diff --git a/briar-api/src/org/briarproject/api/DeviceId.java b/briar-api/src/org/briarproject/api/DeviceId.java
new file mode 100644
index 0000000000000000000000000000000000000000..2b72d681dea60d9c234e954609537f7516494ad4
--- /dev/null
+++ b/briar-api/src/org/briarproject/api/DeviceId.java
@@ -0,0 +1,16 @@
+package org.briarproject.api;
+
+import java.util.Arrays;
+
+/** Type-safe wrapper for a byte array that uniquely identifies a device. */
+public class DeviceId extends UniqueId {
+
+	public DeviceId(byte[] id) {
+		super(id);
+	}
+
+	@Override
+	public boolean equals(Object o) {
+		return o instanceof DeviceId && Arrays.equals(id, ((DeviceId) o).id);
+	}
+}
diff --git a/briar-api/src/org/briarproject/api/db/DatabaseComponent.java b/briar-api/src/org/briarproject/api/db/DatabaseComponent.java
index dd165c481223218ce5cea273a3a3efb372babd89..852affa2db17b4edef84ff581f5bd8fdedefd0a7 100644
--- a/briar-api/src/org/briarproject/api/db/DatabaseComponent.java
+++ b/briar-api/src/org/briarproject/api/db/DatabaseComponent.java
@@ -1,5 +1,6 @@
 package org.briarproject.api.db;
 
+import org.briarproject.api.DeviceId;
 import org.briarproject.api.TransportId;
 import org.briarproject.api.contact.Contact;
 import org.briarproject.api.contact.ContactId;
@@ -137,6 +138,9 @@ public interface DatabaseComponent {
 	/** Returns all contacts associated with the given local pseudonym. */
 	Collection<ContactId> getContacts(AuthorId a) throws DbException;
 
+	/** Returns the unique ID for this device. */
+	DeviceId getDeviceId() throws DbException;
+
 	/** Returns the group with the given ID, if the user subscribes to it. */
 	Group getGroup(GroupId g) throws DbException;
 
diff --git a/briar-core/src/org/briarproject/db/Database.java b/briar-core/src/org/briarproject/db/Database.java
index 9236c6e296142f7f2a306b594e217146a434aeb8..e912671b536bdef0b3a7f2d73a405e9aa8ca06db 100644
--- a/briar-core/src/org/briarproject/db/Database.java
+++ b/briar-core/src/org/briarproject/db/Database.java
@@ -1,5 +1,6 @@
 package org.briarproject.db;
 
+import org.briarproject.api.DeviceId;
 import org.briarproject.api.TransportId;
 import org.briarproject.api.contact.Contact;
 import org.briarproject.api.contact.ContactId;
@@ -256,6 +257,13 @@ interface Database<T> {
 	 */
 	Collection<ContactId> getContacts(T txn, AuthorId a) throws DbException;
 
+	/**
+	 * Returns the unique ID for this device.
+	 * <p>
+	 * Locking: read.
+	 */
+	DeviceId getDeviceId(T txn) throws DbException;
+
 	/**
 	 * Returns the amount of free storage space available to the database, in
 	 * bytes. This is based on the minimum of the space available on the device
diff --git a/briar-core/src/org/briarproject/db/DatabaseComponentImpl.java b/briar-core/src/org/briarproject/db/DatabaseComponentImpl.java
index ccfa60eccf441d6c939b1bdd1afa383be444b336..39c0f796f0faa10cc226c7b317353009a95dc7b0 100644
--- a/briar-core/src/org/briarproject/db/DatabaseComponentImpl.java
+++ b/briar-core/src/org/briarproject/db/DatabaseComponentImpl.java
@@ -1,5 +1,6 @@
 package org.briarproject.db;
 
+import org.briarproject.api.DeviceId;
 import org.briarproject.api.TransportId;
 import org.briarproject.api.contact.Contact;
 import org.briarproject.api.contact.ContactId;
@@ -542,6 +543,23 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		}
 	}
 
+	public DeviceId getDeviceId() throws DbException {
+		lock.readLock().lock();
+		try {
+			T txn = db.startTransaction();
+			try {
+				DeviceId id = db.getDeviceId(txn);
+				db.commitTransaction(txn);
+				return id;
+			} catch (DbException e) {
+				db.abortTransaction(txn);
+				throw e;
+			}
+		} finally {
+			lock.readLock().unlock();
+		}
+	}
+
 	public Group getGroup(GroupId g) throws DbException {
 		lock.readLock().lock();
 		try {
diff --git a/briar-core/src/org/briarproject/db/JdbcDatabase.java b/briar-core/src/org/briarproject/db/JdbcDatabase.java
index 63b6aa18618012da2d65e444e9cdaed0a642e601..411d7246c7dbafea7d075579281e4bc002f32db0 100644
--- a/briar-core/src/org/briarproject/db/JdbcDatabase.java
+++ b/briar-core/src/org/briarproject/db/JdbcDatabase.java
@@ -1,5 +1,6 @@
 package org.briarproject.db;
 
+import org.briarproject.api.DeviceId;
 import org.briarproject.api.TransportId;
 import org.briarproject.api.UniqueId;
 import org.briarproject.api.contact.Contact;
@@ -484,6 +485,11 @@ abstract class JdbcDatabase implements Database<Connection> {
 		if (interrupted) Thread.currentThread().interrupt();
 	}
 
+	public DeviceId getDeviceId(Connection txn) throws DbException {
+		Settings s = getSettings(txn, DEVICE_SETTINGS_NAMESPACE);
+		return new DeviceId(StringUtils.fromHexString(s.get(DEVICE_ID_KEY)));
+	}
+
 	public ContactId addContact(Connection txn, Author remote, AuthorId local)
 			throws DbException {
 		PreparedStatement ps = null;
diff --git a/briar-core/src/org/briarproject/properties/TransportPropertyManagerImpl.java b/briar-core/src/org/briarproject/properties/TransportPropertyManagerImpl.java
index 2d4fc5bcc1779e3758150fe73745a5f9cf70a1a3..5da83e49ddaaef91fb4bd5210adb031bd8a0eea5 100644
--- a/briar-core/src/org/briarproject/properties/TransportPropertyManagerImpl.java
+++ b/briar-core/src/org/briarproject/properties/TransportPropertyManagerImpl.java
@@ -2,6 +2,7 @@ package org.briarproject.properties;
 
 import com.google.inject.Inject;
 
+import org.briarproject.api.DeviceId;
 import org.briarproject.api.FormatException;
 import org.briarproject.api.TransportId;
 import org.briarproject.api.UniqueId;
@@ -43,6 +44,7 @@ import java.util.Map.Entry;
 import java.util.concurrent.locks.ReentrantReadWriteLock;
 import java.util.logging.Logger;
 
+import static java.util.logging.Level.INFO;
 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;
@@ -100,9 +102,10 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 			db.addContactGroup(c, g);
 			db.setVisibility(g.getId(), Collections.singletonList(c));
 			// Copy the latest local properties into the group
+			DeviceId dev = db.getDeviceId();
 			Map<TransportId, TransportProperties> local = getLocalProperties();
 			for (Entry<TransportId, TransportProperties> e : local.entrySet())
-				storeMessage(g.getId(), e.getKey(), e.getValue(), 0);
+				storeMessage(g.getId(), dev, e.getKey(), e.getValue(), 0);
 		} catch (DbException e) {
 			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
 		} catch (FormatException e) {
@@ -141,9 +144,10 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 		return out.toByteArray();
 	}
 
-	private void storeMessage(GroupId g, TransportId t, TransportProperties p,
-			long version) throws DbException, IOException {
-		byte[] body = encodeProperties(t, p, version);
+	private void storeMessage(GroupId g, DeviceId dev, TransportId t,
+			TransportProperties p, long version) throws DbException,
+			IOException {
+		byte[] body = encodeProperties(dev, t, p, version);
 		long now = clock.currentTimeMillis();
 		Message m = messageFactory.createMessage(g, now, body);
 		BdfDictionary d = new BdfDictionary();
@@ -153,13 +157,13 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 		db.addLocalMessage(m, CLIENT_ID, metadataEncoder.encode(d));
 	}
 
-	private byte[] encodeProperties(TransportId t, TransportProperties p,
-			long version) {
+	private byte[] encodeProperties(DeviceId dev, TransportId t,
+			TransportProperties p, long version) {
 		ByteArrayOutputStream out = new ByteArrayOutputStream();
 		BdfWriter w = bdfWriterFactory.createWriter(out);
 		try {
-			// TODO: Device ID
 			w.writeListStart();
+			w.writeRaw(dev.getBytes());
 			w.writeString(t.getString());
 			w.writeInteger(version);
 			w.writeDictionary(p);
@@ -232,8 +236,8 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 		ByteArrayInputStream in = new ByteArrayInputStream(raw,
 				MESSAGE_HEADER_LENGTH, raw.length - MESSAGE_HEADER_LENGTH);
 		BdfReader r = bdfReaderFactory.createReader(in);
-		// TODO: Device ID
 		r.readListStart();
+		r.skipRaw(); // Device ID
 		r.skipString(); // Transport ID
 		r.skipInteger(); // Version
 		r.readDictionaryStart();
@@ -242,9 +246,6 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 			String value = r.readString(MAX_PROPERTY_LENGTH);
 			p.put(key, value);
 		}
-		r.readDictionaryEnd();
-		r.readListEnd();
-		if (!r.eof()) throw new FormatException();
 		return p;
 	}
 
@@ -310,14 +311,19 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 				p = old;
 			}
 			// Store the merged properties in the local group
+			DeviceId dev = db.getDeviceId();
 			long version = latest == null ? 0 : latest.version + 1;
-			storeMessage(localGroup.getId(), t, p, version);
+			storeMessage(localGroup.getId(), dev, t, p, version);
+			if (LOG.isLoggable(INFO)) {
+				LOG.info("Stored local properties for " + t.getString()
+						+ ", version " + 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);
+				storeMessage(g.getId(), dev, t, p, version);
 			}
 		} catch (IOException e) {
 			throw new DbException(e);
diff --git a/briar-core/src/org/briarproject/properties/TransportPropertyValidator.java b/briar-core/src/org/briarproject/properties/TransportPropertyValidator.java
index 0a140dd5bacc5734c4e57f2e7f8b5b5b005df57a..eeee9f333447c2489c62e27d42da582eca6bde9c 100644
--- a/briar-core/src/org/briarproject/properties/TransportPropertyValidator.java
+++ b/briar-core/src/org/briarproject/properties/TransportPropertyValidator.java
@@ -1,6 +1,7 @@
 package org.briarproject.properties;
 
 import org.briarproject.api.FormatException;
+import org.briarproject.api.UniqueId;
 import org.briarproject.api.data.BdfDictionary;
 import org.briarproject.api.data.BdfReader;
 import org.briarproject.api.data.BdfReaderFactory;
@@ -53,10 +54,11 @@ class TransportPropertyValidator implements MessageValidator {
 			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();
+			byte[] deviceId = r.readRaw(UniqueId.LENGTH);
+			if (deviceId.length != UniqueId.LENGTH) throw new FormatException();
+			String transportId = r.readString(MAX_TRANSPORT_ID_LENGTH);
+			if (transportId.length() == 0) throw new FormatException();
 			long version = r.readInteger();
 			if (version < 0) throw new FormatException();
 			r.readDictionaryStart();
@@ -71,7 +73,7 @@ class TransportPropertyValidator implements MessageValidator {
 			if (!r.eof()) throw new FormatException();
 			// Return the metadata
 			BdfDictionary d = new BdfDictionary();
-			d.put("transportId", id);
+			d.put("transportId", transportId);
 			d.put("version", version);
 			d.put("local", false);
 			return metadataEncoder.encode(d);
diff --git a/briar-core/src/org/briarproject/util/StringUtils.java b/briar-core/src/org/briarproject/util/StringUtils.java
index 822831ac05b347daa88b041144a6bf100a93cd04..0753748e88c7c63ac8220d82c4041ee8094266a8 100644
--- a/briar-core/src/org/briarproject/util/StringUtils.java
+++ b/briar-core/src/org/briarproject/util/StringUtils.java
@@ -65,7 +65,8 @@ public class StringUtils {
 	/** Converts the given hex string to a byte array. */
 	public static byte[] fromHexString(String hex) {
 		int len = hex.length();
-		if (len % 2 != 0) throw new IllegalArgumentException("Not a hex string");
+		if (len % 2 != 0)
+			throw new IllegalArgumentException("Not a hex string");
 		byte[] bytes = new byte[len / 2];
 		for (int i = 0, j = 0; i < len; i += 2, j++) {
 			int high = hexDigitToInt(hex.charAt(i));