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.

api/net/sf/briar/api/crypto/CryptoComponent.java

@@ -15,7 +15,7 @@ public interface CryptoComponent {
 
 	ErasableKey deriveMacKey(byte[] secret, boolean initiator);
 
-	byte[] deriveNextSecret(byte[] secret, long connection);
+	byte[] deriveNextSecret(byte[] secret, int index, long connection);
 
 	KeyPair generateKeyPair();
 

api/net/sf/briar/api/db/DatabaseComponent.java

@@ -57,8 +57,7 @@ public interface DatabaseComponent {
 	 * Adds a new contact to the database with the given secrets and returns an
 	 * ID for the contact.
 	 */
-	ContactId addContact(byte[] incomingSecret, byte[] outgoingSecret)
-	throws DbException;
+	ContactId addContact(byte[] inSecret, byte[] outSecret) throws DbException;
 
 	/** Adds a locally generated group message to the database. */
 	void addLocalGroupMessage(Message m) throws DbException;
@@ -160,9 +159,6 @@ public interface DatabaseComponent {
 	Map<ContactId, TransportProperties> getRemoteProperties(TransportId t)
 	throws DbException;
 
-	/** Returns the secret shared with the given contact. */
-	byte[] getSharedSecret(ContactId c, boolean incoming) throws DbException;
-
 	/** Returns the set of groups to which the user subscribes. */
 	Collection<Group> getSubscriptions() throws DbException;
 

api/net/sf/briar/api/transport/BatchConnectionFactory.java

@@ -5,9 +5,9 @@ import net.sf.briar.api.protocol.TransportIndex;
 
 public interface BatchConnectionFactory {
 
-	void createIncomingConnection(TransportIndex i, ContactId c,
+	void createIncomingConnection(ConnectionContext ctx,
 			BatchTransportReader r, byte[] encryptedIv);
 
-	void createOutgoingConnection(TransportIndex i, ContactId c,
+	void createOutgoingConnection(ContactId c, TransportIndex i,
 			BatchTransportWriter w);
 }

api/net/sf/briar/api/transport/ConnectionContext.java

@@ -10,4 +10,6 @@ public interface ConnectionContext {
 	TransportIndex getTransportIndex();
 
 	long getConnectionNumber();
+
+	byte[] getSecret();
 }

api/net/sf/briar/api/transport/ConnectionContextFactory.java

@@ -6,5 +6,8 @@ import net.sf.briar.api.protocol.TransportIndex;
 public interface ConnectionContextFactory {
 
 	ConnectionContext createConnectionContext(ContactId c, TransportIndex i,
-			long connection);
+			long connection, byte[] secret);
+
+	ConnectionContext createNextConnectionContext(ContactId c, TransportIndex i,
+			long connection, byte[] previousSecret);
 }

api/net/sf/briar/api/transport/ConnectionDispatcher.java

@@ -8,10 +8,10 @@ public interface ConnectionDispatcher {
 
 	void dispatchReader(TransportId t, BatchTransportReader r);
 
-	void dispatchWriter(TransportIndex i, ContactId c, BatchTransportWriter w);
+	void dispatchWriter(ContactId c, TransportIndex i, BatchTransportWriter w);
 
 	void dispatchIncomingConnection(TransportId t, StreamTransportConnection s);
 
-	void dispatchOutgoingConnection(TransportIndex i, ContactId c,
+	void dispatchOutgoingConnection(ContactId c, TransportIndex i,
 			StreamTransportConnection s);
 }

api/net/sf/briar/api/transport/ConnectionReaderFactory.java

@@ -2,22 +2,19 @@ package net.sf.briar.api.transport;
 
 import java.io.InputStream;
 
-import net.sf.briar.api.protocol.TransportIndex;
-
 public interface ConnectionReaderFactory {
 
 	/**
 	 * Creates a connection reader for a batch-mode connection or the
-	 * initiator's side of a stream-mode connection. The secret is erased before
-	 * returning.
+	 * initiator's side of a stream-mode connection.
 	 */
-	ConnectionReader createConnectionReader(InputStream in, TransportIndex i,
-			byte[] encryptedIv, byte[] secret);
+	ConnectionReader createConnectionReader(InputStream in,
+			ConnectionContext ctx, byte[] encryptedIv);
 
 	/**
 	 * Creates a connection reader for the responder's side of a stream-mode
-	 * connection. The secret is erased before returning.
+	 * connection.
 	 */
-	ConnectionReader createConnectionReader(InputStream in, TransportIndex i,
-			long connection, byte[] secret);
+	ConnectionReader createConnectionReader(InputStream in,
+			ConnectionContext ctx);
 }

api/net/sf/briar/api/transport/ConnectionWindow.java

@@ -1,6 +1,6 @@
 package net.sf.briar.api.transport;
 
-import java.util.Collection;
+import java.util.Map;
 
 public interface ConnectionWindow {
 
@@ -8,5 +8,5 @@ public interface ConnectionWindow {
 
 	void setSeen(long connection);
 
-	Collection<Long> getUnseen();
+	Map<Long, byte[]> getUnseen();
 }

api/net/sf/briar/api/transport/ConnectionWindowFactory.java

@@ -1,10 +1,13 @@
 package net.sf.briar.api.transport;
 
-import java.util.Collection;
+import java.util.Map;
+
+import net.sf.briar.api.protocol.TransportIndex;
 
 public interface ConnectionWindowFactory {
 
-	ConnectionWindow createConnectionWindow();
+	ConnectionWindow createConnectionWindow(TransportIndex i, byte[] secret);
 
-	ConnectionWindow createConnectionWindow(Collection<Long> unseen);
+	ConnectionWindow createConnectionWindow(TransportIndex i,
+			Map<Long, byte[]> unseen);
 }

api/net/sf/briar/api/transport/ConnectionWriterFactory.java

@@ -2,22 +2,19 @@ package net.sf.briar.api.transport;
 
 import java.io.OutputStream;
 
-import net.sf.briar.api.protocol.TransportIndex;
-
 public interface ConnectionWriterFactory {
 
 	/**
 	 * Creates a connection writer for a batch-mode connection or the
-	 * initiator's side of a stream-mode connection. The secret is erased before
-	 * returning.
+	 * initiator's side of a stream-mode connection.
 	 */
 	ConnectionWriter createConnectionWriter(OutputStream out, long capacity,
-			TransportIndex i, long connection, byte[] secret);
+			ConnectionContext ctx);
 
 	/**
 	 * Creates a connection writer for the responder's side of a stream-mode
-	 * connection. The secret is erased before returning.
+	 * connection.
 	 */
 	ConnectionWriter createConnectionWriter(OutputStream out, long capacity,
-			TransportIndex i, byte[] encryptedIv, byte[] secret);
+			ConnectionContext ctx, byte[] encryptedIv);
 }

api/net/sf/briar/api/transport/StreamConnectionFactory.java

@@ -5,9 +5,9 @@ import net.sf.briar.api.protocol.TransportIndex;
 
 public interface StreamConnectionFactory {
 
-	void createIncomingConnection(TransportIndex i, ContactId c,
+	void createIncomingConnection(ConnectionContext ctx,
 			StreamTransportConnection s, byte[] encryptedIv);
 
-	void createOutgoingConnection(TransportIndex i, ContactId c,
+	void createOutgoingConnection(ContactId c, TransportIndex i,
 			StreamTransportConnection s);
 }