Transport properties client. #229

2026-02-19 06:09:55 +01:00 · 2016-01-22 11:32:39 +00:00
parent baa580c6f4
commit 88475bdd54
66 changed files with 748 additions and 436 deletions
--- a/briar-core/src/org/briarproject/crypto/CryptoModule.java
+++ b/briar-core/src/org/briarproject/crypto/CryptoModule.java
@@ -10,6 +10,7 @@ import org.briarproject.api.crypto.StreamDecrypterFactory;
 import org.briarproject.api.crypto.StreamEncrypterFactory;
 import org.briarproject.api.lifecycle.LifecycleManager;

+import java.security.SecureRandom;
 import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.Executor;
 import java.util.concurrent.ExecutorService;
@@ -57,4 +58,9 @@ public class CryptoModule extends AbstractModule {
 		lifecycleManager.registerForShutdown(cryptoExecutor);
 		return cryptoExecutor;
 	}
+
+	@Provides
+	SecureRandom getSecureRandom(CryptoComponent crypto) {
+		return crypto.getSecureRandom();
+	}
 }
--- a/briar-core/src/org/briarproject/db/Database.java
+++ b/briar-core/src/org/briarproject/db/Database.java
@@ -1,6 +1,5 @@
 package org.briarproject.db;

-import org.briarproject.api.Settings;
 import org.briarproject.api.TransportId;
 import org.briarproject.api.contact.Contact;
 import org.briarproject.api.contact.ContactId;
@@ -10,6 +9,7 @@ import org.briarproject.api.db.StorageStatus;
 import org.briarproject.api.identity.Author;
 import org.briarproject.api.identity.AuthorId;
 import org.briarproject.api.identity.LocalAuthor;
+import org.briarproject.api.settings.Settings;
 import org.briarproject.api.sync.ClientId;
 import org.briarproject.api.sync.Group;
 import org.briarproject.api.sync.GroupId;
--- a/briar-core/src/org/briarproject/db/DatabaseComponentImpl.java
+++ b/briar-core/src/org/briarproject/db/DatabaseComponentImpl.java
@@ -1,6 +1,5 @@
 package org.briarproject.db;

-import org.briarproject.api.Settings;
 import org.briarproject.api.TransportId;
 import org.briarproject.api.contact.Contact;
 import org.briarproject.api.contact.ContactId;
@@ -35,6 +34,7 @@ import org.briarproject.api.identity.Author;
 import org.briarproject.api.identity.AuthorId;
 import org.briarproject.api.identity.LocalAuthor;
 import org.briarproject.api.lifecycle.ShutdownManager;
+import org.briarproject.api.settings.Settings;
 import org.briarproject.api.sync.Ack;
 import org.briarproject.api.sync.ClientId;
 import org.briarproject.api.sync.Group;
--- a/briar-core/src/org/briarproject/db/DatabaseConstants.java
+++ b/briar-core/src/org/briarproject/db/DatabaseConstants.java
@@ -1,5 +1,7 @@
 package org.briarproject.db;

+import org.briarproject.api.settings.Settings;
+
 interface DatabaseConstants {

 	/**
@@ -8,4 +10,34 @@ interface DatabaseConstants {
 	 * limit is reached, additional offers will not be stored.
 	 */
 	int MAX_OFFERED_MESSAGES = 1000;
+
+	/**
+	 * The namespace of the {@link Settings Settings}
+	 * where the database schema version is stored.
+	 */
+	String DB_SETTINGS_NAMESPACE = "db";
+
+	/**
+	 * The {@link Settings Settings} key under which the
+	 * database schema version is stored.
+	 */
+	String SCHEMA_VERSION_KEY = "schemaVersion";
+
+	/**
+	 * The {@link Settings Settings} key under which the
+	 * minimum supported database schema version is stored.
+	 */
+	String MIN_SCHEMA_VERSION_KEY = "minSchemaVersion";
+
+	/**
+	 * The namespace of the {@link Settings Settings}
+	 * where the unique device ID is stored.
+	 */
+	String DEVICE_SETTINGS_NAMESPACE = "device";
+
+	/**
+	 * The {@link Settings Settings} key under which the
+	 * unique device ID is stored.
+	 */
+	String DEVICE_ID_KEY = "deviceId";
 }
--- a/briar-core/src/org/briarproject/db/DatabaseModule.java
+++ b/briar-core/src/org/briarproject/db/DatabaseModule.java
@@ -9,8 +9,9 @@ import org.briarproject.api.db.DatabaseExecutor;
 import org.briarproject.api.event.EventBus;
 import org.briarproject.api.lifecycle.LifecycleManager;
 import org.briarproject.api.lifecycle.ShutdownManager;
-import org.briarproject.system.SystemClock;
+import org.briarproject.api.system.Clock;

+import java.security.SecureRandom;
 import java.sql.Connection;
 import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.Executor;
@@ -39,13 +40,12 @@ public class DatabaseModule extends AbstractModule {
 	}

 	@Override
-	protected void configure() {
-		// Nothing to bind
-	}
+	protected void configure() {}

 	@Provides @Singleton
-	Database<Connection> getDatabase(DatabaseConfig config) {
-		return new H2Database(config, new SystemClock());
+	Database<Connection> getDatabase(DatabaseConfig config,
+			SecureRandom random, Clock clock) {
+		return new H2Database(config, random, clock);
 	}

 	@Provides @Singleton
--- a/briar-core/src/org/briarproject/db/H2Database.java
+++ b/briar-core/src/org/briarproject/db/H2Database.java
@@ -6,6 +6,7 @@ import org.briarproject.api.system.Clock;
 import org.briarproject.util.StringUtils;

 import java.io.File;
+import java.security.SecureRandom;
 import java.sql.Connection;
 import java.sql.DriverManager;
 import java.sql.SQLException;
@@ -25,13 +26,13 @@ class H2Database extends JdbcDatabase {
 	private final String url;

 	@Inject
-	H2Database(DatabaseConfig config, Clock clock) {
-		super(HASH_TYPE, BINARY_TYPE, COUNTER_TYPE, SECRET_TYPE, clock);
+	H2Database(DatabaseConfig config, SecureRandom random, Clock clock) {
+		super(HASH_TYPE, BINARY_TYPE, COUNTER_TYPE, SECRET_TYPE, random, clock);
 		this.config = config;
 		File dir = config.getDatabaseDirectory();
 		String path = new File(dir, "db").getAbsolutePath();
 		url = "jdbc:h2:split:" + path + ";CIPHER=AES;MULTI_THREADED=1"
-				+ ";DB_CLOSE_ON_EXIT=false";
+				+ ";WRITE_DELAY=0;DB_CLOSE_ON_EXIT=false";
 	}

 	public boolean open() throws DbException {
--- a/briar-core/src/org/briarproject/db/JdbcDatabase.java
+++ b/briar-core/src/org/briarproject/db/JdbcDatabase.java
@@ -1,7 +1,7 @@
 package org.briarproject.db;

-import org.briarproject.api.Settings;
 import org.briarproject.api.TransportId;
+import org.briarproject.api.UniqueId;
 import org.briarproject.api.contact.Contact;
 import org.briarproject.api.contact.ContactId;
 import org.briarproject.api.crypto.SecretKey;
@@ -12,6 +12,7 @@ import org.briarproject.api.db.StorageStatus;
 import org.briarproject.api.identity.Author;
 import org.briarproject.api.identity.AuthorId;
 import org.briarproject.api.identity.LocalAuthor;
+import org.briarproject.api.settings.Settings;
 import org.briarproject.api.sync.ClientId;
 import org.briarproject.api.sync.Group;
 import org.briarproject.api.sync.GroupId;
@@ -24,7 +25,9 @@ import org.briarproject.api.system.Clock;
 import org.briarproject.api.transport.IncomingKeys;
 import org.briarproject.api.transport.OutgoingKeys;
 import org.briarproject.api.transport.TransportKeys;
+import org.briarproject.util.StringUtils;

+import java.security.SecureRandom;
 import java.sql.Connection;
 import java.sql.PreparedStatement;
 import java.sql.ResultSet;
@@ -53,6 +56,11 @@ import static org.briarproject.api.sync.SyncConstants.MAX_SUBSCRIPTIONS;
 import static org.briarproject.api.sync.ValidationManager.Status.INVALID;
 import static org.briarproject.api.sync.ValidationManager.Status.UNKNOWN;
 import static org.briarproject.api.sync.ValidationManager.Status.VALID;
+import static org.briarproject.db.DatabaseConstants.DB_SETTINGS_NAMESPACE;
+import static org.briarproject.db.DatabaseConstants.DEVICE_ID_KEY;
+import static org.briarproject.db.DatabaseConstants.DEVICE_SETTINGS_NAMESPACE;
+import static org.briarproject.db.DatabaseConstants.MIN_SCHEMA_VERSION_KEY;
+import static org.briarproject.db.DatabaseConstants.SCHEMA_VERSION_KEY;
 import static org.briarproject.db.ExponentialBackoff.calculateExpiry;

 /**
@@ -61,8 +69,8 @@ import static org.briarproject.db.ExponentialBackoff.calculateExpiry;
 */
 abstract class JdbcDatabase implements Database<Connection> {

-	private static final int SCHEMA_VERSION = 17;
-	private static final int MIN_SCHEMA_VERSION = 17;
+	private static final int SCHEMA_VERSION = 18;
+	private static final int MIN_SCHEMA_VERSION = 18;

 	private static final String CREATE_SETTINGS =
 			"CREATE TABLE settings"
@@ -244,6 +252,7 @@ abstract class JdbcDatabase implements Database<Connection> {

 	// Different database libraries use different names for certain types
 	private final String hashType, binaryType, counterType, secretType;
+	private final SecureRandom random;
 	private final Clock clock;

 	private final LinkedList<Connection> connections =
@@ -260,11 +269,12 @@ abstract class JdbcDatabase implements Database<Connection> {
 	private final Condition connectionsChanged = connectionsLock.newCondition();

 	JdbcDatabase(String hashType, String binaryType, String counterType,
-			String secretType, Clock clock) {
+			String secretType, SecureRandom random, Clock clock) {
 		this.hashType = hashType;
 		this.binaryType = binaryType;
 		this.counterType = counterType;
 		this.secretType = secretType;
+		this.random = random;
 		this.clock = clock;
 	}

@@ -283,6 +293,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			} else {
 				createTables(txn);
 				storeSchemaVersion(txn);
+				storeDeviceId(txn);
 			}
 			commitTransaction(txn);
 		} catch (DbException e) {
@@ -292,19 +303,27 @@ abstract class JdbcDatabase implements Database<Connection> {
 	}

 	private boolean checkSchemaVersion(Connection txn) throws DbException {
-		Settings s = getSettings(txn, "db");
-		int schemaVersion = s.getInt("schemaVersion", -1);
+		Settings s = getSettings(txn, DB_SETTINGS_NAMESPACE);
+		int schemaVersion = s.getInt(SCHEMA_VERSION_KEY, -1);
 		if (schemaVersion == SCHEMA_VERSION) return true;
 		if (schemaVersion < MIN_SCHEMA_VERSION) return false;
-		int minSchemaVersion = s.getInt("minSchemaVersion", -1);
+		int minSchemaVersion = s.getInt(MIN_SCHEMA_VERSION_KEY, -1);
 		return SCHEMA_VERSION >= minSchemaVersion;
 	}

 	private void storeSchemaVersion(Connection txn) throws DbException {
 		Settings s = new Settings();
-		s.putInt("schemaVersion", SCHEMA_VERSION);
-		s.putInt("minSchemaVersion", MIN_SCHEMA_VERSION);
-		mergeSettings(txn, s, "db");
+		s.putInt(SCHEMA_VERSION_KEY, SCHEMA_VERSION);
+		s.putInt(MIN_SCHEMA_VERSION_KEY, MIN_SCHEMA_VERSION);
+		mergeSettings(txn, s, DB_SETTINGS_NAMESPACE);
+	}
+
+	private void storeDeviceId(Connection txn) throws DbException {
+		byte[] deviceId = new byte[UniqueId.LENGTH];
+		random.nextBytes(deviceId);
+		Settings s = new Settings();
+		s.put(DEVICE_ID_KEY, StringUtils.toHexString(deviceId));
+		mergeSettings(txn, s, DEVICE_SETTINGS_NAMESPACE);
 	}

 	private void tryToClose(ResultSet rs) {
--- a/briar-core/src/org/briarproject/forum/ForumModule.java
+++ b/briar-core/src/org/briarproject/forum/ForumModule.java
@@ -16,6 +16,8 @@ import org.briarproject.api.system.Clock;

 import javax.inject.Singleton;

+import static org.briarproject.forum.ForumManagerImpl.CLIENT_ID;
+
 public class ForumModule extends AbstractModule {

 	@Override
@@ -26,16 +28,14 @@ public class ForumModule extends AbstractModule {

 	@Provides @Singleton
 	ForumPostValidator getValidator(ValidationManager validationManager,
-			ForumManager forumManager, CryptoComponent crypto,
-			BdfReaderFactory bdfReaderFactory,
+			CryptoComponent crypto, BdfReaderFactory bdfReaderFactory,
 			BdfWriterFactory bdfWriterFactory,
 			ObjectReader<Author> authorReader, MetadataEncoder metadataEncoder,
 			Clock clock) {
 		ForumPostValidator validator = new ForumPostValidator(crypto,
 				bdfReaderFactory, bdfWriterFactory, authorReader,
 				metadataEncoder, clock);
-		validationManager.registerMessageValidator(forumManager.getClientId(),
-				validator);
+		validationManager.registerMessageValidator(CLIENT_ID, validator);
 		return validator;
 	}
 }
--- a/briar-core/src/org/briarproject/invitation/AliceConnector.java
+++ b/briar-core/src/org/briarproject/invitation/AliceConnector.java
@@ -1,7 +1,5 @@
 package org.briarproject.invitation;

-import org.briarproject.api.TransportId;
-import org.briarproject.api.TransportProperties;
 import org.briarproject.api.contact.ContactManager;
 import org.briarproject.api.crypto.CryptoComponent;
 import org.briarproject.api.crypto.PseudoRandom;
@@ -17,7 +15,6 @@ import org.briarproject.api.identity.LocalAuthor;
 import org.briarproject.api.plugins.ConnectionManager;
 import org.briarproject.api.plugins.duplex.DuplexPlugin;
 import org.briarproject.api.plugins.duplex.DuplexTransportConnection;
-import org.briarproject.api.property.TransportPropertyManager;
 import org.briarproject.api.sync.GroupFactory;
 import org.briarproject.api.system.Clock;
 import org.briarproject.api.transport.KeyManager;
@@ -28,7 +25,6 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.security.GeneralSecurityException;
-import java.util.Map;
 import java.util.logging.Logger;

 import static java.util.logging.Level.INFO;
@@ -47,17 +43,12 @@ class AliceConnector extends Connector {
 			StreamWriterFactory streamWriterFactory,
 			AuthorFactory authorFactory, GroupFactory groupFactory,
 			KeyManager keyManager, ConnectionManager connectionManager,
-			ContactManager contactManager,
-			TransportPropertyManager transportPropertyManager, Clock clock,
-			boolean reuseConnection, ConnectorGroup group, DuplexPlugin plugin,
-			LocalAuthor localAuthor,
-			Map<TransportId, TransportProperties> localProps,
-			PseudoRandom random) {
+			ContactManager contactManager, Clock clock, ConnectorGroup group,
+			DuplexPlugin plugin, LocalAuthor localAuthor, PseudoRandom random) {
 		super(crypto, bdfReaderFactory, bdfWriterFactory, streamReaderFactory,
-				streamWriterFactory, authorFactory, groupFactory,
-				keyManager, connectionManager, contactManager,
-				transportPropertyManager, clock, reuseConnection, group,
-				plugin, localAuthor, localProps, random);
+				streamWriterFactory, authorFactory, groupFactory, keyManager,
+				connectionManager, contactManager, clock, group, plugin,
+				localAuthor, random);
 	}

 	@Override
@@ -152,20 +143,14 @@ class AliceConnector extends Connector {
 		// Derive the invitation nonces
 		byte[] aliceNonce = crypto.deriveSignatureNonce(master, true);
 		byte[] bobNonce = crypto.deriveSignatureNonce(master, false);
-		// Exchange pseudonyms, signed nonces, timestamps and transports
+		// Exchange pseudonyms, signed nonces, and timestamps
 		Author remoteAuthor;
 		long remoteTimestamp;
-		Map<TransportId, TransportProperties> remoteProps;
-		boolean remoteReuseConnection;
 		try {
 			sendPseudonym(w, aliceNonce);
 			sendTimestamp(w, localTimestamp);
-			sendTransportProperties(w);
-			sendConfirmation(w, reuseConnection);
 			remoteAuthor = receivePseudonym(r, bobNonce);
 			remoteTimestamp = receiveTimestamp(r);
-			remoteProps = receiveTransportProperties(r);
-			remoteReuseConnection = receiveConfirmation(r);
 			// Close the outgoing stream and expect EOF on the incoming stream
 			w.close();
 			if (!r.eof()) LOG.warning("Unexpected data at end of connection");
@@ -182,18 +167,17 @@ class AliceConnector extends Connector {
 		}
 		// The agreed timestamp is the minimum of the peers' timestamps
 		long timestamp = Math.min(localTimestamp, remoteTimestamp);
-		// Add the contact and store the transports
+		// Add the contact
 		try {
-			addContact(remoteAuthor, remoteProps, master, timestamp, true);
+			addContact(remoteAuthor, master, timestamp, true);
 		} catch (DbException e) {
 			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
 			tryToClose(conn, true);
 			group.pseudonymExchangeFailed();
 			return;
 		}
-		// Reuse the connection as a transport connection if both peers agree
-		if (reuseConnection && remoteReuseConnection) reuseConnection(conn);
-		else tryToClose(conn, false);
+		// Reuse the connection as a transport connection
+		reuseConnection(conn);
 		// Pseudonym exchange succeeded
 		if (LOG.isLoggable(INFO))
 			LOG.info(pluginName + " pseudonym exchange succeeded");
--- a/briar-core/src/org/briarproject/invitation/BobConnector.java
+++ b/briar-core/src/org/briarproject/invitation/BobConnector.java
@@ -1,7 +1,5 @@
 package org.briarproject.invitation;

-import org.briarproject.api.TransportId;
-import org.briarproject.api.TransportProperties;
 import org.briarproject.api.contact.ContactManager;
 import org.briarproject.api.crypto.CryptoComponent;
 import org.briarproject.api.crypto.PseudoRandom;
@@ -17,7 +15,6 @@ import org.briarproject.api.identity.LocalAuthor;
 import org.briarproject.api.plugins.ConnectionManager;
 import org.briarproject.api.plugins.duplex.DuplexPlugin;
 import org.briarproject.api.plugins.duplex.DuplexTransportConnection;
-import org.briarproject.api.property.TransportPropertyManager;
 import org.briarproject.api.sync.GroupFactory;
 import org.briarproject.api.system.Clock;
 import org.briarproject.api.transport.KeyManager;
@@ -28,7 +25,6 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.security.GeneralSecurityException;
-import java.util.Map;
 import java.util.logging.Logger;

 import static java.util.logging.Level.INFO;
@@ -47,17 +43,12 @@ class BobConnector extends Connector {
 			StreamWriterFactory streamWriterFactory,
 			AuthorFactory authorFactory, GroupFactory groupFactory,
 			KeyManager keyManager, ConnectionManager connectionManager,
-			ContactManager contactManager,
-			TransportPropertyManager transportPropertyManager, Clock clock,
-			boolean reuseConnection, ConnectorGroup group, DuplexPlugin plugin,
-			LocalAuthor localAuthor,
-			Map<TransportId, TransportProperties> localProps,
-			PseudoRandom random) {
+			ContactManager contactManager, Clock clock, ConnectorGroup group,
+			DuplexPlugin plugin, LocalAuthor localAuthor, PseudoRandom random) {
 		super(crypto, bdfReaderFactory, bdfWriterFactory, streamReaderFactory,
-				streamWriterFactory, authorFactory, groupFactory,
-				keyManager, connectionManager, contactManager,
-				transportPropertyManager, clock, reuseConnection, group,
-				plugin, localAuthor, localProps, random);
+				streamWriterFactory, authorFactory, groupFactory, keyManager,
+				connectionManager, contactManager, clock, group, plugin,
+				localAuthor, random);
 	}

 	@Override
@@ -152,20 +143,14 @@ class BobConnector extends Connector {
 		// Derive the nonces
 		byte[] aliceNonce = crypto.deriveSignatureNonce(master, true);
 		byte[] bobNonce = crypto.deriveSignatureNonce(master, false);
-		// Exchange pseudonyms, signed nonces, timestamps and transports
+		// Exchange pseudonyms, signed nonces and timestamps
 		Author remoteAuthor;
 		long remoteTimestamp;
-		Map<TransportId, TransportProperties> remoteProps;
-		boolean remoteReuseConnection;
 		try {
 			remoteAuthor = receivePseudonym(r, aliceNonce);
 			remoteTimestamp = receiveTimestamp(r);
-			remoteProps = receiveTransportProperties(r);
-			remoteReuseConnection = receiveConfirmation(r);
 			sendPseudonym(w, bobNonce);
 			sendTimestamp(w, localTimestamp);
-			sendTransportProperties(w);
-			sendConfirmation(w, reuseConnection);
 			// Close the outgoing stream and expect EOF on the incoming stream
 			w.close();
 			if (!r.eof()) LOG.warning("Unexpected data at end of connection");
@@ -182,18 +167,17 @@ class BobConnector extends Connector {
 		}
 		// The agreed timestamp is the minimum of the peers' timestamps
 		long timestamp = Math.min(localTimestamp, remoteTimestamp);
-		// Add the contact and store the transports
+		// Add the contact
 		try {
-			addContact(remoteAuthor, remoteProps, master, timestamp, false);
+			addContact(remoteAuthor, master, timestamp, false);
 		} catch (DbException e) {
 			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
 			tryToClose(conn, true);
 			group.pseudonymExchangeFailed();
 			return;
 		}
-		// Reuse the connection as a transport connection if both peers agree
-		if (reuseConnection && remoteReuseConnection) reuseConnection(conn);
-		else tryToClose(conn, false);
+		// Reuse the connection as a transport connection
+		reuseConnection(conn);
 		// Pseudonym exchange succeeded
 		if (LOG.isLoggable(INFO))
 			LOG.info(pluginName + " pseudonym exchange succeeded");
--- a/briar-core/src/org/briarproject/invitation/Connector.java
+++ b/briar-core/src/org/briarproject/invitation/Connector.java
@@ -2,7 +2,6 @@ package org.briarproject.invitation;

 import org.briarproject.api.FormatException;
 import org.briarproject.api.TransportId;
-import org.briarproject.api.TransportProperties;
 import org.briarproject.api.contact.ContactId;
 import org.briarproject.api.contact.ContactManager;
 import org.briarproject.api.crypto.CryptoComponent;
@@ -23,7 +22,6 @@ import org.briarproject.api.identity.LocalAuthor;
 import org.briarproject.api.plugins.ConnectionManager;
 import org.briarproject.api.plugins.duplex.DuplexPlugin;
 import org.briarproject.api.plugins.duplex.DuplexTransportConnection;
-import org.briarproject.api.property.TransportPropertyManager;
 import org.briarproject.api.sync.GroupFactory;
 import org.briarproject.api.system.Clock;
 import org.briarproject.api.transport.KeyManager;
@@ -33,16 +31,10 @@ import org.briarproject.api.transport.StreamWriterFactory;
 import java.io.IOException;
 import java.security.GeneralSecurityException;
 import java.util.Arrays;
-import java.util.HashMap;
-import java.util.Map;
-import java.util.Map.Entry;
 import java.util.logging.Logger;

 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
-import static org.briarproject.api.TransportPropertyConstants.MAX_PROPERTIES_PER_TRANSPORT;
-import static org.briarproject.api.TransportPropertyConstants.MAX_PROPERTY_LENGTH;
-import static org.briarproject.api.TransportPropertyConstants.MAX_TRANSPORT_ID_LENGTH;
 import static org.briarproject.api.identity.AuthorConstants.MAX_AUTHOR_NAME_LENGTH;
 import static org.briarproject.api.identity.AuthorConstants.MAX_PUBLIC_KEY_LENGTH;
 import static org.briarproject.api.identity.AuthorConstants.MAX_SIGNATURE_LENGTH;
@@ -64,13 +56,10 @@ abstract class Connector extends Thread {
 	protected final KeyManager keyManager;
 	protected final ConnectionManager connectionManager;
 	protected final ContactManager contactManager;
-	protected final TransportPropertyManager transportPropertyManager;
 	protected final Clock clock;
-	protected final boolean reuseConnection;
 	protected final ConnectorGroup group;
 	protected final DuplexPlugin plugin;
 	protected final LocalAuthor localAuthor;
-	protected final Map<TransportId, TransportProperties> localProps;
 	protected final PseudoRandom random;
 	protected final String pluginName;

@@ -87,12 +76,8 @@ abstract class Connector extends Thread {
 			StreamWriterFactory streamWriterFactory,
 			AuthorFactory authorFactory, GroupFactory groupFactory,
 			KeyManager keyManager, ConnectionManager connectionManager,
-			ContactManager contactManager,
-			TransportPropertyManager transportPropertyManager, Clock clock,
-			boolean reuseConnection, ConnectorGroup group, DuplexPlugin plugin,
-			LocalAuthor localAuthor,
-			Map<TransportId, TransportProperties> localProps,
-			PseudoRandom random) {
+			ContactManager contactManager, Clock clock, ConnectorGroup group,
+			DuplexPlugin plugin, LocalAuthor localAuthor, PseudoRandom random) {
 		super("Connector");
 		this.crypto = crypto;
 		this.bdfReaderFactory = bdfReaderFactory;
@@ -104,13 +89,10 @@ abstract class Connector extends Thread {
 		this.keyManager = keyManager;
 		this.connectionManager = connectionManager;
 		this.contactManager = contactManager;
-		this.transportPropertyManager = transportPropertyManager;
 		this.clock = clock;
-		this.reuseConnection = reuseConnection;
 		this.group = group;
 		this.plugin = plugin;
 		this.localAuthor = localAuthor;
-		this.localProps = localProps;
 		this.random = random;
 		pluginName = plugin.getClass().getName();
 		keyPair = crypto.generateAgreementKeyPair();
@@ -233,57 +215,14 @@ abstract class Connector extends Thread {
 		return timestamp;
 	}

-	protected void sendTransportProperties(BdfWriter w) throws IOException {
-		w.writeListStart();
-		for (Entry<TransportId, TransportProperties> e :
-				localProps.entrySet()) {
-			w.writeString(e.getKey().getString());
-			w.writeDictionary(e.getValue());
-		}
-		w.writeListEnd();
-		w.flush();
-		if (LOG.isLoggable(INFO))
-			LOG.info(pluginName + " sent transport properties");
-	}
-
-	protected Map<TransportId, TransportProperties> receiveTransportProperties(
-			BdfReader r) throws IOException {
-		Map<TransportId, TransportProperties> remoteProps =
-				new HashMap<TransportId, TransportProperties>();
-		r.readListStart();
-		while (!r.hasListEnd()) {
-			String idString = r.readString(MAX_TRANSPORT_ID_LENGTH);
-			if (idString.length() == 0) throw new FormatException();
-			TransportId id = new TransportId(idString);
-			Map<String, String> p = new HashMap<String, String>();
-			r.readDictionaryStart();
-			for (int i = 0; !r.hasDictionaryEnd(); i++) {
-				if (i == MAX_PROPERTIES_PER_TRANSPORT)
-					throw new FormatException();
-				String key = r.readString(MAX_PROPERTY_LENGTH);
-				String value = r.readString(MAX_PROPERTY_LENGTH);
-				p.put(key, value);
-			}
-			r.readDictionaryEnd();
-			remoteProps.put(id, new TransportProperties(p));
-		}
-		r.readListEnd();
-		if (LOG.isLoggable(INFO))
-			LOG.info(pluginName + " received transport properties");
-		return remoteProps;
-	}
-
-	protected void addContact(Author remoteAuthor,
-			Map<TransportId, TransportProperties> remoteProps, SecretKey master,
+	protected ContactId addContact(Author remoteAuthor, SecretKey master,
 			long timestamp, boolean alice) throws DbException {
 		// Add the contact to the database
 		contactId = contactManager.addContact(remoteAuthor,
 				localAuthor.getId());
-		// Store the remote transport properties
-		transportPropertyManager.setRemoteProperties(contactId, remoteProps);
-		// Derive transport keys for each transport shared with the contact
-		keyManager.addContact(contactId, remoteProps.keySet(), master,
-				timestamp, alice);
+		// Derive transport keys
+		keyManager.addContact(contactId, master, timestamp, alice);
+		return contactId;
 	}

 	protected void tryToClose(DuplexTransportConnection conn,
--- a/briar-core/src/org/briarproject/invitation/ConnectorGroup.java
+++ b/briar-core/src/org/briarproject/invitation/ConnectorGroup.java
@@ -1,7 +1,5 @@
 package org.briarproject.invitation;

-import org.briarproject.api.TransportId;
-import org.briarproject.api.TransportProperties;
 import org.briarproject.api.contact.ContactManager;
 import org.briarproject.api.crypto.CryptoComponent;
 import org.briarproject.api.crypto.PseudoRandom;
@@ -19,7 +17,6 @@ import org.briarproject.api.invitation.InvitationTask;
 import org.briarproject.api.plugins.ConnectionManager;
 import org.briarproject.api.plugins.PluginManager;
 import org.briarproject.api.plugins.duplex.DuplexPlugin;
-import org.briarproject.api.property.TransportPropertyManager;
 import org.briarproject.api.sync.GroupFactory;
 import org.briarproject.api.system.Clock;
 import org.briarproject.api.transport.KeyManager;
@@ -28,7 +25,6 @@ import org.briarproject.api.transport.StreamWriterFactory;

 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Map;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -57,12 +53,10 @@ class ConnectorGroup extends Thread implements InvitationTask {
 	private final ConnectionManager connectionManager;
 	private final IdentityManager identityManager;
 	private final ContactManager contactManager;
-	private final TransportPropertyManager transportPropertyManager;
 	private final Clock clock;
 	private final PluginManager pluginManager;
 	private final AuthorId localAuthorId;
 	private final int localInvitationCode, remoteInvitationCode;
-	private final boolean reuseConnection;
 	private final Collection<InvitationListener> listeners;
 	private final AtomicBoolean connected;
 	private final CountDownLatch localConfirmationLatch;
@@ -83,10 +77,8 @@ class ConnectorGroup extends Thread implements InvitationTask {
 			AuthorFactory authorFactory, GroupFactory groupFactory,
 			KeyManager keyManager, ConnectionManager connectionManager,
 			IdentityManager identityManager, ContactManager contactManager,
-			TransportPropertyManager transportPropertyManager, Clock clock,
-			PluginManager pluginManager, AuthorId localAuthorId,
-			int localInvitationCode, int remoteInvitationCode,
-			boolean reuseConnection) {
+			Clock clock, PluginManager pluginManager, AuthorId localAuthorId,
+			int localInvitationCode, int remoteInvitationCode) {
 		super("ConnectorGroup");
 		this.crypto = crypto;
 		this.bdfReaderFactory = bdfReaderFactory;
@@ -99,13 +91,11 @@ class ConnectorGroup extends Thread implements InvitationTask {
 		this.connectionManager = connectionManager;
 		this.identityManager = identityManager;
 		this.contactManager = contactManager;
-		this.transportPropertyManager = transportPropertyManager;
 		this.clock = clock;
 		this.pluginManager = pluginManager;
 		this.localAuthorId = localAuthorId;
 		this.localInvitationCode = localInvitationCode;
 		this.remoteInvitationCode = remoteInvitationCode;
-		this.reuseConnection = reuseConnection;
 		listeners = new CopyOnWriteArrayList<InvitationListener>();
 		connected = new AtomicBoolean(false);
 		localConfirmationLatch = new CountDownLatch(1);
@@ -136,11 +126,9 @@ class ConnectorGroup extends Thread implements InvitationTask {
 	@Override
 	public void run() {
 		LocalAuthor localAuthor;
-		Map<TransportId, TransportProperties> localProps;
-		// Load the local pseudonym and transport properties
+		// Load the local pseudonym
 		try {
 			localAuthor = identityManager.getLocalAuthor(localAuthorId);
-			localProps = transportPropertyManager.getLocalProperties();
 		} catch (DbException e) {
 			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
 			lock.lock();
@@ -157,15 +145,13 @@ class ConnectorGroup extends Thread implements InvitationTask {
 		// Alice is the party with the smaller invitation code
 		if (localInvitationCode < remoteInvitationCode) {
 			for (DuplexPlugin plugin : pluginManager.getInvitationPlugins()) {
-				Connector c = createAliceConnector(plugin, localAuthor,
-						localProps);
+				Connector c = createAliceConnector(plugin, localAuthor);
 				connectors.add(c);
 				c.start();
 			}
 		} else {
 			for (DuplexPlugin plugin: pluginManager.getInvitationPlugins()) {
-				Connector c = createBobConnector(plugin, localAuthor,
-						localProps);
+				Connector c = createBobConnector(plugin, localAuthor);
 				connectors.add(c);
 				c.start();
 			}
@@ -190,27 +176,23 @@ class ConnectorGroup extends Thread implements InvitationTask {
 	}

 	private Connector createAliceConnector(DuplexPlugin plugin,
-			LocalAuthor localAuthor,
-			Map<TransportId, TransportProperties> localProps) {
+			LocalAuthor localAuthor) {
 		PseudoRandom random = crypto.getPseudoRandom(localInvitationCode,
 				remoteInvitationCode);
 		return new AliceConnector(crypto, bdfReaderFactory, bdfWriterFactory,
 				streamReaderFactory, streamWriterFactory, authorFactory,
 				groupFactory, keyManager, connectionManager, contactManager,
-				transportPropertyManager, clock, reuseConnection, this, plugin,
-				localAuthor, localProps, random);
+				clock, this, plugin, localAuthor, random);
 	}

 	private Connector createBobConnector(DuplexPlugin plugin,
-			LocalAuthor localAuthor,
-			Map<TransportId, TransportProperties> localProps) {
+			LocalAuthor localAuthor) {
 		PseudoRandom random = crypto.getPseudoRandom(remoteInvitationCode,
 				localInvitationCode);
 		return new BobConnector(crypto, bdfReaderFactory, bdfWriterFactory,
 				streamReaderFactory, streamWriterFactory, authorFactory,
 				groupFactory, keyManager, connectionManager, contactManager,
-				transportPropertyManager, clock, reuseConnection, this, plugin,
-				localAuthor, localProps, random);
+				clock, this, plugin, localAuthor, random);
 	}

 	public void localConfirmationSucceeded() {
--- a/briar-core/src/org/briarproject/invitation/InvitationTaskFactoryImpl.java
+++ b/briar-core/src/org/briarproject/invitation/InvitationTaskFactoryImpl.java
@@ -11,7 +11,6 @@ import org.briarproject.api.invitation.InvitationTask;
 import org.briarproject.api.invitation.InvitationTaskFactory;
 import org.briarproject.api.plugins.ConnectionManager;
 import org.briarproject.api.plugins.PluginManager;
-import org.briarproject.api.property.TransportPropertyManager;
 import org.briarproject.api.sync.GroupFactory;
 import org.briarproject.api.system.Clock;
 import org.briarproject.api.transport.KeyManager;
@@ -33,7 +32,6 @@ class InvitationTaskFactoryImpl implements InvitationTaskFactory {
 	private final ConnectionManager connectionManager;
 	private final IdentityManager identityManager;
 	private final ContactManager contactManager;
-	private final TransportPropertyManager transportPropertyManager;
 	private final Clock clock;
 	private final PluginManager pluginManager;

@@ -45,7 +43,6 @@ class InvitationTaskFactoryImpl implements InvitationTaskFactory {
 			AuthorFactory authorFactory, GroupFactory groupFactory,
 			KeyManager keyManager, ConnectionManager connectionManager,
 			IdentityManager identityManager, ContactManager contactManager,
-			TransportPropertyManager transportPropertyManager,
 			Clock clock, PluginManager pluginManager) {
 		this.crypto = crypto;
 		this.bdfReaderFactory = bdfReaderFactory;
@@ -58,17 +55,16 @@ class InvitationTaskFactoryImpl implements InvitationTaskFactory {
 		this.connectionManager = connectionManager;
 		this.identityManager = identityManager;
 		this.contactManager = contactManager;
-		this.transportPropertyManager = transportPropertyManager;
 		this.clock = clock;
 		this.pluginManager = pluginManager;
 	}

 	public InvitationTask createTask(AuthorId localAuthorId, int localCode,
-			int remoteCode, boolean reuseConnection) {
+			int remoteCode) {
 		return new ConnectorGroup(crypto, bdfReaderFactory, bdfWriterFactory,
 				streamReaderFactory, streamWriterFactory, authorFactory,
 				groupFactory, keyManager, connectionManager, identityManager,
-				contactManager, transportPropertyManager, clock, pluginManager,
-				localAuthorId, localCode, remoteCode, reuseConnection);
+				contactManager, clock, pluginManager, localAuthorId, localCode,
+				remoteCode);
 	}
 }
--- a/briar-core/src/org/briarproject/messaging/MessagingModule.java
+++ b/briar-core/src/org/briarproject/messaging/MessagingModule.java
@@ -13,6 +13,8 @@ import org.briarproject.api.system.Clock;

 import javax.inject.Singleton;

+import static org.briarproject.messaging.MessagingManagerImpl.CLIENT_ID;
+
 public class MessagingModule extends AbstractModule {

 	@Override
@@ -22,14 +24,11 @@ public class MessagingModule extends AbstractModule {

 	@Provides @Singleton
 	PrivateMessageValidator getValidator(ValidationManager validationManager,
-			MessagingManager messagingManager,
 			BdfReaderFactory bdfReaderFactory, MetadataEncoder metadataEncoder,
 			Clock clock) {
 		PrivateMessageValidator validator = new PrivateMessageValidator(
 				bdfReaderFactory, metadataEncoder, clock);
-		validationManager.registerMessageValidator(
-				messagingManager.getClientId(),
-				validator);
+		validationManager.registerMessageValidator(CLIENT_ID, validator);
 		return validator;
 	}

--- a/briar-core/src/org/briarproject/plugins/ConnectionManagerImpl.java
+++ b/briar-core/src/org/briarproject/plugins/ConnectionManagerImpl.java
@@ -73,8 +73,7 @@ class ConnectionManagerImpl implements ConnectionManager {
 		ioExecutor.execute(new ManageOutgoingDuplexConnection(c, t, d));
 	}

-	private byte[] readTag(TransportId t, TransportConnectionReader r)
-			throws IOException {
+	private byte[] readTag(TransportConnectionReader r) throws IOException {
 		// Read the tag
 		byte[] tag = new byte[TAG_LENGTH];
 		InputStream in = r.getInputStream();
@@ -128,7 +127,7 @@ class ConnectionManagerImpl implements ConnectionManager {
 			// Read and recognise the tag
 			StreamContext ctx;
 			try {
-				byte[] tag = readTag(transportId, reader);
+				byte[] tag = readTag(reader);
 				ctx = keyManager.getStreamContext(transportId, tag);
 			} catch (IOException e) {
 				if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
@@ -228,7 +227,7 @@ class ConnectionManagerImpl implements ConnectionManager {
 			// Read and recognise the tag
 			StreamContext ctx;
 			try {
-				byte[] tag = readTag(transportId, reader);
+				byte[] tag = readTag(reader);
 				ctx = keyManager.getStreamContext(transportId, tag);
 			} catch (IOException e) {
 				if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
@@ -353,7 +352,7 @@ class ConnectionManagerImpl implements ConnectionManager {
 			// Read and recognise the tag
 			StreamContext ctx;
 			try {
-				byte[] tag = readTag(transportId, reader);
+				byte[] tag = readTag(reader);
 				ctx = keyManager.getStreamContext(transportId, tag);
 			} catch (IOException e) {
 				if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
--- a/briar-core/src/org/briarproject/plugins/PluginManagerImpl.java
+++ b/briar-core/src/org/briarproject/plugins/PluginManagerImpl.java
@@ -1,8 +1,6 @@
 package org.briarproject.plugins;

-import org.briarproject.api.Settings;
 import org.briarproject.api.TransportId;
-import org.briarproject.api.TransportProperties;
 import org.briarproject.api.contact.ContactId;
 import org.briarproject.api.db.DatabaseComponent;
 import org.briarproject.api.db.DbException;
@@ -26,7 +24,9 @@ import org.briarproject.api.plugins.simplex.SimplexPlugin;
 import org.briarproject.api.plugins.simplex.SimplexPluginCallback;
 import org.briarproject.api.plugins.simplex.SimplexPluginConfig;
 import org.briarproject.api.plugins.simplex.SimplexPluginFactory;
-import org.briarproject.api.property.TransportPropertyManager;
+import org.briarproject.api.properties.TransportProperties;
+import org.briarproject.api.properties.TransportPropertyManager;
+import org.briarproject.api.settings.Settings;
 import org.briarproject.api.system.Clock;
 import org.briarproject.api.ui.UiCallback;

--- a/briar-core/src/org/briarproject/plugins/tcp/LanTcpPlugin.java
+++ b/briar-core/src/org/briarproject/plugins/tcp/LanTcpPlugin.java
@@ -1,5 +1,9 @@
 package org.briarproject.plugins.tcp;

+import org.briarproject.api.TransportId;
+import org.briarproject.api.plugins.duplex.DuplexPluginCallback;
+import org.briarproject.api.properties.TransportProperties;
+
 import java.net.Inet4Address;
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
@@ -8,10 +12,6 @@ import java.util.LinkedList;
 import java.util.List;
 import java.util.concurrent.Executor;

-import org.briarproject.api.TransportId;
-import org.briarproject.api.TransportProperties;
-import org.briarproject.api.plugins.duplex.DuplexPluginCallback;
-
 class LanTcpPlugin extends TcpPlugin {

 	static final TransportId ID = new TransportId("lan");
--- a/briar-core/src/org/briarproject/plugins/tcp/TcpPlugin.java
+++ b/briar-core/src/org/briarproject/plugins/tcp/TcpPlugin.java
@@ -1,11 +1,11 @@
 package org.briarproject.plugins.tcp;

-import org.briarproject.api.TransportProperties;
 import org.briarproject.api.contact.ContactId;
 import org.briarproject.api.crypto.PseudoRandom;
 import org.briarproject.api.plugins.duplex.DuplexPlugin;
 import org.briarproject.api.plugins.duplex.DuplexPluginCallback;
 import org.briarproject.api.plugins.duplex.DuplexTransportConnection;
+import org.briarproject.api.properties.TransportProperties;
 import org.briarproject.util.StringUtils;

 import java.io.IOException;
--- a/briar-core/src/org/briarproject/plugins/tcp/WanTcpPlugin.java
+++ b/briar-core/src/org/briarproject/plugins/tcp/WanTcpPlugin.java
@@ -1,5 +1,9 @@
 package org.briarproject.plugins.tcp;

+import org.briarproject.api.TransportId;
+import org.briarproject.api.plugins.duplex.DuplexPluginCallback;
+import org.briarproject.api.properties.TransportProperties;
+
 import java.net.Inet4Address;
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
@@ -8,10 +12,6 @@ import java.util.LinkedList;
 import java.util.List;
 import java.util.concurrent.Executor;

-import org.briarproject.api.TransportId;
-import org.briarproject.api.TransportProperties;
-import org.briarproject.api.plugins.duplex.DuplexPluginCallback;
-
 class WanTcpPlugin extends TcpPlugin {

 	static final TransportId ID = new TransportId("wan");
--- a/briar-core/src/org/briarproject/properties/PropertiesModule.java
+++ b/briar-core/src/org/briarproject/properties/PropertiesModule.java
@@ -0,0 +1,40 @@
+package org.briarproject.properties;
+
+import com.google.inject.AbstractModule;
+import com.google.inject.Provides;
+
+import org.briarproject.api.contact.ContactManager;
+import org.briarproject.api.data.BdfReaderFactory;
+import org.briarproject.api.data.MetadataEncoder;
+import org.briarproject.api.properties.TransportPropertyManager;
+import org.briarproject.api.sync.ValidationManager;
+import org.briarproject.api.system.Clock;
+
+import javax.inject.Singleton;
+
+import static org.briarproject.properties.TransportPropertyManagerImpl.CLIENT_ID;
+
+public class PropertiesModule extends AbstractModule {
+
+	@Override
+	protected void configure() {}
+
+	@Provides @Singleton
+	TransportPropertyValidator getValidator(ValidationManager validationManager,
+			BdfReaderFactory bdfReaderFactory, MetadataEncoder metadataEncoder,
+			Clock clock) {
+		TransportPropertyValidator validator = new TransportPropertyValidator(
+				bdfReaderFactory, metadataEncoder, clock);
+		validationManager.registerMessageValidator(CLIENT_ID, validator);
+		return validator;
+	}
+
+	@Provides @Singleton
+	TransportPropertyManager getTransportPropertyManager(
+			ContactManager contactManager,
+			TransportPropertyManagerImpl transportPropertyManager) {
+		contactManager.registerAddContactHook(transportPropertyManager);
+		contactManager.registerRemoveContactHook(transportPropertyManager);
+		return transportPropertyManager;
+	}
+}
--- a/briar-core/src/org/briarproject/properties/TransportPropertyManagerImpl.java
+++ b/briar-core/src/org/briarproject/properties/TransportPropertyManagerImpl.java
@@ -0,0 +1,339 @@
+package org.briarproject.properties;
+
+import com.google.inject.Inject;
+
+import org.briarproject.api.FormatException;
+import org.briarproject.api.TransportId;
+import org.briarproject.api.UniqueId;
+import org.briarproject.api.contact.Contact;
+import org.briarproject.api.contact.ContactId;
+import org.briarproject.api.contact.ContactManager.AddContactHook;
+import org.briarproject.api.contact.ContactManager.RemoveContactHook;
+import org.briarproject.api.data.BdfDictionary;
+import org.briarproject.api.data.BdfReader;
+import org.briarproject.api.data.BdfReaderFactory;
+import org.briarproject.api.data.BdfWriter;
+import org.briarproject.api.data.BdfWriterFactory;
+import org.briarproject.api.data.MetadataEncoder;
+import org.briarproject.api.data.MetadataParser;
+import org.briarproject.api.db.DatabaseComponent;
+import org.briarproject.api.db.DbException;
+import org.briarproject.api.db.Metadata;
+import org.briarproject.api.db.NoSuchSubscriptionException;
+import org.briarproject.api.identity.AuthorId;
+import org.briarproject.api.properties.TransportProperties;
+import org.briarproject.api.properties.TransportPropertyManager;
+import org.briarproject.api.sync.ClientId;
+import org.briarproject.api.sync.Group;
+import org.briarproject.api.sync.GroupFactory;
+import org.briarproject.api.sync.GroupId;
+import org.briarproject.api.sync.Message;
+import org.briarproject.api.sync.MessageFactory;
+import org.briarproject.api.sync.MessageId;
+import org.briarproject.api.system.Clock;
+import org.briarproject.util.StringUtils;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+import java.util.logging.Logger;
+
+import static java.util.logging.Level.WARNING;
+import static org.briarproject.api.properties.TransportPropertyConstants.MAX_PROPERTY_LENGTH;
+import static org.briarproject.api.sync.SyncConstants.MESSAGE_HEADER_LENGTH;
+
+class TransportPropertyManagerImpl implements TransportPropertyManager,
+		AddContactHook, RemoveContactHook {
+
+	static final ClientId CLIENT_ID = new ClientId(StringUtils.fromHexString(
+			"673ea091673561e28f70122f6a8ea8f4"
+					+ "97c3624b86fa07f785bb15f09fb87b4b"));
+
+	private static final byte[] LOCAL_GROUP_DESCRIPTOR = new byte[0];
+
+	private static final Logger LOG =
+			Logger.getLogger(TransportPropertyManagerImpl.class.getName());
+
+	private final DatabaseComponent db;
+	private final GroupFactory groupFactory;
+	private final MessageFactory messageFactory;
+	private final BdfReaderFactory bdfReaderFactory;
+	private final BdfWriterFactory bdfWriterFactory;
+	private final MetadataEncoder metadataEncoder;
+	private final MetadataParser metadataParser;
+	private final Clock clock;
+	private final Group localGroup;
+
+	/** Ensures isolation between database reads and writes. */
+	private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
+
+	@Inject
+	TransportPropertyManagerImpl(DatabaseComponent db, GroupFactory groupFactory,
+			MessageFactory messageFactory, BdfReaderFactory bdfReaderFactory,
+			BdfWriterFactory bdfWriterFactory, MetadataEncoder metadataEncoder,
+			MetadataParser metadataParser, Clock clock) {
+		this.db = db;
+		this.groupFactory = groupFactory;
+		this.messageFactory = messageFactory;
+		this.bdfReaderFactory = bdfReaderFactory;
+		this.bdfWriterFactory = bdfWriterFactory;
+		this.metadataEncoder = metadataEncoder;
+		this.metadataParser = metadataParser;
+		this.clock = clock;
+		localGroup = groupFactory.createGroup(CLIENT_ID,
+				LOCAL_GROUP_DESCRIPTOR);
+	}
+
+	@Override
+	public void addingContact(ContactId c) {
+		lock.writeLock().lock();
+		try {
+			// Create a group to share with the contact
+			Group g = getContactGroup(db.getContact(c));
+			// Subscribe to the group and share it with the contact
+			db.addGroup(g);
+			db.addContactGroup(c, g);
+			db.setVisibility(g.getId(), Collections.singletonList(c));
+			// Copy the latest local properties into the group
+			Map<TransportId, TransportProperties> local = getLocalProperties();
+			for (Entry<TransportId, TransportProperties> e : local.entrySet())
+				storeMessage(g.getId(), e.getKey(), e.getValue(), 0);
+		} catch (DbException e) {
+			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+		} catch (FormatException e) {
+			throw new RuntimeException(e);
+		} catch (IOException e) {
+			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+		} finally {
+			lock.writeLock().unlock();
+		}
+	}
+
+	private Group getContactGroup(Contact c) {
+		AuthorId local = c.getLocalAuthorId();
+		AuthorId remote = c.getAuthor().getId();
+		byte[] descriptor = encodeGroupDescriptor(local, remote);
+		return groupFactory.createGroup(CLIENT_ID, descriptor);
+	}
+
+	private byte[] encodeGroupDescriptor(AuthorId local, AuthorId remote) {
+		ByteArrayOutputStream out = new ByteArrayOutputStream();
+		BdfWriter w = bdfWriterFactory.createWriter(out);
+		try {
+			w.writeListStart();
+			if (UniqueId.IdComparator.INSTANCE.compare(local, remote) < 0) {
+				w.writeRaw(local.getBytes());
+				w.writeRaw(remote.getBytes());
+			} else {
+				w.writeRaw(remote.getBytes());
+				w.writeRaw(local.getBytes());
+			}
+			w.writeListEnd();
+		} catch (IOException e) {
+			// Shouldn't happen with ByteArrayOutputStream
+			throw new RuntimeException(e);
+		}
+		return out.toByteArray();
+	}
+
+	private void storeMessage(GroupId g, TransportId t, TransportProperties p,
+			long version) throws DbException, IOException {
+		byte[] body = encodeProperties(t, p, version);
+		long now = clock.currentTimeMillis();
+		Message m = messageFactory.createMessage(g, now, body);
+		BdfDictionary d = new BdfDictionary();
+		d.put("transportId", t.getString());
+		d.put("version", version);
+		d.put("local", true);
+		db.addLocalMessage(m, CLIENT_ID, metadataEncoder.encode(d));
+	}
+
+	private byte[] encodeProperties(TransportId t, TransportProperties p,
+			long version) {
+		ByteArrayOutputStream out = new ByteArrayOutputStream();
+		BdfWriter w = bdfWriterFactory.createWriter(out);
+		try {
+			// TODO: Device ID
+			w.writeListStart();
+			w.writeString(t.getString());
+			w.writeInteger(version);
+			w.writeDictionary(p);
+			w.writeListEnd();
+		} catch (IOException e) {
+			// Shouldn't happen with ByteArrayOutputStream
+			throw new RuntimeException(e);
+		}
+		return out.toByteArray();
+	}
+
+	@Override
+	public void removingContact(ContactId c) {
+		lock.writeLock().lock();
+		try {
+			db.removeGroup(getContactGroup(db.getContact(c)));
+		} catch (DbException e) {
+			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+		} finally {
+			lock.writeLock().unlock();
+		}
+	}
+
+	@Override
+	public Map<TransportId, TransportProperties> getLocalProperties()
+			throws DbException {
+		lock.readLock().lock();
+		try {
+			// Find the latest local version for each transport
+			Map<TransportId, Latest> latest =
+					findLatest(localGroup.getId(), true);
+			// Retrieve and decode the latest local properties
+			Map<TransportId, TransportProperties> local =
+					new HashMap<TransportId, TransportProperties>();
+			for (Entry<TransportId, Latest> e : latest.entrySet()) {
+				byte[] raw = db.getRawMessage(e.getValue().messageId);
+				local.put(e.getKey(), decodeProperties(raw));
+			}
+			return Collections.unmodifiableMap(local);
+		} catch (NoSuchSubscriptionException e) {
+			// Local group doesn't exist - there are no local properties
+			return Collections.emptyMap();
+		} catch (IOException e) {
+			throw new DbException(e);
+		} finally {
+			lock.readLock().unlock();
+		}
+	}
+
+	private Map<TransportId, Latest> findLatest(GroupId g, boolean local)
+			throws DbException, FormatException {
+		// TODO: Use metadata queries
+		Map<TransportId, Latest> latest = new HashMap<TransportId, Latest>();
+		Map<MessageId, Metadata> metadata = db.getMessageMetadata(g);
+		for (Entry<MessageId, Metadata> e : metadata.entrySet()) {
+			BdfDictionary mm = metadataParser.parse(e.getValue());
+			if (mm.getBoolean("local") != local) continue;
+			TransportId t = new TransportId(mm.getString("transportId"));
+			long version = mm.getInteger("version");
+			Latest l = latest.get(t);
+			if (l == null || version > l.version)
+				latest.put(t, new Latest(e.getKey(), version));
+		}
+		return latest;
+	}
+
+	private TransportProperties decodeProperties(byte[] raw)
+			throws IOException {
+		TransportProperties p = new TransportProperties();
+		ByteArrayInputStream in = new ByteArrayInputStream(raw,
+				MESSAGE_HEADER_LENGTH, raw.length - MESSAGE_HEADER_LENGTH);
+		BdfReader r = bdfReaderFactory.createReader(in);
+		// TODO: Device ID
+		r.readListStart();
+		r.skipString(); // Transport ID
+		r.skipInteger(); // Version
+		r.readDictionaryStart();
+		while (!r.hasDictionaryEnd()) {
+			String key = r.readString(MAX_PROPERTY_LENGTH);
+			String value = r.readString(MAX_PROPERTY_LENGTH);
+			p.put(key, value);
+		}
+		r.readDictionaryEnd();
+		r.readListEnd();
+		if (!r.eof()) throw new FormatException();
+		return p;
+	}
+
+	@Override
+	public TransportProperties getLocalProperties(TransportId t)
+			throws DbException {
+		lock.readLock().lock();
+		try {
+			// Find the latest local version
+			Latest latest = findLatest(localGroup.getId(), true).get(t);
+			if (latest == null) return null;
+			// Retrieve and decode the latest local properties
+			return decodeProperties(db.getRawMessage(latest.messageId));
+		} catch (NoSuchSubscriptionException e) {
+			// Local group doesn't exist - there are no local properties
+			return null;
+		} catch (IOException e) {
+			throw new DbException(e);
+		} finally {
+			lock.readLock().unlock();
+		}
+	}
+
+	@Override
+	public Map<ContactId, TransportProperties> getRemoteProperties(
+			TransportId t) throws DbException {
+		lock.readLock().lock();
+		try {
+			Map<ContactId, TransportProperties> remote =
+					new HashMap<ContactId, TransportProperties>();
+			for (Contact c : db.getContacts())  {
+				Group g = getContactGroup(c);
+				// Find the latest remote version
+				Latest latest = findLatest(g.getId(), false).get(t);
+				if (latest != null) {
+					// Retrieve and decode the latest remote properties
+					byte[] raw = db.getRawMessage(latest.messageId);
+					remote.put(c.getId(), decodeProperties(raw));
+				}
+			}
+			return Collections.unmodifiableMap(remote);
+		} catch (IOException e) {
+			throw new DbException(e);
+		} finally {
+			lock.readLock().unlock();
+		}
+	}
+
+	@Override
+	public void mergeLocalProperties(TransportId t, TransportProperties p)
+			throws DbException {
+		lock.writeLock().lock();
+		try {
+			// Create the local group if necessary
+			db.addGroup(localGroup);
+			// Merge the new properties with any existing properties
+			Latest latest = findLatest(localGroup.getId(), true).get(t);
+			if (latest != null) {
+				byte[] raw = db.getRawMessage(latest.messageId);
+				TransportProperties old = decodeProperties(raw);
+				if (old.equals(p)) return; // Unchanged
+				old.putAll(p);
+				p = old;
+			}
+			// Store the merged properties in the local group
+			long version = latest == null ? 0 : latest.version + 1;
+			storeMessage(localGroup.getId(), t, p, version);
+			// Store the merged properties in each contact's group
+			for (Contact c : db.getContacts()) {
+				Group g = getContactGroup(c);
+				latest = findLatest(g.getId(), true).get(t);
+				version = latest == null ? 0 : latest.version + 1;
+				storeMessage(g.getId(), t, p, version);
+			}
+		} catch (IOException e) {
+			throw new DbException(e);
+		} finally {
+			lock.writeLock().unlock();
+		}
+	}
+
+	private static class Latest {
+
+		private final MessageId messageId;
+		private final long version;
+
+		private Latest(MessageId messageId, long version) {
+			this.messageId = messageId;
+			this.version = version;
+		}
+	}
+}
--- a/briar-core/src/org/briarproject/properties/TransportPropertyValidator.java
+++ b/briar-core/src/org/briarproject/properties/TransportPropertyValidator.java
@@ -0,0 +1,83 @@
+package org.briarproject.properties;
+
+import org.briarproject.api.FormatException;
+import org.briarproject.api.data.BdfDictionary;
+import org.briarproject.api.data.BdfReader;
+import org.briarproject.api.data.BdfReaderFactory;
+import org.briarproject.api.data.MetadataEncoder;
+import org.briarproject.api.db.Metadata;
+import org.briarproject.api.sync.Message;
+import org.briarproject.api.sync.MessageValidator;
+import org.briarproject.api.system.Clock;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.util.logging.Logger;
+
+import javax.inject.Inject;
+
+import static org.briarproject.api.TransportId.MAX_TRANSPORT_ID_LENGTH;
+import static org.briarproject.api.properties.TransportPropertyConstants.MAX_PROPERTIES_PER_TRANSPORT;
+import static org.briarproject.api.properties.TransportPropertyConstants.MAX_PROPERTY_LENGTH;
+import static org.briarproject.api.sync.SyncConstants.MESSAGE_HEADER_LENGTH;
+import static org.briarproject.api.transport.TransportConstants.MAX_CLOCK_DIFFERENCE;
+
+class TransportPropertyValidator implements MessageValidator {
+
+	private static final Logger LOG =
+			Logger.getLogger(TransportPropertyValidator.class.getName());
+
+	private final BdfReaderFactory bdfReaderFactory;
+	private final MetadataEncoder metadataEncoder;
+	private final Clock clock;
+
+	@Inject
+	TransportPropertyValidator(BdfReaderFactory bdfReaderFactory,
+			MetadataEncoder metadataEncoder, Clock clock) {
+		this.bdfReaderFactory = bdfReaderFactory;
+		this.metadataEncoder = metadataEncoder;
+		this.clock = clock;
+	}
+
+	@Override
+	public Metadata validateMessage(Message m) {
+		// Reject the message if it's too far in the future
+		long now = clock.currentTimeMillis();
+		if (m.getTimestamp() - now > MAX_CLOCK_DIFFERENCE) {
+			LOG.info("Timestamp is too far in the future");
+			return null;
+		}
+		try {
+			// Parse the message body
+			byte[] raw = m.getRaw();
+			ByteArrayInputStream in = new ByteArrayInputStream(raw,
+					MESSAGE_HEADER_LENGTH, raw.length - MESSAGE_HEADER_LENGTH);
+			BdfReader r = bdfReaderFactory.createReader(in);
+			// TODO: Device ID
+			r.readListStart();
+			String id = r.readString(MAX_TRANSPORT_ID_LENGTH);
+			if (id.length() == 0) throw new FormatException();
+			long version = r.readInteger();
+			if (version < 0) throw new FormatException();
+			r.readDictionaryStart();
+			for (int i = 0; !r.hasDictionaryEnd(); i++) {
+				if (i == MAX_PROPERTIES_PER_TRANSPORT)
+					throw new FormatException();
+				r.readString(MAX_PROPERTY_LENGTH);
+				r.readString(MAX_PROPERTY_LENGTH);
+			}
+			r.readDictionaryEnd();
+			r.readListEnd();
+			if (!r.eof()) throw new FormatException();
+			// Return the metadata
+			BdfDictionary d = new BdfDictionary();
+			d.put("transportId", id);
+			d.put("version", version);
+			d.put("local", false);
+			return metadataEncoder.encode(d);
+		} catch (IOException e) {
+			LOG.info("Invalid transport update");
+			return null;
+		}
+	}
+}
--- a/briar-core/src/org/briarproject/property/PropertyModule.java
+++ b/briar-core/src/org/briarproject/property/PropertyModule.java
@@ -1,14 +0,0 @@
-package org.briarproject.property;
-
-import com.google.inject.AbstractModule;
-
-import org.briarproject.api.property.TransportPropertyManager;
-
-public class PropertyModule extends AbstractModule {
-
-	@Override
-	protected void configure() {
-		bind(TransportPropertyManager.class).to(
-				TransportPropertyManagerImpl.class);
-	}
-}
--- a/briar-core/src/org/briarproject/property/TransportPropertyManagerImpl.java
+++ b/briar-core/src/org/briarproject/property/TransportPropertyManagerImpl.java
@@ -1,57 +0,0 @@
-package org.briarproject.property;
-
-import com.google.inject.Inject;
-
-import org.briarproject.api.TransportId;
-import org.briarproject.api.TransportProperties;
-import org.briarproject.api.contact.ContactId;
-import org.briarproject.api.db.DatabaseComponent;
-import org.briarproject.api.db.DbException;
-import org.briarproject.api.property.TransportPropertyManager;
-
-import java.util.Collections;
-import java.util.Map;
-
-// Temporary facade during sync protocol refactoring
-class TransportPropertyManagerImpl implements TransportPropertyManager {
-
-	private final DatabaseComponent db;
-
-	@Inject
-	TransportPropertyManagerImpl(DatabaseComponent db) {
-		this.db = db;
-	}
-
-	@Override
-	public Map<TransportId, TransportProperties> getLocalProperties()
-			throws DbException {
-		// TODO
-		return Collections.emptyMap();
-	}
-
-	@Override
-	public TransportProperties getLocalProperties(TransportId t)
-			throws DbException {
-		// TODO
-		return new TransportProperties();
-	}
-
-	@Override
-	public Map<ContactId, TransportProperties> getRemoteProperties(
-			TransportId t) throws DbException {
-		// TODO
-		return Collections.emptyMap();
-	}
-
-	@Override
-	public void mergeLocalProperties(TransportId t, TransportProperties p)
-			throws DbException {
-		// TODO
-	}
-
-	@Override
-	public void setRemoteProperties(ContactId c,
-			Map<TransportId, TransportProperties> p) throws DbException {
-		// TODO
-	}
-}
--- a/briar-core/src/org/briarproject/settings/SettingsManagerImpl.java
+++ b/briar-core/src/org/briarproject/settings/SettingsManagerImpl.java
@@ -2,9 +2,9 @@ package org.briarproject.settings;

 import com.google.inject.Inject;

-import org.briarproject.api.Settings;
 import org.briarproject.api.db.DatabaseComponent;
 import org.briarproject.api.db.DbException;
+import org.briarproject.api.settings.Settings;
 import org.briarproject.api.settings.SettingsManager;

 class SettingsManagerImpl implements SettingsManager {
--- a/briar-core/src/org/briarproject/transport/KeyManagerImpl.java
+++ b/briar-core/src/org/briarproject/transport/KeyManagerImpl.java
@@ -18,7 +18,6 @@ import org.briarproject.api.system.Timer;
 import org.briarproject.api.transport.KeyManager;
 import org.briarproject.api.transport.StreamContext;

-import java.util.Collection;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.concurrent.ConcurrentHashMap;
@@ -71,12 +70,10 @@ class KeyManagerImpl implements KeyManager, Service, EventListener {
 		return true;
 	}

-	public void addContact(ContactId c, Collection<TransportId> transports,
-			SecretKey master, long timestamp, boolean alice) {
-		for (TransportId t : transports) {
-			TransportKeyManager m = managers.get(t);
-			if (m != null) m.addContact(c, master, timestamp, alice);
-		}
+	public void addContact(ContactId c, SecretKey master, long timestamp,
+			boolean alice) {
+		for (TransportKeyManager m : managers.values())
+			m.addContact(c, master, timestamp, alice);
 	}

 	public StreamContext getStreamContext(ContactId c, TransportId t) {