Upgrade handshake protocol to new key agreement method.

2026-02-15 04:18:53 +01:00 · 2023-03-10 16:05:59 +00:00
parent 8d20c5d8b8
commit 462f57c966
9 changed files with 555 additions and 30 deletions
--- a/bramble-api/src/main/java/org/briarproject/bramble/api/crypto/CryptoComponent.java
+++ b/bramble-api/src/main/java/org/briarproject/bramble/api/crypto/CryptoComponent.java
@@ -54,6 +54,38 @@ public interface CryptoComponent {
 			KeyPair ourKeyPair, byte[]... inputs)
 			throws GeneralSecurityException;

+	/**
+	 * Derives a shared secret from two static and two ephemeral key pairs.
+	 * <p>
+	 * Do not use this method for new protocols. The shared secret can be
+	 * re-derived using the ephemeral public keys and both static private
+	 * keys, so keys derived from the shared secret should not be used if
+	 * forward secrecy is required. Use {@link #deriveSharedSecret(String,
+	 * PublicKey, PublicKey, KeyPair, KeyPair, boolean, byte[]...)} instead.
+	 * <p>
+	 * TODO: Remove this after a reasonable migration period (added 2023-03-10).
+	 * <p>
+	 *
+	 * @param label A namespaced label indicating the purpose of this shared
+	 * secret, to prevent it from being repurposed or colliding with a shared
+	 * secret derived for another purpose
+	 * @param theirStaticPublicKey The static public key of the remote party
+	 * @param theirEphemeralPublicKey The ephemeral public key of the remote
+	 * party
+	 * @param ourStaticKeyPair The static key pair of the local party
+	 * @param ourEphemeralKeyPair The ephemeral key pair of the local party
+	 * @param alice True if the local party is Alice
+	 * @param inputs Additional inputs that will be included in the
+	 * derivation of the shared secret
+	 * @return The shared secret
+	 */
+	@Deprecated
+	SecretKey deriveSharedSecretBadly(String label,
+			PublicKey theirStaticPublicKey, PublicKey theirEphemeralPublicKey,
+			KeyPair ourStaticKeyPair, KeyPair ourEphemeralKeyPair,
+			boolean alice, byte[]... inputs)
+			throws GeneralSecurityException;
+
 	/**
 	 * Derives a shared secret from two static and two ephemeral key pairs.
 	 *
--- a/bramble-core/src/main/java/org/briarproject/bramble/contact/HandshakeConstants.java
+++ b/bramble-core/src/main/java/org/briarproject/bramble/contact/HandshakeConstants.java
@@ -5,14 +5,31 @@ import static org.briarproject.bramble.api.crypto.CryptoConstants.MAC_BYTES;
 interface HandshakeConstants {

 	/**
-	 * The current version of the handshake protocol.
+	 * The current major version of the handshake protocol.
 	 */
 	byte PROTOCOL_VERSION = 0;

 	/**
-	 * Label for deriving the master key.
+	 * The current minor version of the handshake protocol.
 	 */
-	String MASTER_KEY_LABEL = "org.briarproject.bramble.handshake/MASTER_KEY";
+	byte PROTOCOL_MINOR_VERSION = 1;
+
+	/**
+	 * Label for deriving the master key when using the deprecated v0.0 key
+	 * derivation method.
+	 * <p>
+	 * TODO: Remove this after a reasonable migration period (added 2023-03-10).
+	 */
+	@Deprecated
+	String MASTER_KEY_LABEL_0_0 =
+			"org.briarproject.bramble.handshake/MASTER_KEY";
+
+	/**
+	 * Label for deriving the master key when using the v0.1 key derivation
+	 * method.
+	 */
+	String MASTER_KEY_LABEL_0_1 =
+			"org.briarproject.bramble.handshake/MASTER_KEY_0_1";

 	/**
 	 * Label for deriving Alice's proof of ownership from the master key.
--- a/bramble-core/src/main/java/org/briarproject/bramble/contact/HandshakeCrypto.java
+++ b/bramble-core/src/main/java/org/briarproject/bramble/contact/HandshakeCrypto.java
@@ -13,11 +13,26 @@ interface HandshakeCrypto {
 	KeyPair generateEphemeralKeyPair();

 	/**
-	 * Derives the master key from the given static and ephemeral keys.
+	 * Derives the master key from the given static and ephemeral keys using
+	 * the deprecated v0.0 key derivation method.
+	 * <p>
+	 * TODO: Remove this after a reasonable migration period (added 2023-03-10).
 	 *
 	 * @param alice Whether the local peer is Alice
 	 */
-	SecretKey deriveMasterKey(PublicKey theirStaticPublicKey,
+	@Deprecated
+	SecretKey deriveMasterKey_0_0(PublicKey theirStaticPublicKey,
+			PublicKey theirEphemeralPublicKey, KeyPair ourStaticKeyPair,
+			KeyPair ourEphemeralKeyPair, boolean alice)
+			throws GeneralSecurityException;
+
+	/**
+	 * Derives the master key from the given static and ephemeral keys using
+	 * the v0.1 key derivation method.
+	 *
+	 * @param alice Whether the local peer is Alice
+	 */
+	SecretKey deriveMasterKey_0_1(PublicKey theirStaticPublicKey,
 			PublicKey theirEphemeralPublicKey, KeyPair ourStaticKeyPair,
 			KeyPair ourEphemeralKeyPair, boolean alice)
 			throws GeneralSecurityException;
--- a/bramble-core/src/main/java/org/briarproject/bramble/contact/HandshakeCryptoImpl.java
+++ b/bramble-core/src/main/java/org/briarproject/bramble/contact/HandshakeCryptoImpl.java
@@ -13,7 +13,8 @@ import javax.inject.Inject;

 import static org.briarproject.bramble.contact.HandshakeConstants.ALICE_PROOF_LABEL;
 import static org.briarproject.bramble.contact.HandshakeConstants.BOB_PROOF_LABEL;
-import static org.briarproject.bramble.contact.HandshakeConstants.MASTER_KEY_LABEL;
+import static org.briarproject.bramble.contact.HandshakeConstants.MASTER_KEY_LABEL_0_0;
+import static org.briarproject.bramble.contact.HandshakeConstants.MASTER_KEY_LABEL_0_1;

@Immutable
@NotNullByDefault
@@ -32,7 +33,8 @@ class HandshakeCryptoImpl implements HandshakeCrypto {
 	}

 	@Override
-	public SecretKey deriveMasterKey(PublicKey theirStaticPublicKey,
+	@Deprecated
+	public SecretKey deriveMasterKey_0_0(PublicKey theirStaticPublicKey,
 			PublicKey theirEphemeralPublicKey, KeyPair ourStaticKeyPair,
 			KeyPair ourEphemeralKeyPair, boolean alice) throws
 			GeneralSecurityException {
@@ -46,9 +48,29 @@ class HandshakeCryptoImpl implements HandshakeCrypto {
 				alice ? ourEphemeral : theirEphemeral,
 				alice ? theirEphemeral : ourEphemeral
 		};
-		return crypto.deriveSharedSecret(MASTER_KEY_LABEL, theirStaticPublicKey,
-				theirEphemeralPublicKey, ourStaticKeyPair, ourEphemeralKeyPair,
-				alice, inputs);
+		return crypto.deriveSharedSecretBadly(MASTER_KEY_LABEL_0_0,
+				theirStaticPublicKey, theirEphemeralPublicKey,
+				ourStaticKeyPair, ourEphemeralKeyPair, alice, inputs);
+	}
+
+	@Override
+	public SecretKey deriveMasterKey_0_1(PublicKey theirStaticPublicKey,
+			PublicKey theirEphemeralPublicKey, KeyPair ourStaticKeyPair,
+			KeyPair ourEphemeralKeyPair, boolean alice) throws
+			GeneralSecurityException {
+		byte[] theirStatic = theirStaticPublicKey.getEncoded();
+		byte[] theirEphemeral = theirEphemeralPublicKey.getEncoded();
+		byte[] ourStatic = ourStaticKeyPair.getPublic().getEncoded();
+		byte[] ourEphemeral = ourEphemeralKeyPair.getPublic().getEncoded();
+		byte[][] inputs = {
+				alice ? ourStatic : theirStatic,
+				alice ? theirStatic : ourStatic,
+				alice ? ourEphemeral : theirEphemeral,
+				alice ? theirEphemeral : ourEphemeral
+		};
+		return crypto.deriveSharedSecret(MASTER_KEY_LABEL_0_1,
+				theirStaticPublicKey, theirEphemeralPublicKey,
+				ourStaticKeyPair, ourEphemeralKeyPair, alice, inputs);
 	}

 	@Override
--- a/bramble-core/src/main/java/org/briarproject/bramble/contact/HandshakeManagerImpl.java
+++ b/bramble-core/src/main/java/org/briarproject/bramble/contact/HandshakeManagerImpl.java
@@ -27,15 +27,20 @@ import java.io.EOFException;
 import java.io.IOException;
 import java.io.InputStream;
 import java.security.GeneralSecurityException;
+import java.util.List;

 import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;

+import static java.util.Arrays.asList;
+import static java.util.Collections.singletonList;
 import static org.briarproject.bramble.api.crypto.CryptoConstants.MAX_AGREEMENT_PUBLIC_KEY_BYTES;
 import static org.briarproject.bramble.contact.HandshakeConstants.PROOF_BYTES;
+import static org.briarproject.bramble.contact.HandshakeConstants.PROTOCOL_MINOR_VERSION;
 import static org.briarproject.bramble.contact.HandshakeConstants.PROTOCOL_VERSION;
-import static org.briarproject.bramble.contact.HandshakeRecordTypes.EPHEMERAL_PUBLIC_KEY;
-import static org.briarproject.bramble.contact.HandshakeRecordTypes.PROOF_OF_OWNERSHIP;
+import static org.briarproject.bramble.contact.HandshakeRecordTypes.RECORD_TYPE_EPHEMERAL_PUBLIC_KEY;
+import static org.briarproject.bramble.contact.HandshakeRecordTypes.RECORD_TYPE_MINOR_VERSION;
+import static org.briarproject.bramble.contact.HandshakeRecordTypes.RECORD_TYPE_PROOF_OF_OWNERSHIP;
 import static org.briarproject.bramble.util.ValidationUtils.checkLength;

@Immutable
@@ -48,7 +53,9 @@ class HandshakeManagerImpl implements HandshakeManager {
 					!isKnownRecordType(r.getRecordType());

 	private static boolean isKnownRecordType(byte type) {
-		return type == EPHEMERAL_PUBLIC_KEY || type == PROOF_OF_OWNERSHIP;
+		return type == RECORD_TYPE_EPHEMERAL_PUBLIC_KEY ||
+				type == RECORD_TYPE_PROOF_OF_OWNERSHIP ||
+				type == RECORD_TYPE_MINOR_VERSION;
 	}

 	private final TransactionManager db;
@@ -94,19 +101,31 @@ class HandshakeManagerImpl implements HandshakeManager {
 				.createRecordWriter(out.getOutputStream());
 		KeyPair ourEphemeralKeyPair =
 				handshakeCrypto.generateEphemeralKeyPair();
-		PublicKey theirEphemeralPublicKey;
+		Pair<Byte, PublicKey> theirMinorVersionAndKey;
 		if (alice) {
+			sendMinorVersion(recordWriter);
 			sendPublicKey(recordWriter, ourEphemeralKeyPair.getPublic());
-			theirEphemeralPublicKey = receivePublicKey(recordReader);
+			theirMinorVersionAndKey = receiveMinorVersionAndKey(recordReader);
 		} else {
-			theirEphemeralPublicKey = receivePublicKey(recordReader);
+			theirMinorVersionAndKey = receiveMinorVersionAndKey(recordReader);
+			sendMinorVersion(recordWriter);
 			sendPublicKey(recordWriter, ourEphemeralKeyPair.getPublic());
 		}
+		byte theirMinorVersion = theirMinorVersionAndKey.getFirst();
+		PublicKey theirEphemeralPublicKey = theirMinorVersionAndKey.getSecond();
 		SecretKey masterKey;
 		try {
-			masterKey = handshakeCrypto.deriveMasterKey(theirStaticPublicKey,
-					theirEphemeralPublicKey, ourStaticKeyPair,
-					ourEphemeralKeyPair, alice);
+			if (theirMinorVersion > 0) {
+				masterKey = handshakeCrypto.deriveMasterKey_0_1(
+						theirStaticPublicKey, theirEphemeralPublicKey,
+						ourStaticKeyPair, ourEphemeralKeyPair, alice);
+			} else {
+				// TODO: Remove this branch after a reasonable migration
+				//  period (added 2023-03-10).
+				masterKey = handshakeCrypto.deriveMasterKey_0_0(
+						theirStaticPublicKey, theirEphemeralPublicKey,
+						ourStaticKeyPair, ourEphemeralKeyPair, alice);
+			}
 		} catch (GeneralSecurityException e) {
 			throw new FormatException();
 		}
@@ -127,34 +146,90 @@ class HandshakeManagerImpl implements HandshakeManager {
 	}

 	private void sendPublicKey(RecordWriter w, PublicKey k) throws IOException {
-		w.writeRecord(new Record(PROTOCOL_VERSION, EPHEMERAL_PUBLIC_KEY,
-				k.getEncoded()));
+		w.writeRecord(new Record(PROTOCOL_VERSION,
+				RECORD_TYPE_EPHEMERAL_PUBLIC_KEY, k.getEncoded()));
 		w.flush();
 	}

-	private PublicKey receivePublicKey(RecordReader r) throws IOException {
-		byte[] key = readRecord(r, EPHEMERAL_PUBLIC_KEY).getPayload();
+	/**
+	 * Receives the remote peer's protocol minor version and ephemeral public
+	 * key.
+	 * <p>
+	 * In version 0.1 of the protocol, each peer sends a minor version record
+	 * followed by an ephemeral public key record.
+	 * <p>
+	 * In version 0.0 of the protocol, each peer sends an ephemeral public key
+	 * record without a preceding minor version record.
+	 * <p>
+	 * Therefore the remote peer's minor version must be non-zero if a minor
+	 * version record is received, and is assumed to be zero if no minor
+	 * version record is received.
+	 */
+	private Pair<Byte, PublicKey> receiveMinorVersionAndKey(RecordReader r)
+			throws IOException {
+		byte theirMinorVersion;
+		PublicKey theirEphemeralPublicKey;
+		// The first record can be either a minor version record or an
+		// ephemeral public key record
+		Record first = readRecord(r, asList(RECORD_TYPE_MINOR_VERSION,
+				RECORD_TYPE_EPHEMERAL_PUBLIC_KEY));
+		if (first.getRecordType() == RECORD_TYPE_MINOR_VERSION) {
+			// The payload must be a single byte giving the remote peer's
+			// protocol minor version, which must be non-zero
+			byte[] payload = first.getPayload();
+			checkLength(payload, 1);
+			theirMinorVersion = payload[0];
+			if (theirMinorVersion == 0) throw new FormatException();
+			// The second record must be an ephemeral public key record
+			Record second = readRecord(r,
+					singletonList(RECORD_TYPE_EPHEMERAL_PUBLIC_KEY));
+			theirEphemeralPublicKey = parsePublicKey(second);
+		} else {
+			// The remote peer did not send a minor version record, so the
+			// remote peer's protocol minor version is assumed to be zero
+			// TODO: Remove this branch after a reasonable migration period
+			//  (added 2023-03-10).
+			theirMinorVersion = 0;
+			theirEphemeralPublicKey = parsePublicKey(first);
+		}
+		return new Pair<>(theirMinorVersion, theirEphemeralPublicKey);
+	}
+
+	private PublicKey parsePublicKey(Record rec) throws IOException {
+		if (rec.getRecordType() != RECORD_TYPE_EPHEMERAL_PUBLIC_KEY) {
+			throw new AssertionError();
+		}
+		byte[] key = rec.getPayload();
 		checkLength(key, 1, MAX_AGREEMENT_PUBLIC_KEY_BYTES);
 		return new AgreementPublicKey(key);
 	}

 	private void sendProof(RecordWriter w, byte[] proof) throws IOException {
-		w.writeRecord(new Record(PROTOCOL_VERSION, PROOF_OF_OWNERSHIP, proof));
+		w.writeRecord(new Record(PROTOCOL_VERSION,
+				RECORD_TYPE_PROOF_OF_OWNERSHIP, proof));
 		w.flush();
 	}

 	private byte[] receiveProof(RecordReader r) throws IOException {
-		byte[] proof = readRecord(r, PROOF_OF_OWNERSHIP).getPayload();
+		Record rec = readRecord(r,
+				singletonList(RECORD_TYPE_PROOF_OF_OWNERSHIP));
+		byte[] proof = rec.getPayload();
 		checkLength(proof, PROOF_BYTES, PROOF_BYTES);
 		return proof;
 	}

-	private Record readRecord(RecordReader r, byte expectedType)
+	private void sendMinorVersion(RecordWriter w) throws IOException {
+		w.writeRecord(new Record(PROTOCOL_VERSION, RECORD_TYPE_MINOR_VERSION,
+				new byte[] {PROTOCOL_MINOR_VERSION}));
+		w.flush();
+	}
+
+	private Record readRecord(RecordReader r, List<Byte> expectedTypes)
 			throws IOException {
 		// Accept records with current protocol version, expected types only
 		RecordPredicate accept = rec ->
 				rec.getProtocolVersion() == PROTOCOL_VERSION &&
-						rec.getRecordType() == expectedType;
+						expectedTypes.contains(rec.getRecordType());
 		Record rec = r.readRecord(accept, IGNORE);
 		if (rec == null) throw new EOFException();
 		return rec;
--- a/bramble-core/src/main/java/org/briarproject/bramble/contact/HandshakeRecordTypes.java
+++ b/bramble-core/src/main/java/org/briarproject/bramble/contact/HandshakeRecordTypes.java
@@ -5,7 +5,9 @@ package org.briarproject.bramble.contact;
 */
 interface HandshakeRecordTypes {

-	byte EPHEMERAL_PUBLIC_KEY = 0;
+	byte RECORD_TYPE_EPHEMERAL_PUBLIC_KEY = 0;

-	byte PROOF_OF_OWNERSHIP = 1;
+	byte RECORD_TYPE_PROOF_OF_OWNERSHIP = 1;
+
+	byte RECORD_TYPE_MINOR_VERSION = 2;
 }
--- a/bramble-core/src/main/java/org/briarproject/bramble/crypto/CryptoComponentImpl.java
+++ b/bramble-core/src/main/java/org/briarproject/bramble/crypto/CryptoComponentImpl.java
@@ -222,7 +222,8 @@ class CryptoComponentImpl implements CryptoComponent {
 	}

 	@Override
-	public SecretKey deriveSharedSecret(String label,
+	@Deprecated
+	public SecretKey deriveSharedSecretBadly(String label,
 			PublicKey theirStaticPublicKey, PublicKey theirEphemeralPublicKey,
 			KeyPair ourStaticKeyPair, KeyPair ourEphemeralKeyPair,
 			boolean alice, byte[]... inputs) throws GeneralSecurityException {
@@ -250,6 +251,35 @@ class CryptoComponentImpl implements CryptoComponent {
 		return new SecretKey(hash);
 	}

+	@Override
+	public SecretKey deriveSharedSecret(String label,
+			PublicKey theirStaticPublicKey, PublicKey theirEphemeralPublicKey,
+			KeyPair ourStaticKeyPair, KeyPair ourEphemeralKeyPair,
+			boolean alice, byte[]... inputs) throws GeneralSecurityException {
+		PrivateKey ourStaticPrivateKey = ourStaticKeyPair.getPrivate();
+		PrivateKey ourEphemeralPrivateKey = ourEphemeralKeyPair.getPrivate();
+		byte[][] hashInputs = new byte[inputs.length + 3][];
+		// Alice ephemeral/Bob ephemeral
+		hashInputs[0] = performRawKeyAgreement(ourEphemeralPrivateKey,
+				theirEphemeralPublicKey);
+		// Alice static/Bob ephemeral, Bob static/Alice ephemeral
+		if (alice) {
+			hashInputs[1] = performRawKeyAgreement(ourStaticPrivateKey,
+					theirEphemeralPublicKey);
+			hashInputs[2] = performRawKeyAgreement(ourEphemeralPrivateKey,
+					theirStaticPublicKey);
+		} else {
+			hashInputs[1] = performRawKeyAgreement(ourEphemeralPrivateKey,
+					theirStaticPublicKey);
+			hashInputs[2] = performRawKeyAgreement(ourStaticPrivateKey,
+					theirEphemeralPublicKey);
+		}
+		arraycopy(inputs, 0, hashInputs, 3, inputs.length);
+		byte[] hash = hash(label, hashInputs);
+		if (hash.length != SecretKey.LENGTH) throw new IllegalStateException();
+		return new SecretKey(hash);
+	}
+
 	@Override
 	public byte[] sign(String label, byte[] toSign, PrivateKey privateKey)
 			throws GeneralSecurityException {
--- a/bramble-core/src/test/java/org/briarproject/bramble/contact/HandshakeManagerImplTest.java
+++ b/bramble-core/src/test/java/org/briarproject/bramble/contact/HandshakeManagerImplTest.java
@@ -0,0 +1,316 @@
+package org.briarproject.bramble.contact;
+
+import org.briarproject.bramble.api.FormatException;
+import org.briarproject.bramble.api.contact.ContactManager;
+import org.briarproject.bramble.api.contact.HandshakeManager.HandshakeResult;
+import org.briarproject.bramble.api.contact.PendingContact;
+import org.briarproject.bramble.api.crypto.KeyPair;
+import org.briarproject.bramble.api.crypto.PrivateKey;
+import org.briarproject.bramble.api.crypto.PublicKey;
+import org.briarproject.bramble.api.crypto.SecretKey;
+import org.briarproject.bramble.api.crypto.TransportCrypto;
+import org.briarproject.bramble.api.db.Transaction;
+import org.briarproject.bramble.api.db.TransactionManager;
+import org.briarproject.bramble.api.identity.IdentityManager;
+import org.briarproject.bramble.api.record.Record;
+import org.briarproject.bramble.api.record.RecordReader;
+import org.briarproject.bramble.api.record.RecordReader.RecordPredicate;
+import org.briarproject.bramble.api.record.RecordReaderFactory;
+import org.briarproject.bramble.api.record.RecordWriter;
+import org.briarproject.bramble.api.record.RecordWriterFactory;
+import org.briarproject.bramble.api.transport.StreamWriter;
+import org.briarproject.bramble.test.BrambleMockTestCase;
+import org.briarproject.bramble.test.DbExpectations;
+import org.briarproject.bramble.test.PredicateMatcher;
+import org.jmock.Expectations;
+import org.junit.Test;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.util.Arrays;
+
+import static org.briarproject.bramble.contact.HandshakeConstants.PROOF_BYTES;
+import static org.briarproject.bramble.contact.HandshakeConstants.PROTOCOL_MINOR_VERSION;
+import static org.briarproject.bramble.contact.HandshakeConstants.PROTOCOL_VERSION;
+import static org.briarproject.bramble.contact.HandshakeRecordTypes.RECORD_TYPE_EPHEMERAL_PUBLIC_KEY;
+import static org.briarproject.bramble.contact.HandshakeRecordTypes.RECORD_TYPE_MINOR_VERSION;
+import static org.briarproject.bramble.contact.HandshakeRecordTypes.RECORD_TYPE_PROOF_OF_OWNERSHIP;
+import static org.briarproject.bramble.test.TestUtils.getAgreementPrivateKey;
+import static org.briarproject.bramble.test.TestUtils.getAgreementPublicKey;
+import static org.briarproject.bramble.test.TestUtils.getPendingContact;
+import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
+import static org.briarproject.bramble.test.TestUtils.getSecretKey;
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+
+public class HandshakeManagerImplTest extends BrambleMockTestCase {
+
+	private final TransactionManager db =
+			context.mock(TransactionManager.class);
+	private final IdentityManager identityManager =
+			context.mock(IdentityManager.class);
+	private final ContactManager contactManager =
+			context.mock(ContactManager.class);
+	private final TransportCrypto transportCrypto =
+			context.mock(TransportCrypto.class);
+	private final HandshakeCrypto handshakeCrypto =
+			context.mock(HandshakeCrypto.class);
+	private final RecordReaderFactory recordReaderFactory =
+			context.mock(RecordReaderFactory.class);
+	private final RecordWriterFactory recordWriterFactory =
+			context.mock(RecordWriterFactory.class);
+	private final RecordReader recordReader = context.mock(RecordReader.class);
+	private final RecordWriter recordWriter = context.mock(RecordWriter.class);
+	private final StreamWriter streamWriter = context.mock(StreamWriter.class);
+
+	private final PendingContact pendingContact = getPendingContact();
+	private final PublicKey theirStaticPublicKey =
+			pendingContact.getPublicKey();
+	private final PublicKey ourStaticPublicKey = getAgreementPublicKey();
+	private final PrivateKey ourStaticPrivateKey = getAgreementPrivateKey();
+	private final KeyPair ourStaticKeyPair =
+			new KeyPair(ourStaticPublicKey, ourStaticPrivateKey);
+	private final PublicKey theirEphemeralPublicKey = getAgreementPublicKey();
+	private final PublicKey ourEphemeralPublicKey = getAgreementPublicKey();
+	private final PrivateKey ourEphemeralPrivateKey = getAgreementPrivateKey();
+	private final KeyPair ourEphemeralKeyPair =
+			new KeyPair(ourEphemeralPublicKey, ourEphemeralPrivateKey);
+	private final SecretKey masterKey = getSecretKey();
+	private final byte[] ourProof = getRandomBytes(PROOF_BYTES);
+	private final byte[] theirProof = getRandomBytes(PROOF_BYTES);
+
+	private final InputStream in = new ByteArrayInputStream(new byte[0]);
+	private final OutputStream out = new ByteArrayOutputStream(0);
+
+	private final HandshakeManagerImpl handshakeManager =
+			new HandshakeManagerImpl(db, identityManager, contactManager,
+					transportCrypto, handshakeCrypto, recordReaderFactory,
+					recordWriterFactory);
+
+	@Test
+	public void testHandshakeAsAliceWithPeerVersion_0_1() throws Exception {
+		testHandshakeWithPeerVersion_0_1(true);
+	}
+
+	@Test
+	public void testHandshakeAsBobWithPeerVersion_0_1() throws Exception {
+		testHandshakeWithPeerVersion_0_1(false);
+	}
+
+	private void testHandshakeWithPeerVersion_0_1(boolean alice)
+			throws Exception {
+		expectPrepareForHandshake(alice);
+		expectSendMinorVersion();
+		expectSendKey();
+		// Remote peer sends minor version, so use new key derivation
+		expectReceiveMinorVersion();
+		expectReceiveKey();
+		expectDeriveMasterKey_0_1(alice);
+		expectDeriveProof(alice);
+		expectSendProof();
+		expectReceiveProof();
+		expectSendEof();
+		expectReceiveEof();
+		expectVerifyOwnership(alice, true);
+
+		HandshakeResult result = handshakeManager.handshake(
+				pendingContact.getId(), in, streamWriter);
+
+		assertArrayEquals(masterKey.getBytes(),
+				result.getMasterKey().getBytes());
+		assertEquals(alice, result.isAlice());
+	}
+
+	@Test
+	public void testHandshakeAsAliceWithPeerVersion_0_0() throws Exception {
+		testHandshakeWithPeerVersion_0_0(true);
+	}
+
+	@Test
+	public void testHandshakeAsBobWithPeerVersion_0_0() throws Exception {
+		testHandshakeWithPeerVersion_0_0(false);
+	}
+
+	private void testHandshakeWithPeerVersion_0_0(boolean alice)
+			throws Exception {
+		expectPrepareForHandshake(alice);
+		expectSendMinorVersion();
+		expectSendKey();
+		// Remote peer does not send minor version, so use old key derivation
+		expectReceiveKey();
+		expectDeriveMasterKey_0_0(alice);
+		expectDeriveProof(alice);
+		expectSendProof();
+		expectReceiveProof();
+		expectSendEof();
+		expectReceiveEof();
+		expectVerifyOwnership(alice, true);
+
+		HandshakeResult result = handshakeManager.handshake(
+				pendingContact.getId(), in, streamWriter);
+
+		assertArrayEquals(masterKey.getBytes(),
+				result.getMasterKey().getBytes());
+		assertEquals(alice, result.isAlice());
+	}
+
+	@Test(expected = FormatException.class)
+	public void testProofOfOwnershipNotVerifiedAsAlice() throws Exception {
+		testProofOfOwnershipNotVerified(true);
+	}
+
+	@Test(expected = FormatException.class)
+	public void testProofOfOwnershipNotVerifiedAsBob() throws Exception {
+		testProofOfOwnershipNotVerified(false);
+	}
+
+	private void testProofOfOwnershipNotVerified(boolean alice)
+			throws Exception {
+		expectPrepareForHandshake(alice);
+		expectSendMinorVersion();
+		expectSendKey();
+		expectReceiveMinorVersion();
+		expectReceiveKey();
+		expectDeriveMasterKey_0_1(alice);
+		expectDeriveProof(alice);
+		expectSendProof();
+		expectReceiveProof();
+		expectSendEof();
+		expectReceiveEof();
+		expectVerifyOwnership(alice, false);
+
+		handshakeManager.handshake(pendingContact.getId(), in, streamWriter);
+	}
+
+	private void expectPrepareForHandshake(boolean alice) throws Exception {
+		Transaction txn = new Transaction(null, true);
+
+		context.checking(new DbExpectations() {{
+			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
+			oneOf(contactManager).getPendingContact(txn,
+					pendingContact.getId());
+			will(returnValue(pendingContact));
+			oneOf(identityManager).getHandshakeKeys(txn);
+			will(returnValue(ourStaticKeyPair));
+			oneOf(transportCrypto).isAlice(theirStaticPublicKey,
+					ourStaticKeyPair);
+			will(returnValue(alice));
+			oneOf(recordReaderFactory).createRecordReader(in);
+			will(returnValue(recordReader));
+			oneOf(streamWriter).getOutputStream();
+			will(returnValue(out));
+			oneOf(recordWriterFactory).createRecordWriter(out);
+			will(returnValue(recordWriter));
+			oneOf(handshakeCrypto).generateEphemeralKeyPair();
+			will(returnValue(ourEphemeralKeyPair));
+		}});
+	}
+
+	private void expectSendMinorVersion() throws Exception {
+		expectWriteRecord(new Record(PROTOCOL_VERSION,
+				RECORD_TYPE_MINOR_VERSION,
+				new byte[] {PROTOCOL_MINOR_VERSION}));
+	}
+
+	private void expectReceiveMinorVersion() throws Exception {
+		expectReadRecord(new Record(PROTOCOL_VERSION,
+				RECORD_TYPE_MINOR_VERSION,
+				new byte[] {PROTOCOL_MINOR_VERSION}));
+	}
+
+	private void expectSendKey() throws Exception {
+		expectWriteRecord(new Record(PROTOCOL_VERSION,
+				RECORD_TYPE_EPHEMERAL_PUBLIC_KEY,
+				ourEphemeralPublicKey.getEncoded()));
+	}
+
+	private void expectReceiveKey() throws Exception {
+		expectReadRecord(new Record(PROTOCOL_VERSION,
+				RECORD_TYPE_EPHEMERAL_PUBLIC_KEY,
+				theirEphemeralPublicKey.getEncoded()));
+	}
+
+	private void expectDeriveMasterKey_0_1(boolean alice) throws Exception {
+		context.checking(new Expectations() {{
+			oneOf(handshakeCrypto).deriveMasterKey_0_1(theirStaticPublicKey,
+					theirEphemeralPublicKey, ourStaticKeyPair,
+					ourEphemeralKeyPair, alice);
+			will(returnValue(masterKey));
+		}});
+	}
+
+	private void expectDeriveMasterKey_0_0(boolean alice) throws Exception {
+		context.checking(new Expectations() {{
+			oneOf(handshakeCrypto).deriveMasterKey_0_0(theirStaticPublicKey,
+					theirEphemeralPublicKey, ourStaticKeyPair,
+					ourEphemeralKeyPair, alice);
+			will(returnValue(masterKey));
+		}});
+	}
+
+	private void expectDeriveProof(boolean alice) {
+		context.checking(new Expectations() {{
+			oneOf(handshakeCrypto).proveOwnership(masterKey, alice);
+			will(returnValue(ourProof));
+		}});
+	}
+
+	private void expectSendProof() throws Exception {
+		expectWriteRecord(new Record(PROTOCOL_VERSION,
+				RECORD_TYPE_PROOF_OF_OWNERSHIP, ourProof));
+	}
+
+	private void expectReceiveProof() throws Exception {
+		expectReadRecord(new Record(PROTOCOL_VERSION,
+				RECORD_TYPE_PROOF_OF_OWNERSHIP, theirProof));
+	}
+
+	private void expectSendEof() throws Exception {
+		context.checking(new Expectations() {{
+			oneOf(streamWriter).sendEndOfStream();
+		}});
+	}
+
+	private void expectReceiveEof() throws Exception {
+		context.checking(new Expectations() {{
+			oneOf(recordReader).readRecord(with(any(RecordPredicate.class)),
+					with(any(RecordPredicate.class)));
+			will(returnValue(null));
+		}});
+	}
+
+	private void expectVerifyOwnership(boolean alice, boolean verified) {
+		context.checking(new Expectations() {{
+			oneOf(handshakeCrypto).verifyOwnership(masterKey, !alice,
+					theirProof);
+			will(returnValue(verified));
+		}});
+	}
+
+	private void expectWriteRecord(Record record) throws Exception {
+		context.checking(new Expectations() {{
+			oneOf(recordWriter).writeRecord(with(new PredicateMatcher<>(
+					Record.class, r -> recordEquals(record, r))));
+			oneOf(recordWriter).flush();
+		}});
+	}
+
+	private boolean recordEquals(Record expected, Record actual) {
+		return expected.getProtocolVersion() == actual.getProtocolVersion() &&
+				expected.getRecordType() == actual.getRecordType() &&
+				Arrays.equals(expected.getPayload(), actual.getPayload());
+	}
+
+	private void expectReadRecord(Record record) throws Exception {
+		context.checking(new Expectations() {{
+			// Test that the `accept` predicate passed to the reader would
+			// accept the expected record
+			oneOf(recordReader).readRecord(with(new PredicateMatcher<>(
+							RecordPredicate.class, rp -> rp.test(record))),
+					with(any(RecordPredicate.class)));
+			will(returnValue(record));
+		}});
+	}
+}
--- a/bramble-core/src/test/java/org/briarproject/bramble/crypto/KeyAgreementTest.java
+++ b/bramble-core/src/test/java/org/briarproject/bramble/crypto/KeyAgreementTest.java
@@ -60,6 +60,22 @@ public class KeyAgreementTest extends BrambleTestCase {
 		assertArrayEquals(aShared.getBytes(), bShared.getBytes());
 	}

+	@Test
+	public void testDerivesStaticEphemeralSharedSecretBadly() throws Exception {
+		String label = getRandomString(123);
+		KeyPair aStatic = crypto.generateAgreementKeyPair();
+		KeyPair aEphemeral = crypto.generateAgreementKeyPair();
+		KeyPair bStatic = crypto.generateAgreementKeyPair();
+		KeyPair bEphemeral = crypto.generateAgreementKeyPair();
+		SecretKey aShared = crypto.deriveSharedSecretBadly(label,
+				bStatic.getPublic(), bEphemeral.getPublic(), aStatic,
+				aEphemeral, true, inputs);
+		SecretKey bShared = crypto.deriveSharedSecretBadly(label,
+				aStatic.getPublic(), aEphemeral.getPublic(), bStatic,
+				bEphemeral, false, inputs);
+		assertArrayEquals(aShared.getBytes(), bShared.getBytes());
+	}
+
 	@Test
 	public void testDerivesStaticEphemeralSharedSecret() throws Exception {
 		String label = getRandomString(123);