Forward secrecy.

Each connection's keys are derived from a secret that is erased after
deriving the keys and the secret for the next connection.

components/net/sf/briar/crypto/CryptoComponentImpl.java

@@ -88,14 +88,14 @@ class CryptoComponentImpl implements CryptoComponent {
 		if(secret.length != SECRET_KEY_BYTES)
 			throw new IllegalArgumentException();
 		ErasableKey key = new ErasableKeyImpl(secret, SECRET_KEY_ALGO);
-		// The context must leave four bytes free for the length
-		if(context.length + 4 > SECRET_KEY_BYTES)
+		// The context must leave two bytes free for the length
+		if(context.length + 2 > SECRET_KEY_BYTES)
 			throw new IllegalArgumentException();
 		byte[] input = new byte[SECRET_KEY_BYTES];
-		// The initial bytes of the input are the context
-		System.arraycopy(context, 0, input, 0, context.length);
-		// The final bytes of the input are the length as a big-endian uint32
-		ByteUtils.writeUint32(context.length, input, input.length - 4);
+		// The input starts with the length of the context as a big-endian int16
+		ByteUtils.writeUint16(context.length, input, 0);
+		// The remaining bytes of the input are the context
+		System.arraycopy(context, 0, input, 2, context.length);
 		// Initialise the counter to zero
 		byte[] zero = new byte[KEY_DERIVATION_IV_BYTES];
 		IvParameterSpec iv = new IvParameterSpec(zero);
@@ -110,12 +110,15 @@ class CryptoComponentImpl implements CryptoComponent {
 		}
 	}
 
-	public byte[] deriveNextSecret(byte[] secret, long connection) {
+	public byte[] deriveNextSecret(byte[] secret, int index, long connection) {
+		if(index < 0 || index > ByteUtils.MAX_16_BIT_UNSIGNED)
+			throw new IllegalArgumentException();
 		if(connection < 0 || connection > ByteUtils.MAX_32_BIT_UNSIGNED)
 			throw new IllegalArgumentException();
-		byte[] context = new byte[NEXT.length + 4];
+		byte[] context = new byte[NEXT.length + 6];
 		System.arraycopy(NEXT, 0, context, 0, NEXT.length);
-		ByteUtils.writeUint32(connection, context, NEXT.length);
+		ByteUtils.writeUint16(index, context, NEXT.length);
+		ByteUtils.writeUint32(connection, context, NEXT.length + 2);
 		return counterModeKdf(secret, context);
 	}
 

components/net/sf/briar/crypto/ErasableKeyImpl.java

@@ -3,6 +3,7 @@ package net.sf.briar.crypto;
 import java.util.Arrays;
 
 import net.sf.briar.api.crypto.ErasableKey;
+import net.sf.briar.util.ByteUtils;
 
 class ErasableKeyImpl implements ErasableKey {
 
@@ -34,7 +35,7 @@ class ErasableKeyImpl implements ErasableKey {
 
 	public void erase() {
 		if(erased) throw new IllegalStateException();
-		for(int i = 0; i < key.length; i++) key[i] = 0;
+		ByteUtils.erase(key);
 		erased = true;
 	}
 

components/net/sf/briar/db/Database.java

@@ -84,10 +84,14 @@ interface Database<T> {
 	 * Adds a new contact to the database with the given secrets and returns an
 	 * ID for the contact.
 	 * <p>
+	 * Any secrets generated by the method are stored in the given collection
+	 * and should be erased by the caller once the transaction has been
+	 * committed or aborted.
+	 * <p>
 	 * Locking: contact write.
 	 */
-	ContactId addContact(T txn, byte[] incomingSecret, byte[] outgoingSecret)
-	throws DbException;
+	ContactId addContact(T txn, byte[] inSecret, byte[] outSecret,
+			Collection<byte[]> erase) throws DbException;
 
 	/**
 	 * Returns false if the given message is already in the database. Otherwise
@@ -187,10 +191,14 @@ interface Database<T> {
 	 * Returns an outgoing connection context for the given contact and
 	 * transport.
 	 * <p>
+	 * Any secrets generated by the method are stored in the given collection
+	 * and should be erased by the caller once the transaction has been
+	 * committed or aborted.
+	 * <p>
 	 * Locking: contact read, window write.
 	 */
-	ConnectionContext getConnectionContext(T txn, ContactId c, TransportIndex i)
-	throws DbException;
+	ConnectionContext getConnectionContext(T txn, ContactId c, TransportIndex i,
+			Collection<byte[]> erase) throws DbException;
 
 	/**
 	 * Returns the connection reordering window for the given contact and
@@ -373,14 +381,6 @@ interface Database<T> {
 	Collection<MessageId> getSendableMessages(T txn, ContactId c, int capacity)
 	throws DbException;
 
-	/**
-	 * Returns the secret shared with the given contact.
-	 * <p>
-	 * Locking: contact read.
-	 */
-	byte[] getSharedSecret(T txn, ContactId c, boolean incoming)
-	throws DbException;
-
 	/**
 	 * Returns true if the given message has been starred.
 	 * <p>

components/net/sf/briar/db/DatabaseComponentImpl.java

@@ -62,6 +62,7 @@ import net.sf.briar.api.protocol.writers.SubscriptionUpdateWriter;
 import net.sf.briar.api.protocol.writers.TransportUpdateWriter;
 import net.sf.briar.api.transport.ConnectionContext;
 import net.sf.briar.api.transport.ConnectionWindow;
+import net.sf.briar.util.ByteUtils;
 
 import com.google.inject.Inject;
 
@@ -136,23 +137,24 @@ DatabaseCleaner.Callback {
 		}
 	}
 
-	public ContactId addContact(byte[] incomingSecret, byte[] outgoingSecret)
+	public ContactId addContact(byte[] inSecret, byte[] outSecret)
 	throws DbException {
-		if(LOG.isLoggable(Level.FINE)) LOG.fine("Adding contact");
 		ContactId c;
+		Collection<byte[]> erase = new ArrayList<byte[]>();
 		contactLock.writeLock().lock();
 		try {
 			T txn = db.startTransaction();
 			try {
-				c = db.addContact(txn, incomingSecret, outgoingSecret);
+				c = db.addContact(txn, inSecret, outSecret, erase);
 				db.commitTransaction(txn);
-				if(LOG.isLoggable(Level.FINE)) LOG.fine("Added contact " + c);
 			} catch(DbException e) {
 				db.abortTransaction(txn);
 				throw e;
 			}
 		} finally {
 			contactLock.writeLock().unlock();
+			// Erase the secrets after committing or aborting the transaction
+			for(byte[] b : erase) ByteUtils.erase(b);
 		}
 		// Call the listeners outside the lock
 		callListeners(new ContactAddedEvent(c));
@@ -703,6 +705,7 @@ DatabaseCleaner.Callback {
 
 	public ConnectionContext getConnectionContext(ContactId c, TransportIndex i)
 	throws DbException {
+		Collection<byte[]> erase = new ArrayList<byte[]>();
 		contactLock.readLock().lock();
 		try {
 			if(!containsContact(c)) throw new NoSuchContactException();
@@ -710,7 +713,8 @@ DatabaseCleaner.Callback {
 			try {
 				T txn = db.startTransaction();
 				try {
-					ConnectionContext ctx = db.getConnectionContext(txn, c, i);
+					ConnectionContext ctx =
+						db.getConnectionContext(txn, c, i, erase);
 					db.commitTransaction(txn);
 					return ctx;
 				} catch(DbException e) {
@@ -722,6 +726,8 @@ DatabaseCleaner.Callback {
 			}
 		} finally {
 			contactLock.readLock().unlock();
+			// Erase the secrets after committing or aborting the transaction
+			for(byte[] b : erase) ByteUtils.erase(b);
 		}
 	}
 
@@ -907,25 +913,6 @@ DatabaseCleaner.Callback {
 		}
 	}
 
-	public byte[] getSharedSecret(ContactId c, boolean incoming)
-	throws DbException {
-		contactLock.readLock().lock();
-		try {
-			if(!containsContact(c)) throw new NoSuchContactException();
-			T txn = db.startTransaction();
-			try {
-				byte[] secret = db.getSharedSecret(txn, c, incoming);
-				db.commitTransaction(txn);
-				return secret;
-			} catch(DbException e) {
-				db.abortTransaction(txn);
-				throw e;
-			}
-		} finally {
-			contactLock.readLock().unlock();
-		}
-	}
-
 	public Collection<Group> getSubscriptions() throws DbException {
 		subscriptionLock.readLock().lock();
 		try {

components/net/sf/briar/db/H2Database.java

@@ -29,6 +29,11 @@ class H2Database extends JdbcDatabase {
 	private static final Logger LOG =
 		Logger.getLogger(H2Database.class.getName());
 
+	private static final String HASH_TYPE = "BINARY(32)";
+	private static final String BINARY_TYPE = "BINARY";
+	private static final String COUNTER_TYPE = "INT NOT NULL AUTO_INCREMENT";
+	private static final String SECRET_TYPE = "BINARY(32)";
+
 	private final File home;
 	private final Password password;
 	private final String url;
@@ -42,7 +47,7 @@ class H2Database extends JdbcDatabase {
 			ConnectionWindowFactory connectionWindowFactory,
 			GroupFactory groupFactory) {
 		super(connectionContextFactory, connectionWindowFactory, groupFactory,
-				"BINARY(32)", "BINARY", "INT NOT NULL AUTO_INCREMENT");
+				HASH_TYPE, BINARY_TYPE, COUNTER_TYPE, SECRET_TYPE);
 		home = new File(dir, "db");
 		this.password = password;
 		url = "jdbc:h2:split:" + home.getPath()

components/net/sf/briar/db/JdbcDatabase.java

@@ -58,8 +58,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 	private static final String CREATE_CONTACTS =
 		"CREATE TABLE contacts"
 		+ " (contactId COUNTER,"
-		+ " incomingSecret BINARY NOT NULL,"
-		+ " outgoingSecret BINARY NOT NULL,"
 		+ " PRIMARY KEY (contactId))";
 
 	private static final String CREATE_MESSAGES =
@@ -221,7 +219,8 @@ abstract class JdbcDatabase implements Database<Connection> {
 		"CREATE TABLE connections"
 		+ " (contactId INT NOT NULL,"
 		+ " index INT NOT NULL,"
-		+ " outgoing BIGINT NOT NULL,"
+		+ " connection BIGINT NOT NULL,"
+		+ " secret SECRET NOT NULL,"
 		+ " PRIMARY KEY (contactId, index),"
 		+ " FOREIGN KEY (contactId) REFERENCES contacts (contactId)"
 		+ " ON DELETE CASCADE)";
@@ -231,6 +230,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 		+ " (contactId INT NOT NULL,"
 		+ " index INT NOT NULL,"
 		+ " unseen BIGINT NOT NULL,"
+		+ " secret SECRET NOT NULL,"
 		+ " PRIMARY KEY (contactId, index, unseen),"
 		+ " FOREIGN KEY (contactId) REFERENCES contacts (contactId)"
 		+ " ON DELETE CASCADE)";
@@ -271,7 +271,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 	private final ConnectionWindowFactory connectionWindowFactory;
 	private final GroupFactory groupFactory;
 	// Different database libraries use different names for certain types
-	private final String hashType, binaryType, counterType;
+	private final String hashType, binaryType, counterType, secretType;
 
 	private final LinkedList<Connection> connections =
 		new LinkedList<Connection>(); // Locking: self
@@ -284,13 +284,14 @@ abstract class JdbcDatabase implements Database<Connection> {
 	JdbcDatabase(ConnectionContextFactory connectionContextFactory,
 			ConnectionWindowFactory connectionWindowFactory,
 			GroupFactory groupFactory, String hashType, String binaryType,
-			String counterType) {
+			String counterType, String secretType) {
 		this.connectionContextFactory = connectionContextFactory;
 		this.connectionWindowFactory = connectionWindowFactory;
 		this.groupFactory = groupFactory;
 		this.hashType = hashType;
 		this.binaryType = binaryType;
 		this.counterType = counterType;
+		this.secretType = secretType;
 	}
 
 	protected void open(boolean resume, File dir, String driverClass)
@@ -371,6 +372,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 		s = s.replaceAll("HASH", hashType);
 		s = s.replaceAll("BINARY", binaryType);
 		s = s.replaceAll("COUNTER", counterType);
+		s = s.replaceAll("SECRET", secretType);
 		return s;
 	}
 
@@ -515,17 +517,14 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
-	public ContactId addContact(Connection txn, byte[] incomingSecret,
-			byte[] outgoingSecret) throws DbException {
+	public ContactId addContact(Connection txn, byte[] inSecret,
+			byte[] outSecret, Collection<byte[]> erase) throws DbException {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
 			// Create a new contact row
-			String sql = "INSERT INTO contacts (incomingSecret, outgoingSecret)"
-				+ " VALUES (?, ?)";
+			String sql = "INSERT INTO contacts DEFAULT VALUES";
 			ps = txn.prepareStatement(sql);
-			ps.setBytes(1, incomingSecret);
-			ps.setBytes(2, outgoingSecret);
 			int affected = ps.executeUpdate();
 			if(affected != 1) throw new DbStateException();
 			ps.close();
@@ -558,13 +557,20 @@ abstract class JdbcDatabase implements Database<Connection> {
 			affected = ps.executeUpdate();
 			if(affected != 1) throw new DbStateException();
 			ps.close();
-			// Initialise the connection numbers for all transports
-			sql = "INSERT INTO connections (contactId, index, outgoing)"
-				+ " VALUES (?, ?, ZERO())";
+			// Initialise the outgoing connection contexts for all transports
+			sql = "INSERT INTO connections"
+				+ " (contactId, index, connection, secret)"
+				+ " VALUES (?, ?, ZERO(), ?)";
 			ps = txn.prepareStatement(sql);
 			ps.setInt(1, c.getInt());
 			for(int i = 0; i < ProtocolConstants.MAX_TRANSPORTS; i++) {
 				ps.setInt(2, i);
+				ConnectionContext ctx =
+					connectionContextFactory.createNextConnectionContext(c,
+							new TransportIndex(i), 0L, outSecret);
+				byte[] secret = ctx.getSecret();
+				erase.add(secret);
+				ps.setBytes(3, secret);
 				ps.addBatch();
 			}
 			int[] batchAffected = ps.executeBatch();
@@ -574,18 +580,23 @@ abstract class JdbcDatabase implements Database<Connection> {
 				if(batchAffected[i] != 1) throw new DbStateException();
 			}
 			ps.close();
-			// Initialise the connection windows for all transports
-			sql = "INSERT INTO connectionWindows (contactId, index, unseen)"
-				+ " VALUES (?, ?, ?)";
+			// Initialise the incoming connection windows for all transports
+			sql = "INSERT INTO connectionWindows"
+				+ " (contactId, index, unseen, secret)"
+				+ " VALUES (?, ?, ?, ?)";
 			ps = txn.prepareStatement(sql);
 			ps.setInt(1, c.getInt());
 			int batchSize = 0;
 			for(int i = 0; i < ProtocolConstants.MAX_TRANSPORTS; i++) {
 				ps.setInt(2, i);
 				ConnectionWindow w =
-					connectionWindowFactory.createConnectionWindow();
-				for(long l : w.getUnseen()) {
-					ps.setLong(3, l);
+					connectionWindowFactory.createConnectionWindow(
+							new TransportIndex(i), inSecret);
+				for(Entry<Long, byte[]> e : w.getUnseen().entrySet()) {
+					ps.setLong(3, e.getKey());
+					byte[] secret = e.getValue();
+					erase.add(secret);
+					ps.setBytes(4, secret);
 					ps.addBatch();
 					batchSize++;
 				}
@@ -945,31 +956,43 @@ abstract class JdbcDatabase implements Database<Connection> {
 	}
 
 	public ConnectionContext getConnectionContext(Connection txn, ContactId c,
-			TransportIndex i) throws DbException {
+			TransportIndex i, Collection<byte[]> erase) throws DbException {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
-			String sql = "UPDATE connections SET outgoing = outgoing + 1"
-				+ " WHERE contactId = ? AND index = ?";
-			ps = txn.prepareStatement(sql);
-			ps.setInt(1, c.getInt());
-			ps.setInt(2, i.getInt());
-			int affected = ps.executeUpdate();
-			if(affected != 1) throw new DbStateException();
-			ps.close();
-			sql = "SELECT outgoing FROM connections"
+			// Retrieve the current context
+			String sql = "SELECT connection, secret FROM connections"
 				+ " WHERE contactId = ? AND index = ?";
 			ps = txn.prepareStatement(sql);
 			ps.setInt(1, c.getInt());
 			ps.setInt(2, i.getInt());
 			rs = ps.executeQuery();
 			if(!rs.next()) throw new DbStateException();
-			long outgoing = rs.getLong(1);
+			long connection = rs.getLong(1);
+			byte[] secret = rs.getBytes(2);
 			if(rs.next()) throw new DbStateException();
 			rs.close();
 			ps.close();
-			return connectionContextFactory.createConnectionContext(c, i,
-					outgoing);
+			ConnectionContext ctx =
+				connectionContextFactory.createConnectionContext(c, i,
+						connection, secret);
+			// Calculate and store the next context
+			ConnectionContext next =
+				connectionContextFactory.createNextConnectionContext(c, i,
+						connection + 1, secret);
+			byte[] nextSecret = next.getSecret();
+			erase.add(nextSecret);
+			sql = "UPDATE connections"
+				+ " SET connection = connection + 1, secret = ?"
+				+ " WHERE contactId = ? AND index = ?";
+			ps = txn.prepareStatement(sql);
+			ps.setBytes(1, nextSecret);
+			ps.setInt(2, c.getInt());
+			ps.setInt(3, i.getInt());
+			int affected = ps.executeUpdate();
+			if(affected != 1) throw new DbStateException();
+			ps.close();
+			return ctx;
 		} catch(SQLException e) {
 			tryToClose(rs);
 			tryToClose(ps);
@@ -982,17 +1005,17 @@ abstract class JdbcDatabase implements Database<Connection> {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
-			String sql = "SELECT unseen FROM connectionWindows"
+			String sql = "SELECT unseen, secret FROM connectionWindows"
 				+ " WHERE contactId = ? AND index = ?";
 			ps = txn.prepareStatement(sql);
 			ps.setInt(1, c.getInt());
 			ps.setInt(2, i.getInt());
 			rs = ps.executeQuery();
-			Collection<Long> unseen = new ArrayList<Long>();
-			while(rs.next()) unseen.add(rs.getLong(1));
+			Map<Long, byte[]> unseen = new HashMap<Long, byte[]>();
+			while(rs.next()) unseen.put(rs.getLong(1), rs.getBytes(2));
 			rs.close();
 			ps.close();
-			return connectionWindowFactory.createConnectionWindow(unseen);
+			return connectionWindowFactory.createConnectionWindow(i, unseen);
 		} catch(SQLException e) {
 			tryToClose(rs);
 			tryToClose(ps);
@@ -1652,29 +1675,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
-	public byte[] getSharedSecret(Connection txn, ContactId c, boolean incoming)
-	throws DbException {
-		PreparedStatement ps = null;
-		ResultSet rs = null;
-		try {
-			String col = incoming ? "incomingSecret" : "outgoingSecret";
-			String sql = "SELECT " + col + " FROM contacts WHERE contactId = ?";
-			ps = txn.prepareStatement(sql);
-			ps.setInt(1, c.getInt());
-			rs = ps.executeQuery();
-			if(!rs.next()) throw new DbStateException();
-			byte[] secret = rs.getBytes(1);
-			if(rs.next()) throw new DbStateException();
-			rs.close();
-			ps.close();
-			return secret;
-		} catch(SQLException e) {
-			tryToClose(rs);
-			tryToClose(ps);
-			throw new DbException(e);
-		}
-	}
-
 	public boolean getStarred(Connection txn, MessageId m) throws DbException {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
@@ -2197,14 +2197,16 @@ abstract class JdbcDatabase implements Database<Connection> {
 			ps.executeUpdate();
 			ps.close();
 			// Store the new connection window
-			sql = "INSERT INTO connectionWindows (contactId, index, unseen)"
-				+ " VALUES(?, ?, ?)";
+			sql = "INSERT INTO connectionWindows"
+				+ " (contactId, index, unseen, secret)"
+				+ " VALUES(?, ?, ?, ?)";
 			ps = txn.prepareStatement(sql);
 			ps.setInt(1, c.getInt());
 			ps.setInt(2, i.getInt());
-			Collection<Long> unseen = w.getUnseen();
-			for(long l : unseen) {
-				ps.setLong(3, l);
+			Map<Long, byte[]> unseen = w.getUnseen();
+			for(Entry<Long, byte[]> e : unseen.entrySet()) {
+				ps.setLong(3, e.getKey());
+				ps.setBytes(4, e.getValue());
 				ps.addBatch();
 			}
 			int[] affectedBatch = ps.executeBatch();

components/net/sf/briar/plugins/PluginManagerImpl.java

@@ -292,7 +292,7 @@ class PluginManagerImpl implements PluginManager {
 
 		public void writerCreated(ContactId c, BatchTransportWriter w) {
 			assert index != null;
-			dispatcher.dispatchWriter(index, c, w);
+			dispatcher.dispatchWriter(c, index, w);
 		}
 	}
 
@@ -307,7 +307,7 @@ class PluginManagerImpl implements PluginManager {
 		public void outgoingConnectionCreated(ContactId c,
 				StreamTransportConnection s) {
 			assert index != null;
-			dispatcher.dispatchOutgoingConnection(index, c, s);
+			dispatcher.dispatchOutgoingConnection(c, index, s);
 		}
 	}
 }

components/net/sf/briar/transport/ConnectionContextFactoryImpl.java

@@ -1,14 +1,31 @@
 package net.sf.briar.transport;
 
 import net.sf.briar.api.ContactId;
+import net.sf.briar.api.crypto.CryptoComponent;
 import net.sf.briar.api.protocol.TransportIndex;
 import net.sf.briar.api.transport.ConnectionContext;
 import net.sf.briar.api.transport.ConnectionContextFactory;
 
+import com.google.inject.Inject;
+
 class ConnectionContextFactoryImpl implements ConnectionContextFactory {
 
+	private final CryptoComponent crypto;
+
+	@Inject
+	ConnectionContextFactoryImpl(CryptoComponent crypto) {
+		this.crypto = crypto;
+	}
+
 	public ConnectionContext createConnectionContext(ContactId c,
-			TransportIndex i, long connection) {
-		return new ConnectionContextImpl(c, i, connection);
+			TransportIndex i, long connection, byte[] secret) {
+		return new ConnectionContextImpl(c, i, connection, secret);
+	}
+
+	public ConnectionContext createNextConnectionContext(ContactId c,
+			TransportIndex i, long connection, byte[] previousSecret) {
+		byte[] secret = crypto.deriveNextSecret(previousSecret, i.getInt(),
+				connection);
+		return new ConnectionContextImpl(c, i, connection, secret);
 	}
 }

components/net/sf/briar/transport/ConnectionContextImpl.java

@@ -9,12 +9,14 @@ class ConnectionContextImpl implements ConnectionContext {
 	private final ContactId contactId;
 	private final TransportIndex transportIndex;
 	private final long connectionNumber;
+	private final byte[] secret;
 
 	ConnectionContextImpl(ContactId contactId, TransportIndex transportIndex,
-			long connectionNumber) {
+			long connectionNumber, byte[] secret) {
 		this.contactId = contactId;
 		this.transportIndex = transportIndex;
 		this.connectionNumber = connectionNumber;
+		this.secret = secret;
 	}
 
 	public ContactId getContactId() {
@@ -28,4 +30,8 @@ class ConnectionContextImpl implements ConnectionContext {
 	public long getConnectionNumber() {
 		return connectionNumber;
 	}
+
+	public byte[] getSecret() {
+		return secret;
+	}
 }

components/net/sf/briar/transport/ConnectionDispatcherImpl.java

@@ -62,8 +62,7 @@ public class ConnectionDispatcherImpl implements ConnectionDispatcher {
 			r.dispose(false);
 			return;
 		}
-		batchConnFactory.createIncomingConnection(ctx.getTransportIndex(),
-				ctx.getContactId(), r, encryptedIv);
+		batchConnFactory.createIncomingConnection(ctx, r, encryptedIv);
 	}
 
 	private byte[] readIv(InputStream in) throws IOException {
@@ -77,9 +76,9 @@ public class ConnectionDispatcherImpl implements ConnectionDispatcher {
 		return b;
 	}
 
-	public void dispatchWriter(TransportIndex i, ContactId c,
+	public void dispatchWriter(ContactId c, TransportIndex i,
 			BatchTransportWriter w) {
-		batchConnFactory.createOutgoingConnection(i, c, w);
+		batchConnFactory.createOutgoingConnection(c, i, w);
 	}
 
 	public void dispatchIncomingConnection(TransportId t,
@@ -106,12 +105,11 @@ public class ConnectionDispatcherImpl implements ConnectionDispatcher {
 			s.dispose(false);
 			return;
 		}
-		streamConnFactory.createIncomingConnection(ctx.getTransportIndex(),
-				ctx.getContactId(), s, encryptedIv);
+		streamConnFactory.createIncomingConnection(ctx, s, encryptedIv);
 	}
 
-	public void dispatchOutgoingConnection(TransportIndex i, ContactId c,
+	public void dispatchOutgoingConnection(ContactId c, TransportIndex i,
 			StreamTransportConnection s) {
-		streamConnFactory.createOutgoingConnection(i, c, s);
+		streamConnFactory.createOutgoingConnection(c, i, s);
 	}
 }

components/net/sf/briar/transport/ConnectionReaderFactoryImpl.java

@@ -7,12 +7,13 @@ import javax.crypto.BadPaddingException;
 import javax.crypto.Cipher;
 import javax.crypto.IllegalBlockSizeException;
 import javax.crypto.Mac;
-import net.sf.briar.api.crypto.ErasableKey;
 
 import net.sf.briar.api.crypto.CryptoComponent;
-import net.sf.briar.api.protocol.TransportIndex;
+import net.sf.briar.api.crypto.ErasableKey;
+import net.sf.briar.api.transport.ConnectionContext;
 import net.sf.briar.api.transport.ConnectionReader;
 import net.sf.briar.api.transport.ConnectionReaderFactory;
+import net.sf.briar.util.ByteUtils;
 
 import com.google.inject.Inject;
 
@@ -26,10 +27,10 @@ class ConnectionReaderFactoryImpl implements ConnectionReaderFactory {
 	}
 
 	public ConnectionReader createConnectionReader(InputStream in,
-			TransportIndex i, byte[] encryptedIv, byte[] secret) {
+			ConnectionContext ctx, byte[] encryptedIv) {
 		// Decrypt the IV
 		Cipher ivCipher = crypto.getIvCipher();
-		ErasableKey ivKey = crypto.deriveIvKey(secret, true);
+		ErasableKey ivKey = crypto.deriveIvKey(ctx.getSecret(), true);
 		byte[] iv;
 		try {
 			ivCipher.init(Cipher.DECRYPT_MODE, ivKey);
@@ -42,27 +43,25 @@ class ConnectionReaderFactoryImpl implements ConnectionReaderFactory {
 			throw new IllegalArgumentException(badKey);
 		}
 		// Validate the IV
-		if(!IvEncoder.validateIv(iv, true, i))
+		if(!IvEncoder.validateIv(iv, true, ctx))
 			throw new IllegalArgumentException();
-		// Copy the connection number
-		long connection = IvEncoder.getConnectionNumber(iv);
-		return createConnectionReader(in, true, i, connection, secret);
+		return createConnectionReader(in, true, ctx);
 	}
 
 	public ConnectionReader createConnectionReader(InputStream in,
-			TransportIndex i, long connection, byte[] secret) {
-		return createConnectionReader(in, false, i, connection, secret);
+			ConnectionContext ctx) {
+		return createConnectionReader(in, false, ctx);
 	}
 
 	private ConnectionReader createConnectionReader(InputStream in,
-			boolean initiator, TransportIndex i, long connection,
-			byte[] secret) {
+			boolean initiator, ConnectionContext ctx) {
 		// Derive the keys and erase the secret
+		byte[] secret = ctx.getSecret();
 		ErasableKey frameKey = crypto.deriveFrameKey(secret, initiator);
 		ErasableKey macKey = crypto.deriveMacKey(secret, initiator);
-		for(int j = 0; j < secret.length; j++) secret[j] = 0;
+		ByteUtils.erase(secret);
 		// Create the decrypter
-		byte[] iv = IvEncoder.encodeIv(initiator, i, connection);
+		byte[] iv = IvEncoder.encodeIv(initiator, ctx);
 		Cipher frameCipher = crypto.getFrameCipher();
 		ConnectionDecrypter decrypter = new ConnectionDecrypterImpl(in, iv,
 				frameCipher, frameKey);

components/net/sf/briar/transport/ConnectionRecogniserImpl.java

@@ -8,25 +8,26 @@ import java.util.Collection;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.Map;
+import java.util.Map.Entry;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
 import javax.crypto.BadPaddingException;
 import javax.crypto.Cipher;
 import javax.crypto.IllegalBlockSizeException;
-import net.sf.briar.api.crypto.ErasableKey;
 
 import net.sf.briar.api.Bytes;
 import net.sf.briar.api.ContactId;
 import net.sf.briar.api.crypto.CryptoComponent;
+import net.sf.briar.api.crypto.ErasableKey;
 import net.sf.briar.api.db.DatabaseComponent;
 import net.sf.briar.api.db.DbException;
 import net.sf.briar.api.db.NoSuchContactException;
 import net.sf.briar.api.db.event.ContactRemovedEvent;
 import net.sf.briar.api.db.event.DatabaseEvent;
 import net.sf.briar.api.db.event.DatabaseListener;
-import net.sf.briar.api.db.event.TransportAddedEvent;
 import net.sf.briar.api.db.event.RemoteTransportsUpdatedEvent;
+import net.sf.briar.api.db.event.TransportAddedEvent;
 import net.sf.briar.api.protocol.Transport;
 import net.sf.briar.api.protocol.TransportId;
 import net.sf.briar.api.protocol.TransportIndex;
@@ -75,30 +76,29 @@ DatabaseListener {
 	}
 
 	private synchronized void calculateIvs(ContactId c) throws DbException {
-		byte[] secret = db.getSharedSecret(c, true);
-		ErasableKey ivKey = crypto.deriveIvKey(secret, true);
-		for(int i = 0; i < secret.length; i++) secret[i] = 0;
 		for(TransportId t : localTransportIds) {
 			TransportIndex i = db.getRemoteIndex(c, t);
 			if(i != null) {
 				ConnectionWindow w = db.getConnectionWindow(c, i);
-				calculateIvs(c, i, ivKey, w);
+				calculateIvs(c, i, w);
 			}
 		}
 	}
 
 	private synchronized void calculateIvs(ContactId c, TransportIndex i,
-			ErasableKey ivKey, ConnectionWindow w)
-	throws DbException {
-		for(Long unseen : w.getUnseen()) {
+			ConnectionWindow w) throws DbException {
+		for(Entry<Long, byte[]> e : w.getUnseen().entrySet()) {
+			long unseen = e.getKey();
+			byte[] secret = e.getValue();
+			ErasableKey ivKey = crypto.deriveIvKey(secret, true);
 			Bytes iv = new Bytes(encryptIv(i, unseen, ivKey));
-			expected.put(iv, new ConnectionContextImpl(c, i, unseen));
+			expected.put(iv, new ConnectionContextImpl(c, i, unseen, secret));
 		}
 	}
 
 	private synchronized byte[] encryptIv(TransportIndex i, long connection,
 			ErasableKey ivKey) {
-		byte[] iv = IvEncoder.encodeIv(true, i, connection);
+		byte[] iv = IvEncoder.encodeIv(true, i.getInt(), connection);
 		try {
 			ivCipher.init(Cipher.ENCRYPT_MODE, ivKey);
 			return ivCipher.doFinal(iv);
@@ -133,10 +133,7 @@ DatabaseListener {
 				TransportIndex i1 = ctx1.getTransportIndex();
 				if(c1.equals(c) && i1.equals(i)) it.remove();
 			}
-			byte[] secret = db.getSharedSecret(c, true);
-			ErasableKey ivKey = crypto.deriveIvKey(secret, true);
-			for(int j = 0; j < secret.length; j++) secret[j] = 0;
-			calculateIvs(c, i, ivKey, w);
+			calculateIvs(c, i, w);
 		} catch(NoSuchContactException e) {
 			// The contact was removed - clean up when we get the event
 		}
@@ -185,13 +182,10 @@ DatabaseListener {
 	private synchronized void calculateIvs(TransportId t) throws DbException {
 		for(ContactId c : db.getContacts()) {
 			try {
-				byte[] secret = db.getSharedSecret(c, true);
-				ErasableKey ivKey = crypto.deriveIvKey(secret, true);
-				for(int i = 0; i < secret.length; i++) secret[i] = 0;
 				TransportIndex i = db.getRemoteIndex(c, t);
 				if(i != null) {
 					ConnectionWindow w = db.getConnectionWindow(c, i);
-					calculateIvs(c, i, ivKey, w);
+					calculateIvs(c, i, w);
 				}
 			} catch(NoSuchContactException e) {
 				// The contact was removed - clean up when we get the event

components/net/sf/briar/transport/ConnectionWindowFactoryImpl.java

@@ -1,17 +1,30 @@
 package net.sf.briar.transport;
 
-import java.util.Collection;
+import java.util.Map;
 
+import net.sf.briar.api.crypto.CryptoComponent;
+import net.sf.briar.api.protocol.TransportIndex;
 import net.sf.briar.api.transport.ConnectionWindow;
 import net.sf.briar.api.transport.ConnectionWindowFactory;
 
+import com.google.inject.Inject;
+
 class ConnectionWindowFactoryImpl implements ConnectionWindowFactory {
 
-	public ConnectionWindow createConnectionWindow() {
-		return new ConnectionWindowImpl();
+	private final CryptoComponent crypto;
+
+	@Inject
+	ConnectionWindowFactoryImpl(CryptoComponent crypto) {
+		this.crypto = crypto;
 	}
 
-	public ConnectionWindow createConnectionWindow(Collection<Long> unseen) {
-		return new ConnectionWindowImpl(unseen);
+	public ConnectionWindow createConnectionWindow(TransportIndex i,
+			byte[] secret) {
+		return new ConnectionWindowImpl(crypto, i, secret);
+	}
+
+	public ConnectionWindow createConnectionWindow(TransportIndex i,
+			Map<Long, byte[]> unseen) {
+		return new ConnectionWindowImpl(crypto, i, unseen);
 	}
 }

components/net/sf/briar/transport/ConnectionWindowImpl.java

@@ -2,28 +2,38 @@ package net.sf.briar.transport;
 
 import static net.sf.briar.api.protocol.ProtocolConstants.CONNECTION_WINDOW_SIZE;
 
-import java.util.Collection;
-import java.util.Set;
-import java.util.TreeSet;
+import java.util.HashMap;
+import java.util.Map;
 
+import net.sf.briar.api.crypto.CryptoComponent;
+import net.sf.briar.api.protocol.TransportIndex;
 import net.sf.briar.api.transport.ConnectionWindow;
 import net.sf.briar.util.ByteUtils;
 
 class ConnectionWindowImpl implements ConnectionWindow {
 
-	private final Set<Long> unseen;
+	private final CryptoComponent crypto;
+	private final int index;
+	private final Map<Long, byte[]> unseen;
 
 	private long centre;
 
-	ConnectionWindowImpl() {
-		unseen = new TreeSet<Long>();
-		for(long l = 0; l < CONNECTION_WINDOW_SIZE / 2; l++) unseen.add(l);
+	ConnectionWindowImpl(CryptoComponent crypto, TransportIndex i,
+			byte[] secret) {
+		this.crypto = crypto;
+		index = i.getInt();
+		unseen = new HashMap<Long, byte[]>();
+		for(long l = 0; l < CONNECTION_WINDOW_SIZE / 2; l++) {
+			secret = crypto.deriveNextSecret(secret, index, l);
+			unseen.put(l, secret);
+		}
 		centre = 0;
 	}
 
-	ConnectionWindowImpl(Collection<Long> unseen) {
+	ConnectionWindowImpl(CryptoComponent crypto, TransportIndex i,
+			Map<Long, byte[]> unseen) {
 		long min = Long.MAX_VALUE, max = Long.MIN_VALUE;
-		for(long l : unseen) {
+		for(long l : unseen.keySet()) {
 			if(l < 0 || l > ByteUtils.MAX_32_BIT_UNSIGNED)
 				throw new IllegalArgumentException();
 			if(l < min) min = l;
@@ -31,15 +41,17 @@ class ConnectionWindowImpl implements ConnectionWindow {
 		}
 		if(max - min > CONNECTION_WINDOW_SIZE)
 			throw new IllegalArgumentException();
-		this.unseen = new TreeSet<Long>(unseen);
 		centre = max - CONNECTION_WINDOW_SIZE / 2 + 1;
 		for(long l = centre; l <= max; l++) {
-			if(!this.unseen.contains(l)) throw new IllegalArgumentException();
+			if(!unseen.containsKey(l)) throw new IllegalArgumentException();
 		}
+		this.crypto = crypto;
+		index = i.getInt();
+		this.unseen = unseen;
 	}
 
 	public boolean isSeen(long connection) {
-		return !unseen.contains(connection);
+		return !unseen.containsKey(connection);
 	}
 
 	public void setSeen(long connection) {
@@ -47,14 +59,26 @@ class ConnectionWindowImpl implements ConnectionWindow {
 		long top = getTop(centre);
 		if(connection < bottom || connection > top)
 			throw new IllegalArgumentException();
-		if(!unseen.remove(connection)) throw new IllegalArgumentException();
+		if(!unseen.containsKey(connection))
+			throw new IllegalArgumentException();
 		if(connection >= centre) {
 			centre = connection + 1;
 			long newBottom = getBottom(centre);
 			long newTop = getTop(centre);
-			for(long l = bottom; l < newBottom; l++) unseen.remove(l);
-			for(long l = top + 1; l <= newTop; l++) unseen.add(l);
+			for(long l = bottom; l < newBottom; l++) {
+				byte[] expired = unseen.remove(l);
+				if(expired != null) ByteUtils.erase(expired);
+			}
+			byte[] topSecret = unseen.get(top);
+			assert topSecret != null;
+			for(long l = top + 1; l <= newTop; l++) {
+				topSecret = crypto.deriveNextSecret(topSecret, index, l);
+				unseen.put(l, topSecret);
+			}
 		}
+		byte[] seen = unseen.remove(connection);
+		assert seen != null;
+		ByteUtils.erase(seen);
 	}
 
 	// Returns the lowest value contained in a window with the given centre
@@ -68,7 +92,7 @@ class ConnectionWindowImpl implements ConnectionWindow {
 				centre + CONNECTION_WINDOW_SIZE / 2 - 1);
 	}
 
-	public Collection<Long> getUnseen() {
+	public Map<Long, byte[]> getUnseen() {
 		return unseen;
 	}
 }

components/net/sf/briar/transport/ConnectionWriterFactoryImpl.java

@@ -7,12 +7,13 @@ import javax.crypto.BadPaddingException;
 import javax.crypto.Cipher;
 import javax.crypto.IllegalBlockSizeException;
 import javax.crypto.Mac;
-import net.sf.briar.api.crypto.ErasableKey;
 
 import net.sf.briar.api.crypto.CryptoComponent;
-import net.sf.briar.api.protocol.TransportIndex;
+import net.sf.briar.api.crypto.ErasableKey;
+import net.sf.briar.api.transport.ConnectionContext;
 import net.sf.briar.api.transport.ConnectionWriter;
 import net.sf.briar.api.transport.ConnectionWriterFactory;
+import net.sf.briar.util.ByteUtils;
 
 import com.google.inject.Inject;
 
@@ -26,17 +27,15 @@ class ConnectionWriterFactoryImpl implements ConnectionWriterFactory {
 	}
 
 	public ConnectionWriter createConnectionWriter(OutputStream out,
-			long capacity, TransportIndex i, long connection, byte[] secret) {
-		return createConnectionWriter(out, capacity, true, i, connection,
-				secret);
+			long capacity, ConnectionContext ctx) {
+		return createConnectionWriter(out, capacity, true, ctx);
 	}
 
 	public ConnectionWriter createConnectionWriter(OutputStream out,
-			long capacity, TransportIndex i, byte[] encryptedIv,
-			byte[] secret) {
+			long capacity, ConnectionContext ctx, byte[] encryptedIv) {
 		// Decrypt the IV
 		Cipher ivCipher = crypto.getIvCipher();
-		ErasableKey ivKey = crypto.deriveIvKey(secret, true);
+		ErasableKey ivKey = crypto.deriveIvKey(ctx.getSecret(), true);
 		byte[] iv;
 		try {
 			ivCipher.init(Cipher.DECRYPT_MODE, ivKey);
@@ -49,26 +48,23 @@ class ConnectionWriterFactoryImpl implements ConnectionWriterFactory {
 			throw new RuntimeException(badKey);
 		}
 		// Validate the IV
-		if(!IvEncoder.validateIv(iv, true, i))
+		if(!IvEncoder.validateIv(iv, true, ctx))
 			throw new IllegalArgumentException();
-		// Copy the connection number
-		long connection = IvEncoder.getConnectionNumber(iv);
-		return createConnectionWriter(out, capacity, false, i, connection,
-				secret);
+		return createConnectionWriter(out, capacity, false, ctx);
 	}
 
 	private ConnectionWriter createConnectionWriter(OutputStream out,
-			long capacity, boolean initiator, TransportIndex i, long connection,
-			byte[] secret) {
+			long capacity, boolean initiator, ConnectionContext ctx) {
 		// Derive the keys and erase the secret
+		byte[] secret = ctx.getSecret();
 		ErasableKey ivKey = crypto.deriveIvKey(secret, initiator);
 		ErasableKey frameKey = crypto.deriveFrameKey(secret, initiator);
 		ErasableKey macKey = crypto.deriveMacKey(secret, initiator);
-		for(int j = 0; j < secret.length; j++) secret[j] = 0;
+		ByteUtils.erase(secret);
 		// Create the encrypter
 		Cipher ivCipher = crypto.getIvCipher();
 		Cipher frameCipher = crypto.getFrameCipher();
-		byte[] iv = IvEncoder.encodeIv(initiator, i, connection);
+		byte[] iv = IvEncoder.encodeIv(initiator, ctx);
 		ConnectionEncrypter encrypter = new ConnectionEncrypterImpl(out,
 				capacity, iv, ivCipher, frameCipher, ivKey, frameKey);
 		// Create the writer

components/net/sf/briar/transport/IvEncoder.java

@@ -1,18 +1,22 @@
 package net.sf.briar.transport;
 
 import static net.sf.briar.api.transport.TransportConstants.IV_LENGTH;
-import net.sf.briar.api.protocol.TransportIndex;
+import net.sf.briar.api.transport.ConnectionContext;
 import net.sf.briar.util.ByteUtils;
 
 class IvEncoder {
 
-	static byte[] encodeIv(boolean initiator, TransportIndex i,
-			long connection) {
+	static byte[] encodeIv(boolean initiator, ConnectionContext ctx) {
+		return encodeIv(initiator, ctx.getTransportIndex().getInt(),
+				ctx.getConnectionNumber());
+	}
+
+	static byte[] encodeIv(boolean initiator, int index, long connection) {
 		byte[] iv = new byte[IV_LENGTH];
 		// Bit 31 is the initiator flag
 		if(initiator) iv[3] = 1;
-		// Encode the transport identifier as an unsigned 16-bit integer
-		ByteUtils.writeUint16(i.getInt(), iv, 4);
+		// Encode the transport index as an unsigned 16-bit integer
+		ByteUtils.writeUint16(index, iv, 4);
 		// Encode the connection number as an unsigned 32-bit integer
 		ByteUtils.writeUint32(connection, iv, 6);
 		return iv;
@@ -24,7 +28,14 @@ class IvEncoder {
 		ByteUtils.writeUint32(frame, iv, 10);
 	}
 
-	static boolean validateIv(byte[] iv, boolean initiator, TransportIndex i) {
+	static boolean validateIv(byte[] iv, boolean initiator,
+			ConnectionContext ctx) {
+		return validateIv(iv, initiator, ctx.getTransportIndex().getInt(),
+				ctx.getConnectionNumber());
+	}
+
+	static boolean validateIv(byte[] iv, boolean initiator, int index,
+			long connection) {
 		if(iv.length != IV_LENGTH) return false;
 		// Check that the reserved bits are all zero
 		for(int j = 0; j < 2; j++) if(iv[j] != 0) return false;
@@ -32,8 +43,10 @@ class IvEncoder {
 		for(int j = 10; j < iv.length; j++) if(iv[j] != 0) return false;
 		// Check that the initiator flag matches
 		if(initiator != getInitiatorFlag(iv)) return false;
-		// Check that the transport ID matches
-		if(i.getInt() != getTransportId(iv)) return false;
+		// Check that the transport index matches
+		if(index != getTransportIndex(iv)) return false;
+		// Check that the connection number matches
+		if(connection != getConnectionNumber(iv)) return false;
 		// The IV is valid
 		return true;
 	}
@@ -43,7 +56,7 @@ class IvEncoder {
 		return (iv[3] & 1) == 1;
 	}
 
-	static int getTransportId(byte[] iv) {
+	static int getTransportIndex(byte[] iv) {
 		if(iv.length != IV_LENGTH) throw new IllegalArgumentException();
 		return ByteUtils.readUint16(iv, 4);
 	}

components/net/sf/briar/transport/batch/BatchConnectionFactoryImpl.java

@@ -8,6 +8,7 @@ import net.sf.briar.api.protocol.writers.ProtocolWriterFactory;
 import net.sf.briar.api.transport.BatchConnectionFactory;
 import net.sf.briar.api.transport.BatchTransportReader;
 import net.sf.briar.api.transport.BatchTransportWriter;
+import net.sf.briar.api.transport.ConnectionContext;
 import net.sf.briar.api.transport.ConnectionReaderFactory;
 import net.sf.briar.api.transport.ConnectionWriterFactory;
 
@@ -33,11 +34,10 @@ class BatchConnectionFactoryImpl implements BatchConnectionFactory {
 		this.protoWriterFactory = protoWriterFactory;
 	}
 
-	public void createIncomingConnection(TransportIndex i, ContactId c,
+	public void createIncomingConnection(ConnectionContext ctx,
 			BatchTransportReader r, byte[] encryptedIv) {
 		final IncomingBatchConnection conn = new IncomingBatchConnection(
-				connReaderFactory, db, protoReaderFactory, i, c, r,
-				encryptedIv);
+				connReaderFactory, db, protoReaderFactory, ctx, r, encryptedIv);
 		Runnable read = new Runnable() {
 			public void run() {
 				conn.read();
@@ -46,10 +46,10 @@ class BatchConnectionFactoryImpl implements BatchConnectionFactory {
 		new Thread(read).start();
 	}
 
-	public void createOutgoingConnection(TransportIndex i, ContactId c,
+	public void createOutgoingConnection(ContactId c, TransportIndex i,
 			BatchTransportWriter w) {
 		final OutgoingBatchConnection conn = new OutgoingBatchConnection(
-				connWriterFactory, db, protoWriterFactory, i, c, w);
+				connWriterFactory, db, protoWriterFactory, c, i, w);
 		Runnable write = new Runnable() {
 			public void run() {
 				conn.write();

components/net/sf/briar/transport/batch/IncomingBatchConnection.java

@@ -13,9 +13,9 @@ import net.sf.briar.api.protocol.Batch;
 import net.sf.briar.api.protocol.ProtocolReader;
 import net.sf.briar.api.protocol.ProtocolReaderFactory;
 import net.sf.briar.api.protocol.SubscriptionUpdate;
-import net.sf.briar.api.protocol.TransportIndex;
 import net.sf.briar.api.protocol.TransportUpdate;
 import net.sf.briar.api.transport.BatchTransportReader;
+import net.sf.briar.api.transport.ConnectionContext;
 import net.sf.briar.api.transport.ConnectionReader;
 import net.sf.briar.api.transport.ConnectionReaderFactory;
 
@@ -27,46 +27,43 @@ class IncomingBatchConnection {
 	private final ConnectionReaderFactory connFactory;
 	private final DatabaseComponent db;
 	private final ProtocolReaderFactory protoFactory;
-	private final TransportIndex transportIndex;
-	private final ContactId contactId;
+	private final ConnectionContext ctx;
 	private final BatchTransportReader reader;
 	private final byte[] encryptedIv;
 
 	IncomingBatchConnection(ConnectionReaderFactory connFactory,
 			DatabaseComponent db, ProtocolReaderFactory protoFactory,
-			TransportIndex transportIndex, ContactId contactId,
-			BatchTransportReader reader, byte[] encryptedIv) {
+			ConnectionContext ctx, BatchTransportReader reader,
+			byte[] encryptedIv) {
 		this.connFactory = connFactory;
 		this.db = db;
 		this.protoFactory = protoFactory;
-		this.transportIndex = transportIndex;
-		this.contactId = contactId;
+		this.ctx = ctx;
 		this.reader = reader;
 		this.encryptedIv = encryptedIv;
 	}
 
 	void read() {
 		try {
-			byte[] secret = db.getSharedSecret(contactId, true);
 			ConnectionReader conn = connFactory.createConnectionReader(
-					reader.getInputStream(), transportIndex, encryptedIv,
-					secret);
+					reader.getInputStream(), ctx, encryptedIv);
 			ProtocolReader proto = protoFactory.createProtocolReader(
 					conn.getInputStream());
+			ContactId c = ctx.getContactId();
 			// Read packets until EOF
 			while(!proto.eof()) {
 				if(proto.hasAck()) {
 					Ack a = proto.readAck();
-					db.receiveAck(contactId, a);
+					db.receiveAck(c, a);
 				} else if(proto.hasBatch()) {
 					Batch b = proto.readBatch();
-					db.receiveBatch(contactId, b);
+					db.receiveBatch(c, b);
 				} else if(proto.hasSubscriptionUpdate()) {
 					SubscriptionUpdate s = proto.readSubscriptionUpdate();
-					db.receiveSubscriptionUpdate(contactId, s);
+					db.receiveSubscriptionUpdate(c, s);
 				} else if(proto.hasTransportUpdate()) {
 					TransportUpdate t = proto.readTransportUpdate();
-					db.receiveTransportUpdate(contactId, t);
+					db.receiveTransportUpdate(c, t);
 				} else {
 					throw new FormatException();
 				}

components/net/sf/briar/transport/batch/OutgoingBatchConnection.java

@@ -29,30 +29,28 @@ class OutgoingBatchConnection {
 	private final ConnectionWriterFactory connFactory;
 	private final DatabaseComponent db;
 	private final ProtocolWriterFactory protoFactory;
-	private final TransportIndex transportIndex;
 	private final ContactId contactId;
+	private final TransportIndex transportIndex;
 	private final BatchTransportWriter writer;
 
 	OutgoingBatchConnection(ConnectionWriterFactory connFactory,
 			DatabaseComponent db, ProtocolWriterFactory protoFactory,
-			TransportIndex transportIndex, ContactId contactId,
+			ContactId contactId, TransportIndex transportIndex,
 			BatchTransportWriter writer) {
 		this.connFactory = connFactory;
 		this.db = db;
 		this.protoFactory = protoFactory;
-		this.transportIndex = transportIndex;
 		this.contactId = contactId;
+		this.transportIndex = transportIndex;
 		this.writer = writer;
 	}
 
 	void write() {
 		try {
-			byte[] secret = db.getSharedSecret(contactId, false);
-			ConnectionContext ctx =
-				db.getConnectionContext(contactId, transportIndex);
+			ConnectionContext ctx = db.getConnectionContext(contactId,
+					transportIndex);
 			ConnectionWriter conn = connFactory.createConnectionWriter(
-					writer.getOutputStream(), writer.getCapacity(),
-					transportIndex, ctx.getConnectionNumber(), secret);
+					writer.getOutputStream(), writer.getCapacity(), ctx);
 			OutputStream out = conn.getOutputStream();
 			// There should be enough space for a packet
 			long capacity = conn.getRemainingCapacity();

components/net/sf/briar/transport/stream/IncomingStreamConnection.java

@@ -2,12 +2,11 @@ package net.sf.briar.transport.stream;
 
 import java.io.IOException;
 
-import net.sf.briar.api.ContactId;
 import net.sf.briar.api.db.DatabaseComponent;
 import net.sf.briar.api.db.DbException;
 import net.sf.briar.api.protocol.ProtocolReaderFactory;
-import net.sf.briar.api.protocol.TransportIndex;
 import net.sf.briar.api.protocol.writers.ProtocolWriterFactory;
+import net.sf.briar.api.transport.ConnectionContext;
 import net.sf.briar.api.transport.ConnectionReader;
 import net.sf.briar.api.transport.ConnectionReaderFactory;
 import net.sf.briar.api.transport.ConnectionWriter;
@@ -16,35 +15,32 @@ import net.sf.briar.api.transport.StreamTransportConnection;
 
 public class IncomingStreamConnection extends StreamConnection {
 
+	private final ConnectionContext ctx;
 	private final byte[] encryptedIv;
 
 	IncomingStreamConnection(ConnectionReaderFactory connReaderFactory,
 			ConnectionWriterFactory connWriterFactory, DatabaseComponent db,
 			ProtocolReaderFactory protoReaderFactory,
 			ProtocolWriterFactory protoWriterFactory,
-			TransportIndex transportIndex, ContactId contactId,
-			StreamTransportConnection connection,
+			ConnectionContext ctx, StreamTransportConnection connection,
 			byte[] encryptedIv) {
 		super(connReaderFactory, connWriterFactory, db, protoReaderFactory,
-				protoWriterFactory, transportIndex, contactId, connection);
+				protoWriterFactory, ctx.getContactId(), connection);
+		this.ctx = ctx;
 		this.encryptedIv = encryptedIv;
 	}
 
 	@Override
 	protected ConnectionReader createConnectionReader() throws DbException,
 	IOException {
-		byte[] secret = db.getSharedSecret(contactId, true);
 		return connReaderFactory.createConnectionReader(
-				connection.getInputStream(), transportIndex, encryptedIv,
-				secret);
+				connection.getInputStream(), ctx, encryptedIv);
 	}
 
 	@Override
 	protected ConnectionWriter createConnectionWriter() throws DbException,
 	IOException {
-		byte[] secret = db.getSharedSecret(contactId, false);
 		return connWriterFactory.createConnectionWriter(
-				connection.getOutputStream(), Long.MAX_VALUE, transportIndex,
-				encryptedIv, secret);
+				connection.getOutputStream(), Long.MAX_VALUE, ctx, encryptedIv);
 	}
 }

components/net/sf/briar/transport/stream/OutgoingStreamConnection.java

@@ -17,43 +17,40 @@ import net.sf.briar.api.transport.StreamTransportConnection;
 
 public class OutgoingStreamConnection extends StreamConnection {
 
+	private final TransportIndex transportIndex;
+
 	private ConnectionContext ctx = null; // Locking: this
 
 	OutgoingStreamConnection(ConnectionReaderFactory connReaderFactory,
 			ConnectionWriterFactory connWriterFactory, DatabaseComponent db,
 			ProtocolReaderFactory protoReaderFactory,
-			ProtocolWriterFactory protoWriterFactory,
-			TransportIndex transportIndex, ContactId contactId,
+			ProtocolWriterFactory protoWriterFactory, ContactId contactId,
+			TransportIndex transportIndex,
 			StreamTransportConnection connection) {
 		super(connReaderFactory, connWriterFactory, db, protoReaderFactory,
-				protoWriterFactory, transportIndex, contactId, connection);
+				protoWriterFactory, contactId, connection);
+		this.transportIndex = transportIndex;
 	}
 
 	@Override
 	protected ConnectionReader createConnectionReader() throws DbException,
 	IOException {
 		synchronized(this) {
-			if(ctx == null) {
+			if(ctx == null)
 				ctx = db.getConnectionContext(contactId, transportIndex);
-			}
 		}
-		byte[] secret = db.getSharedSecret(contactId, true);
 		return connReaderFactory.createConnectionReader(
-				connection.getInputStream(), transportIndex,
-				ctx.getConnectionNumber(), secret);
+				connection.getInputStream(), ctx);
 	}
 
 	@Override
 	protected ConnectionWriter createConnectionWriter() throws DbException,
 	IOException {
 		synchronized(this) {
-			if(ctx == null) {
+			if(ctx == null)
 				ctx = db.getConnectionContext(contactId, transportIndex);
-			}
 		}
-		byte[] secret = db.getSharedSecret(contactId, false);
 		return connWriterFactory.createConnectionWriter(
-				connection.getOutputStream(), Long.MAX_VALUE, transportIndex,
-				ctx.getConnectionNumber(), secret);
+				connection.getOutputStream(), Long.MAX_VALUE, ctx);
 	}
 }

components/net/sf/briar/transport/stream/StreamConnection.java

@@ -29,7 +29,6 @@ import net.sf.briar.api.protocol.ProtocolReader;
 import net.sf.briar.api.protocol.ProtocolReaderFactory;
 import net.sf.briar.api.protocol.Request;
 import net.sf.briar.api.protocol.SubscriptionUpdate;
-import net.sf.briar.api.protocol.TransportIndex;
 import net.sf.briar.api.protocol.TransportUpdate;
 import net.sf.briar.api.protocol.writers.AckWriter;
 import net.sf.briar.api.protocol.writers.BatchWriter;
@@ -56,7 +55,6 @@ abstract class StreamConnection implements DatabaseListener {
 	protected final DatabaseComponent db;
 	protected final ProtocolReaderFactory protoReaderFactory;
 	protected final ProtocolWriterFactory protoWriterFactory;
-	protected final TransportIndex transportIndex;
 	protected final ContactId contactId;
 	protected final StreamTransportConnection connection;
 
@@ -69,15 +67,13 @@ abstract class StreamConnection implements DatabaseListener {
 	StreamConnection(ConnectionReaderFactory connReaderFactory,
 			ConnectionWriterFactory connWriterFactory, DatabaseComponent db,
 			ProtocolReaderFactory protoReaderFactory,
-			ProtocolWriterFactory protoWriterFactory,
-			TransportIndex transportIndex, ContactId contactId,
+			ProtocolWriterFactory protoWriterFactory, ContactId contactId,
 			StreamTransportConnection connection) {
 		this.connReaderFactory = connReaderFactory;
 		this.connWriterFactory = connWriterFactory;
 		this.db = db;
 		this.protoReaderFactory = protoReaderFactory;
 		this.protoWriterFactory = protoWriterFactory;
-		this.transportIndex = transportIndex;
 		this.contactId = contactId;
 		this.connection = connection;
 	}

components/net/sf/briar/transport/stream/StreamConnectionFactoryImpl.java

@@ -5,6 +5,7 @@ import net.sf.briar.api.db.DatabaseComponent;
 import net.sf.briar.api.protocol.ProtocolReaderFactory;
 import net.sf.briar.api.protocol.TransportIndex;
 import net.sf.briar.api.protocol.writers.ProtocolWriterFactory;
+import net.sf.briar.api.transport.ConnectionContext;
 import net.sf.briar.api.transport.ConnectionReaderFactory;
 import net.sf.briar.api.transport.ConnectionWriterFactory;
 import net.sf.briar.api.transport.StreamConnectionFactory;
@@ -32,11 +33,11 @@ public class StreamConnectionFactoryImpl implements StreamConnectionFactory {
 		this.protoWriterFactory = protoWriterFactory;
 	}
 
-	public void createIncomingConnection(TransportIndex i, ContactId c,
+	public void createIncomingConnection(ConnectionContext ctx,
 			StreamTransportConnection s, byte[] encryptedIv) {
 		final StreamConnection conn = new IncomingStreamConnection(
 				connReaderFactory, connWriterFactory, db, protoReaderFactory,
-				protoWriterFactory, i, c, s, encryptedIv);
+				protoWriterFactory, ctx, s, encryptedIv);
 		Runnable write = new Runnable() {
 			public void run() {
 				conn.write();
@@ -51,11 +52,11 @@ public class StreamConnectionFactoryImpl implements StreamConnectionFactory {
 		new Thread(read).start();
 	}
 
-	public void createOutgoingConnection(TransportIndex i, ContactId c,
+	public void createOutgoingConnection(ContactId c, TransportIndex i,
 			StreamTransportConnection s) {
 		final StreamConnection conn = new OutgoingStreamConnection(
 				connReaderFactory, connWriterFactory, db, protoReaderFactory,
-				protoWriterFactory, i, c, s);
+				protoWriterFactory, c, i, s);
 		Runnable write = new Runnable() {
 			public void run() {
 				conn.write();