataException {
@@ -1513,6 +1521,9 @@ public class Block {
 	public void orphan() throws DataException {
 		LOGGER.trace(() -> String.format("Orphaning block %d", this.blockData.getHeight()));
 
+		// Log some debugging info relating to the block weight calculation
+		this.logDebugInfo();
+
 		// Return AT fees and delete AT states from repository
 		orphanAtFeesAndStates();
 
@@ -1787,7 +1798,7 @@ public class Block {
 			// Find all accounts in share bin. getShareBin() returns null for minter accounts that are also founders, so they are effectively filtered out.
 			AccountLevelShareBin accountLevelShareBin = accountLevelShareBins.get(binIndex);
 			// Object reference compare is OK as all references are read-only from blockchain config.
-			List<ExpandedAccount> binnedAccounts = expandedAccounts.stream().filter(accountInfo -> accountInfo.getShareBin() == accountLevelShareBin).collect(Collectors.toList());
+			List<ExpandedAccount> binnedAccounts = expandedAccounts.stream().filter(accountInfo -> accountInfo.getShareBin(this.blockData.getHeight()) == accountLevelShareBin).collect(Collectors.toList());
 
 			// No online accounts in this bin? Skip to next one
 			if (binnedAccounts.isEmpty())
@@ -1985,4 +1996,37 @@ public class Block {
 		this.repository.getAccountRepository().tidy();
 	}
 
+	private void logDebugInfo() {
+		try {
+			// Avoid calculations if possible. We have to check against INFO here, since Level.isMoreSpecificThan() confusingly uses <= rather than just <
+			if (LOGGER.getLevel().isMoreSpecificThan(Level.INFO))
+				return;
+
+			if (this.repository == null || this.getMinter() == null || this.getBlockData() == null)
+				return;
+
+			int minterLevel = Account.getRewardShareEffectiveMintingLevel(this.repository, this.getMinter().getPublicKey());
+
+			LOGGER.debug(String.format("======= BLOCK %d (%.8s) =======", this.getBlockData().getHeight(), Base58.encode(this.getSignature())));
+			LOGGER.debug(String.format("Timestamp: %d", this.getBlockData().getTimestamp()));
+			LOGGER.debug(String.format("Minter level: %d", minterLevel));
+			LOGGER.debug(String.format("Online accounts: %d", this.getBlockData().getOnlineAccountsCount()));
+
+			BlockSummaryData blockSummaryData = new BlockSummaryData(this.getBlockData());
+			if (this.getParent() == null || this.getParent().getSignature() == null || blockSummaryData == null || minterLevel == 0)
+				return;
+
+			blockSummaryData.setMinterLevel(minterLevel);
+			BigInteger blockWeight = calcBlockWeight(this.getParent().getHeight(), this.getParent().getSignature(), blockSummaryData);
+			BigInteger keyDistance = calcKeyDistance(this.getParent().getHeight(), this.getParent().getSignature(), blockSummaryData.getMinterPublicKey(), blockSummaryData.getMinterLevel());
+			NumberFormat formatter = new DecimalFormat("0.###E0");
+
+			LOGGER.debug(String.format("Key distance: %s", formatter.format(keyDistance)));
+			LOGGER.debug(String.format("Weight: %s", formatter.format(blockWeight)));
+
+		} catch (DataException e) {
+			LOGGER.info(() -> String.format("Unable to log block debugging info: %s", e.getMessage()));
+		}
+	}
+
 }

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

@@ -70,7 +70,10 @@ public class BlockChain {
 	private GenesisBlock.GenesisInfo genesisInfo;
 
 	public enum FeatureTrigger {
-		atFindNextTransactionFix;
+		atFindNextTransactionFix,
+		newBlockSigHeight,
+		shareBinFix,
+		calcChainWeightTimestamp;
 	}
 
 	/** Map of which blockchain features are enabled when (height/timestamp) */
@@ -376,6 +379,18 @@ public class BlockChain {
 		return this.featureTriggers.get(FeatureTrigger.atFindNextTransactionFix.name()).intValue();
 	}
 
+	public int getNewBlockSigHeight() {
+		return this.featureTriggers.get(FeatureTrigger.newBlockSigHeight.name()).intValue();
+	}
+
+	public int getShareBinFixHeight() {
+		return this.featureTriggers.get(FeatureTrigger.shareBinFix.name()).intValue();
+	}
+
+	public long getCalcChainWeightTimestamp() {
+		return this.featureTriggers.get(FeatureTrigger.calcChainWeightTimestamp.name()).longValue();
+	}
+
 	// More complex getters for aspects that change by height or timestamp
 
 	public long getRewardAtHeight(int ourHeight) {

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

@@ -135,16 +135,19 @@ public class BlockMinter extends Thread {
 				// Disregard peers that have "misbehaved" recently
 				peers.removeIf(Controller.hasMisbehaved);
 
-				// Disregard peers that don't have a recent block
-				peers.removeIf(Controller.hasNoRecentBlock);
+				// Disregard peers that don't have a recent block, but only if we're not in recovery mode.
+				// In that mode, we want to allow minting on top of older blocks, to recover stalled networks.
+				if (Controller.getInstance().getRecoveryMode() == false)
+					peers.removeIf(Controller.hasNoRecentBlock);
 
 				// Don't mint if we don't have enough up-to-date peers as where would the transactions/consensus come from?
 				if (peers.size() < Settings.getInstance().getMinBlockchainPeers())
 					continue;
 
-				// If our latest block isn't recent then we need to synchronize instead of minting.
+				// If our latest block isn't recent then we need to synchronize instead of minting, unless we're in recovery mode.
 				if (!peers.isEmpty() && lastBlockData.getTimestamp() < minLatestBlockTimestamp)
-					continue;
+					if (Controller.getInstance().getRecoveryMode() == false)
+						continue;
 
 				// There are enough peers with a recent block and our latest block is recent
 				// so go ahead and mint a block if possible.
@@ -165,6 +168,14 @@ public class BlockMinter extends Thread {
 				// Do we need to build any potential new blocks?
 				List<PrivateKeyAccount> newBlocksMintingAccounts = mintingAccountsData.stream().map(accountData -> new PrivateKeyAccount(repository, accountData.getPrivateKey())).collect(Collectors.toList());
 
+				// We might need to sit the next block out, if one of our minting accounts signed the previous one
+				final byte[] previousBlockMinter = previousBlockData.getMinterPublicKey();
+				final boolean mintedLastBlock = mintingAccountsData.stream().anyMatch(mintingAccount -> Arrays.equals(mintingAccount.getPublicKey(), previousBlockMinter));
+				if (mintedLastBlock) {
+					LOGGER.trace(String.format("One of our keys signed the last block, so we won't sign the next one"));
+					continue;
+				}
+
 				for (PrivateKeyAccount mintingAccount : newBlocksMintingAccounts) {
 					// First block does the AT heavy-lifting
 					if (newBlocks.isEmpty()) {
@@ -282,15 +293,17 @@ public class BlockMinter extends Thread {
 						RewardShareData rewardShareData = repository.getAccountRepository().getRewardShare(newBlock.getBlockData().getMinterPublicKey());
 
 						if (rewardShareData != null) {
-							LOGGER.info(String.format("Minted block %d, sig %.8s by %s on behalf of %s",
+							LOGGER.info(String.format("Minted block %d, sig %.8s, parent sig: %.8s by %s on behalf of %s",
 									newBlock.getBlockData().getHeight(),
 									Base58.encode(newBlock.getBlockData().getSignature()),
+									Base58.encode(newBlock.getParent().getSignature()),
 									rewardShareData.getMinter(),
 									rewardShareData.getRecipient()));
 						} else {
-							LOGGER.info(String.format("Minted block %d, sig %.8s by %s",
+							LOGGER.info(String.format("Minted block %d, sig %.8s, parent sig: %.8s by %s",
 									newBlock.getBlockData().getHeight(),
 									Base58.encode(newBlock.getBlockData().getSignature()),
+									Base58.encode(newBlock.getParent().getSignature()),
 									newBlock.getMinter().getAddress()));
 						}
 

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

@@ -67,8 +67,8 @@ import org.qortal.gui.SysTray;
 import org.qortal.network.Network;
 import org.qortal.network.Peer;
 import org.qortal.network.message.ArbitraryDataMessage;
-import org.qortal.network.message.BlockMessage;
 import org.qortal.network.message.BlockSummariesMessage;
+import org.qortal.network.message.CachedBlockMessage;
 import org.qortal.network.message.GetArbitraryDataMessage;
 import org.qortal.network.message.GetBlockMessage;
 import org.qortal.network.message.GetBlockSummariesMessage;
@@ -121,6 +121,7 @@ public class Controller extends Thread {
 	private static final long NTP_PRE_SYNC_CHECK_PERIOD = 5 * 1000L; // ms
 	private static final long NTP_POST_SYNC_CHECK_PERIOD = 5 * 60 * 1000L; // ms
 	private static final long DELETE_EXPIRED_INTERVAL = 5 * 60 * 1000L; // ms
+	private static final long RECOVERY_MODE_TIMEOUT = 10 * 60 * 1000L; // ms
 
 	// To do with online accounts list
 	private static final long ONLINE_ACCOUNTS_TASKS_INTERVAL = 10 * 1000L; // ms
@@ -143,16 +144,15 @@ public class Controller extends Thread {
 	private ExecutorService callbackExecutor = Executors.newFixedThreadPool(3);
 	private volatile boolean notifyGroupMembershipChange = false;
 
-	private static final int BLOCK_CACHE_SIZE = 10; // To cover typical Synchronizer request + a few spare
 	/** Latest blocks on our chain. Note: tail/last is the latest block. */
 	private final Deque<BlockData> latestBlocks = new LinkedList<>();
 
 	/** Cache of BlockMessages, indexed by block signature */
 	@SuppressWarnings("serial")
-	private final LinkedHashMap<ByteArray, BlockMessage> blockMessageCache = new LinkedHashMap<>() {
+	private final LinkedHashMap<ByteArray, CachedBlockMessage> blockMessageCache = new LinkedHashMap<>() {
 		@Override
-		protected boolean removeEldestEntry(Map.Entry<ByteArray, BlockMessage> eldest) {
-			return this.size() > BLOCK_CACHE_SIZE;
+		protected boolean removeEldestEntry(Map.Entry<ByteArray, CachedBlockMessage> eldest) {
+			return this.size() > Settings.getInstance().getBlockCacheSize();
 		}
 	};
 
@@ -176,6 +176,11 @@ public class Controller extends Thread {
 	/** Latest block signatures from other peers that we know are on inferior chains. */
 	List<ByteArray> inferiorChainSignatures = new ArrayList<>();
 
+	/** Recovery mode, which is used to bring back a stalled network */
+	private boolean recoveryMode = false;
+	private boolean peersAvailable = true; // peersAvailable must default to true
+	private long timePeersLastAvailable = 0;
+
 	/**
 	 * Map of recent requests for ARBITRARY transaction data payloads.
 	 * <p>
@@ -319,11 +324,12 @@ public class Controller extends Thread {
 		// Set initial chain height/tip
 		try (final Repository repository = RepositoryManager.getRepository()) {
 			BlockData blockData = repository.getBlockRepository().getLastBlock();
+			int blockCacheSize = Settings.getInstance().getBlockCacheSize();
 
 			synchronized (this.latestBlocks) {
 				this.latestBlocks.clear();
 
-				for (int i = 0; i < BLOCK_CACHE_SIZE && blockData != null; ++i) {
+				for (int i = 0; i < blockCacheSize && blockData != null; ++i) {
 					this.latestBlocks.addFirst(blockData);
 					blockData = repository.getBlockRepository().fromHeight(blockData.getHeight() - 1);
 				}
@@ -358,6 +364,10 @@ public class Controller extends Thread {
 		}
 	}
 
+	public boolean getRecoveryMode() {
+		return this.recoveryMode;
+	}
+
 	// Entry point
 
 	public static void main(String[] args) {
@@ -613,6 +623,11 @@ public class Controller extends Thread {
 		return peerChainTipData == null || peerChainTipData.getLastBlockSignature() == null || inferiorChainTips.contains(new ByteArray(peerChainTipData.getLastBlockSignature()));
 	};
 
+	public static final Predicate<Peer> hasOldVersion = peer -> {
+		final String minPeerVersion = Settings.getInstance().getMinPeerVersion();
+		return peer.isAtLeastVersion(minPeerVersion) == false;
+	};
+
 	private void potentiallySynchronize() throws InterruptedException {
 		// Already synchronizing via another thread?
 		if (this.isSynchronizing)
@@ -629,6 +644,17 @@ public class Controller extends Thread {
 		// Disregard peers that don't have a recent block
 		peers.removeIf(hasNoRecentBlock);
 
+		// Disregard peers that are on an old version
+		peers.removeIf(hasOldVersion);
+
+		checkRecoveryModeForPeers(peers);
+		if (recoveryMode) {
+			peers = Network.getInstance().getHandshakedPeers();
+			peers.removeIf(hasOnlyGenesisBlock);
+			peers.removeIf(hasMisbehaved);
+			peers.removeIf(hasOldVersion);
+		}
+
 		// Check we have enough peers to potentially synchronize
 		if (peers.size() < Settings.getInstance().getMinBlockchainPeers())
 			return;
@@ -639,9 +665,31 @@ public class Controller extends Thread {
 		// Disregard peers that are on the same block as last sync attempt and we didn't like their chain
 		peers.removeIf(hasInferiorChainTip);
 
+		final int peersBeforeComparison = peers.size();
+
+		// Request recent block summaries from the remaining peers, and locate our common block with each
+		Synchronizer.getInstance().findCommonBlocksWithPeers(peers);
+
+		// Compare the peers against each other, and against our chain, which will return an updated list excluding those without common blocks
+		peers = Synchronizer.getInstance().comparePeers(peers);
+
+		// We may have added more inferior chain tips when comparing peers, so remove any peers that are currently on those chains
+		peers.removeIf(hasInferiorChainTip);
+
+		final int peersRemoved = peersBeforeComparison - peers.size();
+		if (peersRemoved > 0)
+			LOGGER.info(String.format("Ignoring %d peers on inferior chains. Peers remaining: %d", peersRemoved, peers.size()));
+
 		if (peers.isEmpty())
 			return;
 
+		if (peers.size() > 1) {
+			StringBuilder finalPeersString = new StringBuilder();
+			for (Peer peer : peers)
+				finalPeersString = finalPeersString.length() > 0 ? finalPeersString.append(", ").append(peer) : finalPeersString.append(peer);
+			LOGGER.info(String.format("Choosing random peer from: [%s]", finalPeersString.toString()));
+		}
+
 		// Pick random peer to sync with
 		int index = new SecureRandom().nextInt(peers.size());
 		Peer peer = peers.get(index);
@@ -744,6 +792,46 @@ public class Controller extends Thread {
 		}
 	}
 
+	private boolean checkRecoveryModeForPeers(List<Peer> qualifiedPeers) {
+		List<Peer> handshakedPeers = Network.getInstance().getHandshakedPeers();
+
+		if (handshakedPeers.size() > 0) {
+			// There is at least one handshaked peer
+			if (qualifiedPeers.isEmpty()) {
+				// There are no 'qualified' peers - i.e. peers that have a recent block we can sync to
+				boolean werePeersAvailable = peersAvailable;
+				peersAvailable = false;
+
+				// If peers only just became unavailable, update our record of the time they were last available
+				if (werePeersAvailable)
+					timePeersLastAvailable = NTP.getTime();
+
+				// If enough time has passed, enter recovery mode, which lifts some restrictions on who we can sync with and when we can mint
+				if (NTP.getTime() - timePeersLastAvailable > RECOVERY_MODE_TIMEOUT) {
+					if (recoveryMode == false) {
+						LOGGER.info(String.format("Peers have been unavailable for %d minutes. Entering recovery mode...", RECOVERY_MODE_TIMEOUT/60/1000));
+						recoveryMode = true;
+					}
+				}
+			} else {
+				// We now have at least one peer with a recent block, so we can exit recovery mode and sync normally
+				peersAvailable = true;
+				if (recoveryMode) {
+					LOGGER.info("Peers have become available again. Exiting recovery mode...");
+					recoveryMode = false;
+				}
+			}
+		}
+		return recoveryMode;
+	}
+
+	public void addInferiorChainSignature(byte[] inferiorSignature) {
+		// Update our list of inferior chain tips
+		ByteArray inferiorChainSignature = new ByteArray(inferiorSignature);
+		if (!inferiorChainSignatures.contains(inferiorChainSignature))
+			inferiorChainSignatures.add(inferiorChainSignature);
+	}
+
 	public static class StatusChangeEvent implements Event {
 		public StatusChangeEvent() {
 		}
@@ -775,7 +863,7 @@ public class Controller extends Thread {
 				actionText = Translator.INSTANCE.translate("SysTray", "MINTING_DISABLED");
 		}
 
-		String tooltip = String.format("%s - %d %s - %s %d", actionText, numberOfPeers, connectionsText, heightText, height);
+		String tooltip = String.format("%s - %d %s - %s %d", actionText, numberOfPeers, connectionsText, heightText, height) + "\n" + String.format("Build version: %s", this.buildVersion);
 		SysTray.getInstance().setToolTipText(tooltip);
 
 		this.callbackExecutor.execute(() -> {
@@ -933,6 +1021,7 @@ public class Controller extends Thread {
 	public void onNewBlock(BlockData latestBlockData) {
 		// Protective copy
 		BlockData blockDataCopy = new BlockData(latestBlockData);
+		int blockCacheSize = Settings.getInstance().getBlockCacheSize();
 
 		synchronized (this.latestBlocks) {
 			BlockData cachedChainTip = this.latestBlocks.peekLast();
@@ -942,7 +1031,7 @@ public class Controller extends Thread {
 				this.latestBlocks.addLast(latestBlockData);
 
 				// Trim if necessary
-				if (this.latestBlocks.size() >= BLOCK_CACHE_SIZE)
+				if (this.latestBlocks.size() >= blockCacheSize)
 					this.latestBlocks.pollFirst();
 			} else {
 				if (cachedChainTip != null)
@@ -1150,14 +1239,15 @@ public class Controller extends Thread {
 
 		ByteArray signatureAsByteArray = new ByteArray(signature);
 
-		BlockMessage cachedBlockMessage = this.blockMessageCache.get(signatureAsByteArray);
+		CachedBlockMessage cachedBlockMessage = this.blockMessageCache.get(signatureAsByteArray);
+		int blockCacheSize = Settings.getInstance().getBlockCacheSize();
 
 		// Check cached latest block message
 		if (cachedBlockMessage != null) {
 			this.stats.getBlockMessageStats.cacheHits.incrementAndGet();
 
 			// We need to duplicate it to prevent multiple threads setting ID on the same message
-			BlockMessage clonedBlockMessage = cachedBlockMessage.cloneWithNewId(message.getId());
+			CachedBlockMessage clonedBlockMessage = cachedBlockMessage.cloneWithNewId(message.getId());
 
 			if (!peer.sendMessage(clonedBlockMessage))
 				peer.disconnect("failed to send block");
@@ -1185,15 +1275,18 @@ public class Controller extends Thread {
 
 			Block block = new Block(repository, blockData);
 
-			BlockMessage blockMessage = new BlockMessage(block);
+			CachedBlockMessage blockMessage = new CachedBlockMessage(block);
 			blockMessage.setId(message.getId());
 
 			// This call also causes the other needed data to be pulled in from repository
-			if (!peer.sendMessage(blockMessage))
+			if (!peer.sendMessage(blockMessage)) {
 				peer.disconnect("failed to send block");
+				// Don't fall-through to caching because failure to send might be from failure to build message
+				return;
+			}
 
 			// If request is for a recent block, cache it
-			if (getChainHeight() - blockData.getHeight() <= BLOCK_CACHE_SIZE) {
+			if (getChainHeight() - blockData.getHeight() <= blockCacheSize) {
 				this.stats.getBlockMessageStats.cacheFills.incrementAndGet();
 
 				this.blockMessageCache.put(new ByteArray(blockData.getSignature()), blockMessage);
@@ -1207,6 +1300,18 @@ public class Controller extends Thread {
 		TransactionMessage transactionMessage = (TransactionMessage) message;
 		TransactionData transactionData = transactionMessage.getTransactionData();
 
+		/*
+		 *  If we can't obtain blockchain lock immediately,
+		 *  e.g. Synchronizer is active, or another transaction is taking a while to validate,
+		 *  then we're using up a network thread for ages and clogging things up
+		 *  so bail out early
+		 */
+		ReentrantLock blockchainLock = Controller.getInstance().getBlockchainLock();
+		if (!blockchainLock.tryLock()) {
+			LOGGER.trace(() -> String.format("Too busy to import %s transaction %s from peer %s", transactionData.getType().name(), Base58.encode(transactionData.getSignature()), peer));
+			return;
+		}
+
 		try (final Repository repository = RepositoryManager.getRepository()) {
 			Transaction transaction = Transaction.fromData(repository, transactionData);
 
@@ -1236,6 +1341,8 @@ public class Controller extends Thread {
 			LOGGER.debug(() -> String.format("Imported %s transaction %s from peer %s", transactionData.getType().name(), Base58.encode(transactionData.getSignature()), peer));
 		} catch (DataException e) {
 			LOGGER.error(String.format("Repository issue while processing transaction %s from peer %s", Base58.encode(transactionData.getSignature()), peer), e);
+		} finally {
+			blockchainLock.unlock();
 		}
 	}
 

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

@@ -8,6 +8,7 @@ import java.util.Arrays;
 import java.util.List;
 import java.util.concurrent.locks.ReentrantLock;
 import java.util.stream.Collectors;
+import java.util.Iterator;
 
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
@@ -15,8 +16,10 @@ import org.qortal.account.Account;
 import org.qortal.account.PublicKeyAccount;
 import org.qortal.block.Block;
 import org.qortal.block.Block.ValidationResult;
+import org.qortal.block.BlockChain;
 import org.qortal.data.block.BlockData;
 import org.qortal.data.block.BlockSummaryData;
+import org.qortal.data.block.CommonBlockData;
 import org.qortal.data.network.PeerChainTipData;
 import org.qortal.data.transaction.RewardShareTransactionData;
 import org.qortal.data.transaction.TransactionData;
@@ -32,17 +35,29 @@ import org.qortal.network.message.Message.MessageType;
 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.utils.Base58;
+import org.qortal.utils.NTP;
 
 public class Synchronizer {
 
 	private static final Logger LOGGER = LogManager.getLogger(Synchronizer.class);
 
+	/** Max number of new blocks we aim to add to chain tip in each sync round */
+	private static final int SYNC_BATCH_SIZE = 200; // XXX move to Settings?
+
+	/** Initial jump back of block height when searching for common block with peer */
 	private static final int INITIAL_BLOCK_STEP = 8;
-	private static final int MAXIMUM_BLOCK_STEP = 500;
+	/** Maximum jump back of block height when searching for common block with peer */
+	private static final int MAXIMUM_BLOCK_STEP = 128;
+
+	/** Maximum difference in block height between tip and peer's common block before peer is considered TOO DIVERGENT */
 	private static final int MAXIMUM_COMMON_DELTA = 240; // XXX move to Settings?
-	private static final int SYNC_BATCH_SIZE = 200;
+
+	/** Maximum number of block signatures we ask from peer in one go */
+	private static final int MAXIMUM_REQUEST_SIZE = 200; // XXX move to Settings?
+
 
 	private static Synchronizer instance;
 
@@ -62,6 +77,381 @@ public class Synchronizer {
 		return instance;
 	}
 
+
+	/**
+	 * Iterate through a list of supplied peers, and attempt to find our common block with each.
+	 * If a common block is found, its summary will be retained in the peer's commonBlockSummary property, for processing later.
+	 * <p>
+	 * Will return <tt>SynchronizationResult.OK</tt> on success.
+	 * <p>
+	 * @param peers
+	 * @return SynchronizationResult.OK if the process completed successfully, or a different SynchronizationResult if something went wrong.
+	 * @throws InterruptedException
+	 */
+	public SynchronizationResult findCommonBlocksWithPeers(List<Peer> peers) throws InterruptedException {
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			try {
+
+				if (peers.size() == 0)
+					return SynchronizationResult.NOTHING_TO_DO;
+
+				// If our latest block is very old, it's best that we don't try and determine the best peers to sync to.
+				// This is because it can involve very large chain comparisons, which is too intensive.
+				// In reality, most forking problems occur near the chain tips, so we will reserve this functionality for those situations.
+				final Long minLatestBlockTimestamp = Controller.getMinimumLatestBlockTimestamp();
+				if (minLatestBlockTimestamp == null)
+					return SynchronizationResult.REPOSITORY_ISSUE;
+
+				final BlockData ourLatestBlockData = repository.getBlockRepository().getLastBlock();
+				if (ourLatestBlockData.getTimestamp() < minLatestBlockTimestamp) {
+					LOGGER.debug(String.format("Our latest block is very old, so we won't collect common block info from peers"));
+					return SynchronizationResult.NOTHING_TO_DO;
+				}
+
+				LOGGER.debug(String.format("Searching for common blocks with %d peers...", peers.size()));
+				final long startTime = System.currentTimeMillis();
+				int commonBlocksFound = 0;
+
+				for (Peer peer : peers) {
+					// Are we shutting down?
+					if (Controller.isStopping())
+						return SynchronizationResult.SHUTTING_DOWN;
+
+					// Check if we can use the cached common block data, by comparing the peer's current chain tip against the peer's chain tip when we last found our common block
+					if (peer.canUseCachedCommonBlockData()) {
+						LOGGER.debug(String.format("Skipping peer %s because we already have the latest common block data in our cache. Cached common block sig is %.08s", peer, Base58.encode(peer.getCommonBlockData().getCommonBlockSummary().getSignature())));
+						commonBlocksFound++;
+						continue;
+					}
+
+					// Cached data is stale, so clear it and repopulate
+					peer.setCommonBlockData(null);
+
+					// Search for the common block
+					Synchronizer.getInstance().findCommonBlockWithPeer(peer, repository);
+					if (peer.getCommonBlockData() != null)
+						commonBlocksFound++;
+				}
+
+				final long totalTimeTaken = System.currentTimeMillis() - startTime;
+				LOGGER.info(String.format("Finished searching for common blocks with %d peer%s. Found: %d. Total time taken: %d ms", peers.size(), (peers.size() != 1 ? "s" : ""), commonBlocksFound, totalTimeTaken));
+
+				return SynchronizationResult.OK;
+			} finally {
+				repository.discardChanges(); // Free repository locks, if any, also in case anything went wrong
+			}
+		} catch (DataException e) {
+			LOGGER.error("Repository issue during synchronization with peer", e);
+			return SynchronizationResult.REPOSITORY_ISSUE;
+		}
+	}
+
+	/**
+	 * Attempt to find the find our common block with supplied peer.
+	 * If a common block is found, its summary will be retained in the peer's commonBlockSummary property, for processing later.
+	 * <p>
+	 * Will return <tt>SynchronizationResult.OK</tt> on success.
+	 * <p>
+	 * @param peer
+	 * @param repository
+	 * @return SynchronizationResult.OK if the process completed successfully, or a different SynchronizationResult if something went wrong.
+	 * @throws InterruptedException
+	 */
+	public SynchronizationResult findCommonBlockWithPeer(Peer peer, Repository repository) throws InterruptedException {
+		try {
+			final BlockData ourLatestBlockData = repository.getBlockRepository().getLastBlock();
+			final int ourInitialHeight = ourLatestBlockData.getHeight();
+
+			PeerChainTipData peerChainTipData = peer.getChainTipData();
+			int peerHeight = peerChainTipData.getLastHeight();
+			byte[] peersLastBlockSignature = peerChainTipData.getLastBlockSignature();
+
+			byte[] ourLastBlockSignature = ourLatestBlockData.getSignature();
+			LOGGER.debug(String.format("Fetching summaries from peer %s at height %d, sig %.8s, ts %d; our height %d, sig %.8s, ts %d", peer,
+					peerHeight, Base58.encode(peersLastBlockSignature), peer.getChainTipData().getLastBlockTimestamp(),
+					ourInitialHeight, Base58.encode(ourLastBlockSignature), ourLatestBlockData.getTimestamp()));
+
+			List<BlockSummaryData> peerBlockSummaries = new ArrayList<>();
+			SynchronizationResult findCommonBlockResult = fetchSummariesFromCommonBlock(repository, peer, ourInitialHeight, false, peerBlockSummaries);
+			if (findCommonBlockResult != SynchronizationResult.OK) {
+				// Logging performed by fetchSummariesFromCommonBlock() above
+				peer.setCommonBlockData(null);
+				return findCommonBlockResult;
+			}
+
+			// First summary is common block
+			final BlockData commonBlockData = repository.getBlockRepository().fromSignature(peerBlockSummaries.get(0).getSignature());
+			final BlockSummaryData commonBlockSummary = new BlockSummaryData(commonBlockData);
+			final int commonBlockHeight = commonBlockData.getHeight();
+			final byte[] commonBlockSig = commonBlockData.getSignature();
+			final String commonBlockSig58 = Base58.encode(commonBlockSig);
+			LOGGER.debug(String.format("Common block with peer %s is at height %d, sig %.8s, ts %d", peer,
+					commonBlockHeight, commonBlockSig58, commonBlockData.getTimestamp()));
+			peerBlockSummaries.remove(0);
+
+			// Store the common block summary against the peer, and the current chain tip (for caching)
+			peer.setCommonBlockData(new CommonBlockData(commonBlockSummary, peerChainTipData));
+
+			return SynchronizationResult.OK;
+		} catch (DataException e) {
+			LOGGER.error("Repository issue during synchronization with peer", e);
+			return SynchronizationResult.REPOSITORY_ISSUE;
+		}
+	}
+
+
+	/**
+	 * Compare a list of peers to determine the best peer(s) to sync to next.
+	 * <p>
+	 * Will return a filtered list of peers on success, or an identical list of peers on failure.
+	 * This allows us to fall back to legacy behaviour (random selection from the entire list of peers), if we are unable to make the comparison.
+	 * <p>
+	 * @param peers
+	 * @return a list of peers, possibly filtered.
+	 * @throws InterruptedException
+	 */
+	public List<Peer> comparePeers(List<Peer> peers) throws InterruptedException {
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			try {
+
+				// If our latest block is very old, it's best that we don't try and determine the best peers to sync to.
+				// This is because it can involve very large chain comparisons, which is too intensive.
+				// In reality, most forking problems occur near the chain tips, so we will reserve this functionality for those situations.
+				final Long minLatestBlockTimestamp = Controller.getMinimumLatestBlockTimestamp();
+				if (minLatestBlockTimestamp == null)
+					return peers;
+
+				final BlockData ourLatestBlockData = repository.getBlockRepository().getLastBlock();
+				if (ourLatestBlockData.getTimestamp() < minLatestBlockTimestamp) {
+					LOGGER.debug(String.format("Our latest block is very old, so we won't filter the peers list"));
+					return peers;
+				}
+
+				// We will switch to a new chain weight consensus algorithm at a hard fork, so determine if this has happened yet
+				boolean usingSameLengthChainWeight = (NTP.getTime() >= BlockChain.getInstance().getCalcChainWeightTimestamp());
+				LOGGER.debug(String.format("Using %s chain weight consensus algorithm", (usingSameLengthChainWeight ? "same-length" : "variable-length")));
+
+				// Retrieve a list of unique common blocks from this list of peers
+				List<BlockSummaryData> commonBlocks = this.uniqueCommonBlocks(peers);
+
+				// Order common blocks by height, in ascending order
+				// This is essential for the logic below to make the correct decisions when discarding chains - do not remove
+				commonBlocks.sort((b1, b2) -> Integer.valueOf(b1.getHeight()).compareTo(Integer.valueOf(b2.getHeight())));
+
+				// Get our latest height
+				final int ourHeight = ourLatestBlockData.getHeight();
+
+				// Create a placeholder to track of common blocks that we can discard due to being inferior chains
+				int dropPeersAfterCommonBlockHeight = 0;
+
+				// Remove peers with no common block data
+				Iterator iterator = peers.iterator();
+				while (iterator.hasNext()) {
+					Peer peer = (Peer) iterator.next();
+					if (peer.getCommonBlockData() == null) {
+						LOGGER.debug(String.format("Removed peer %s because it has no common block data", peer));
+						iterator.remove();
+					}
+				}
+
+				// Loop through each group of common blocks
+				for (BlockSummaryData commonBlockSummary : commonBlocks) {
+					List<Peer> peersSharingCommonBlock = peers.stream().filter(peer -> peer.getCommonBlockData().getCommonBlockSummary().equals(commonBlockSummary)).collect(Collectors.toList());
+
+					// Check if we need to discard this group of peers
+					if (dropPeersAfterCommonBlockHeight > 0) {
+						if (commonBlockSummary.getHeight() > dropPeersAfterCommonBlockHeight) {
+							// We have already determined that the correct chain diverged from a lower height. We are safe to skip these peers.
+							for (Peer peer : peersSharingCommonBlock) {
+								LOGGER.debug(String.format("Peer %s has common block at height %d but the superior chain is at height %d. Removing it from this round.", peer, commonBlockSummary.getHeight(), dropPeersAfterCommonBlockHeight));
+								Controller.getInstance().addInferiorChainSignature(peer.getChainTipData().getLastBlockSignature());
+							}
+							continue;
+						}
+					}
+
+					// Calculate the length of the shortest peer chain sharing this common block, including our chain
+					final int ourAdditionalBlocksAfterCommonBlock = ourHeight - commonBlockSummary.getHeight();
+					int minChainLength = this.calculateMinChainLengthOfPeers(peersSharingCommonBlock, commonBlockSummary);
+
+					// Fetch block summaries from each peer
+					for (Peer peer : peersSharingCommonBlock) {
+
+						// If we're shutting down, just return the latest peer list
+						if (Controller.isStopping())
+							return peers;
+
+						// Count the number of blocks this peer has beyond our common block
+						final int peerHeight = peer.getChainTipData().getLastHeight();
+						final int peerAdditionalBlocksAfterCommonBlock = peerHeight - commonBlockSummary.getHeight();
+						// Limit the number of blocks we are comparing. FUTURE: we could request more in batches, but there may not be a case when this is needed
+						int summariesRequired = Math.min(peerAdditionalBlocksAfterCommonBlock, MAXIMUM_REQUEST_SIZE);
+
+						// Check if we can use the cached common block summaries, by comparing the peer's current chain tip against the peer's chain tip when we last found our common block
+						boolean useCachedSummaries = false;
+						if (peer.canUseCachedCommonBlockData()) {
+							if (peer.getCommonBlockData().getBlockSummariesAfterCommonBlock() != null) {
+								if (peer.getCommonBlockData().getBlockSummariesAfterCommonBlock().size() == summariesRequired) {
+									LOGGER.debug(String.format("Using cached block summaries for peer %s", peer));
+									useCachedSummaries = true;
+								}
+							}
+						}
+
+						if (useCachedSummaries == false) {
+							if (summariesRequired > 0) {
+								LOGGER.trace(String.format("Requesting %d block summar%s from peer %s after common block %.8s. Peer height: %d", summariesRequired, (summariesRequired != 1 ? "ies" : "y"), peer, Base58.encode(commonBlockSummary.getSignature()), peerHeight));
+
+								List<BlockSummaryData> blockSummaries = this.getBlockSummaries(peer, commonBlockSummary.getSignature(), summariesRequired);
+								peer.getCommonBlockData().setBlockSummariesAfterCommonBlock(blockSummaries);
+
+								if (blockSummaries != null) {
+									LOGGER.trace(String.format("Peer %s returned %d block summar%s", peer, blockSummaries.size(), (blockSummaries.size() != 1 ? "ies" : "y")));
+
+									if (blockSummaries.size() < summariesRequired)
+										// This could mean that the peer has re-orged. But we still have the same common block, so it's safe to proceed with this set of signatures instead.
+										LOGGER.debug(String.format("Peer %s returned %d block summar%s instead of expected %d", peer, blockSummaries.size(), (blockSummaries.size() != 1 ? "ies" : "y"), summariesRequired));
+								}
+							} else {
+								// There are no block summaries after this common block
+								peer.getCommonBlockData().setBlockSummariesAfterCommonBlock(null);
+							}
+						}
+
+						// Reduce minChainLength if needed. If we don't have any blocks, this peer will be excluded from chain weight comparisons later in the process, so we shouldn't update minChainLength
+						List <BlockSummaryData> peerBlockSummaries = peer.getCommonBlockData().getBlockSummariesAfterCommonBlock();
+						if (peerBlockSummaries != null && peerBlockSummaries.size() > 0)
+							if (peerBlockSummaries.size() < minChainLength)
+								minChainLength = peerBlockSummaries.size();
+					}
+
+					// Fetch our corresponding block summaries. Limit to MAXIMUM_REQUEST_SIZE, in order to make the comparison fairer, as peers have been limited too
+					final int ourSummariesRequired = Math.min(ourAdditionalBlocksAfterCommonBlock, MAXIMUM_REQUEST_SIZE);
+					LOGGER.trace(String.format("About to fetch our block summaries from %d to %d. Our height: %d", commonBlockSummary.getHeight() + 1, commonBlockSummary.getHeight() + ourSummariesRequired, ourHeight));
+					List<BlockSummaryData> ourBlockSummaries = repository.getBlockRepository().getBlockSummaries(commonBlockSummary.getHeight() + 1, commonBlockSummary.getHeight() + ourSummariesRequired);
+					if (ourBlockSummaries.isEmpty()) {
+						LOGGER.debug(String.format("We don't have any block summaries so can't compare our chain against peers with this common block. We can still compare them against each other."));
+					}
+					else {
+						populateBlockSummariesMinterLevels(repository, ourBlockSummaries);
+						// Reduce minChainLength if we have less summaries
+						if (ourBlockSummaries.size() < minChainLength)
+							minChainLength = ourBlockSummaries.size();
+					}
+
+					// Create array to hold peers for comparison
+					List<Peer> superiorPeersForComparison = new ArrayList<>();
+
+					// Calculate max height for chain weight comparisons
+					int maxHeightForChainWeightComparisons = commonBlockSummary.getHeight() + minChainLength;
+
+					// Calculate our chain weight
+					BigInteger ourChainWeight = BigInteger.valueOf(0);
+					if (ourBlockSummaries.size() > 0)
+						ourChainWeight = Block.calcChainWeight(commonBlockSummary.getHeight(), commonBlockSummary.getSignature(), ourBlockSummaries, maxHeightForChainWeightComparisons);
+
+					NumberFormat formatter = new DecimalFormat("0.###E0");
+					NumberFormat accurateFormatter = new DecimalFormat("0.################E0");
+					LOGGER.debug(String.format("Our chain weight based on %d blocks is %s", (usingSameLengthChainWeight ? minChainLength : ourBlockSummaries.size()), formatter.format(ourChainWeight)));
+
+					LOGGER.debug(String.format("Listing peers with common block %.8s...", Base58.encode(commonBlockSummary.getSignature())));
+					for (Peer peer : peersSharingCommonBlock) {
+						final int peerHeight = peer.getChainTipData().getLastHeight();
+						final int peerAdditionalBlocksAfterCommonBlock = peerHeight - commonBlockSummary.getHeight();
+						final CommonBlockData peerCommonBlockData = peer.getCommonBlockData();
+
+						if (peerCommonBlockData == null || peerCommonBlockData.getBlockSummariesAfterCommonBlock() == null || peerCommonBlockData.getBlockSummariesAfterCommonBlock().isEmpty()) {
+							// No response - remove this peer for now
+							LOGGER.debug(String.format("Peer %s doesn't have any block summaries - removing it from this round", peer));
+							peers.remove(peer);
+							continue;
+						}
+
+						final List<BlockSummaryData> peerBlockSummariesAfterCommonBlock = peerCommonBlockData.getBlockSummariesAfterCommonBlock();
+						populateBlockSummariesMinterLevels(repository, peerBlockSummariesAfterCommonBlock);
+
+						// Calculate cumulative chain weight of this blockchain subset, from common block to highest mutual block held by all peers in this group.
+						LOGGER.debug(String.format("About to calculate chain weight based on %d blocks for peer %s with common block %.8s (peer has %d blocks after common block)", (usingSameLengthChainWeight ? minChainLength : peerBlockSummariesAfterCommonBlock.size()), peer, Base58.encode(commonBlockSummary.getSignature()), peerAdditionalBlocksAfterCommonBlock));
+						BigInteger peerChainWeight = Block.calcChainWeight(commonBlockSummary.getHeight(), commonBlockSummary.getSignature(), peerBlockSummariesAfterCommonBlock, maxHeightForChainWeightComparisons);
+						peer.getCommonBlockData().setChainWeight(peerChainWeight);
+						LOGGER.debug(String.format("Chain weight of peer %s based on %d blocks (%d - %d) is %s", peer, (usingSameLengthChainWeight ? minChainLength : peerBlockSummariesAfterCommonBlock.size()), peerBlockSummariesAfterCommonBlock.get(0).getHeight(), peerBlockSummariesAfterCommonBlock.get(peerBlockSummariesAfterCommonBlock.size()-1).getHeight(), formatter.format(peerChainWeight)));
+
+						// Compare against our chain - if our blockchain has greater weight then don't synchronize with peer (or any others in this group)
+						if (ourChainWeight.compareTo(peerChainWeight) > 0) {
+							// This peer is on an inferior chain - remove it
+							LOGGER.debug(String.format("Peer %s is on an inferior chain to us - removing it from this round", peer));
+							peers.remove(peer);
+						}
+						else {
+							// Our chain is inferior
+							LOGGER.debug(String.format("Peer %s is on a better chain to us. We will compare the other peers sharing this common block against each other, and drop all peers sharing higher common blocks.", peer));
+							dropPeersAfterCommonBlockHeight = commonBlockSummary.getHeight();
+							superiorPeersForComparison.add(peer);
+						}
+					}
+
+					// Now that we have selected the best peers, compare them against each other and remove any with lower weights
+					if (superiorPeersForComparison.size() > 0) {
+						BigInteger bestChainWeight = null;
+						for (Peer peer : superiorPeersForComparison) {
+							// Increase bestChainWeight if needed
+							if (bestChainWeight == null || peer.getCommonBlockData().getChainWeight().compareTo(bestChainWeight) >= 0)
+								bestChainWeight = peer.getCommonBlockData().getChainWeight();
+						}
+						for (Peer peer : superiorPeersForComparison) {
+							// Check if we should discard an inferior peer
+							if (peer.getCommonBlockData().getChainWeight().compareTo(bestChainWeight) < 0) {
+								BigInteger difference = bestChainWeight.subtract(peer.getCommonBlockData().getChainWeight());
+								LOGGER.debug(String.format("Peer %s has a lower chain weight (difference: %s) than other peer(s) in this group - removing it from this round.", peer, accurateFormatter.format(difference)));
+								peers.remove(peer);
+							}
+						}
+					}
+				}
+
+				return peers;
+			} finally {
+				repository.discardChanges(); // Free repository locks, if any, also in case anything went wrong
+			}
+		} catch (DataException e) {
+			LOGGER.error("Repository issue during peer comparison", e);
+			return peers;
+		}
+	}
+
+	private List<BlockSummaryData> uniqueCommonBlocks(List<Peer> peers) {
+		List<BlockSummaryData> commonBlocks = new ArrayList<>();
+
+		for (Peer peer : peers) {
+			if (peer.getCommonBlockData() != null && peer.getCommonBlockData().getCommonBlockSummary() != null) {
+				LOGGER.debug(String.format("Peer %s has common block %.8s", peer, Base58.encode(peer.getCommonBlockData().getCommonBlockSummary().getSignature())));
+
+				BlockSummaryData commonBlockSummary = peer.getCommonBlockData().getCommonBlockSummary();
+				if (!commonBlocks.contains(commonBlockSummary))
+					commonBlocks.add(commonBlockSummary);
+			}
+			else {
+				LOGGER.debug(String.format("Peer %s has no common block data. Skipping...", peer));
+			}
+		}
+
+		return commonBlocks;
+	}
+
+	private int calculateMinChainLengthOfPeers(List<Peer> peersSharingCommonBlock, BlockSummaryData commonBlockSummary) {
+		// Calculate the length of the shortest peer chain sharing this common block
+		int minChainLength = 0;
+		for (Peer peer : peersSharingCommonBlock) {
+			final int peerHeight = peer.getChainTipData().getLastHeight();
+			final int peerAdditionalBlocksAfterCommonBlock = peerHeight - commonBlockSummary.getHeight();
+
+			if (peerAdditionalBlocksAfterCommonBlock < minChainLength || minChainLength == 0)
+				minChainLength = peerAdditionalBlocksAfterCommonBlock;
+		}
+		return minChainLength;
+	}
+
+
 	/**
 	 * Attempt to synchronize blockchain with peer.
 	 * <p>
@@ -97,9 +487,12 @@ public class Synchronizer {
 
 					List<BlockSummaryData> peerBlockSummaries = new ArrayList<>();
 					SynchronizationResult findCommonBlockResult = fetchSummariesFromCommonBlock(repository, peer, ourInitialHeight, force, peerBlockSummaries);
-					if (findCommonBlockResult != SynchronizationResult.OK)
+					if (findCommonBlockResult != SynchronizationResult.OK) {
 						// Logging performed by fetchSummariesFromCommonBlock() above
+						// Clear our common block cache for this peer
+						peer.setCommonBlockData(null);
 						return findCommonBlockResult;
+					}
 
 					// First summary is common block
 					final BlockData commonBlockData = repository.getBlockRepository().fromSignature(peerBlockSummaries.get(0).getSignature());
@@ -244,9 +637,13 @@ public class Synchronizer {
 		// Currently we work forward from common block until we hit a block we don't have
 		// TODO: rewrite as modified binary search!
 		int i;
-		for (i = 1; i < blockSummariesFromCommon.size(); ++i)
+		for (i = 1; i < blockSummariesFromCommon.size(); ++i) {
+			if (Controller.isStopping())
+				return SynchronizationResult.SHUTTING_DOWN;
+
 			if (!repository.getBlockRepository().exists(blockSummariesFromCommon.get(i).getSignature()))
 				break;
+		}
 
 		// Note: index i - 1 isn't cleared: List.subList is fromIndex inclusive to toIndex exclusive
 		blockSummariesFromCommon.subList(0, i - 1).clear();
@@ -295,6 +692,9 @@ public class Synchronizer {
 
 				// Check peer sent valid heights
 				for (int i = 0; i < moreBlockSummaries.size(); ++i) {
+					if (Controller.isStopping())
+						return SynchronizationResult.SHUTTING_DOWN;
+
 					++lastSummaryHeight;
 
 					BlockSummaryData blockSummary = moreBlockSummaries.get(i);
@@ -316,7 +716,7 @@ public class Synchronizer {
 			populateBlockSummariesMinterLevels(repository, ourBlockSummaries);
 			populateBlockSummariesMinterLevels(repository, peerBlockSummaries);
 
-			final int mutualHeight = commonBlockHeight - 1 + Math.min(ourBlockSummaries.size(), peerBlockSummaries.size());
+			final int mutualHeight = commonBlockHeight + Math.min(ourBlockSummaries.size(), peerBlockSummaries.size());
 
 			// Calculate cumulative chain weights of both blockchain subsets, from common block to highest mutual block.
 			BigInteger ourChainWeight = Block.calcChainWeight(commonBlockHeight, commonBlockSig, ourBlockSummaries, mutualHeight);
@@ -341,52 +741,155 @@ public class Synchronizer {
 		final byte[] commonBlockSig = commonBlockData.getSignature();
 		String commonBlockSig58 = Base58.encode(commonBlockSig);
 
+		byte[] latestPeerSignature = commonBlockSig;
+		int height = commonBlockHeight;
+
 		LOGGER.debug(() -> String.format("Fetching peer %s chain from height %d, sig %.8s", peer, commonBlockHeight, commonBlockSig58));
 
-		int ourHeight = ourInitialHeight;
+		final int maxRetries = Settings.getInstance().getMaxRetries();
 
 		// Overall plan: fetch peer's blocks first, then orphan, then apply
 
 		// Convert any leftover (post-common) block summaries into signatures to request from peer
 		List<byte[]> peerBlockSignatures = peerBlockSummaries.stream().map(BlockSummaryData::getSignature).collect(Collectors.toList());
 
-		// Fetch remaining block signatures, if needed
-		int numberSignaturesRequired = peerBlockSignatures.size() - (peerHeight - commonBlockHeight);
-		if (numberSignaturesRequired > 0) {
-			byte[] latestPeerSignature = peerBlockSignatures.isEmpty() ? commonBlockSig : peerBlockSignatures.get(peerBlockSignatures.size() - 1);
-
-			LOGGER.trace(String.format("Requesting %d signature%s after height %d, sig %.8s",
-					numberSignaturesRequired, (numberSignaturesRequired != 1 ? "s": ""), ourHeight, Base58.encode(latestPeerSignature)));
-
-			List<byte[]> moreBlockSignatures = this.getBlockSignatures(peer, latestPeerSignature, numberSignaturesRequired);
-
-			if (moreBlockSignatures == null || moreBlockSignatures.isEmpty()) {
-				LOGGER.info(String.format("Peer %s failed to respond with more block signatures after height %d, sig %.8s", peer,
-						ourHeight, Base58.encode(latestPeerSignature)));
-				return SynchronizationResult.NO_REPLY;
-			}
-
-			LOGGER.trace(String.format("Received %s signature%s", peerBlockSignatures.size(), (peerBlockSignatures.size() != 1 ? "s" : "")));
-
-			peerBlockSignatures.addAll(moreBlockSignatures);
-		}
-
-		// Fetch blocks using signatures
-		LOGGER.debug(String.format("Fetching new blocks from peer %s", peer));
+		// Keep a list of blocks received so far
 		List<Block> peerBlocks = new ArrayList<>();
 
-		for (byte[] blockSignature : peerBlockSignatures) {
-			Block newBlock = this.fetchBlock(repository, peer, blockSignature);
+		// Calculate the total number of additional blocks this peer has beyond the common block
+		int additionalPeerBlocksAfterCommonBlock = peerHeight - commonBlockHeight;
+		// Subtract the number of signatures that we already have, as we don't need to request them again
+		int numberSignaturesRequired = additionalPeerBlocksAfterCommonBlock - peerBlockSignatures.size();
+
+		int retryCount = 0;
+		while (height < peerHeight) {
+			if (Controller.isStopping())
+				return SynchronizationResult.SHUTTING_DOWN;
+
+            // Ensure we don't request more than MAXIMUM_REQUEST_SIZE
+            int numberRequested = Math.min(numberSignaturesRequired, MAXIMUM_REQUEST_SIZE);
+
+            // Do we need more signatures?
+			if (peerBlockSignatures.isEmpty() && numberRequested > 0) {
+                LOGGER.trace(String.format("Requesting %d signature%s after height %d, sig %.8s",
+                        numberRequested, (numberRequested != 1 ? "s" : ""), height, Base58.encode(latestPeerSignature)));
+
+                peerBlockSignatures = this.getBlockSignatures(peer, latestPeerSignature, numberRequested);
+
+                if (peerBlockSignatures == null || peerBlockSignatures.isEmpty()) {
+                    LOGGER.info(String.format("Peer %s failed to respond with more block signatures after height %d, sig %.8s", peer,
+                            height, Base58.encode(latestPeerSignature)));
+
+					// Clear our cache of common block summaries for this peer, as they are likely to be invalid
+					CommonBlockData cachedCommonBlockData = peer.getCommonBlockData();
+					if (cachedCommonBlockData != null)
+						cachedCommonBlockData.setBlockSummariesAfterCommonBlock(null);
+
+                    // If we have already received recent or newer blocks from this peer, go ahead and apply them
+                    if (peerBlocks.size() > 0) {
+						final BlockData ourLatestBlockData = repository.getBlockRepository().getLastBlock();
+                    	final Block peerLatestBlock = peerBlocks.get(peerBlocks.size() - 1);
+						final Long minLatestBlockTimestamp = Controller.getMinimumLatestBlockTimestamp();
+						if (ourLatestBlockData != null && peerLatestBlock != null && minLatestBlockTimestamp != null) {
+
+							// If we have received at least one recent block, we can apply them
+							if (peerLatestBlock.getBlockData().getTimestamp() > minLatestBlockTimestamp) {
+								LOGGER.debug("Newly received blocks are recent, so we will apply them");
+								break;
+							}
+
+							// If our latest block is very old....
+							if (ourLatestBlockData.getTimestamp() < minLatestBlockTimestamp) {
+								// ... and we have received a block that is more recent than our latest block ...
+								if (peerLatestBlock.getBlockData().getTimestamp() > ourLatestBlockData.getTimestamp()) {
+									// ... then apply the blocks, as it takes us a step forward.
+									// This is particularly useful when starting up a node that was on a small fork when it was last shut down.
+									// In these cases, we now allow the node to sync forward, and get onto the main chain again.
+									// Without this, we would require that the node syncs ENTIRELY with this peer,
+									// and any problems downloading a block would cause all progress to be lost.
+									LOGGER.debug(String.format("Newly received blocks are %d ms newer than our latest block - so we will apply them", peerLatestBlock.getBlockData().getTimestamp() - ourLatestBlockData.getTimestamp()));
+									break;
+								}
+							}
+						}
+                    }
+                    // Otherwise, give up and move on to the next peer, to avoid putting our chain into an outdated state
+                    return SynchronizationResult.NO_REPLY;
+                }
+
+                numberSignaturesRequired = peerHeight - height - peerBlockSignatures.size();
+                LOGGER.trace(String.format("Received %s signature%s", peerBlockSignatures.size(), (peerBlockSignatures.size() != 1 ? "s" : "")));
+			}
+
+			if (peerBlockSignatures.isEmpty()) {
+				LOGGER.trace(String.format("No more signatures or blocks to request from peer %s", peer));
+				break;
+			}
+
+			byte[] nextPeerSignature = peerBlockSignatures.get(0);
+			int nextHeight = height + 1;
+
+			LOGGER.trace(String.format("Fetching block %d, sig %.8s from %s", nextHeight, Base58.encode(nextPeerSignature), peer));
+			Block newBlock = this.fetchBlock(repository, peer, nextPeerSignature);
 
 			if (newBlock == null) {
 				LOGGER.info(String.format("Peer %s failed to respond with block for height %d, sig %.8s", peer,
-						ourHeight, Base58.encode(blockSignature)));
-				return SynchronizationResult.NO_REPLY;
+						nextHeight, Base58.encode(nextPeerSignature)));
+
+				if (retryCount >= maxRetries) {
+
+					// If we have already received recent or newer blocks from this peer, go ahead and apply them
+					if (peerBlocks.size() > 0) {
+						final BlockData ourLatestBlockData = repository.getBlockRepository().getLastBlock();
+						final Block peerLatestBlock = peerBlocks.get(peerBlocks.size() - 1);
+						final Long minLatestBlockTimestamp = Controller.getMinimumLatestBlockTimestamp();
+						if (ourLatestBlockData != null && peerLatestBlock != null && minLatestBlockTimestamp != null) {
+
+							// If we have received at least one recent block, we can apply them
+							if (peerLatestBlock.getBlockData().getTimestamp() > minLatestBlockTimestamp) {
+								LOGGER.debug("Newly received blocks are recent, so we will apply them");
+								break;
+							}
+
+							// If our latest block is very old....
+							if (ourLatestBlockData.getTimestamp() < minLatestBlockTimestamp) {
+								// ... and we have received a block that is more recent than our latest block ...
+								if (peerLatestBlock.getBlockData().getTimestamp() > ourLatestBlockData.getTimestamp()) {
+									// ... then apply the blocks, as it takes us a step forward.
+									// This is particularly useful when starting up a node that was on a small fork when it was last shut down.
+									// In these cases, we now allow the node to sync forward, and get onto the main chain again.
+									// Without this, we would require that the node syncs ENTIRELY with this peer,
+									// and any problems downloading a block would cause all progress to be lost.
+									LOGGER.debug(String.format("Newly received blocks are %d ms newer than our latest block - so we will apply them", peerLatestBlock.getBlockData().getTimestamp() - ourLatestBlockData.getTimestamp()));
+									break;
+								}
+							}
+						}
+					}
+					// Otherwise, give up and move on to the next peer, to avoid putting our chain into an outdated state
+					return SynchronizationResult.NO_REPLY;
+
+				} else {
+					// Re-fetch signatures, in case the peer is now on a different fork
+					peerBlockSignatures.clear();
+					numberSignaturesRequired = peerHeight - height;
+
+					// Retry until retryCount reaches maxRetries
+					retryCount++;
+					int triesRemaining = maxRetries - retryCount;
+					LOGGER.info(String.format("Re-issuing request to peer %s (%d attempt%s remaining)", peer, triesRemaining, (triesRemaining != 1 ? "s" : "")));
+					continue;
+				}
 			}
 
+			// Reset retryCount because the last request succeeded
+			retryCount = 0;
+
+			LOGGER.trace(String.format("Fetched block %d, sig %.8s from %s", nextHeight, Base58.encode(latestPeerSignature), peer));
+
 			if (!newBlock.isSignatureValid()) {
 				LOGGER.info(String.format("Peer %s sent block with invalid signature for height %d, sig %.8s", peer,
-						ourHeight, Base58.encode(blockSignature)));
+						nextHeight, Base58.encode(latestPeerSignature)));
 				return SynchronizationResult.INVALID_DATA;
 			}
 
@@ -395,12 +898,18 @@ public class Synchronizer {
 				transaction.setInitialApprovalStatus();
 
 			peerBlocks.add(newBlock);
+
+			// Now that we've received this block, we can increase our height and move on to the next one
+			latestPeerSignature = nextPeerSignature;
+			peerBlockSignatures.remove(0);
+			++height;
 		}
 
 		// Unwind to common block (unless common block is our latest block)
-		LOGGER.debug(String.format("Orphaning blocks back to common block height %d, sig %.8s", commonBlockHeight, commonBlockSig58));
+		int ourHeight = ourInitialHeight;
+		LOGGER.debug(String.format("Orphaning blocks back to common block height %d, sig %.8s. Our height: %d", commonBlockHeight, commonBlockSig58, ourHeight));
 
-		BlockData orphanBlockData = repository.getBlockRepository().fromHeight(ourHeight);
+		BlockData orphanBlockData = repository.getBlockRepository().fromHeight(ourInitialHeight);
 		while (ourHeight > commonBlockHeight) {
 			if (Controller.isStopping())
 				return SynchronizationResult.SHUTTING_DOWN;
@@ -422,10 +931,13 @@ public class Synchronizer {
 		LOGGER.debug(String.format("Orphaned blocks back to height %d, sig %.8s - applying new blocks from peer %s", commonBlockHeight, commonBlockSig58, peer));
 
 		for (Block newBlock : peerBlocks) {
+			if (Controller.isStopping())
+				return SynchronizationResult.SHUTTING_DOWN;
+
 			ValidationResult blockResult = newBlock.isValid();
 			if (blockResult != ValidationResult.OK) {
 				LOGGER.info(String.format("Peer %s sent invalid block for height %d, sig %.8s: %s", peer,
-						ourHeight, Base58.encode(newBlock.getSignature()), blockResult.name()));
+						newBlock.getBlockData().getHeight(), Base58.encode(newBlock.getSignature()), blockResult.name()));
 				return SynchronizationResult.INVALID_DATA;
 			}
 
@@ -469,7 +981,8 @@ public class Synchronizer {
 
 			// Do we need more signatures?
 			if (peerBlockSignatures.isEmpty()) {
-				int numberRequested = maxBatchHeight - ourHeight;
+				int numberRequested = Math.min(maxBatchHeight - ourHeight, MAXIMUM_REQUEST_SIZE);
+
 				LOGGER.trace(String.format("Requesting %d signature%s after height %d, sig %.8s",
 						numberRequested, (numberRequested != 1 ? "s": ""), ourHeight, Base58.encode(latestPeerSignature)));
 
@@ -573,6 +1086,9 @@ public class Synchronizer {
 		final int firstBlockHeight = blockSummaries.get(0).getHeight();
 
 		for (int i = 0; i < blockSummaries.size(); ++i) {
+			if (Controller.isStopping())
+				return;
+
 			BlockSummaryData blockSummary = blockSummaries.get(i);
 
 			// Qortal: minter is always a reward-share, so find actual minter and get their effective minting level

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

@@ -23,7 +23,7 @@ public interface AcctTradeBot {
 	public ResponseResult startResponse(Repository repository, ATData atData, ACCT acct,
 			CrossChainTradeData crossChainTradeData, String foreignKey, String receivingAddress) throws DataException;
 
-	public boolean canDelete(Repository repository, TradeBotData tradeBotData);
+	public boolean canDelete(Repository repository, TradeBotData tradeBotData) throws DataException;
 
 	public void progress(Repository repository, TradeBotData tradeBotData) throws DataException, ForeignBlockchainException;
 

src/main/java/org/qortal/controller/tradebot/BitcoinACCTv1TradeBot.java

@@ -345,11 +345,15 @@ public class BitcoinACCTv1TradeBot implements AcctTradeBot {
 	}
 
 	@Override
-	public boolean canDelete(Repository repository, TradeBotData tradeBotData) {
+	public boolean canDelete(Repository repository, TradeBotData tradeBotData) throws DataException {
 		State tradeBotState = State.valueOf(tradeBotData.getStateValue());
 		if (tradeBotState == null)
 			return true;
 
+		// If the AT doesn't exist then we might as well let the user tidy up
+		if (!repository.getATRepository().exists(tradeBotData.getAtAddress()))
+			return true;
+
 		switch (tradeBotState) {
 			case BOB_WAITING_FOR_AT_CONFIRM:
 			case ALICE_DONE:
@@ -378,7 +382,16 @@ public class BitcoinACCTv1TradeBot implements AcctTradeBot {
 			// Attempt to fetch AT data
 			atData = repository.getATRepository().fromATAddress(tradeBotData.getAtAddress());
 			if (atData == null) {
-				LOGGER.warn(() -> String.format("Unable to fetch trade AT %s from repository", tradeBotData.getAtAddress()));
+				LOGGER.debug(() -> String.format("Unable to fetch trade AT %s from repository", tradeBotData.getAtAddress()));
+
+				// If it has been over 24 hours since we last updated this trade-bot entry then assume AT is never coming back
+				// and so wipe the trade-bot entry
+				if (tradeBotData.getTimestamp() + MAX_AT_CONFIRMATION_PERIOD < NTP.getTime()) {
+					LOGGER.info(() -> String.format("AT %s has been gone for too long - deleting trade-bot entry", tradeBotData.getAtAddress()));
+					repository.getCrossChainRepository().delete(tradeBotData.getTradePrivateKey());
+					repository.saveChanges();
+				}
+
 				return;
 			}
 

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

@@ -211,6 +211,9 @@ public class LitecoinACCTv1TradeBot implements AcctTradeBot {
 
 		TradeBot.updateTradeBotState(repository, tradeBotData, () -> String.format("Built AT %s. Waiting for deployment", atAddress));
 
+		// Attempt to backup the trade bot data
+		TradeBot.backupTradeBotData(repository);
+
 		// Return to user for signing and broadcast as we don't have their Qortal private key
 		try {
 			return DeployAtTransactionTransformer.toBytes(deployAtTransactionData);
@@ -283,6 +286,9 @@ public class LitecoinACCTv1TradeBot implements AcctTradeBot {
 				tradeForeignPublicKey, tradeForeignPublicKeyHash,
 				crossChainTradeData.expectedForeignAmount, xprv58, null, lockTimeA, receivingPublicKeyHash);
 
+		// Attempt to backup the trade bot data
+		TradeBot.backupTradeBotData(repository);
+
 		// Check we have enough funds via xprv58 to fund P2SH to cover expectedForeignAmount
 		long p2shFee;
 		try {
@@ -343,11 +349,15 @@ public class LitecoinACCTv1TradeBot implements AcctTradeBot {
 	}
 
 	@Override
-	public boolean canDelete(Repository repository, TradeBotData tradeBotData) {
+	public boolean canDelete(Repository repository, TradeBotData tradeBotData) throws DataException {
 		State tradeBotState = State.valueOf(tradeBotData.getStateValue());
 		if (tradeBotState == null)
 			return true;
 
+		// If the AT doesn't exist then we might as well let the user tidy up
+		if (!repository.getATRepository().exists(tradeBotData.getAtAddress()))
+			return true;
+
 		switch (tradeBotState) {
 			case BOB_WAITING_FOR_AT_CONFIRM:
 			case ALICE_DONE:
@@ -376,7 +386,16 @@ public class LitecoinACCTv1TradeBot implements AcctTradeBot {
 			// Attempt to fetch AT data
 			atData = repository.getATRepository().fromATAddress(tradeBotData.getAtAddress());
 			if (atData == null) {
-				LOGGER.warn(() -> String.format("Unable to fetch trade AT %s from repository", tradeBotData.getAtAddress()));
+				LOGGER.debug(() -> String.format("Unable to fetch trade AT %s from repository", tradeBotData.getAtAddress()));
+
+				// If it has been over 24 hours since we last updated this trade-bot entry then assume AT is never coming back
+				// and so wipe the trade-bot entry
+				if (tradeBotData.getTimestamp() + MAX_AT_CONFIRMATION_PERIOD < NTP.getTime()) {
+					LOGGER.info(() -> String.format("AT %s has been gone for too long - deleting trade-bot entry", tradeBotData.getAtAddress()));
+					repository.getCrossChainRepository().delete(tradeBotData.getTradePrivateKey());
+					repository.saveChanges();
+				}
+
 				return;
 			}
 

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

@@ -7,6 +7,7 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Random;
+import java.util.concurrent.locks.ReentrantLock;
 
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
@@ -267,6 +268,22 @@ public class TradeBot implements Listener {
 		return secret;
 	}
 
+	/*package*/ static void backupTradeBotData(Repository repository) {
+		// Attempt to backup the trade bot data. This an optional step and doesn't impact trading, so don't throw an exception on failure
+		try {
+			LOGGER.info("About to backup trade bot data...");
+			ReentrantLock blockchainLock = Controller.getInstance().getBlockchainLock();
+			blockchainLock.lockInterruptibly();
+			try {
+				repository.exportNodeLocalData(true);
+			} finally {
+				blockchainLock.unlock();
+			}
+		} catch (InterruptedException | DataException e) {
+			LOGGER.info(String.format("Failed to obtain blockchain lock when exporting trade bot data: %s", e.getMessage()));
+		}
+	}
+
 	/** Updates trade-bot entry to new state, with current timestamp, logs message and notifies state-change listeners. */
 	/*package*/ static void updateTradeBotState(Repository repository, TradeBotData tradeBotData,
 			String newState, int newStateValue, Supplier<String> logMessageSupplier) throws DataException {

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

@@ -42,35 +42,32 @@ public class Bitcoin extends Bitcoiny {
 			public Collection<ElectrumX.Server> getServers() {
 				return Arrays.asList(
 						// Servers chosen on NO BASIS WHATSOEVER from various sources!
-						new Server("enode.duckdns.org", Server.ConnectionType.SSL, 50002),
-						new Server("electrumx.ml", Server.ConnectionType.SSL, 50002),
-						new Server("electrum.bitkoins.nl", Server.ConnectionType.SSL, 50512),
-						new Server("btc.electroncash.dk", Server.ConnectionType.SSL, 60002),
-						new Server("electrumx.electricnewyear.net", Server.ConnectionType.SSL, 50002),
-						new Server("dxm.no-ip.biz", Server.ConnectionType.TCP, 50001),
-						new Server("kirsche.emzy.de", Server.ConnectionType.TCP, 50001),
-						new Server("2AZZARITA.hopto.org", Server.ConnectionType.TCP, 50001),
-						new Server("xtrum.com", Server.ConnectionType.TCP, 50001),
-						new Server("electrum.srvmin.network", Server.ConnectionType.TCP, 50001),
-						new Server("electrumx.alexridevski.net", Server.ConnectionType.TCP, 50001),
-						new Server("bitcoin.lukechilds.co", Server.ConnectionType.TCP, 50001),
-						new Server("electrum.poiuty.com", Server.ConnectionType.TCP, 50001),
-						new Server("horsey.cryptocowboys.net", Server.ConnectionType.TCP, 50001),
+						new Server("128.0.190.26", Server.ConnectionType.SSL, 50002),
+						new Server("hodlers.beer", Server.ConnectionType.SSL, 50002),
+						new Server("electrumx.erbium.eu", Server.ConnectionType.TCP, 50001),
+						new Server("electrumx.erbium.eu", Server.ConnectionType.SSL, 50002),
+						new Server("btc.lastingcoin.net", Server.ConnectionType.SSL, 50002),
+						new Server("electrum.bitaroo.net", Server.ConnectionType.SSL, 50002),
+						new Server("bitcoin.grey.pw", Server.ConnectionType.SSL, 50002),
+						new Server("2electrumx.hopto.me", Server.ConnectionType.SSL, 56022),
+						new Server("185.64.116.15", Server.ConnectionType.SSL, 50002),
+						new Server("kirsche.emzy.de", Server.ConnectionType.SSL, 50002),
+						new Server("alviss.coinjoined.com", Server.ConnectionType.SSL, 50002),
+						new Server("electrum.emzy.de", Server.ConnectionType.SSL, 50002),
 						new Server("electrum.emzy.de", Server.ConnectionType.TCP, 50001),
-						new Server("electrum-server.ninja", Server.ConnectionType.TCP, 50081),
-						new Server("bitcoin.electrumx.multicoin.co", Server.ConnectionType.TCP, 50001),
-						new Server("esx.geekhosters.com", Server.ConnectionType.TCP, 50001),
-						new Server("bitcoin.grey.pw", Server.ConnectionType.TCP, 50003),
-						new Server("exs.ignorelist.com", Server.ConnectionType.TCP, 50001),
-						new Server("electrum.coinext.com.br", Server.ConnectionType.TCP, 50001),
-						new Server("bitcoin.aranguren.org", Server.ConnectionType.TCP, 50001),
-						new Server("skbxmit.coinjoined.com", Server.ConnectionType.TCP, 50001),
-						new Server("alviss.coinjoined.com", Server.ConnectionType.TCP, 50001),
-						new Server("electrum2.privateservers.network", Server.ConnectionType.TCP, 50001),
-						new Server("electrumx.schulzemic.net", Server.ConnectionType.TCP, 50001),
-						new Server("bitcoins.sk", Server.ConnectionType.TCP, 56001),
-						new Server("node.mendonca.xyz", Server.ConnectionType.TCP, 50001),
-						new Server("bitcoin.aranguren.org", Server.ConnectionType.TCP, 50001));
+						new Server("vmd71287.contaboserver.net", Server.ConnectionType.SSL, 50002),
+						new Server("btc.litepay.ch", Server.ConnectionType.SSL, 50002),
+						new Server("electrum.stippy.com", Server.ConnectionType.SSL, 50002),
+						new Server("xtrum.com", Server.ConnectionType.SSL, 50002),
+						new Server("electrum.acinq.co", Server.ConnectionType.SSL, 50002),
+						new Server("electrum2.taborsky.cz", Server.ConnectionType.SSL, 50002),
+						new Server("vmd63185.contaboserver.net", Server.ConnectionType.SSL, 50002),
+						new Server("electrum2.privateservers.network", Server.ConnectionType.SSL, 50002),
+						new Server("electrumx.alexridevski.net", Server.ConnectionType.SSL, 50002),
+						new Server("192.166.219.200", Server.ConnectionType.SSL, 50002),
+						new Server("2ex.digitaleveryware.com", Server.ConnectionType.SSL, 50002),
+						new Server("dxm.no-ip.biz", Server.ConnectionType.SSL, 50002),
+						new Server("caleb.vegas", Server.ConnectionType.SSL, 50002));
 			}
 
 			@Override
@@ -96,10 +93,8 @@ public class Bitcoin extends Bitcoiny {
 			@Override
 			public Collection<ElectrumX.Server> getServers() {
 				return Arrays.asList(
-						new Server("electrum.blockstream.info", Server.ConnectionType.TCP, 60001),
-						new Server("electrum.blockstream.info", Server.ConnectionType.SSL, 60002),
+						new Server("tn.not.fyi", Server.ConnectionType.SSL, 55002),
 						new Server("electrumx-test.1209k.com", Server.ConnectionType.SSL, 50002),
-						new Server("testnet.qtornado.com", Server.ConnectionType.TCP, 51001),
 						new Server("testnet.qtornado.com", Server.ConnectionType.SSL, 51002),
 						new Server("testnet.aranguren.org", Server.ConnectionType.TCP, 51001),
 						new Server("testnet.aranguren.org", Server.ConnectionType.SSL, 51002),

src/main/java/org/qortal/data/block/BlockSummaryData.java

@@ -2,6 +2,7 @@ package org.qortal.data.block;
 
 import javax.xml.bind.annotation.XmlAccessType;
 import javax.xml.bind.annotation.XmlAccessorType;
+import java.util.Arrays;
 
 @XmlAccessorType(XmlAccessType.FIELD)
 public class BlockSummaryData {
@@ -84,4 +85,21 @@ public class BlockSummaryData {
 		this.minterLevel = minterLevel;
 	}
 
+
+	@Override
+	public boolean equals(Object o) {
+		if (this == o)
+			return true;
+
+		if (o == null || getClass() != o.getClass())
+			return false;
+
+		BlockSummaryData otherBlockSummary = (BlockSummaryData) o;
+		if (this.getSignature() == null || otherBlockSummary.getSignature() == null)
+			return false;
+
+		// Treat two block summaries as equal if they have matching signatures
+		return Arrays.equals(this.getSignature(), otherBlockSummary.getSignature());
+	}
+
 }

src/main/java/org/qortal/data/block/CommonBlockData.java

@@ -0,0 +1,56 @@
+package org.qortal.data.block;
+
+import org.qortal.data.network.PeerChainTipData;
+
+import javax.xml.bind.annotation.XmlAccessType;
+import javax.xml.bind.annotation.XmlAccessorType;
+import java.math.BigInteger;
+import java.util.List;
+
+@XmlAccessorType(XmlAccessType.FIELD)
+public class CommonBlockData {
+
+	// Properties
+	private BlockSummaryData commonBlockSummary = null;
+	private List<BlockSummaryData> blockSummariesAfterCommonBlock = null;
+	private BigInteger chainWeight = null;
+	private PeerChainTipData chainTipData = null;
+
+	// Constructors
+
+	protected CommonBlockData() {
+	}
+
+	public CommonBlockData(BlockSummaryData commonBlockSummary, PeerChainTipData chainTipData) {
+		this.commonBlockSummary = commonBlockSummary;
+		this.chainTipData = chainTipData;
+	}
+
+
+	// Getters / setters
+
+	public BlockSummaryData getCommonBlockSummary() {
+		return this.commonBlockSummary;
+	}
+
+	public List<BlockSummaryData> getBlockSummariesAfterCommonBlock() {
+		return this.blockSummariesAfterCommonBlock;
+	}
+
+	public void setBlockSummariesAfterCommonBlock(List<BlockSummaryData> blockSummariesAfterCommonBlock) {
+		this.blockSummariesAfterCommonBlock = blockSummariesAfterCommonBlock;
+	}
+
+	public BigInteger getChainWeight() {
+		return this.chainWeight;
+	}
+
+	public void setChainWeight(BigInteger chainWeight) {
+		this.chainWeight = chainWeight;
+	}
+
+	public PeerChainTipData getChainTipData() {
+		return this.chainTipData;
+	}
+
+}

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

@@ -4,7 +4,6 @@ import java.util.Arrays;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.regex.Matcher;
-import java.util.regex.Pattern;
 
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
@@ -51,7 +50,7 @@ public enum Handshake {
 
 			String versionString = helloMessage.getVersionString();
 
-			Matcher matcher = VERSION_PATTERN.matcher(versionString);
+			Matcher matcher = peer.VERSION_PATTERN.matcher(versionString);
 			if (!matcher.lookingAt()) {
 				LOGGER.debug(() -> String.format("Peer %s sent invalid HELLO version string '%s'", peer, versionString));
 				return null;
@@ -72,6 +71,15 @@ public enum Handshake {
 			peer.setPeersConnectionTimestamp(peersConnectionTimestamp);
 			peer.setPeersVersion(versionString, version);
 
+			if (Settings.getInstance().getAllowConnectionsWithOlderPeerVersions() == false) {
+				// Ensure the peer is running at least the minimum version allowed for connections
+				final String minPeerVersion = Settings.getInstance().getMinPeerVersion();
+				if (peer.isAtLeastVersion(minPeerVersion) == false) {
+					LOGGER.info(String.format("Ignoring peer %s because it is on an old version (%s)", peer, versionString));
+					return null;
+				}
+			}
+
 			return CHALLENGE;
 		}
 
@@ -244,8 +252,6 @@ public enum Handshake {
 	/** Maximum allowed difference between peer's reported timestamp and when they connected, in milliseconds. */
 	private static final long MAX_TIMESTAMP_DELTA = 30 * 1000L; // ms
 
-	private static final Pattern VERSION_PATTERN = Pattern.compile(Controller.VERSION_PREFIX + "(\\d{1,3})\\.(\\d{1,5})\\.(\\d{1,5})");
-
 	private static final long PEER_VERSION_131 = 0x0100030001L;
 
 	private static final int POW_BUFFER_SIZE_PRE_131 = 8 * 1024 * 1024; // bytes

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

@@ -15,13 +15,18 @@ import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Random;
+import java.util.Arrays;
 import java.util.concurrent.ArrayBlockingQueue;
 import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.TimeUnit;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
+import org.qortal.controller.Controller;
+import org.qortal.data.block.CommonBlockData;
 import org.qortal.data.network.PeerChainTipData;
 import org.qortal.data.network.PeerData;
 import org.qortal.network.message.ChallengeMessage;
@@ -46,7 +51,7 @@ public class Peer {
 	private static final int CONNECT_TIMEOUT = 2000; // ms
 
 	/** Maximum time to wait for a message reply to arrive from peer. (ms) */
-	private static final int RESPONSE_TIMEOUT = 2000; // ms
+	private static final int RESPONSE_TIMEOUT = 3000; // ms
 
 	/**
 	 * Interval between PING messages to a peer. (ms)
@@ -85,6 +90,9 @@ public class Peer {
 
 	byte[] ourChallenge;
 
+	// Versioning
+	public static final Pattern VERSION_PATTERN = Pattern.compile(Controller.VERSION_PREFIX + "(\\d{1,3})\\.(\\d{1,5})\\.(\\d{1,5})");
+
 	// Peer info
 
 	private final Object peerInfoLock = new Object();
@@ -106,6 +114,9 @@ public class Peer {
 	/** Latest block info as reported by peer. */
 	private PeerChainTipData peersChainTipData;
 
+	/** Our common block with this peer */
+	private CommonBlockData commonBlockData;
+
 	// Constructors
 
 	/** Construct unconnected, outbound Peer using socket address in peer data */
@@ -272,6 +283,18 @@ public class Peer {
 		}
 	}
 
+	public CommonBlockData getCommonBlockData() {
+		synchronized (this.peerInfoLock) {
+			return this.commonBlockData;
+		}
+	}
+
+	public void setCommonBlockData(CommonBlockData commonBlockData) {
+		synchronized (this.peerInfoLock) {
+			this.commonBlockData = commonBlockData;
+		}
+	}
+
 	/*package*/ void queueMessage(Message message) {
 		if (!this.pendingMessages.offer(message))
 			LOGGER.info(() -> String.format("No room to queue message from peer %s - discarding", this));
@@ -507,6 +530,7 @@ public class Peer {
 			}
 		} catch (MessageException e) {
 			LOGGER.warn(String.format("Failed to send %s message with ID %d to peer %s: %s", message.getType().name(), message.getId(), this, e.getMessage()));
+			return false;
 		} catch (IOException e) {
 			// Send failure
 			return false;
@@ -615,6 +639,54 @@ public class Peer {
 		}
 	}
 
+
+	// Minimum version
+
+	public boolean isAtLeastVersion(String minVersionString) {
+		if (minVersionString == null)
+			return false;
+
+		// Add the version prefix
+		minVersionString = Controller.VERSION_PREFIX + minVersionString;
+
+		Matcher matcher = VERSION_PATTERN.matcher(minVersionString);
+		if (!matcher.lookingAt())
+			return false;
+
+		// We're expecting 3 positive shorts, so we can convert 1.2.3 into 0x0100020003
+		long minVersion = 0;
+		for (int g = 1; g <= 3; ++g) {
+			long value = Long.parseLong(matcher.group(g));
+
+			if (value < 0 || value > Short.MAX_VALUE)
+				return false;
+
+			minVersion <<= 16;
+			minVersion |= value;
+		}
+
+		return this.getPeersVersion() >= minVersion;
+	}
+
+
+	// Common block data
+
+	public boolean canUseCachedCommonBlockData() {
+		PeerChainTipData peerChainTipData = this.getChainTipData();
+		CommonBlockData commonBlockData = this.getCommonBlockData();
+
+		if (peerChainTipData != null && commonBlockData != null) {
+			PeerChainTipData commonBlockChainTipData = commonBlockData.getChainTipData();
+			if (peerChainTipData.getLastBlockSignature() != null && commonBlockChainTipData != null && commonBlockChainTipData.getLastBlockSignature() != null) {
+				if (Arrays.equals(peerChainTipData.getLastBlockSignature(), commonBlockChainTipData.getLastBlockSignature())) {
+					return true;
+				}
+			}
+		}
+		return false;
+	}
+
+
 	// Utility methods
 
 	/** Returns true if ports and addresses (or hostnames) match */

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

@@ -0,0 +1,70 @@
+package org.qortal.network.message;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.UnsupportedEncodingException;
+import java.nio.ByteBuffer;
+
+import org.qortal.block.Block;
+import org.qortal.transform.TransformationException;
+import org.qortal.transform.block.BlockTransformer;
+
+import com.google.common.primitives.Ints;
+
+// This is an OUTGOING-only Message which more readily lends itself to being cached
+public class CachedBlockMessage extends Message {
+
+	private Block block = null;
+	private byte[] cachedBytes = null;
+
+	public CachedBlockMessage(Block block) {
+		super(MessageType.BLOCK);
+
+		this.block = block;
+	}
+
+	private CachedBlockMessage(byte[] cachedBytes) {
+		super(MessageType.BLOCK);
+
+		this.block = null;
+		this.cachedBytes = cachedBytes;
+	}
+	
+	public static Message fromByteBuffer(int id, ByteBuffer byteBuffer) throws UnsupportedEncodingException {
+		throw new UnsupportedOperationException("CachedBlockMessage is for outgoing messages only");
+	}
+
+	@Override
+	protected byte[] toData() {
+		// Already serialized?
+		if (this.cachedBytes != null)
+			return cachedBytes;
+
+		if (this.block == null)
+			return null;
+
+		try {
+			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+
+			bytes.write(Ints.toByteArray(this.block.getBlockData().getHeight()));
+
+			bytes.write(BlockTransformer.toBytes(this.block));
+
+			this.cachedBytes = bytes.toByteArray();
+			// We no longer need source Block
+			// and Block contains repository handle which is highly likely to be invalid after this call
+			this.block = null;
+
+			return this.cachedBytes;
+		} catch (TransformationException | IOException e) {
+			return null;
+		}
+	}
+
+	public CachedBlockMessage cloneWithNewId(int newId) {
+		CachedBlockMessage clone = new CachedBlockMessage(this.cachedBytes);
+		clone.setId(newId);
+		return clone;
+	}
+
+}

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

@@ -98,7 +98,7 @@ public interface ATRepository {
 	 */
 	public List<ATStateData> getMatchingFinalATStatesQuorum(byte[] codeHash, Boolean isFinished,
 			Integer dataByteOffset, Long expectedValue,
-			int minimumCount, long minimumPeriod) throws DataException;
+			int minimumCount, int maximumCount, long minimumPeriod) throws DataException;
 
 	/**
 	 * Returns all ATStateData for a given block height.

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

@@ -49,7 +49,7 @@ public interface Repository extends AutoCloseable {
 
 	public void performPeriodicMaintenance() throws DataException;
 
-	public void exportNodeLocalData() throws DataException;
+	public void exportNodeLocalData(boolean keepArchivedCopy) throws DataException;
 
 	public void importDataFromFile(String filename) throws DataException;
 

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

@@ -1,5 +1,6 @@
 package org.qortal.repository;
 
+import java.util.EnumSet;
 import java.util.List;
 import java.util.Map;
 
@@ -251,6 +252,14 @@ public interface TransactionRepository {
 	 */
 	public List<TransactionData> getUnconfirmedTransactions(TransactionType txType, byte[] creatorPublicKey) throws DataException;
 
+	/**
+	 * Returns list of unconfirmed transactions excluding specified type(s).
+	 * 
+	 * @return list of transactions, or empty if none.
+	 * @throws DataException
+	 */
+	public List<TransactionData> getUnconfirmedTransactions(EnumSet<TransactionType> excludedTxTypes) throws DataException;
+
 	/**
 	 * Remove transaction from unconfirmed transactions pile.
 	 * 

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

@@ -454,7 +454,7 @@ public class HSQLDBATRepository implements ATRepository {
 	@Override
 	public List<ATStateData> getMatchingFinalATStatesQuorum(byte[] codeHash, Boolean isFinished,
 			Integer dataByteOffset, Long expectedValue,
-			int minimumCount, long minimumPeriod) throws DataException {
+			int minimumCount, int maximumCount, long minimumPeriod) throws DataException {
 		// We need most recent entry first so we can use its timestamp to slice further results
 		List<ATStateData> mostRecentStates = this.getMatchingFinalATStates(codeHash, isFinished,
 				dataByteOffset, expectedValue, null,
@@ -510,7 +510,8 @@ public class HSQLDBATRepository implements ATRepository {
 		bindParams.add(minimumHeight);
 		bindParams.add(minimumCount);
 
-		sql.append("ORDER BY FinalATStates.height DESC");
+		sql.append("ORDER BY FinalATStates.height DESC LIMIT ?");
+		bindParams.add(maximumCount);
 
 		List<ATStateData> atStates = new ArrayList<>();
 

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

@@ -52,6 +52,7 @@ import org.qortal.repository.TransactionRepository;
 import org.qortal.repository.VotingRepository;
 import org.qortal.repository.hsqldb.transaction.HSQLDBTransactionRepository;
 import org.qortal.settings.Settings;
+import org.qortal.utils.NTP;
 
 public class HSQLDBRepository implements Repository {
 
@@ -459,10 +460,44 @@ public class HSQLDBRepository implements Repository {
 	}
 
 	@Override
-	public void exportNodeLocalData() throws DataException {
+	public void exportNodeLocalData(boolean keepArchivedCopy) throws DataException {
+
+		// Create the qortal-backup folder if it doesn't exist
+		Path backupPath = Paths.get("qortal-backup");
+		try {
+			Files.createDirectories(backupPath);
+		} catch (IOException e) {
+			LOGGER.info("Unable to create backup folder");
+			throw new DataException("Unable to create backup folder");
+		}
+
+		// We need to rename or delete an existing TradeBotStates backup before creating a new one
+		File tradeBotStatesBackupFile = new File("qortal-backup/TradeBotStates.script");
+		if (tradeBotStatesBackupFile.exists()) {
+			if (keepArchivedCopy) {
+				// Rename existing TradeBotStates backup, to make sure that we're not overwriting any keys
+				File archivedBackupFile = new File(String.format("qortal-backup/TradeBotStates-archive-%d.script", NTP.getTime()));
+				if (tradeBotStatesBackupFile.renameTo(archivedBackupFile))
+					LOGGER.info(String.format("Moved existing TradeBotStates backup file to %s", archivedBackupFile.getPath()));
+				else
+					throw new DataException("Unable to rename existing TradeBotStates backup");
+			} else {
+				// Delete existing copy
+				LOGGER.info("Deleting existing TradeBotStates backup because it is being replaced with a new one");
+				tradeBotStatesBackupFile.delete();
+			}
+		}
+
+		// There's currently no need to take an archived copy of the MintingAccounts data - just delete the old one if it exists
+		File mintingAccountsBackupFile = new File("qortal-backup/MintingAccounts.script");
+		if (mintingAccountsBackupFile.exists()) {
+			LOGGER.info("Deleting existing MintingAccounts backup because it is being replaced with a new one");
+			mintingAccountsBackupFile.delete();
+		}
+
 		try (Statement stmt = this.connection.createStatement()) {
-			stmt.execute("PERFORM EXPORT SCRIPT FOR TABLE MintingAccounts DATA TO 'MintingAccounts.script'");
-			stmt.execute("PERFORM EXPORT SCRIPT FOR TABLE TradeBotStates DATA TO 'TradeBotStates.script'");
+			stmt.execute("PERFORM EXPORT SCRIPT FOR TABLE MintingAccounts DATA TO 'qortal-backup/MintingAccounts.script'");
+			stmt.execute("PERFORM EXPORT SCRIPT FOR TABLE TradeBotStates DATA TO 'qortal-backup/TradeBotStates.script'");
 			LOGGER.info("Exported sensitive/node-local data: minting keys and trade bot states");
 		} catch (SQLException e) {
 			throw new DataException("Unable to export sensitive/node-local data from repository");
@@ -475,12 +510,12 @@ public class HSQLDBRepository implements Repository {
 			LOGGER.info(() -> String.format("Importing data into repository from %s", filename));
 
 			String escapedFilename = stmt.enquoteLiteral(filename);
-			stmt.execute("PERFORM IMPORT SCRIPT DATA FROM " + escapedFilename + " STOP ON ERROR");
+			stmt.execute("PERFORM IMPORT SCRIPT DATA FROM " + escapedFilename + " CONTINUE ON ERROR");
 
 			LOGGER.info(() -> String.format("Imported data into repository from %s", filename));
 		} catch (SQLException e) {
 			LOGGER.info(() -> String.format("Failed to import data into repository from %s: %s", filename, e.getMessage()));
-			throw new DataException("Unable to export sensitive/node-local data from repository: " + e.getMessage());
+			throw new DataException("Unable to import sensitive/node-local data to repository: " + e.getMessage());
 		}
 	}
 
@@ -681,7 +716,7 @@ public class HSQLDBRepository implements Repository {
 	/**
 	 * Execute PreparedStatement and return changed row count.
 	 * 
-	 * @param preparedStatement
+	 * @param sql
 	 * @param objects
 	 * @return number of changed rows
 	 * @throws SQLException
@@ -693,8 +728,8 @@ public class HSQLDBRepository implements Repository {
 	/**
 	 * Execute batched PreparedStatement
 	 * 
-	 * @param preparedStatement
-	 * @param objects
+	 * @param sql
+	 * @param batchedObjects
 	 * @return number of changed rows
 	 * @throws SQLException
 	 */
@@ -818,7 +853,7 @@ public class HSQLDBRepository implements Repository {
 	 * 
 	 * @param tableName
 	 * @param whereClause
-	 * @param objects
+	 * @param batchedObjects
 	 * @throws SQLException
 	 */
 	public int deleteBatch(String tableName, String whereClause, List<Object[]> batchedObjects) throws SQLException {
@@ -931,6 +966,8 @@ public class HSQLDBRepository implements Repository {
 
 	/** Logs other HSQLDB sessions then returns passed exception */
 	public SQLException examineException(SQLException e) {
+		// TODO: could log at DEBUG for deadlocks by checking RepositoryManager.isDeadlockRelated(e)?
+
 		LOGGER.error(() -> String.format("[Session %d] HSQLDB error: %s", this.sessionId, e.getMessage()), e);
 
 		logStatements();

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

@@ -14,11 +14,11 @@ import org.hsqldb.jdbc.HSQLDBPool;
 import org.qortal.repository.DataException;
 import org.qortal.repository.Repository;
 import org.qortal.repository.RepositoryFactory;
+import org.qortal.settings.Settings;
 
 public class HSQLDBRepositoryFactory implements RepositoryFactory {
 
 	private static final Logger LOGGER = LogManager.getLogger(HSQLDBRepositoryFactory.class);
-	private static final int POOL_SIZE = 100;
 
 	/** Log getConnection() calls that take longer than this. (ms) */
 	private static final long SLOW_CONNECTION_THRESHOLD = 1000L;
@@ -57,7 +57,7 @@ public class HSQLDBRepositoryFactory implements RepositoryFactory {
 			HSQLDBRepository.attemptRecovery(connectionUrl);
 		}
 
-		this.connectionPool = new HSQLDBPool(POOL_SIZE);
+		this.connectionPool = new HSQLDBPool(Settings.getInstance().getRepositoryConnectionPoolSize());
 		this.connectionPool.setUrl(this.connectionUrl);
 
 		Properties properties = new Properties();

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

@@ -9,6 +9,7 @@ import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.util.ArrayList;
 import java.util.EnumMap;
+import java.util.EnumSet;
 import java.util.List;
 import java.util.Map;
 
@@ -1181,6 +1182,51 @@ public class HSQLDBTransactionRepository implements TransactionRepository {
 		}
 	}
 
+	@Override
+	public List<TransactionData> getUnconfirmedTransactions(EnumSet<TransactionType> excludedTxTypes) throws DataException {
+		StringBuilder sql = new StringBuilder(1024);
+		sql.append("SELECT signature FROM UnconfirmedTransactions ");
+		sql.append("JOIN Transactions USING (signature) ");
+		sql.append("WHERE type NOT IN (");
+
+		boolean firstTxType = true;
+		for (TransactionType txType : excludedTxTypes) {
+			if (firstTxType)
+				firstTxType = false;
+			else
+				sql.append(", ");
+
+			sql.append(txType.value);
+		}
+
+		sql.append(")");
+		sql.append("ORDER BY created_when, signature");
+
+		List<TransactionData> transactions = new ArrayList<>();
+
+		// Find transactions with no corresponding row in BlockTransactions
+		try (ResultSet resultSet = this.repository.checkedExecute(sql.toString())) {
+			if (resultSet == null)
+				return transactions;
+
+			do {
+				byte[] signature = resultSet.getBytes(1);
+
+				TransactionData transactionData = this.fromSignature(signature);
+
+				if (transactionData == null)
+					// Something inconsistent with the repository
+					throw new DataException(String.format("Unable to fetch unconfirmed transaction %s from repository?", Base58.encode(signature)));
+
+				transactions.add(transactionData);
+			} while (resultSet.next());
+
+			return transactions;
+		} catch (SQLException | DataException e) {
+			throw new DataException("Unable to fetch unconfirmed transactions from repository", e);
+		}
+	}
+
 	@Override
 	public void confirmTransaction(byte[] signature) throws DataException {
 		try {

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

@@ -52,7 +52,7 @@ public class Settings {
 	// UI servers
 	private int uiPort = 12388;
 	private String[] uiLocalServers = new String[] {
-		"localhost", "127.0.0.1", "172.24.1.1", "qor.tal"
+		"localhost", "127.0.0.1"
 	};
 	private String[] uiRemoteServers = new String[] {
 		"node1.qortal.org", "node2.qortal.org", "node3.qortal.org", "node4.qortal.org", "node5.qortal.org",
@@ -89,6 +89,8 @@ public class Settings {
 	private long repositoryCheckpointInterval = 60 * 60 * 1000L; // 1 hour (ms) default
 	/** Whether to show a notification when we perform repository 'checkpoint'. */
 	private boolean showCheckpointNotification = false;
+	/* How many blocks to cache locally. Defaulted to 10, which covers a typical Synchronizer request + a few spare */
+	private int blockCacheSize = 10;
 
 	/** How long to keep old, full, AT state data (ms). */
 	private long atStatesMaxLifetime = 2 * 7 * 24 * 60 * 60 * 1000L; // milliseconds
@@ -120,6 +122,15 @@ public class Settings {
 	private int maxNetworkThreadPoolSize = 20;
 	/** Maximum number of threads for network proof-of-work compute, used during handshaking. */
 	private int networkPoWComputePoolSize = 2;
+	/** Maximum number of retry attempts if a peer fails to respond with the requested data */
+	private int maxRetries = 2;
+
+	/** Minimum peer version number required in order to sync with them */
+	private String minPeerVersion = "1.5.0";
+	/** Whether to allow connections with peers below minPeerVersion
+	 * If true, we won't sync with them but they can still sync with us, and will show in the peers list
+	 * If false, sync will be blocked both ways, and they will not appear in the peers list */
+	private boolean allowConnectionsWithOlderPeerVersions = true;
 
 	// Which blockchains this node is running
 	private String blockchainConfig = null; // use default from resources
@@ -134,6 +145,8 @@ public class Settings {
 	private Long slowQueryThreshold = null;
 	/** Repository storage path. */
 	private String repositoryPath = "db";
+	/** Repository connection pool size. Needs to be a bit bigger than maxNetworkThreadPoolSize */
+	private int repositoryConnectionPoolSize = 100;
 
 	// Auto-update sources
 	private String[] autoUpdateRepos = new String[] {
@@ -361,6 +374,10 @@ public class Settings {
 		return this.maxTransactionTimestampFuture;
 	}
 
+	public int getBlockCacheSize() {
+		return this.blockCacheSize;
+	}
+
 	public boolean isTestNet() {
 		return this.isTestNet;
 	}
@@ -400,6 +417,12 @@ public class Settings {
 		return this.networkPoWComputePoolSize;
 	}
 
+	public int getMaxRetries() { return this.maxRetries; }
+
+	public String getMinPeerVersion() { return this.minPeerVersion; }
+
+	public boolean getAllowConnectionsWithOlderPeerVersions() { return this.allowConnectionsWithOlderPeerVersions; }
+
 	public String getBlockchainConfig() {
 		return this.blockchainConfig;
 	}
@@ -424,6 +447,10 @@ public class Settings {
 		return this.repositoryPath;
 	}
 
+	public int getRepositoryConnectionPoolSize() {
+		return this.repositoryConnectionPoolSize;
+	}
+
 	public boolean isAutoUpdateEnabled() {
 		return this.autoUpdateEnabled;
 	}

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

@@ -4,6 +4,7 @@ import java.math.BigInteger;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Comparator;
+import java.util.EnumSet;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
@@ -605,7 +606,8 @@ public abstract class Transaction {
 	public static List<TransactionData> getUnconfirmedTransactions(Repository repository) throws DataException {
 		BlockData latestBlockData = repository.getBlockRepository().getLastBlock();
 
-		List<TransactionData> unconfirmedTransactions = repository.getTransactionRepository().getUnconfirmedTransactions();
+		EnumSet<TransactionType> excludedTxTypes = EnumSet.of(TransactionType.CHAT, TransactionType.PRESENCE);
+		List<TransactionData> unconfirmedTransactions = repository.getTransactionRepository().getUnconfirmedTransactions(excludedTxTypes);
 
 		unconfirmedTransactions.sort(getDataComparator());
 

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

@@ -326,24 +326,36 @@ public class BlockTransformer extends Transformer {
 		}
 	}
 
-	public static byte[] getMinterSignatureFromReference(byte[] blockReference) {
-		return Arrays.copyOf(blockReference, MINTER_SIGNATURE_LENGTH);
+	private static byte[] getReferenceBytesForMinterSignature(int blockHeight, byte[] reference) {
+		int newBlockSigTriggerHeight = BlockChain.getInstance().getNewBlockSigHeight();
+
+		return blockHeight >= newBlockSigTriggerHeight
+				// 'new' block sig uses all of previous block's signature
+				? reference
+				// 'old' block sig only uses first 64 bytes of previous block's signature
+				: Arrays.copyOf(reference, MINTER_SIGNATURE_LENGTH);
 	}
 
-	public static byte[] getBytesForMinterSignature(BlockData blockData) throws TransformationException {
-		byte[] minterSignature = getMinterSignatureFromReference(blockData.getReference());
+	public static byte[] getBytesForMinterSignature(BlockData blockData) {
+		byte[] referenceBytes = getReferenceBytesForMinterSignature(blockData.getHeight(), blockData.getReference());
 
-		return getBytesForMinterSignature(minterSignature, blockData.getMinterPublicKey(), blockData.getEncodedOnlineAccounts());
+		return getBytesForMinterSignature(referenceBytes, blockData.getMinterPublicKey(), blockData.getEncodedOnlineAccounts());
 	}
 
-	public static byte[] getBytesForMinterSignature(byte[] minterSignature, byte[] minterPublicKey, byte[] encodedOnlineAccounts) {
-		byte[] bytes = new byte[MINTER_SIGNATURE_LENGTH + MINTER_PUBLIC_KEY_LENGTH + encodedOnlineAccounts.length];
+	public static byte[] getBytesForMinterSignature(BlockData parentBlockData, byte[] minterPublicKey, byte[] encodedOnlineAccounts) {
+		byte[] referenceBytes = getReferenceBytesForMinterSignature(parentBlockData.getHeight() + 1, parentBlockData.getSignature());
 
-		System.arraycopy(minterSignature, 0, bytes, 0, MINTER_SIGNATURE_LENGTH);
+		return getBytesForMinterSignature(referenceBytes, minterPublicKey, encodedOnlineAccounts);
+	}
 
-		System.arraycopy(minterPublicKey, 0, bytes, MINTER_SIGNATURE_LENGTH, MINTER_PUBLIC_KEY_LENGTH);
+	private static byte[] getBytesForMinterSignature(byte[] referenceBytes, byte[] minterPublicKey, byte[] encodedOnlineAccounts) {
+		byte[] bytes = new byte[referenceBytes.length + MINTER_PUBLIC_KEY_LENGTH + encodedOnlineAccounts.length];
 
-		System.arraycopy(encodedOnlineAccounts, 0, bytes, MINTER_SIGNATURE_LENGTH + MINTER_PUBLIC_KEY_LENGTH, encodedOnlineAccounts.length);
+		System.arraycopy(referenceBytes, 0, bytes, 0, referenceBytes.length);
+
+		System.arraycopy(minterPublicKey, 0, bytes, referenceBytes.length, MINTER_PUBLIC_KEY_LENGTH);
+
+		System.arraycopy(encodedOnlineAccounts, 0, bytes, referenceBytes.length + MINTER_PUBLIC_KEY_LENGTH, encodedOnlineAccounts.length);
 
 		return bytes;
 	}

src/main/resources/blockchain.json

@@ -48,7 +48,10 @@
 		"minutesPerBlock": 1
 	},
 	"featureTriggers": {
-		"atFindNextTransactionFix": 275000
+		"atFindNextTransactionFix": 275000,
+		"newBlockSigHeight": 320000,
+		"shareBinFix": 399000,
+		"calcChainWeightTimestamp": 1620579600000
 	},
 	"genesisInfo": {
 		"version": 4,

src/main/resources/i18n/ApiError_it.properties

@@ -0,0 +1,72 @@
+#Generated by ResourceBundle Editor (http://essiembre.github.io/eclipse-rbe/)
+# Keys are from api.ApiError enum
+# Italian translation by Pabs 2021
+
+# La modifica della lingua dell'UI è fatta nel file Settings.json
+#
+# "localeLang": "it",
+# Si prega ricordare la virgola alla fine, se questo comando non è sull'ultima riga
+
+ADDRESS_UNKNOWN = indirizzo account sconosciuto
+
+BLOCKCHAIN_NEEDS_SYNC = blockchain deve prima sincronizzarsi
+
+# Blocks
+BLOCK_UNKNOWN = blocco sconosciuto
+
+BTC_BALANCE_ISSUE = saldo Bitcoin insufficiente
+
+BTC_NETWORK_ISSUE = Bitcoin/ElectrumX problema di rete
+
+BTC_TOO_SOON = troppo presto per trasmettere transazione Bitcoin (tempo di blocco / tempo di blocco mediano)
+
+CANNOT_MINT = l'account non può coniare
+
+GROUP_UNKNOWN = gruppo sconosciuto
+
+INVALID_ADDRESS = indirizzo non valido
+
+# Assets
+INVALID_ASSET_ID = identificazione risorsa non valida
+
+INVALID_CRITERIA = criteri di ricerca non validi
+
+INVALID_DATA = dati non validi
+
+INVALID_HEIGHT = altezza blocco non valida
+
+INVALID_NETWORK_ADDRESS = indirizzo di rete non valido
+
+INVALID_ORDER_ID = identificazione di ordine di risorsa non valida
+
+INVALID_PRIVATE_KEY = chiave privata non valida
+
+INVALID_PUBLIC_KEY = chiave pubblica non valida
+
+INVALID_REFERENCE = riferimento non valido
+
+# Validation
+INVALID_SIGNATURE = firma non valida
+
+JSON = Impossibile analizzare il messaggio JSON
+
+NAME_UNKNOWN = nome sconosciuto
+
+NON_PRODUCTION = questa chiamata API non è consentita per i sistemi di produzione
+
+NO_TIME_SYNC = nessuna sincronizzazione dell'orologio ancora
+
+ORDER_UNKNOWN = identificazione di ordine di risorsa sconosciuta
+
+PUBLIC_KEY_NOT_FOUND = chiave pubblica non trovata
+
+REPOSITORY_ISSUE = errore del repositorio
+
+# This one is special in that caller expected to pass two additional strings, hence the two %s
+TRANSACTION_INVALID = transazione non valida: %s (%s)
+
+TRANSACTION_UNKNOWN = transazione sconosciuta
+
+TRANSFORMATION_ERROR = non è stato possibile trasformare JSON in transazione
+
+UNAUTHORIZED = Chiamata API non autorizzata

src/main/resources/i18n/SysTray_it.properties

@@ -0,0 +1,46 @@
+#Generated by ResourceBundle Editor (http://essiembre.github.io/eclipse-rbe/)
+# SysTray pop-up menu
+# Italian translation by Pabs 2021
+
+APPLYING_UPDATE_AND_RESTARTING = Applicando aggiornamento automatico e riavviando...
+
+AUTO_UPDATE = Aggiornamento automatico
+
+BLOCK_HEIGHT = altezza
+
+CHECK_TIME_ACCURACY = Controlla la precisione dell'ora
+
+CONNECTING = Collegando
+
+CONNECTION = connessione
+
+CONNECTIONS = connessioni
+
+CREATING_BACKUP_OF_DB_FILES = Creazione di backup dei file di database...
+
+DB_BACKUP = Backup del database
+
+DB_CHECKPOINT = Punto di controllo del database
+
+EXIT = Uscita
+
+MINTING_DISABLED = NON coniando
+
+MINTING_ENABLED = \u2714 Coniando
+
+# Nagging about lack of NTP time sync
+NTP_NAG_CAPTION = L'orologio del computer è impreciso!
+
+NTP_NAG_TEXT_UNIX = Installare servizio NTP per ottenere un orologio preciso.
+
+NTP_NAG_TEXT_WINDOWS = Seleziona "Sincronizza orologio" dal menu per correggere.
+
+OPEN_UI = Apri UI
+
+PERFORMING_DB_CHECKPOINT = Salvataggio delle modifiche al database non salvate...
+
+SYNCHRONIZE_CLOCK = Sincronizza orologio
+
+SYNCHRONIZING_BLOCKCHAIN = Sincronizzando
+
+SYNCHRONIZING_CLOCK = Sincronizzando orologio

src/main/resources/i18n/TransactionValidity_it.properties

@@ -0,0 +1,185 @@
+# Italian translation by Pabs 2021
+
+ACCOUNT_ALREADY_EXISTS = l'account gia esiste
+
+ACCOUNT_CANNOT_REWARD_SHARE = l'account non può fare la condivisione di ricompensa
+
+ALREADY_GROUP_ADMIN = è già amministratore del gruppo
+
+ALREADY_GROUP_MEMBER = è già membro del gruppo
+
+ALREADY_VOTED_FOR_THAT_OPTION = già votato per questa opzione
+
+ASSET_ALREADY_EXISTS = risorsa già esistente
+
+ASSET_DOES_NOT_EXIST = risorsa non esistente
+
+ASSET_DOES_NOT_MATCH_AT = l'asset non corrisponde all'asset di AT
+
+ASSET_NOT_SPENDABLE = la risorsa non è spendibile
+
+AT_ALREADY_EXISTS = AT gia esiste
+
+AT_IS_FINISHED = AT ha finito
+
+AT_UNKNOWN = AT sconosciuto
+
+BANNED_FROM_GROUP = divietato dal gruppo
+
+BAN_EXISTS = il divieto esiste già
+
+BAN_UNKNOWN = divieto sconosciuto
+
+BUYER_ALREADY_OWNER = l'acquirente è già proprietario
+
+CHAT = Le transazioni CHAT non sono mai valide per l'inclusione nei blocchi
+
+CLOCK_NOT_SYNCED = orologio non sincronizzato
+
+DUPLICATE_OPTION = opzione duplicata
+
+GROUP_ALREADY_EXISTS = gruppo già esistente
+
+GROUP_APPROVAL_DECIDED = approvazione di gruppo già decisa
+
+GROUP_APPROVAL_NOT_REQUIRED = approvazione di gruppo non richiesto
+
+GROUP_DOES_NOT_EXIST = gruppo non esiste
+
+GROUP_ID_MISMATCH = identificazione di gruppo non corrispondente
+
+GROUP_OWNER_CANNOT_LEAVE = il proprietario del gruppo non può lasciare il gruppo
+
+HAVE_EQUALS_WANT = la risorsa avere è uguale a la risorsa volere
+
+INCORRECT_NONCE = PoW nonce sbagliato
+
+INSUFFICIENT_FEE = tariffa insufficiente
+
+INVALID_ADDRESS = indirizzo non valido
+
+INVALID_AMOUNT = importo non valido
+
+INVALID_ASSET_OWNER = proprietario della risorsa non valido
+
+INVALID_AT_TRANSACTION = transazione AT non valida
+
+INVALID_AT_TYPE_LENGTH = lunghezza di "tipo" AT non valida
+
+INVALID_CREATION_BYTES = byte di creazione non validi
+
+INVALID_DATA_LENGTH = lunghezza di dati non valida
+
+INVALID_DESCRIPTION_LENGTH = lunghezza della descrizione non valida
+
+INVALID_GROUP_APPROVAL_THRESHOLD = soglia di approvazione del gruppo non valida
+
+INVALID_GROUP_BLOCK_DELAY = ritardo del blocco di approvazione del gruppo non valido
+
+INVALID_GROUP_ID = identificazione di gruppo non valida
+
+INVALID_GROUP_OWNER = proprietario di gruppo non valido
+
+INVALID_LIFETIME = durata della vita non valida
+
+INVALID_NAME_LENGTH = lunghezza del nome non valida
+
+INVALID_NAME_OWNER = proprietario del nome non valido
+
+INVALID_OPTIONS_COUNT = conteggio di opzioni non validi
+
+INVALID_OPTION_LENGTH = lunghezza di opzioni non valida
+
+INVALID_ORDER_CREATOR = creatore dell'ordine non valido
+
+INVALID_PAYMENTS_COUNT = conteggio pagamenti non validi
+
+INVALID_PUBLIC_KEY = chiave pubblica non valida
+
+INVALID_QUANTITY = quantità non valida
+
+INVALID_REFERENCE = riferimento non valido
+
+INVALID_RETURN = ritorno non valido
+
+INVALID_REWARD_SHARE_PERCENT = percentuale condivisione di ricompensa non valida
+
+INVALID_SELLER = venditore non valido
+
+INVALID_TAGS_LENGTH = lunghezza dei "tag" non valida
+
+INVALID_TX_GROUP_ID = identificazione di gruppo di transazioni non valida
+
+INVALID_VALUE_LENGTH = lunghezza "valore" non valida
+
+INVITE_UNKNOWN = invito di gruppo sconosciuto
+
+JOIN_REQUEST_EXISTS = la richiesta di iscrizione al gruppo già esiste
+
+MAXIMUM_REWARD_SHARES =  numero massimo di condivisione di ricompensa raggiunto per l'account
+
+MISSING_CREATOR = creatore mancante
+
+MULTIPLE_NAMES_FORBIDDEN = è vietata la registrazione di multipli nomi per account
+
+NAME_ALREADY_FOR_SALE = nome già in vendita
+
+NAME_ALREADY_REGISTERED = nome già registrato
+
+NAME_DOES_NOT_EXIST = il nome non esiste
+
+NAME_NOT_FOR_SALE = il nome non è in vendita
+
+NAME_NOT_NORMALIZED = il nome non è in forma "normalizzata" Unicode
+
+NEGATIVE_AMOUNT = importo non valido / negativo
+
+NEGATIVE_FEE = tariffa non valida / negativa
+
+NEGATIVE_PRICE = prezzo non valido / negativo
+
+NOT_GROUP_ADMIN = l'account non è un amministratore di gruppo
+
+NOT_GROUP_MEMBER = l'account non è un membro del gruppo
+
+NOT_MINTING_ACCOUNT = l'account non può coniare
+
+NOT_YET_RELEASED = funzione non ancora rilasciata
+
+NO_BALANCE = equilibrio insufficiente
+
+NO_BLOCKCHAIN_LOCK = nodo di blockchain attualmente occupato
+
+NO_FLAG_PERMISSION = l'account non dispone di questa autorizzazione
+
+OK = OK
+
+ORDER_ALREADY_CLOSED = l'ordine di scambio di risorsa è già chiuso
+
+ORDER_DOES_NOT_EXIST =  l'ordine di scambio di risorsa non esiste
+
+POLL_ALREADY_EXISTS = il sondaggio già esiste
+
+POLL_DOES_NOT_EXIST = il sondaggio non esiste
+
+POLL_OPTION_DOES_NOT_EXIST = le opzioni di sondaggio non esistono
+
+PUBLIC_KEY_UNKNOWN = chiave pubblica sconosciuta
+
+REWARD_SHARE_UNKNOWN = condivisione di ricompensa sconosciuta
+
+SELF_SHARE_EXISTS = condivisione di sé (condivisione di ricompensa) già esiste
+
+TIMESTAMP_TOO_NEW = timestamp troppo nuovo
+
+TIMESTAMP_TOO_OLD = timestamp troppo vecchio
+
+TOO_MANY_UNCONFIRMED = l'account ha troppe transazioni non confermate in sospeso
+
+TRANSACTION_ALREADY_CONFIRMED = la transazione è già confermata
+
+TRANSACTION_ALREADY_EXISTS = la transazione già esiste
+
+TRANSACTION_UNKNOWN = transazione sconosciuta
+
+TX_GROUP_ID_MISMATCH = identificazione di gruppo della transazione non corrisponde

src/test/java/org/qortal/test/ChainWeightTests.java

@@ -3,12 +3,15 @@ package org.qortal.test;
 import static org.junit.Assert.*;
 
 import java.math.BigInteger;
+import java.text.DecimalFormat;
+import java.text.NumberFormat;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Random;
 
 import org.qortal.account.Account;
 import org.qortal.block.Block;
+import org.qortal.block.BlockChain;
 import org.qortal.data.block.BlockSummaryData;
 import org.qortal.repository.DataException;
 import org.qortal.repository.Repository;
@@ -17,12 +20,21 @@ import org.qortal.test.common.Common;
 import org.qortal.test.common.TestAccount;
 import org.qortal.transform.Transformer;
 import org.qortal.transform.block.BlockTransformer;
+import org.qortal.utils.NTP;
 import org.junit.Before;
+import org.junit.BeforeClass;
 import org.junit.Test;
 
 public class ChainWeightTests extends Common {
 
 	private static final Random RANDOM = new Random();
+	private static final NumberFormat FORMATTER = new DecimalFormat("0.###E0");
+
+	@BeforeClass
+	public static void beforeClass() {
+		// We need this so that NTP.getTime() in Block.calcChainWeight() doesn't return null, causing NPE
+		NTP.setFixedOffset(0L);
+	}
 
 	@Before
 	public void beforeTest() throws DataException {
@@ -89,7 +101,97 @@ public class ChainWeightTests extends Common {
 		}
 	}
 
-	// Check that a longer chain beats a shorter chain
+	// Demonstrates that typical key distance ranges from roughly 1E75 to 1E77
+	@Test
+	public void testKeyDistances() {
+		byte[] parentMinterKey = new byte[Transformer.PUBLIC_KEY_LENGTH];
+		byte[] testKey = new byte[Transformer.PUBLIC_KEY_LENGTH];
+
+		for (int i = 0; i < 50; ++i) {
+			int parentHeight = RANDOM.nextInt(50000);
+			RANDOM.nextBytes(parentMinterKey);
+			RANDOM.nextBytes(testKey);
+			int minterLevel = RANDOM.nextInt(10) + 1;
+
+			BigInteger keyDistance = Block.calcKeyDistance(parentHeight, parentMinterKey, testKey, minterLevel);
+
+			System.out.println(String.format("Parent height: %d, minter level: %d, distance: %s",
+					parentHeight,
+					minterLevel,
+					FORMATTER.format(keyDistance)));
+		}
+	}
+
+	// If typical key distance ranges from 1E75 to 1E77
+	// then we want lots of online accounts to push a 1E75 distance
+	// towards 1E77 so that it competes with a 1E77 key that has hardly any online accounts
+	// 1E75 is approx. 2**249 so maybe that's a good value for Block.ACCOUNTS_COUNT_SHIFT
+	@Test
+	public void testMoreAccountsVersusKeyDistance() throws DataException {
+		BigInteger minimumBetterKeyDistance = BigInteger.TEN.pow(77);
+		BigInteger maximumWorseKeyDistance = BigInteger.TEN.pow(75);
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			final byte[] parentMinterKey = new byte[Transformer.PUBLIC_KEY_LENGTH];
+
+			TestAccount betterAccount = Common.getTestAccount(repository, "bob-reward-share");
+			byte[] betterKey = betterAccount.getPublicKey();
+			int betterMinterLevel = Account.getRewardShareEffectiveMintingLevel(repository, betterKey);
+
+			TestAccount worseAccount = Common.getTestAccount(repository, "dilbert-reward-share");
+			byte[] worseKey = worseAccount.getPublicKey();
+			int worseMinterLevel = Account.getRewardShareEffectiveMintingLevel(repository, worseKey);
+
+			// This is to check that the hard-coded keys ARE actually better/worse as expected, before moving on testing more online accounts
+			BigInteger betterKeyDistance;
+			BigInteger worseKeyDistance;
+
+			int parentHeight = 0;
+			do {
+				++parentHeight;
+				betterKeyDistance = Block.calcKeyDistance(parentHeight, parentMinterKey, betterKey, betterMinterLevel);
+				worseKeyDistance = Block.calcKeyDistance(parentHeight, parentMinterKey, worseKey, worseMinterLevel);
+			} while (betterKeyDistance.compareTo(minimumBetterKeyDistance) < 0 || worseKeyDistance.compareTo(maximumWorseKeyDistance) > 0);
+
+			System.out.println(String.format("Parent height: %d, better key distance: %s, worse key distance: %s",
+					parentHeight,
+					FORMATTER.format(betterKeyDistance),
+					FORMATTER.format(worseKeyDistance)));
+
+			for (int accountsCountShift = 244; accountsCountShift <= 256; accountsCountShift += 2) {
+				for (int worseAccountsCount = 1; worseAccountsCount <= 101; worseAccountsCount += 25) {
+					for (int betterAccountsCount = 1; betterAccountsCount <= 1001; betterAccountsCount += 250) {
+						BlockSummaryData worseKeyBlockSummary = new BlockSummaryData(parentHeight + 1, null, worseKey, betterAccountsCount);
+						BlockSummaryData betterKeyBlockSummary = new BlockSummaryData(parentHeight + 1, null, betterKey, worseAccountsCount);
+
+						populateBlockSummaryMinterLevel(repository, worseKeyBlockSummary);
+						populateBlockSummaryMinterLevel(repository, betterKeyBlockSummary);
+
+						BigInteger worseKeyBlockWeight = calcBlockWeight(parentHeight, parentMinterKey, worseKeyBlockSummary, accountsCountShift);
+						BigInteger betterKeyBlockWeight = calcBlockWeight(parentHeight, parentMinterKey, betterKeyBlockSummary, accountsCountShift);
+
+						System.out.println(String.format("Shift: %d, worse key: %d accounts, %s diff; better key: %d accounts: %s diff; winner: %s",
+								accountsCountShift,
+								betterAccountsCount, // used with worseKey
+								FORMATTER.format(worseKeyBlockWeight),
+								worseAccountsCount, // used with betterKey
+								FORMATTER.format(betterKeyBlockWeight),
+								worseKeyBlockWeight.compareTo(betterKeyBlockWeight) > 0 ? "worse key/better accounts" : "better key/worse accounts"
+								));
+					}
+				}
+
+				System.out.println();
+			}
+		}
+	}
+
+	private static BigInteger calcBlockWeight(int parentHeight, byte[] parentBlockSignature, BlockSummaryData blockSummaryData, int accountsCountShift) {
+		BigInteger keyDistance = Block.calcKeyDistance(parentHeight, parentBlockSignature, blockSummaryData.getMinterPublicKey(), blockSummaryData.getMinterLevel());
+		return BigInteger.valueOf(blockSummaryData.getOnlineAccountsCount()).shiftLeft(accountsCountShift).add(keyDistance);
+	}
+
+	// Check that a longer chain has same weight as shorter/truncated chain
 	@Test
 	public void testLongerChain() throws DataException {
 		try (final Repository repository = RepositoryManager.getRepository()) {
@@ -97,18 +199,20 @@ public class ChainWeightTests extends Common {
 			BlockSummaryData commonBlockSummary = genBlockSummary(repository, commonBlockHeight);
 			byte[] commonBlockGeneratorKey = commonBlockSummary.getMinterPublicKey();
 
-			List<BlockSummaryData> shorterChain = genBlockSummaries(repository, 3, commonBlockSummary);
-			List<BlockSummaryData> longerChain = genBlockSummaries(repository, shorterChain.size() + 1, commonBlockSummary);
-
-			populateBlockSummariesMinterLevels(repository, shorterChain);
+			List<BlockSummaryData> longerChain = genBlockSummaries(repository, 6, commonBlockSummary);
 			populateBlockSummariesMinterLevels(repository, longerChain);
 
+			List<BlockSummaryData> shorterChain = longerChain.subList(0, longerChain.size() / 2);
+
 			final int mutualHeight = commonBlockHeight - 1 + Math.min(shorterChain.size(), longerChain.size());
 
 			BigInteger shorterChainWeight = Block.calcChainWeight(commonBlockHeight, commonBlockGeneratorKey, shorterChain, mutualHeight);
 			BigInteger longerChainWeight = Block.calcChainWeight(commonBlockHeight, commonBlockGeneratorKey, longerChain, mutualHeight);
 
-			assertEquals("longer chain should have greater weight", 1, longerChainWeight.compareTo(shorterChainWeight));
+			if (NTP.getTime() >= BlockChain.getInstance().getCalcChainWeightTimestamp())
+				assertEquals("longer chain should have same weight", 0, longerChainWeight.compareTo(shorterChainWeight));
+			else
+				assertEquals("longer chain should have greater weight", 1, longerChainWeight.compareTo(shorterChainWeight));
 		}
 	}
 

src/test/java/org/qortal/test/minting/RewardTests.java

@@ -336,4 +336,457 @@ public class RewardTests extends Common {
 		}
 	}
 
+	/** Test rewards for level 1 and 2 accounts both pre and post the shareBinFix, including orphaning back through the feature trigger block */
+	@Test
+	public void testLevel1And2Rewards() throws DataException {
+		Common.useSettings("test-settings-v2-reward-levels.json");
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+
+			List<PrivateKeyAccount> mintingAndOnlineAccounts = new ArrayList<>();
+
+			// Alice self share online
+			PrivateKeyAccount aliceSelfShare = Common.getTestAccount(repository, "alice-reward-share");
+			mintingAndOnlineAccounts.add(aliceSelfShare);
+
+			// Bob self-share NOT online
+
+			// Chloe self share online
+			byte[] chloeRewardSharePrivateKey = AccountUtils.rewardShare(repository, "chloe", "chloe", 0);
+			PrivateKeyAccount chloeRewardShareAccount = new PrivateKeyAccount(repository, chloeRewardSharePrivateKey);
+			mintingAndOnlineAccounts.add(chloeRewardShareAccount);
+
+			// Dilbert self share online
+			byte[] dilbertRewardSharePrivateKey = AccountUtils.rewardShare(repository, "dilbert", "dilbert", 0);
+			PrivateKeyAccount dilbertRewardShareAccount = new PrivateKeyAccount(repository, dilbertRewardSharePrivateKey);
+			mintingAndOnlineAccounts.add(dilbertRewardShareAccount);
+
+			// Mint a couple of blocks so that we are able to orphan them later
+			for (int i=0; i<2; i++)
+				BlockMinter.mintTestingBlock(repository, mintingAndOnlineAccounts.toArray(new PrivateKeyAccount[0]));
+
+			// Ensure that the levels are as we expect
+			assertEquals(1, (int) Common.getTestAccount(repository, "alice").getLevel());
+			assertEquals(1, (int) Common.getTestAccount(repository, "bob").getLevel());
+			assertEquals(1, (int) Common.getTestAccount(repository, "chloe").getLevel());
+			assertEquals(2, (int) Common.getTestAccount(repository, "dilbert").getLevel());
+
+			// Ensure that only Alice is a founder
+			assertEquals(1, getFlags(repository, "alice"));
+			assertEquals(0, getFlags(repository, "bob"));
+			assertEquals(0, getFlags(repository, "chloe"));
+			assertEquals(0, getFlags(repository, "dilbert"));
+
+			// Now that everyone is at level 1 or 2, we can capture initial balances
+			Map<String, Map<Long, Long>> initialBalances = AccountUtils.getBalances(repository, Asset.QORT, Asset.LEGACY_QORA, Asset.QORT_FROM_QORA);
+			final long aliceInitialBalance = initialBalances.get("alice").get(Asset.QORT);
+			final long bobInitialBalance = initialBalances.get("bob").get(Asset.QORT);
+			final long chloeInitialBalance = initialBalances.get("chloe").get(Asset.QORT);
+			final long dilbertInitialBalance = initialBalances.get("dilbert").get(Asset.QORT);
+
+			// Mint a block
+			final long blockReward = BlockUtils.getNextBlockReward(repository);
+			BlockMinter.mintTestingBlock(repository, mintingAndOnlineAccounts.toArray(new PrivateKeyAccount[0]));
+
+			// Ensure we are at the correct height and block reward value
+			assertEquals(6, (int) repository.getBlockRepository().getLastBlock().getHeight());
+			assertEquals(10000000000L, blockReward);
+
+			/*
+			 * Alice, Chloe, and Dilbert are 'online'. Bob is offline.
+			 * Chloe is level 1, Dilbert is level 2.
+			 * One founder online (Alice, who is also level 1).
+			 * No legacy QORA holders.
+			 *
+			 * Chloe and Dilbert should receive equal shares of the 5% block reward for Level 1 and 2
+			 * Alice should receive the remainder (95%)
+			 */
+
+			// We are after the shareBinFix feature trigger, so we expect level 1 and 2 to share the same reward (5%)
+			final int level1And2SharePercent = 5_00; // 5%
+			final long level1And2ShareAmount = (blockReward * level1And2SharePercent) / 100L / 100L;
+			final long expectedReward = level1And2ShareAmount / 2; // The reward is split between Chloe and Dilbert
+			final long expectedFounderReward = blockReward - level1And2ShareAmount; // Alice should receive the remainder
+
+			// Validate the balances to ensure that the correct post-shareBinFix distribution is being applied
+			assertEquals(500000000, level1And2ShareAmount);
+			AccountUtils.assertBalance(repository, "alice", Asset.QORT, aliceInitialBalance+expectedFounderReward);
+			AccountUtils.assertBalance(repository, "bob", Asset.QORT, bobInitialBalance); // Bob not online so his balance remains the same
+			AccountUtils.assertBalance(repository, "chloe", Asset.QORT, chloeInitialBalance+expectedReward);
+			AccountUtils.assertBalance(repository, "dilbert", Asset.QORT, dilbertInitialBalance+expectedReward);
+
+			// Now orphan the latest block. This brings us to the threshold of the shareBinFix feature trigger.
+			BlockUtils.orphanBlocks(repository, 1);
+			assertEquals(5, (int) repository.getBlockRepository().getLastBlock().getHeight());
+
+			// Ensure the latest post-fix block rewards have been subtracted and they have returned to their initial values
+			AccountUtils.assertBalance(repository, "alice", Asset.QORT, aliceInitialBalance);
+			AccountUtils.assertBalance(repository, "bob", Asset.QORT, bobInitialBalance); // Bob not online so his balance remains the same
+			AccountUtils.assertBalance(repository, "chloe", Asset.QORT, chloeInitialBalance);
+			AccountUtils.assertBalance(repository, "dilbert", Asset.QORT, dilbertInitialBalance);
+
+			// Orphan another block. This time, the block that was orphaned was prior to the shareBinFix feature trigger.
+			BlockUtils.orphanBlocks(repository, 1);
+			assertEquals(4, (int) repository.getBlockRepository().getLastBlock().getHeight());
+
+			// Prior to the fix, the levels were incorrectly grouped
+			// Chloe should receive 100% of the level 1 reward, and Dilbert should receive 100% of the level 2+3 reward
+			final int level1SharePercent = 5_00; // 5%
+			final int level2And3SharePercent = 10_00; // 10%
+			final long level1ShareAmountBeforeFix = (blockReward * level1SharePercent) / 100L / 100L;
+			final long level2And3ShareAmountBeforeFix = (blockReward * level2And3SharePercent) / 100L / 100L;
+			final long expectedFounderRewardBeforeFix = blockReward - level1ShareAmountBeforeFix - level2And3ShareAmountBeforeFix; // Alice should receive the remainder
+
+			// Validate the share amounts and balances
+			assertEquals(500000000, level1ShareAmountBeforeFix);
+			assertEquals(1000000000, level2And3ShareAmountBeforeFix);
+			AccountUtils.assertBalance(repository, "alice", Asset.QORT, aliceInitialBalance-expectedFounderRewardBeforeFix);
+			AccountUtils.assertBalance(repository, "bob", Asset.QORT, bobInitialBalance); // Bob not online so his balance remains the same
+			AccountUtils.assertBalance(repository, "chloe", Asset.QORT, chloeInitialBalance-level1ShareAmountBeforeFix);
+			AccountUtils.assertBalance(repository, "dilbert", Asset.QORT, dilbertInitialBalance-level2And3ShareAmountBeforeFix);
+
+			// Orphan the latest block one last time
+			BlockUtils.orphanBlocks(repository, 1);
+			assertEquals(3, (int) repository.getBlockRepository().getLastBlock().getHeight());
+
+			// Validate balances
+			AccountUtils.assertBalance(repository, "alice", Asset.QORT, aliceInitialBalance-(expectedFounderRewardBeforeFix*2));
+			AccountUtils.assertBalance(repository, "bob", Asset.QORT, bobInitialBalance); // Bob not online so his balance remains the same
+			AccountUtils.assertBalance(repository, "chloe", Asset.QORT, chloeInitialBalance-(level1ShareAmountBeforeFix*2));
+			AccountUtils.assertBalance(repository, "dilbert", Asset.QORT, dilbertInitialBalance-(level2And3ShareAmountBeforeFix*2));
+
+		}
+	}
+
+	/** Test rewards for level 3 and 4 accounts */
+	@Test
+	public void testLevel3And4Rewards() throws DataException {
+		Common.useSettings("test-settings-v2-reward-levels.json");
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+
+			List<Integer> cumulativeBlocksByLevel = BlockChain.getInstance().getCumulativeBlocksByLevel();
+			List<PrivateKeyAccount> mintingAndOnlineAccounts = new ArrayList<>();
+
+			// Alice self share online
+			PrivateKeyAccount aliceSelfShare = Common.getTestAccount(repository, "alice-reward-share");
+			mintingAndOnlineAccounts.add(aliceSelfShare);
+
+			// Bob self-share online
+			byte[] bobRewardSharePrivateKey = AccountUtils.rewardShare(repository, "bob", "bob", 0);
+			PrivateKeyAccount bobRewardShareAccount = new PrivateKeyAccount(repository, bobRewardSharePrivateKey);
+			mintingAndOnlineAccounts.add(bobRewardShareAccount);
+
+			// Chloe self share online
+			byte[] chloeRewardSharePrivateKey = AccountUtils.rewardShare(repository, "chloe", "chloe", 0);
+			PrivateKeyAccount chloeRewardShareAccount = new PrivateKeyAccount(repository, chloeRewardSharePrivateKey);
+			mintingAndOnlineAccounts.add(chloeRewardShareAccount);
+
+			// Dilbert self share online
+			byte[] dilbertRewardSharePrivateKey = AccountUtils.rewardShare(repository, "dilbert", "dilbert", 0);
+			PrivateKeyAccount dilbertRewardShareAccount = new PrivateKeyAccount(repository, dilbertRewardSharePrivateKey);
+			mintingAndOnlineAccounts.add(dilbertRewardShareAccount);
+			
+			// Mint enough blocks to bump testAccount levels to 3 and 4
+			final int minterBlocksNeeded = cumulativeBlocksByLevel.get(4) - 20; // 20 blocks before level 4, so that the test accounts reach the correct levels
+			for (int bc = 0; bc < minterBlocksNeeded; ++bc)
+				BlockMinter.mintTestingBlock(repository, mintingAndOnlineAccounts.toArray(new PrivateKeyAccount[0]));
+
+			// Ensure that the levels are as we expect
+			assertEquals(3, (int) Common.getTestAccount(repository, "alice").getLevel());
+			assertEquals(3, (int) Common.getTestAccount(repository, "bob").getLevel());
+			assertEquals(3, (int) Common.getTestAccount(repository, "chloe").getLevel());
+			assertEquals(4, (int) Common.getTestAccount(repository, "dilbert").getLevel());
+
+			// Now that everyone is at level 3 or 4, we can capture initial balances
+			Map<String, Map<Long, Long>> initialBalances = AccountUtils.getBalances(repository, Asset.QORT, Asset.LEGACY_QORA, Asset.QORT_FROM_QORA);
+			final long aliceInitialBalance = initialBalances.get("alice").get(Asset.QORT);
+			final long bobInitialBalance = initialBalances.get("bob").get(Asset.QORT);
+			final long chloeInitialBalance = initialBalances.get("chloe").get(Asset.QORT);
+			final long dilbertInitialBalance = initialBalances.get("dilbert").get(Asset.QORT);
+
+			// Mint a block
+			final long blockReward = BlockUtils.getNextBlockReward(repository);
+			BlockMinter.mintTestingBlock(repository, mintingAndOnlineAccounts.toArray(new PrivateKeyAccount[0]));
+
+			// Ensure we are using the correct block reward value
+			assertEquals(100000000L, blockReward);
+
+			/*
+			 * Alice, Bob, Chloe, and Dilbert are 'online'.
+			 * Bob and Chloe are level 3; Dilbert is level 4.
+			 * One founder online (Alice, who is also level 3).
+			 * No legacy QORA holders.
+			 *
+			 * Chloe, Bob and Dilbert should receive equal shares of the 10% block reward for level 3 and 4
+			 * Alice should receive the remainder (90%)
+			 */
+
+			// We are after the shareBinFix feature trigger, so we expect level 3 and 4 to share the same reward (10%)
+			final int level3And4SharePercent = 10_00; // 10%
+			final long level3And4ShareAmount = (blockReward * level3And4SharePercent) / 100L / 100L;
+			final long expectedReward = level3And4ShareAmount / 3; // The reward is split between Bob, Chloe, and Dilbert
+			final long expectedFounderReward = blockReward - level3And4ShareAmount; // Alice should receive the remainder
+
+			// Validate the balances to ensure that the correct post-shareBinFix distribution is being applied
+			AccountUtils.assertBalance(repository, "alice", Asset.QORT, aliceInitialBalance+expectedFounderReward);
+			AccountUtils.assertBalance(repository, "bob", Asset.QORT, bobInitialBalance+expectedReward);
+			AccountUtils.assertBalance(repository, "chloe", Asset.QORT, chloeInitialBalance+expectedReward);
+			AccountUtils.assertBalance(repository, "dilbert", Asset.QORT, dilbertInitialBalance+expectedReward);
+
+		}
+	}
+
+	/** Test rewards for level 5 and 6 accounts */
+	@Test
+	public void testLevel5And6Rewards() throws DataException {
+		Common.useSettings("test-settings-v2-reward-levels.json");
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+
+			List<Integer> cumulativeBlocksByLevel = BlockChain.getInstance().getCumulativeBlocksByLevel();
+			List<PrivateKeyAccount> mintingAndOnlineAccounts = new ArrayList<>();
+
+			// Alice self share online
+			PrivateKeyAccount aliceSelfShare = Common.getTestAccount(repository, "alice-reward-share");
+			mintingAndOnlineAccounts.add(aliceSelfShare);
+
+			// Bob self-share not initially online
+
+			// Chloe self share online
+			byte[] chloeRewardSharePrivateKey = AccountUtils.rewardShare(repository, "chloe", "chloe", 0);
+			PrivateKeyAccount chloeRewardShareAccount = new PrivateKeyAccount(repository, chloeRewardSharePrivateKey);
+			mintingAndOnlineAccounts.add(chloeRewardShareAccount);
+
+			// Dilbert self share online
+			byte[] dilbertRewardSharePrivateKey = AccountUtils.rewardShare(repository, "dilbert", "dilbert", 0);
+			PrivateKeyAccount dilbertRewardShareAccount = new PrivateKeyAccount(repository, dilbertRewardSharePrivateKey);
+			mintingAndOnlineAccounts.add(dilbertRewardShareAccount);
+
+			// Mint enough blocks to bump testAccount levels to 5 and 6
+			final int minterBlocksNeeded = cumulativeBlocksByLevel.get(6) - 20; // 20 blocks before level 6, so that the test accounts reach the correct levels
+			for (int bc = 0; bc < minterBlocksNeeded; ++bc)
+				BlockMinter.mintTestingBlock(repository, mintingAndOnlineAccounts.toArray(new PrivateKeyAccount[0]));
+
+			// Bob self-share now comes online
+			byte[] bobRewardSharePrivateKey = AccountUtils.rewardShare(repository, "bob", "bob", 0);
+			PrivateKeyAccount bobRewardShareAccount = new PrivateKeyAccount(repository, bobRewardSharePrivateKey);
+			mintingAndOnlineAccounts.add(bobRewardShareAccount);
+
+			// Ensure that the levels are as we expect
+			assertEquals(5, (int) Common.getTestAccount(repository, "alice").getLevel());
+			assertEquals(1, (int) Common.getTestAccount(repository, "bob").getLevel());
+			assertEquals(5, (int) Common.getTestAccount(repository, "chloe").getLevel());
+			assertEquals(6, (int) Common.getTestAccount(repository, "dilbert").getLevel());
+
+			// Now that everyone is at level 5 or 6 (except Bob who has only just started minting, so is at level 1), we can capture initial balances
+			Map<String, Map<Long, Long>> initialBalances = AccountUtils.getBalances(repository, Asset.QORT, Asset.LEGACY_QORA, Asset.QORT_FROM_QORA);
+			final long aliceInitialBalance = initialBalances.get("alice").get(Asset.QORT);
+			final long bobInitialBalance = initialBalances.get("bob").get(Asset.QORT);
+			final long chloeInitialBalance = initialBalances.get("chloe").get(Asset.QORT);
+			final long dilbertInitialBalance = initialBalances.get("dilbert").get(Asset.QORT);
+
+			// Mint a block
+			final long blockReward = BlockUtils.getNextBlockReward(repository);
+			BlockMinter.mintTestingBlock(repository, mintingAndOnlineAccounts.toArray(new PrivateKeyAccount[0]));
+
+			// Ensure we are using the correct block reward value
+			assertEquals(100000000L, blockReward);
+
+			/*
+			 * Alice, Bob, Chloe, and Dilbert are 'online'.
+			 * Bob is level 1; Chloe is level 5; Dilbert is level 6.
+			 * One founder online (Alice, who is also level 5).
+			 * No legacy QORA holders.
+			 *
+			 * Chloe and Dilbert should receive equal shares of the 15% block reward for level 5 and 6
+			 * Bob should receive all of the level 1 and 2 reward (5%)
+			 * Alice should receive the remainder (80%)
+			 */
+
+			// We are after the shareBinFix feature trigger, so we expect level 5 and 6 to share the same reward (15%)
+			final int level1And2SharePercent = 5_00; // 5%
+			final int level5And6SharePercent = 15_00; // 10%
+			final long level1And2ShareAmount = (blockReward * level1And2SharePercent) / 100L / 100L;
+			final long level5And6ShareAmount = (blockReward * level5And6SharePercent) / 100L / 100L;
+			final long expectedLevel1And2Reward = level1And2ShareAmount; // The reward is given entirely to Bob
+			final long expectedLevel5And6Reward = level5And6ShareAmount / 2; // The reward is split between Chloe and Dilbert
+			final long expectedFounderReward = blockReward - level1And2ShareAmount - level5And6ShareAmount; // Alice should receive the remainder
+
+			// Validate the balances to ensure that the correct post-shareBinFix distribution is being applied
+			AccountUtils.assertBalance(repository, "alice", Asset.QORT, aliceInitialBalance+expectedFounderReward);
+			AccountUtils.assertBalance(repository, "bob", Asset.QORT, bobInitialBalance+expectedLevel1And2Reward);
+			AccountUtils.assertBalance(repository, "chloe", Asset.QORT, chloeInitialBalance+expectedLevel5And6Reward);
+			AccountUtils.assertBalance(repository, "dilbert", Asset.QORT, dilbertInitialBalance+expectedLevel5And6Reward);
+
+		}
+	}
+
+	/** Test rewards for level 7 and 8 accounts */
+	@Test
+	public void testLevel7And8Rewards() throws DataException {
+		Common.useSettings("test-settings-v2-reward-levels.json");
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+
+			List<Integer> cumulativeBlocksByLevel = BlockChain.getInstance().getCumulativeBlocksByLevel();
+			List<PrivateKeyAccount> mintingAndOnlineAccounts = new ArrayList<>();
+
+			// Alice self share online
+			PrivateKeyAccount aliceSelfShare = Common.getTestAccount(repository, "alice-reward-share");
+			mintingAndOnlineAccounts.add(aliceSelfShare);
+
+			// Bob self-share NOT online
+
+			// Chloe self share online
+			byte[] chloeRewardSharePrivateKey = AccountUtils.rewardShare(repository, "chloe", "chloe", 0);
+			PrivateKeyAccount chloeRewardShareAccount = new PrivateKeyAccount(repository, chloeRewardSharePrivateKey);
+			mintingAndOnlineAccounts.add(chloeRewardShareAccount);
+
+			// Dilbert self share online
+			byte[] dilbertRewardSharePrivateKey = AccountUtils.rewardShare(repository, "dilbert", "dilbert", 0);
+			PrivateKeyAccount dilbertRewardShareAccount = new PrivateKeyAccount(repository, dilbertRewardSharePrivateKey);
+			mintingAndOnlineAccounts.add(dilbertRewardShareAccount);
+
+			// Mint enough blocks to bump testAccount levels to 7 and 8
+			final int minterBlocksNeeded = cumulativeBlocksByLevel.get(8) - 20; // 20 blocks before level 8, so that the test accounts reach the correct levels
+			for (int bc = 0; bc < minterBlocksNeeded; ++bc)
+				BlockMinter.mintTestingBlock(repository, mintingAndOnlineAccounts.toArray(new PrivateKeyAccount[0]));
+
+			// Ensure that the levels are as we expect
+			assertEquals(7, (int) Common.getTestAccount(repository, "alice").getLevel());
+			assertEquals(1, (int) Common.getTestAccount(repository, "bob").getLevel());
+			assertEquals(7, (int) Common.getTestAccount(repository, "chloe").getLevel());
+			assertEquals(8, (int) Common.getTestAccount(repository, "dilbert").getLevel());
+
+			// Now that everyone is at level 7 or 8 (except Bob who has only just started minting, so is at level 1), we can capture initial balances
+			Map<String, Map<Long, Long>> initialBalances = AccountUtils.getBalances(repository, Asset.QORT, Asset.LEGACY_QORA, Asset.QORT_FROM_QORA);
+			final long aliceInitialBalance = initialBalances.get("alice").get(Asset.QORT);
+			final long bobInitialBalance = initialBalances.get("bob").get(Asset.QORT);
+			final long chloeInitialBalance = initialBalances.get("chloe").get(Asset.QORT);
+			final long dilbertInitialBalance = initialBalances.get("dilbert").get(Asset.QORT);
+
+			// Mint a block
+			final long blockReward = BlockUtils.getNextBlockReward(repository);
+			BlockMinter.mintTestingBlock(repository, mintingAndOnlineAccounts.toArray(new PrivateKeyAccount[0]));
+
+			// Ensure we are using the correct block reward value
+			assertEquals(100000000L, blockReward);
+
+			/*
+			 * Alice, Chloe, and Dilbert are 'online'.
+			 * Chloe is level 7; Dilbert is level 8.
+			 * One founder online (Alice, who is also level 7).
+			 * No legacy QORA holders.
+			 *
+			 * Chloe and Dilbert should receive equal shares of the 20% block reward for level 7 and 8
+			 * Alice should receive the remainder (80%)
+			 */
+
+			// We are after the shareBinFix feature trigger, so we expect level 7 and 8 to share the same reward (20%)
+			final int level7And8SharePercent = 20_00; // 20%
+			final long level7And8ShareAmount = (blockReward * level7And8SharePercent) / 100L / 100L;
+			final long expectedLevel7And8Reward = level7And8ShareAmount / 2; // The reward is split between Chloe and Dilbert
+			final long expectedFounderReward = blockReward - level7And8ShareAmount; // Alice should receive the remainder
+
+			// Validate the balances to ensure that the correct post-shareBinFix distribution is being applied
+			AccountUtils.assertBalance(repository, "alice", Asset.QORT, aliceInitialBalance+expectedFounderReward);
+			AccountUtils.assertBalance(repository, "bob", Asset.QORT, bobInitialBalance); // Bob not online so his balance remains the same
+			AccountUtils.assertBalance(repository, "chloe", Asset.QORT, chloeInitialBalance+expectedLevel7And8Reward);
+			AccountUtils.assertBalance(repository, "dilbert", Asset.QORT, dilbertInitialBalance+expectedLevel7And8Reward);
+
+		}
+	}
+
+	/** Test rewards for level 9 and 10 accounts */
+	@Test
+	public void testLevel9And10Rewards() throws DataException {
+		Common.useSettings("test-settings-v2-reward-levels.json");
+
+		try (final Repository repository = RepositoryManager.getRepository()) {
+
+			List<Integer> cumulativeBlocksByLevel = BlockChain.getInstance().getCumulativeBlocksByLevel();
+			List<PrivateKeyAccount> mintingAndOnlineAccounts = new ArrayList<>();
+
+			// Alice self share online
+			PrivateKeyAccount aliceSelfShare = Common.getTestAccount(repository, "alice-reward-share");
+			mintingAndOnlineAccounts.add(aliceSelfShare);
+
+			// Bob self-share not initially online
+
+			// Chloe self share online
+			byte[] chloeRewardSharePrivateKey = AccountUtils.rewardShare(repository, "chloe", "chloe", 0);
+			PrivateKeyAccount chloeRewardShareAccount = new PrivateKeyAccount(repository, chloeRewardSharePrivateKey);
+			mintingAndOnlineAccounts.add(chloeRewardShareAccount);
+
+			// Dilbert self share online
+			byte[] dilbertRewardSharePrivateKey = AccountUtils.rewardShare(repository, "dilbert", "dilbert", 0);
+			PrivateKeyAccount dilbertRewardShareAccount = new PrivateKeyAccount(repository, dilbertRewardSharePrivateKey);
+			mintingAndOnlineAccounts.add(dilbertRewardShareAccount);
+
+			// Mint enough blocks to bump testAccount levels to 9 and 10
+			final int minterBlocksNeeded = cumulativeBlocksByLevel.get(10) - 20; // 20 blocks before level 10, so that the test accounts reach the correct levels
+			for (int bc = 0; bc < minterBlocksNeeded; ++bc)
+				BlockMinter.mintTestingBlock(repository, mintingAndOnlineAccounts.toArray(new PrivateKeyAccount[0]));
+
+			// Bob self-share now comes online
+			byte[] bobRewardSharePrivateKey = AccountUtils.rewardShare(repository, "bob", "bob", 0);
+			PrivateKeyAccount bobRewardShareAccount = new PrivateKeyAccount(repository, bobRewardSharePrivateKey);
+			mintingAndOnlineAccounts.add(bobRewardShareAccount);
+
+			// Ensure that the levels are as we expect
+			assertEquals(9, (int) Common.getTestAccount(repository, "alice").getLevel());
+			assertEquals(1, (int) Common.getTestAccount(repository, "bob").getLevel());
+			assertEquals(9, (int) Common.getTestAccount(repository, "chloe").getLevel());
+			assertEquals(10, (int) Common.getTestAccount(repository, "dilbert").getLevel());
+
+			// Now that everyone is at level 7 or 8 (except Bob who has only just started minting, so is at level 1), we can capture initial balances
+			Map<String, Map<Long, Long>> initialBalances = AccountUtils.getBalances(repository, Asset.QORT, Asset.LEGACY_QORA, Asset.QORT_FROM_QORA);
+			final long aliceInitialBalance = initialBalances.get("alice").get(Asset.QORT);
+			final long bobInitialBalance = initialBalances.get("bob").get(Asset.QORT);
+			final long chloeInitialBalance = initialBalances.get("chloe").get(Asset.QORT);
+			final long dilbertInitialBalance = initialBalances.get("dilbert").get(Asset.QORT);
+
+			// Mint a block
+			final long blockReward = BlockUtils.getNextBlockReward(repository);
+			BlockMinter.mintTestingBlock(repository, mintingAndOnlineAccounts.toArray(new PrivateKeyAccount[0]));
+
+			// Ensure we are using the correct block reward value
+			assertEquals(100000000L, blockReward);
+
+			/*
+			 * Alice, Bob, Chloe, and Dilbert are 'online'.
+			 * Bob is level 1; Chloe is level 9; Dilbert is level 10.
+			 * One founder online (Alice, who is also level 9).
+			 * No legacy QORA holders.
+			 *
+			 * Chloe and Dilbert should receive equal shares of the 25% block reward for level 9 and 10
+			 * Bob should receive all of the level 1 and 2 reward (5%)
+			 * Alice should receive the remainder (70%)
+			 */
+
+			// We are after the shareBinFix feature trigger, so we expect level 9 and 10 to share the same reward (25%)
+			final int level1And2SharePercent = 5_00; // 5%
+			final int level9And10SharePercent = 25_00; // 25%
+			final long level1And2ShareAmount = (blockReward * level1And2SharePercent) / 100L / 100L;
+			final long level9And10ShareAmount = (blockReward * level9And10SharePercent) / 100L / 100L;
+			final long expectedLevel1And2Reward = level1And2ShareAmount; // The reward is given entirely to Bob
+			final long expectedLevel9And10Reward = level9And10ShareAmount / 2; // The reward is split between Chloe and Dilbert
+			final long expectedFounderReward = blockReward - level1And2ShareAmount - level9And10ShareAmount; // Alice should receive the remainder
+
+			// Validate the balances to ensure that the correct post-shareBinFix distribution is being applied
+			AccountUtils.assertBalance(repository, "alice", Asset.QORT, aliceInitialBalance+expectedFounderReward);
+			AccountUtils.assertBalance(repository, "bob", Asset.QORT, bobInitialBalance+expectedLevel1And2Reward);
+			AccountUtils.assertBalance(repository, "chloe", Asset.QORT, chloeInitialBalance+expectedLevel9And10Reward);
+			AccountUtils.assertBalance(repository, "dilbert", Asset.QORT, dilbertInitialBalance+expectedLevel9And10Reward);
+
+		}
+	}
+
+
+	private int getFlags(Repository repository, String name) throws DataException {
+		TestAccount testAccount = Common.getTestAccount(repository, name);
+		return repository.getAccountRepository().getAccount(testAccount.getAddress()).getFlags();
+	}
+
 }

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

@@ -45,7 +45,10 @@
 		"qortalTimestamp": 0,
 		"newAssetPricingTimestamp": 0,
 		"groupApprovalTimestamp": 0,
-		"atFindNextTransactionFix": 0
+		"atFindNextTransactionFix": 0,
+		"newBlockSigHeight": 999999,
+		"shareBinFix": 999999,
+		"calcChainWeightTimestamp": 0
 	},
 	"genesisInfo": {
 		"version": 4,

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

@@ -45,7 +45,10 @@
 		"qortalTimestamp": 0,
 		"newAssetPricingTimestamp": 0,
 		"groupApprovalTimestamp": 0,
-		"atFindNextTransactionFix": 0
+		"atFindNextTransactionFix": 0,
+		"newBlockSigHeight": 999999,
+		"shareBinFix": 999999,
+		"calcChainWeightTimestamp": 0
 	},
 	"genesisInfo": {
 		"version": 4,

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

@@ -45,7 +45,10 @@
 		"qortalTimestamp": 0,
 		"newAssetPricingTimestamp": 0,
 		"groupApprovalTimestamp": 0,
-		"atFindNextTransactionFix": 0
+		"atFindNextTransactionFix": 0,
+		"newBlockSigHeight": 999999,
+		"shareBinFix": 999999,
+		"calcChainWeightTimestamp": 0
 	},
 	"genesisInfo": {
 		"version": 4,

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

@@ -45,7 +45,10 @@
 		"qortalTimestamp": 0,
 		"newAssetPricingTimestamp": 0,
 		"groupApprovalTimestamp": 0,
-		"atFindNextTransactionFix": 0
+		"atFindNextTransactionFix": 0,
+		"newBlockSigHeight": 999999,
+		"shareBinFix": 999999,
+		"calcChainWeightTimestamp": 0
 	},
 	"genesisInfo": {
 		"version": 4,

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

@@ -45,7 +45,10 @@
 		"qortalTimestamp": 0,
 		"newAssetPricingTimestamp": 0,
 		"groupApprovalTimestamp": 0,
-		"atFindNextTransactionFix": 0
+		"atFindNextTransactionFix": 0,
+		"newBlockSigHeight": 999999,
+		"shareBinFix": 999999,
+		"calcChainWeightTimestamp": 0
 	},
 	"genesisInfo": {
 		"version": 4,

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

@@ -0,0 +1,75 @@
+{
+	"isTestChain": true,
+	"blockTimestampMargin": 500,
+	"transactionExpiryPeriod": 86400000,
+	"maxBlockSize": 2097152,
+	"maxBytesPerUnitFee": 1024,
+	"unitFee": "0.1",
+	"requireGroupForApproval": false,
+	"minAccountLevelToRewardShare": 5,
+	"maxRewardSharesPerMintingAccount": 20,
+	"founderEffectiveMintingLevel": 10,
+	"onlineAccountSignaturesMinLifetime": 3600000,
+	"onlineAccountSignaturesMaxLifetime": 86400000,
+	"rewardsByHeight": [
+		{ "height": 1, "reward": 100 },
+		{ "height": 11, "reward": 10 },
+		{ "height": 21, "reward": 1 }
+	],
+	"sharesByLevel": [
+		{ "levels": [ 1, 2 ], "share": 0.05 },
+		{ "levels": [ 3, 4 ], "share": 0.10 },
+		{ "levels": [ 5, 6 ], "share": 0.15 },
+		{ "levels": [ 7, 8 ], "share": 0.20 },
+		{ "levels": [ 9, 10 ], "share": 0.25 }
+	],
+	"qoraHoldersShare": 0.20,
+	"qoraPerQortReward": 250,
+	"blocksNeededByLevel": [ 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 ],
+	"blockTimingsByHeight": [
+		{ "height": 1, "target": 60000, "deviation": 30000, "power": 0.2 }
+	],
+	"ciyamAtSettings": {
+		"feePerStep": "0.0001",
+		"maxStepsPerRound": 500,
+		"stepsPerFunctionCall": 10,
+		"minutesPerBlock": 1
+	},
+	"featureTriggers": {
+		"messageHeight": 0,
+		"atHeight": 0,
+		"assetsTimestamp": 0,
+		"votingTimestamp": 0,
+		"arbitraryTimestamp": 0,
+		"powfixTimestamp": 0,
+		"qortalTimestamp": 0,
+		"newAssetPricingTimestamp": 0,
+		"groupApprovalTimestamp": 0,
+		"atFindNextTransactionFix": 0,
+		"newBlockSigHeight": 999999,
+		"shareBinFix": 6,
+		"calcChainWeightTimestamp": 0
+	},
+	"genesisInfo": {
+		"version": 4,
+		"timestamp": 0,
+		"transactions": [
+			{ "type": "ISSUE_ASSET", "assetName": "QORT", "description": "QORT native coin", "data": "", "quantity": 0, "isDivisible": true, "fee": 0 },
+			{ "type": "ISSUE_ASSET", "assetName": "Legacy-QORA", "description": "Representative legacy QORA", "quantity": 0, "isDivisible": true, "data": "{}", "isUnspendable": true },
+			{ "type": "ISSUE_ASSET", "assetName": "QORT-from-QORA", "description": "QORT gained from holding legacy QORA", "quantity": 0, "isDivisible": true, "data": "{}", "isUnspendable": true },
+
+			{ "type": "GENESIS", "recipient": "QgV4s3xnzLhVBEJxcYui4u4q11yhUHsd9v", "amount": "1000000000" },
+			{ "type": "GENESIS", "recipient": "QixPbJUwsaHsVEofJdozU9zgVqkK6aYhrK", "amount": "1000000" },
+			{ "type": "GENESIS", "recipient": "QaUpHNhT3Ygx6avRiKobuLdusppR5biXjL", "amount": "1000000" },
+			{ "type": "GENESIS", "recipient": "Qci5m9k4rcwe4ruKrZZQKka4FzUUMut3er", "amount": "1000000" },
+
+			{ "type": "ACCOUNT_FLAGS", "target": "QgV4s3xnzLhVBEJxcYui4u4q11yhUHsd9v", "andMask": -1, "orMask": 1, "xorMask": 0 },
+			{ "type": "REWARD_SHARE", "minterPublicKey": "2tiMr5LTpaWCgbRvkPK8TFd7k63DyHJMMFFsz9uBf1ZP", "recipient": "QgV4s3xnzLhVBEJxcYui4u4q11yhUHsd9v", "rewardSharePublicKey": "7PpfnvLSG7y4HPh8hE7KoqAjLCkv7Ui6xw4mKAkbZtox", "sharePercent": 100 },
+
+			{ "type": "ACCOUNT_LEVEL", "target": "QgV4s3xnzLhVBEJxcYui4u4q11yhUHsd9v", "level": 1 },
+			{ "type": "ACCOUNT_LEVEL", "target": "QixPbJUwsaHsVEofJdozU9zgVqkK6aYhrK", "level": 1 },
+			{ "type": "ACCOUNT_LEVEL", "target": "QaUpHNhT3Ygx6avRiKobuLdusppR5biXjL", "level": 1 },
+			{ "type": "ACCOUNT_LEVEL", "target": "Qci5m9k4rcwe4ruKrZZQKka4FzUUMut3er", "level": 2 }
+		]
+	}
+}

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

@@ -45,7 +45,10 @@
 		"qortalTimestamp": 0,
 		"newAssetPricingTimestamp": 0,
 		"groupApprovalTimestamp": 0,
-		"atFindNextTransactionFix": 0
+		"atFindNextTransactionFix": 0,
+		"newBlockSigHeight": 999999,
+		"shareBinFix": 999999,
+		"calcChainWeightTimestamp": 0
 	},
 	"genesisInfo": {
 		"version": 4,

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

@@ -45,7 +45,10 @@
 		"qortalTimestamp": 0,
 		"newAssetPricingTimestamp": 0,
 		"groupApprovalTimestamp": 0,
-		"atFindNextTransactionFix": 0
+		"atFindNextTransactionFix": 0,
+		"newBlockSigHeight": 999999,
+		"shareBinFix": 999999,
+		"calcChainWeightTimestamp": 0
 	},
 	"genesisInfo": {
 		"version": 4,

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

@@ -0,0 +1,7 @@
+{
+  "restrictedApi": false,
+  "blockchainConfig": "src/test/resources/test-chain-v2-reward-levels.json",
+  "wipeUnconfirmedOnStart": false,
+  "testNtpOffset": 0,
+  "minPeers": 0
+}

stop.sh

@@ -21,13 +21,19 @@ fi
 read pid 2>/dev/null <run.pid
 is_pid_valid=$?
 
+# Swap out the API port if the --testnet (or -t) argument is specified
+api_port=12391
+if [[ "$@" = *"--testnet"* ]] || [[  "$@" = *"-t"* ]]; then
+  api_port=62391
+fi
+
 # Ensure curl is installed
 curl_path=$(which curl)
 
 if [[ -f $curl_path ]]; then
 
 	echo 'Calling GET /admin/stop on local Qortal node'
-	if curl --url http://localhost:12391/admin/stop 1>/dev/null 2>&1; then
+	if curl --url "http://localhost:${api_port}/admin/stop" 1>/dev/null 2>&1; then
 		echo "Qortal node responded and should be shutting down"
 
 		if [ "${is_pid_valid}" -eq 0 ]; then
@@ -42,7 +48,7 @@ if [[ -f $curl_path ]]; then
 		fi
 		exit 0
 	else
-		echo "${red}No response from Qortal node - not running?${normal}"
+		echo "${red}No response from Qortal node - not running on port ${api_port}?${normal}"
 		exit 1
 	fi
 

tools/publish-auto-update.pl

@@ -57,9 +57,11 @@ $timestamp *= 1000; # Convert to milliseconds
 
 # locate sha256 utility
 my $SHA256 = `which sha256sum || which sha256`;
+chomp $SHA256;
+die("Can't find sha256sum or sha256\n") unless length($SHA256) > 0;
 
 # SHA256 of actual update file
-my $sha256 = `git show auto-update-${commit_hash}:${project}.update | ${SHA256}`;
+my $sha256 = `git show auto-update-${commit_hash}:${project}.update | ${SHA256} | head -c 64`;
 die("Can't calculate SHA256 of ${project}.update\n") unless $sha256 =~ m/(\S{64})/;
 chomp $sha256;