Include namespaced labels in crypto operations.

bramble-api/src/main/java/org/briarproject/bramble/api/contact/ContactExchangeTask.java

@@ -12,6 +12,27 @@ import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 @NotNullByDefault
 public interface ContactExchangeTask {
 
+	/**
+	 * Label for deriving Alice's header key from the master secret.
+	 */
+	String ALICE_KEY_LABEL =
+			"org.briarproject.bramble.contact/ALICE_HEADER_KEY";
+
+	/**
+	 * Label for deriving Bob's header key from the master secret.
+	 */
+	String BOB_KEY_LABEL = "org.briarproject.bramble.contact/BOB_HEADER_KEY";
+
+	/**
+	 * Label for deriving Alice's key binding nonce from the master secret.
+	 */
+	String ALICE_NONCE_LABEL = "org.briarproject.bramble.contact/ALICE_NONCE";
+
+	/**
+	 * Label for deriving Bob's key binding nonce from the master secret.
+	 */
+	String BOB_NONCE_LABEL = "org.briarproject.bramble.contact/BOB_NONCE";
+
 	/**
 	 * Exchanges contact information with a remote peer.
 	 */

bramble-api/src/main/java/org/briarproject/bramble/api/crypto/CryptoComponent.java

@@ -27,95 +27,74 @@ public interface CryptoComponent {
 	KeyParser getMessageKeyParser();
 
 	/**
-	 * Derives a stream header key from the given master secret.
-	 * @param alice whether the key is for use by Alice or Bob.
+	 * Derives another secret key from the given secret key.
+	 *
+	 * @param label a namespaced label indicating the purpose of the derived
+	 * key, to prevent it from being repurposed or colliding with a key derived
+	 * for another purpose
 	 */
-	SecretKey deriveHeaderKey(SecretKey master, boolean alice);
+	SecretKey deriveKey(String label, SecretKey k, byte[]... inputs);
 
 	/**
-	 * Derives a message authentication code key from the given master secret.
-	 * @param alice whether the key is for use by Alice or Bob.
+	 * Derives a nonce from the given secret key that can be used for key
+	 * binding.
+	 *
+	 * @param label a namespaced label indicating the purpose of this nonce,
+	 * to prevent it from being repurposed or colliding with a nonce derived
+	 * for another purpose
 	 */
-	SecretKey deriveMacKey(SecretKey master, boolean alice);
-
-	/**
-	 * Derives a nonce from the given master secret for one of the parties to
-	 * sign.
-	 * @param alice whether the nonce is for use by Alice or Bob.
-	 */
-	byte[] deriveSignatureNonce(SecretKey master, boolean alice);
+	byte[] deriveKeyBindingNonce(String label, SecretKey k);
 
 	/**
 	 * Derives a commitment to the provided public key.
 	 * <p/>
-	 * Part of BQP.
+	 * Used by the key exchange protocol.
 	 *
 	 * @param publicKey the public key
 	 * @return the commitment to the provided public key.
 	 */
-	byte[] deriveKeyCommitment(byte[] publicKey);
+	byte[] deriveKeyCommitment(PublicKey publicKey);
 
 	/**
 	 * Derives a common shared secret from two public keys and one of the
 	 * corresponding private keys.
-	 * <p/>
-	 * Part of BQP.
 	 *
-	 * @param theirPublicKey the ephemeral public key of the remote party
-	 * @param ourKeyPair our ephemeral keypair
-	 * @param alice true if ourKeyPair belongs to Alice
+	 * @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 theirPublicKey the public key of the remote party
+	 * @param ourKeyPair the key pair of the local party
+	 * @param alice true if the local party is Alice
 	 * @return the shared secret
 	 */
-	SecretKey deriveSharedSecret(byte[] theirPublicKey, KeyPair ourKeyPair,
-			boolean alice) throws GeneralSecurityException;
+	SecretKey deriveSharedSecret(String label, PublicKey theirPublicKey,
+			KeyPair ourKeyPair, boolean alice) throws GeneralSecurityException;
 
 	/**
 	 * Derives the content of a confirmation record.
 	 * <p/>
-	 * Part of BQP.
+	 * Used by the key exchange protocol.
 	 *
 	 * @param sharedSecret the common shared secret
-	 * @param theirPayload the commit payload from the remote party
-	 * @param ourPayload the commit payload we sent
+	 * @param theirPayload the key exchange payload of the remote party
+	 * @param ourPayload the key exchange payload of the local party
 	 * @param theirPublicKey the ephemeral public key of the remote party
-	 * @param ourKeyPair our ephemeral keypair
-	 * @param alice true if ourKeyPair belongs to Alice
+	 * @param ourKeyPair our ephemeral key pair of the local party
+	 * @param alice true if the local party is Alice
 	 * @param aliceRecord true if the confirmation record is for use by Alice
 	 * @return the confirmation record
 	 */
 	byte[] deriveConfirmationRecord(SecretKey sharedSecret,
 			byte[] theirPayload, byte[] ourPayload,
-			byte[] theirPublicKey, KeyPair ourKeyPair,
+			PublicKey theirPublicKey, KeyPair ourKeyPair,
 			boolean alice, boolean aliceRecord);
 
-	/**
-	 * Derives a master secret from the given shared secret.
-	 * <p/>
-	 * Part of BQP.
-	 *
-	 * @param sharedSecret the common shared secret
-	 * @return the master secret
-	 */
-	SecretKey deriveMasterSecret(SecretKey sharedSecret);
-
-	/**
-	 * Derives a master secret from two public keys and one of the corresponding
-	 * private keys.
-	 * <p/>
-	 * This is a helper method that calls
-	 * deriveMasterSecret(deriveSharedSecret(theirPublicKey, ourKeyPair, alice))
-	 *
-	 * @param theirPublicKey the ephemeral public key of the remote party
-	 * @param ourKeyPair our ephemeral keypair
-	 * @param alice true if ourKeyPair belongs to Alice
-	 * @return the shared secret
-	 */
-	SecretKey deriveMasterSecret(byte[] theirPublicKey, KeyPair ourKeyPair,
-			boolean alice) throws GeneralSecurityException;
-
 	/**
 	 * Derives initial transport keys for the given transport in the given
 	 * rotation period from the given master secret.
+	 * <p/>
+	 * Used by the transport security protocol.
+	 *
 	 * @param alice whether the keys are for use by Alice or Bob.
 	 */
 	TransportKeys deriveTransportKeys(TransportId t, SecretKey master,
@@ -124,18 +103,25 @@ public interface CryptoComponent {
 	/**
 	 * Rotates the given transport keys to the given rotation period. If the
 	 * keys are for a future rotation period they are not rotated.
+	 * <p/>
+	 * Used by the transport security protocol.
 	 */
 	TransportKeys rotateTransportKeys(TransportKeys k, long rotationPeriod);
 
-	/** Encodes the pseudo-random tag that is used to recognise a stream. */
+	/**
+	 * Encodes the pseudo-random tag that is used to recognise a stream.
+	 * <p/>
+	 * Used by the transport security protocol.
+	 */
 	void encodeTag(byte[] tag, SecretKey tagKey, int protocolVersion,
 			long streamNumber);
 
 	/**
 	 * Signs the given byte[] with the given ECDSA private key.
 	 *
-	 * @param label A label specific to this signature
-	 *              to ensure that the signature cannot be repurposed
+	 * @param label a namespaced label indicating the purpose of this
+	 * signature, to prevent it from being repurposed or colliding with a
+	 * signature created for another purpose
 	 */
 	byte[] sign(String label, byte[] toSign, byte[] privateKey)
 			throws GeneralSecurityException;
@@ -153,8 +139,9 @@ public interface CryptoComponent {
 	 * Verifies that the given signature is valid for the signed data
 	 * and the given ECDSA public key.
 	 *
-	 * @param label A label that was specific to this signature
-	 *              to ensure that the signature cannot be repurposed
+	 * @param label a namespaced label indicating the purpose of this
+	 * signature, to prevent it from being repurposed or colliding with a
+	 * signature created for another purpose
 	 * @return true if the signature was valid, false otherwise.
 	 */
 	boolean verify(String label, byte[] signedData, byte[] publicKey,
@@ -175,23 +162,22 @@ public interface CryptoComponent {
 	 * Returns the hash of the given inputs. The inputs are unambiguously
 	 * combined by prefixing each input with its length.
 	 *
-	 * @param label A label specific to this hash to ensure that hashes
-	 *              calculated for distinct purposes don't collide.
+	 * @param label a namespaced label indicating the purpose of this hash, to
+	 * prevent it from being repurposed or colliding with a hash created for
+	 * another purpose
 	 */
 	byte[] hash(String label, byte[]... inputs);
 
-	/**
-	 * Returns the length of hashes produced by
-	 * the {@link CryptoComponent#hash(String, byte[]...)} method.
-	 */
-	int getHashLength();
-
 	/**
 	 * Returns a message authentication code with the given key over the
 	 * given inputs. The inputs are unambiguously combined by prefixing each
 	 * input with its length.
+	 *
+	 * @param label a namespaced label indicating the purpose of this MAC, to
+	 * prevent it from being repurposed or colliding with a MAC created for
+	 * another purpose
 	 */
-	byte[] mac(SecretKey macKey, byte[]... inputs);
+	byte[] mac(String label, SecretKey macKey, byte[]... inputs);
 
 	/**
 	 * Encrypts and authenticates the given plaintext so it can be written to

bramble-api/src/main/java/org/briarproject/bramble/api/identity/AuthorId.java

@@ -16,7 +16,7 @@ public class AuthorId extends UniqueId {
 	/**
 	 * Label for hashing authors to calculate their identities.
 	 */
-	public static final String LABEL = "org.briarproject.bramble.AUTHOR_ID";
+	public static final String LABEL = "org.briarproject.bramble/AUTHOR_ID";
 
 	public AuthorId(byte[] id) {
 		super(id);

bramble-api/src/main/java/org/briarproject/bramble/api/keyagreement/KeyAgreementConstants.java

@@ -5,7 +5,7 @@ public interface KeyAgreementConstants {
 	/**
 	 * The current version of the BQP protocol.
 	 */
-	byte PROTOCOL_VERSION = 2;
+	byte PROTOCOL_VERSION = 3;
 
 	/**
 	 * The length of the record header in bytes.
@@ -22,7 +22,10 @@ public interface KeyAgreementConstants {
 	 */
 	int COMMIT_LENGTH = 16;
 
-	long CONNECTION_TIMEOUT = 20 * 1000; // Milliseconds
+	/**
+	 * The connection timeout in milliseconds.
+	 */
+	long CONNECTION_TIMEOUT = 20 * 1000;
 
 	/**
 	 * The transport identifier for Bluetooth.
@@ -33,4 +36,16 @@ public interface KeyAgreementConstants {
 	 * The transport identifier for LAN.
 	 */
 	int TRANSPORT_ID_LAN = 1;
+
+	/**
+	 * Label for deriving the shared secret.
+	 */
+	String SHARED_SECRET_LABEL =
+			"org.briarproject.bramble.keyagreement/SHARED_SECRET";
+
+	/**
+	 * Label for deriving the master secret.
+	 */
+	String MASTER_SECRET_LABEL =
+			"org.briarproject.bramble.keyagreement/MASTER_SECRET";
 }

bramble-api/src/main/java/org/briarproject/bramble/api/sync/GroupId.java

@@ -15,7 +15,7 @@ public class GroupId extends UniqueId {
 	/**
 	 * Label for hashing groups to calculate their identifiers.
 	 */
-	public static final String LABEL = "org.briarproject.bramble.GROUP_ID";
+	public static final String LABEL = "org.briarproject.bramble/GROUP_ID";
 
 	public GroupId(byte[] id) {
 		super(id);

bramble-api/src/main/java/org/briarproject/bramble/api/sync/MessageId.java

@@ -16,7 +16,7 @@ public class MessageId extends UniqueId {
 	/**
 	 * Label for hashing messages to calculate their identifiers.
 	 */
-	public static final String LABEL = "org.briarproject.bramble.MESSAGE_ID";
+	public static final String LABEL = "org.briarproject.bramble/MESSAGE_ID";
 
 	public MessageId(byte[] id) {
 		super(id);

bramble-core/src/main/java/org/briarproject/bramble/contact/ContactExchangeTaskImpl.java

@@ -141,8 +141,9 @@ class ContactExchangeTaskImpl extends Thread implements ContactExchangeTask {
 		}
 
 		// Derive the header keys for the transport streams
-		SecretKey aliceHeaderKey = crypto.deriveHeaderKey(masterSecret, true);
-		SecretKey bobHeaderKey = crypto.deriveHeaderKey(masterSecret, false);
+		SecretKey aliceHeaderKey = crypto.deriveKey(ALICE_KEY_LABEL,
+				masterSecret);
+		SecretKey bobHeaderKey = crypto.deriveKey(BOB_KEY_LABEL, masterSecret);
 
 		// Create the readers
 		InputStream streamReader =
@@ -156,8 +157,10 @@ class ContactExchangeTaskImpl extends Thread implements ContactExchangeTask {
 		BdfWriter w = bdfWriterFactory.createWriter(streamWriter);
 
 		// Derive the nonces to be signed
-		byte[] aliceNonce = crypto.deriveSignatureNonce(masterSecret, true);
-		byte[] bobNonce = crypto.deriveSignatureNonce(masterSecret, false);
+		byte[] aliceNonce = crypto.deriveKeyBindingNonce(ALICE_NONCE_LABEL,
+				masterSecret);
+		byte[] bobNonce = crypto.deriveKeyBindingNonce(BOB_NONCE_LABEL,
+				masterSecret);
 
 		// Exchange pseudonyms, signed nonces, and timestamps
 		long localTimestamp = clock.currentTimeMillis();
@@ -312,8 +315,7 @@ class ContactExchangeTaskImpl extends Thread implements ContactExchangeTask {
 		return contactId;
 	}
 
-	private void tryToClose(DuplexTransportConnection conn,
-			boolean exception) {
+	private void tryToClose(DuplexTransportConnection conn, boolean exception) {
 		try {
 			LOG.info("Closing connection");
 			conn.getReader().dispose(exception, true);

bramble-core/src/main/java/org/briarproject/bramble/crypto/CryptoComponentImpl.java

@@ -30,7 +30,6 @@ import org.spongycastle.crypto.params.ECPrivateKeyParameters;
 import org.spongycastle.crypto.params.ECPublicKeyParameters;
 import org.spongycastle.crypto.params.KeyParameter;
 
-import java.nio.charset.Charset;
 import java.security.GeneralSecurityException;
 import java.security.NoSuchAlgorithmException;
 import java.security.Provider;
@@ -65,39 +64,25 @@ class CryptoComponentImpl implements CryptoComponent {
 	private static final int PBKDF_SALT_BYTES = 32; // 256 bits
 	private static final int PBKDF_TARGET_MILLIS = 500;
 	private static final int PBKDF_SAMPLES = 30;
-	private static final int HASH_SIZE = 256 / 8;
 
-	private static byte[] ascii(String s) {
-		return s.getBytes(Charset.forName("US-ASCII"));
-	}
-
-	// KDF labels for contact exchange stream header key derivation
-	private static final byte[] A_INVITE = ascii("ALICE_INVITATION_KEY");
-	private static final byte[] B_INVITE = ascii("BOB_INVITATION_KEY");
-	// KDF labels for contact exchange signature nonce derivation
-	private static final byte[] A_SIG_NONCE = ascii("ALICE_SIGNATURE_NONCE");
-	private static final byte[] B_SIG_NONCE = ascii("BOB_SIGNATURE_NONCE");
 	// Hash label for BQP public key commitment derivation
-	private static final String COMMIT =
-			"org.briarproject.bramble.COMMIT";
-	// Hash label for shared secret derivation
-	private static final String SHARED_SECRET =
-			"org.briarproject.bramble.SHARED_SECRET";
+	private static final String COMMIT_LABEL =
+			"org.briarproject.bramble.keyagreement/COMMIT";
 	// KDF label for BQP confirmation key derivation
-	private static final byte[] CONFIRMATION_KEY = ascii("CONFIRMATION_KEY");
-	// KDF label for master key derivation
-	private static final byte[] MASTER_KEY = ascii("MASTER_KEY");
+	private static final String CONFIRMATION_KEY_LABEL =
+			"org.briarproject.bramble.keyagreement/CONFIRMATION_KEY";
+	// MAC label for BQP confirmation record
+	private static final String CONFIRMATION_MAC_LABEL =
+			"org.briarproject.bramble.keyagreement/CONFIRMATION_MAC";
+
 	// KDF labels for tag key derivation
-	private static final byte[] A_TAG = ascii("ALICE_TAG_KEY");
-	private static final byte[] B_TAG = ascii("BOB_TAG_KEY");
+	private static final String A_TAG = "ALICE_TAG_KEY";
+	private static final String B_TAG = "BOB_TAG_KEY";
 	// KDF labels for header key derivation
-	private static final byte[] A_HEADER = ascii("ALICE_HEADER_KEY");
-	private static final byte[] B_HEADER = ascii("BOB_HEADER_KEY");
-	// KDF labels for MAC key derivation
-	private static final byte[] A_MAC = ascii("ALICE_MAC_KEY");
-	private static final byte[] B_MAC = ascii("BOB_MAC_KEY");
+	private static final String A_HEADER = "ALICE_HEADER_KEY";
+	private static final String B_HEADER = "BOB_HEADER_KEY";
 	// KDF label for key rotation
-	private static final byte[] ROTATE = ascii("ROTATE");
+	private static final String ROTATE = "ROTATE";
 
 	private final SecureRandom secureRandom;
 	private final ECKeyPairGenerator agreementKeyPairGenerator;
@@ -263,25 +248,19 @@ class CryptoComponentImpl implements CryptoComponent {
 	}
 
 	@Override
-	public SecretKey deriveHeaderKey(SecretKey master,
-			boolean alice) {
-		return new SecretKey(macKdf(master, alice ? A_INVITE : B_INVITE));
+	public SecretKey deriveKey(String label, SecretKey k,
+			byte[]... inputs) {
+		return new SecretKey(macKdf(label, k, inputs));
 	}
 
 	@Override
-	public SecretKey deriveMacKey(SecretKey master, boolean alice) {
-		return new SecretKey(macKdf(master, alice ? A_MAC : B_MAC));
+	public byte[] deriveKeyBindingNonce(String label, SecretKey k) {
+		return macKdf(label, k);
 	}
 
 	@Override
-	public byte[] deriveSignatureNonce(SecretKey master,
-			boolean alice) {
-		return macKdf(master, alice ? A_SIG_NONCE : B_SIG_NONCE);
-	}
-
-	@Override
-	public byte[] deriveKeyCommitment(byte[] publicKey) {
-		byte[] hash = hash(COMMIT, publicKey);
+	public byte[] deriveKeyCommitment(PublicKey publicKey) {
+		byte[] hash = hash(COMMIT_LABEL, publicKey.getEncoded());
 		// The output is the first COMMIT_LENGTH bytes of the hash
 		byte[] commitment = new byte[COMMIT_LENGTH];
 		System.arraycopy(hash, 0, commitment, 0, COMMIT_LENGTH);
@@ -289,55 +268,45 @@ class CryptoComponentImpl implements CryptoComponent {
 	}
 
 	@Override
-	public SecretKey deriveSharedSecret(byte[] theirPublicKey,
+	public SecretKey deriveSharedSecret(String label, PublicKey theirPublicKey,
 			KeyPair ourKeyPair, boolean alice) throws GeneralSecurityException {
 		PrivateKey ourPriv = ourKeyPair.getPrivate();
-		PublicKey theirPub = agreementKeyParser.parsePublicKey(theirPublicKey);
-		byte[] raw = performRawKeyAgreement(ourPriv, theirPub);
+		byte[] raw = performRawKeyAgreement(ourPriv, theirPublicKey);
 		byte[] alicePub, bobPub;
 		if (alice) {
 			alicePub = ourKeyPair.getPublic().getEncoded();
-			bobPub = theirPublicKey;
+			bobPub = theirPublicKey.getEncoded();
 		} else {
-			alicePub = theirPublicKey;
+			alicePub = theirPublicKey.getEncoded();
 			bobPub = ourKeyPair.getPublic().getEncoded();
 		}
-		return new SecretKey(hash(SHARED_SECRET, raw, alicePub, bobPub));
+		return new SecretKey(hash(label, raw, alicePub, bobPub));
 	}
 
 	@Override
 	public byte[] deriveConfirmationRecord(SecretKey sharedSecret,
-			byte[] theirPayload, byte[] ourPayload, byte[] theirPublicKey,
+			byte[] theirPayload, byte[] ourPayload, PublicKey theirPublicKey,
 			KeyPair ourKeyPair, boolean alice, boolean aliceRecord) {
-		SecretKey ck = new SecretKey(macKdf(sharedSecret, CONFIRMATION_KEY));
+		SecretKey ck = deriveKey(CONFIRMATION_KEY_LABEL, sharedSecret);
 		byte[] alicePayload, alicePub, bobPayload, bobPub;
 		if (alice) {
 			alicePayload = ourPayload;
 			alicePub = ourKeyPair.getPublic().getEncoded();
 			bobPayload = theirPayload;
-			bobPub = theirPublicKey;
+			bobPub = theirPublicKey.getEncoded();
 		} else {
 			alicePayload = theirPayload;
-			alicePub = theirPublicKey;
+			alicePub = theirPublicKey.getEncoded();
 			bobPayload = ourPayload;
 			bobPub = ourKeyPair.getPublic().getEncoded();
 		}
-		if (aliceRecord)
-			return macKdf(ck, alicePayload, alicePub, bobPayload, bobPub);
-		else
-			return macKdf(ck, bobPayload, bobPub, alicePayload, alicePub);
-	}
-
-	@Override
-	public SecretKey deriveMasterSecret(SecretKey sharedSecret) {
-		return new SecretKey(macKdf(sharedSecret, MASTER_KEY));
-	}
-
-	@Override
-	public SecretKey deriveMasterSecret(byte[] theirPublicKey,
-			KeyPair ourKeyPair, boolean alice) throws GeneralSecurityException {
-		return deriveMasterSecret(deriveSharedSecret(
-				theirPublicKey, ourKeyPair, alice));
+		if (aliceRecord) {
+			return macKdf(CONFIRMATION_MAC_LABEL, ck, alicePayload, alicePub,
+					bobPayload, bobPub);
+		} else {
+			return macKdf(CONFIRMATION_MAC_LABEL, ck, bobPayload, bobPub,
+					alicePayload, alicePub);
+		}
 	}
 
 	@Override
@@ -396,19 +365,19 @@ class CryptoComponentImpl implements CryptoComponent {
 	private SecretKey rotateKey(SecretKey k, long rotationPeriod) {
 		byte[] period = new byte[INT_64_BYTES];
 		ByteUtils.writeUint64(rotationPeriod, period, 0);
-		return new SecretKey(macKdf(k, ROTATE, period));
+		return deriveKey(ROTATE, k, period);
 	}
 
 	private SecretKey deriveTagKey(SecretKey master, TransportId t,
 			boolean alice) {
 		byte[] id = StringUtils.toUtf8(t.getString());
-		return new SecretKey(macKdf(master, alice ? A_TAG : B_TAG, id));
+		return deriveKey(alice ? A_TAG : B_TAG, master, id);
 	}
 
 	private SecretKey deriveHeaderKey(SecretKey master, TransportId t,
 			boolean alice) {
 		byte[] id = StringUtils.toUtf8(t.getString());
-		return new SecretKey(macKdf(master, alice ? A_HEADER : B_HEADER, id));
+		return deriveKey(alice ? A_HEADER : B_HEADER, master, id);
 	}
 
 	@Override
@@ -513,14 +482,13 @@ class CryptoComponentImpl implements CryptoComponent {
 	}
 
 	@Override
-	public int getHashLength() {
-		return HASH_SIZE;
-	}
-
-	@Override
-	public byte[] mac(SecretKey macKey, byte[]... inputs) {
+	public byte[] mac(String label, SecretKey macKey, byte[]... inputs) {
+		byte[] labelBytes = StringUtils.toUtf8(label);
 		Digest mac = new Blake2sDigest(macKey.getBytes());
 		byte[] length = new byte[INT_32_BYTES];
+		ByteUtils.writeUint32(labelBytes.length, length, 0);
+		mac.update(length, 0, length.length);
+		mac.update(labelBytes, 0, labelBytes.length);
 		for (byte[] input : inputs) {
 			ByteUtils.writeUint32(input.length, length, 0);
 			mac.update(length, 0, length.length);
@@ -614,26 +582,11 @@ class CryptoComponentImpl implements CryptoComponent {
 
 	// Key derivation function based on a pseudo-random function - see
 	// NIST SP 800-108, section 5.1
-	private byte[] macKdf(SecretKey key, byte[]... inputs) {
-		// Initialise the PRF
-		Digest prf = new Blake2sDigest(key.getBytes());
-		// The output of the PRF must be long enough to use as a key
-		int macLength = prf.getDigestSize();
-		if (macLength < SecretKey.LENGTH) throw new IllegalStateException();
-		// Calculate the PRF over the concatenated length-prefixed inputs
-		byte[] length = new byte[INT_32_BYTES];
-		for (byte[] input : inputs) {
-			ByteUtils.writeUint32(input.length, length, 0);
-			prf.update(length, 0, length.length);
-			prf.update(input, 0, input.length);
-		}
-		byte[] mac = new byte[macLength];
-		prf.doFinal(mac, 0);
-		// The output is the first SecretKey.LENGTH bytes of the MAC
-		if (mac.length == SecretKey.LENGTH) return mac;
-		byte[] truncated = new byte[SecretKey.LENGTH];
-		System.arraycopy(mac, 0, truncated, 0, truncated.length);
-		return truncated;
+	private byte[] macKdf(String label, SecretKey k, byte[]... inputs) {
+		byte[] mac = mac(label, k, inputs);
+		// The output of the PRF must be usable as a key
+		if (mac.length != SecretKey.LENGTH) throw new IllegalStateException();
+		return mac;
 	}
 
 	// Password-based key derivation function - see PKCS#5 v2.1, section 5.2

bramble-core/src/main/java/org/briarproject/bramble/keyagreement/KeyAgreementConnector.java

@@ -70,8 +70,8 @@ class KeyAgreementConnector {
 	public Payload listen(KeyPair localKeyPair) {
 		LOG.info("Starting BQP listeners");
 		// Derive commitment
-		byte[] commitment = crypto.deriveKeyCommitment(
-				localKeyPair.getPublic().getEncoded());
+		byte[] commitment =
+				crypto.deriveKeyCommitment(localKeyPair.getPublic());
 		// Start all listeners and collect their descriptors
 		List<TransportDescriptor> descriptors = new ArrayList<>();
 		for (DuplexPlugin plugin : pluginManager.getKeyAgreementPlugins()) {

bramble-core/src/main/java/org/briarproject/bramble/keyagreement/KeyAgreementProtocol.java

@@ -2,6 +2,8 @@ package org.briarproject.bramble.keyagreement;
 
 import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.crypto.KeyPair;
+import org.briarproject.bramble.api.crypto.KeyParser;
+import org.briarproject.bramble.api.crypto.PublicKey;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.keyagreement.Payload;
 import org.briarproject.bramble.api.keyagreement.PayloadEncoder;
@@ -11,6 +13,9 @@ import java.io.IOException;
 import java.security.GeneralSecurityException;
 import java.util.Arrays;
 
+import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.MASTER_SECRET_LABEL;
+import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.SHARED_SECRET_LABEL;
+
 /**
  * Implementation of the BQP protocol.
  * <p/>
@@ -86,7 +91,7 @@ class KeyAgreementProtocol {
 	 */
 	SecretKey perform() throws AbortException, IOException {
 		try {
-			byte[] theirPublicKey;
+			PublicKey theirPublicKey;
 			if (alice) {
 				sendKey();
 				// Alice waits here until Bob obtains her payload.
@@ -104,7 +109,7 @@ class KeyAgreementProtocol {
 				receiveConfirm(s, theirPublicKey);
 				sendConfirm(s, theirPublicKey);
 			}
-			return crypto.deriveMasterSecret(s);
+			return crypto.deriveKey(MASTER_SECRET_LABEL, s);
 		} catch (AbortException e) {
 			sendAbort(e.getCause() != null);
 			throw e;
@@ -115,25 +120,32 @@ class KeyAgreementProtocol {
 		transport.sendKey(ourKeyPair.getPublic().getEncoded());
 	}
 
-	private byte[] receiveKey() throws AbortException {
-		byte[] publicKey = transport.receiveKey();
+	private PublicKey receiveKey() throws AbortException {
+		byte[] publicKeyBytes = transport.receiveKey();
 		callbacks.initialRecordReceived();
-		byte[] expected = crypto.deriveKeyCommitment(publicKey);
-		if (!Arrays.equals(expected, theirPayload.getCommitment()))
+		KeyParser keyParser = crypto.getAgreementKeyParser();
+		try {
+			PublicKey publicKey = keyParser.parsePublicKey(publicKeyBytes);
+			byte[] expected = crypto.deriveKeyCommitment(publicKey);
+			if (!Arrays.equals(expected, theirPayload.getCommitment()))
+				throw new AbortException();
+			return publicKey;
+		} catch (GeneralSecurityException e) {
 			throw new AbortException();
-		return publicKey;
+		}
 	}
 
-	private SecretKey deriveSharedSecret(byte[] theirPublicKey)
+	private SecretKey deriveSharedSecret(PublicKey theirPublicKey)
 			throws AbortException {
 		try {
-			return crypto.deriveSharedSecret(theirPublicKey, ourKeyPair, alice);
+			return crypto.deriveSharedSecret(SHARED_SECRET_LABEL,
+					theirPublicKey, ourKeyPair, alice);
 		} catch (GeneralSecurityException e) {
 			throw new AbortException(e);
 		}
 	}
 
-	private void sendConfirm(SecretKey s, byte[] theirPublicKey)
+	private void sendConfirm(SecretKey s, PublicKey theirPublicKey)
 			throws IOException {
 		byte[] confirm = crypto.deriveConfirmationRecord(s,
 				payloadEncoder.encode(theirPayload),
@@ -143,7 +155,7 @@ class KeyAgreementProtocol {
 		transport.sendConfirm(confirm);
 	}
 
-	private void receiveConfirm(SecretKey s, byte[] theirPublicKey)
+	private void receiveConfirm(SecretKey s, PublicKey theirPublicKey)
 			throws AbortException {
 		byte[] confirm = transport.receiveConfirm();
 		byte[] expected = crypto.deriveConfirmationRecord(s,

bramble-core/src/test/java/org/briarproject/bramble/crypto/KeyAgreementTest.java

@@ -3,40 +3,25 @@ package org.briarproject.bramble.crypto;
 import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.crypto.KeyPair;
 import org.briarproject.bramble.api.crypto.SecretKey;
-import org.briarproject.bramble.api.system.SecureRandomProvider;
 import org.briarproject.bramble.test.BrambleTestCase;
 import org.briarproject.bramble.test.TestSecureRandomProvider;
 import org.junit.Test;
 
+import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.SHARED_SECRET_LABEL;
 import static org.junit.Assert.assertArrayEquals;
 
 public class KeyAgreementTest extends BrambleTestCase {
 
-	@Test
-	public void testDeriveMasterSecret() throws Exception {
-		SecureRandomProvider
-				secureRandomProvider = new TestSecureRandomProvider();
-		CryptoComponent crypto = new CryptoComponentImpl(secureRandomProvider);
-		KeyPair aPair = crypto.generateAgreementKeyPair();
-		byte[] aPub = aPair.getPublic().getEncoded();
-		KeyPair bPair = crypto.generateAgreementKeyPair();
-		byte[] bPub = bPair.getPublic().getEncoded();
-		SecretKey aMaster = crypto.deriveMasterSecret(aPub, bPair, true);
-		SecretKey bMaster = crypto.deriveMasterSecret(bPub, aPair, false);
-		assertArrayEquals(aMaster.getBytes(), bMaster.getBytes());
-	}
-
 	@Test
 	public void testDeriveSharedSecret() throws Exception {
-		SecureRandomProvider
-				secureRandomProvider = new TestSecureRandomProvider();
-		CryptoComponent crypto = new CryptoComponentImpl(secureRandomProvider);
+		CryptoComponent crypto =
+				new CryptoComponentImpl(new TestSecureRandomProvider());
 		KeyPair aPair = crypto.generateAgreementKeyPair();
-		byte[] aPub = aPair.getPublic().getEncoded();
 		KeyPair bPair = crypto.generateAgreementKeyPair();
-		byte[] bPub = bPair.getPublic().getEncoded();
-		SecretKey aShared = crypto.deriveSharedSecret(bPub, aPair, true);
-		SecretKey bShared = crypto.deriveSharedSecret(aPub, bPair, false);
+		SecretKey aShared = crypto.deriveSharedSecret(SHARED_SECRET_LABEL,
+				bPair.getPublic(), aPair, true);
+		SecretKey bShared = crypto.deriveSharedSecret(SHARED_SECRET_LABEL,
+				aPair.getPublic(), bPair, false);
 		assertArrayEquals(aShared.getBytes(), bShared.getBytes());
 	}
 }

bramble-core/src/test/java/org/briarproject/bramble/crypto/MacTest.java

@@ -4,42 +4,49 @@ import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.test.BrambleTestCase;
 import org.briarproject.bramble.test.TestSecureRandomProvider;
-import org.briarproject.bramble.test.TestUtils;
 import org.junit.Test;
 
 import java.util.Arrays;
 
+import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
+import static org.briarproject.bramble.test.TestUtils.getSecretKey;
+import static org.briarproject.bramble.util.StringUtils.getRandomString;
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertFalse;
 
 public class MacTest extends BrambleTestCase {
 
-	private final CryptoComponent crypto;
+	private final CryptoComponent crypto =
+			new CryptoComponentImpl(new TestSecureRandomProvider());
 
-	private final SecretKey k = TestUtils.getSecretKey();
-	private final byte[] inputBytes = TestUtils.getRandomBytes(123);
-	private final byte[] inputBytes1 = TestUtils.getRandomBytes(234);
-	private final byte[] inputBytes2 = new byte[0];
-
-	public MacTest() {
-		crypto = new CryptoComponentImpl(new TestSecureRandomProvider());
-	}
+	private final SecretKey key1 = getSecretKey(), key2 = getSecretKey();
+	private final String label1 = getRandomString(123);
+	private final String label2 = getRandomString(123);
+	private final byte[] input1 = getRandomBytes(123);
+	private final byte[] input2 = getRandomBytes(234);
+	private final byte[] input3 = new byte[0];
 
 	@Test
 	public void testIdenticalKeysAndInputsProduceIdenticalMacs() {
 		// Calculate the MAC twice - the results should be identical
-		byte[] mac = crypto.mac(k, inputBytes, inputBytes1, inputBytes2);
-		byte[] mac1 = crypto.mac(k, inputBytes, inputBytes1, inputBytes2);
+		byte[] mac = crypto.mac(label1, key1, input1, input2, input3);
+		byte[] mac1 = crypto.mac(label1, key1, input1, input2, input3);
 		assertArrayEquals(mac, mac1);
 	}
 
+	@Test
+	public void testDifferentLabelsProduceDifferentMacs() {
+		// Calculate the MAC with each label - the results should be different
+		byte[] mac = crypto.mac(label1, key1, input1, input2, input3);
+		byte[] mac1 = crypto.mac(label2, key1, input1, input2, input3);
+		assertFalse(Arrays.equals(mac, mac1));
+	}
+
 	@Test
 	public void testDifferentKeysProduceDifferentMacs() {
-		// Generate second random key
-		SecretKey k1 = TestUtils.getSecretKey();
 		// Calculate the MAC with each key - the results should be different
-		byte[] mac = crypto.mac(k, inputBytes, inputBytes1, inputBytes2);
-		byte[] mac1 = crypto.mac(k1, inputBytes, inputBytes1, inputBytes2);
+		byte[] mac = crypto.mac(label1, key1, input1, input2, input3);
+		byte[] mac1 = crypto.mac(label1, key2, input1, input2, input3);
 		assertFalse(Arrays.equals(mac, mac1));
 	}
 
@@ -47,8 +54,8 @@ public class MacTest extends BrambleTestCase {
 	public void testDifferentInputsProduceDifferentMacs() {
 		// Calculate the MAC with the inputs in different orders - the results
 		// should be different
-		byte[] mac = crypto.mac(k, inputBytes, inputBytes1, inputBytes2);
-		byte[] mac1 = crypto.mac(k, inputBytes2, inputBytes1, inputBytes);
+		byte[] mac = crypto.mac(label1, key1, input1, input2, input3);
+		byte[] mac1 = crypto.mac(label1, key1, input3, input2, input1);
 		assertFalse(Arrays.equals(mac, mac1));
 	}
 

bramble-core/src/test/java/org/briarproject/bramble/keyagreement/KeyAgreementProtocolTest.java

@@ -2,12 +2,12 @@ package org.briarproject.bramble.keyagreement;
 
 import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.crypto.KeyPair;
+import org.briarproject.bramble.api.crypto.KeyParser;
 import org.briarproject.bramble.api.crypto.PublicKey;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.keyagreement.Payload;
 import org.briarproject.bramble.api.keyagreement.PayloadEncoder;
 import org.briarproject.bramble.test.BrambleTestCase;
-import org.briarproject.bramble.test.TestUtils;
 import org.jmock.Expectations;
 import org.jmock.auto.Mock;
 import org.jmock.integration.junit4.JUnitRuleMockery;
@@ -16,6 +16,10 @@ import org.junit.Rule;
 import org.junit.Test;
 
 import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.COMMIT_LENGTH;
+import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.MASTER_SECRET_LABEL;
+import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.SHARED_SECRET_LABEL;
+import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
+import static org.briarproject.bramble.test.TestUtils.getSecretKey;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.is;
 import static org.junit.Assert.assertThat;
@@ -28,34 +32,31 @@ public class KeyAgreementProtocolTest extends BrambleTestCase {
 		setImposteriser(ClassImposteriser.INSTANCE);
 	}};
 
-	private static final byte[] ALICE_PUBKEY = TestUtils.getRandomBytes(32);
-	private static final byte[] ALICE_COMMIT =
-			TestUtils.getRandomBytes(COMMIT_LENGTH);
-	private static final byte[] ALICE_PAYLOAD =
-			TestUtils.getRandomBytes(COMMIT_LENGTH + 8);
+	private final PublicKey alicePubKey =
+			context.mock(PublicKey.class, "alice");
+	private final byte[] alicePubKeyBytes = getRandomBytes(32);
+	private final byte[] aliceCommit = getRandomBytes(COMMIT_LENGTH);
+	private final byte[] alicePayload = getRandomBytes(COMMIT_LENGTH + 8);
+	private final byte[] aliceConfirm = getRandomBytes(SecretKey.LENGTH);
 
-	private static final byte[] BOB_PUBKEY = TestUtils.getRandomBytes(32);
-	private static final byte[] BOB_COMMIT =
-			TestUtils.getRandomBytes(COMMIT_LENGTH);
-	private static final byte[] BOB_PAYLOAD =
-			TestUtils.getRandomBytes(COMMIT_LENGTH + 19);
+	private final PublicKey bobPubKey = context.mock(PublicKey.class, "bob");
+	private final byte[] bobPubKeyBytes = getRandomBytes(32);
+	private final byte[] bobCommit = getRandomBytes(COMMIT_LENGTH);
+	private final byte[] bobPayload = getRandomBytes(COMMIT_LENGTH + 19);
+	private final byte[] bobConfirm = getRandomBytes(SecretKey.LENGTH);
 
-	private static final byte[] ALICE_CONFIRM =
-			TestUtils.getRandomBytes(SecretKey.LENGTH);
-	private static final byte[] BOB_CONFIRM =
-			TestUtils.getRandomBytes(SecretKey.LENGTH);
-
-	private static final byte[] BAD_PUBKEY = TestUtils.getRandomBytes(32);
-	private static final byte[] BAD_COMMIT =
-			TestUtils.getRandomBytes(COMMIT_LENGTH);
-	private static final byte[] BAD_CONFIRM =
-			TestUtils.getRandomBytes(SecretKey.LENGTH);
+	private final PublicKey badPubKey = context.mock(PublicKey.class, "bad");
+	private final byte[] badPubKeyBytes = getRandomBytes(32);
+	private final byte[] badCommit = getRandomBytes(COMMIT_LENGTH);
+	private final byte[] badConfirm = getRandomBytes(SecretKey.LENGTH);
 
 	@Mock
 	KeyAgreementProtocol.Callbacks callbacks;
 	@Mock
 	CryptoComponent crypto;
 	@Mock
+	KeyParser keyParser;
+	@Mock
 	PayloadEncoder payloadEncoder;
 	@Mock
 	KeyAgreementTransport transport;
@@ -65,11 +66,11 @@ public class KeyAgreementProtocolTest extends BrambleTestCase {
 	@Test
 	public void testAliceProtocol() throws Exception {
 		// set up
-		Payload theirPayload = new Payload(BOB_COMMIT, null);
-		Payload ourPayload = new Payload(ALICE_COMMIT, null);
+		Payload theirPayload = new Payload(bobCommit, null);
+		Payload ourPayload = new Payload(aliceCommit, null);
 		KeyPair ourKeyPair = new KeyPair(ourPubKey, null);
-		SecretKey sharedSecret = TestUtils.getSecretKey();
-		SecretKey masterSecret = TestUtils.getSecretKey();
+		SecretKey sharedSecret = getSecretKey();
+		SecretKey masterSecret = getSecretKey();
 
 		KeyAgreementProtocol protocol =
 				new KeyAgreementProtocol(callbacks, crypto, payloadEncoder,
@@ -79,46 +80,51 @@ public class KeyAgreementProtocolTest extends BrambleTestCase {
 		context.checking(new Expectations() {{
 			// Helpers
 			allowing(payloadEncoder).encode(ourPayload);
-			will(returnValue(ALICE_PAYLOAD));
+			will(returnValue(alicePayload));
 			allowing(payloadEncoder).encode(theirPayload);
-			will(returnValue(BOB_PAYLOAD));
+			will(returnValue(bobPayload));
 			allowing(ourPubKey).getEncoded();
-			will(returnValue(ALICE_PUBKEY));
+			will(returnValue(alicePubKeyBytes));
+			allowing(crypto).getAgreementKeyParser();
+			will(returnValue(keyParser));
 
 			// Alice sends her public key
-			oneOf(transport).sendKey(ALICE_PUBKEY);
+			oneOf(transport).sendKey(alicePubKeyBytes);
 
 			// Alice receives Bob's public key
 			oneOf(callbacks).connectionWaiting();
 			oneOf(transport).receiveKey();
-			will(returnValue(BOB_PUBKEY));
+			will(returnValue(bobPubKeyBytes));
 			oneOf(callbacks).initialRecordReceived();
+			oneOf(keyParser).parsePublicKey(bobPubKeyBytes);
+			will(returnValue(bobPubKey));
 
 			// Alice verifies Bob's public key
-			oneOf(crypto).deriveKeyCommitment(BOB_PUBKEY);
-			will(returnValue(BOB_COMMIT));
+			oneOf(crypto).deriveKeyCommitment(bobPubKey);
+			will(returnValue(bobCommit));
 
 			// Alice computes shared secret
-			oneOf(crypto).deriveSharedSecret(BOB_PUBKEY, ourKeyPair, true);
+			oneOf(crypto).deriveSharedSecret(SHARED_SECRET_LABEL, bobPubKey,
+					ourKeyPair, true);
 			will(returnValue(sharedSecret));
 
 			// Alice sends her confirmation record
-			oneOf(crypto).deriveConfirmationRecord(sharedSecret, BOB_PAYLOAD,
-					ALICE_PAYLOAD, BOB_PUBKEY, ourKeyPair, true, true);
-			will(returnValue(ALICE_CONFIRM));
-			oneOf(transport).sendConfirm(ALICE_CONFIRM);
+			oneOf(crypto).deriveConfirmationRecord(sharedSecret, bobPayload,
+					alicePayload, bobPubKey, ourKeyPair, true, true);
+			will(returnValue(aliceConfirm));
+			oneOf(transport).sendConfirm(aliceConfirm);
 
 			// Alice receives Bob's confirmation record
 			oneOf(transport).receiveConfirm();
-			will(returnValue(BOB_CONFIRM));
+			will(returnValue(bobConfirm));
 
 			// Alice verifies Bob's confirmation record
-			oneOf(crypto).deriveConfirmationRecord(sharedSecret, BOB_PAYLOAD,
-					ALICE_PAYLOAD, BOB_PUBKEY, ourKeyPair, true, false);
-			will(returnValue(BOB_CONFIRM));
+			oneOf(crypto).deriveConfirmationRecord(sharedSecret, bobPayload,
+					alicePayload, bobPubKey, ourKeyPair, true, false);
+			will(returnValue(bobConfirm));
 
 			// Alice computes master secret
-			oneOf(crypto).deriveMasterSecret(sharedSecret);
+			oneOf(crypto).deriveKey(MASTER_SECRET_LABEL, sharedSecret);
 			will(returnValue(masterSecret));
 		}});
 
@@ -129,11 +135,11 @@ public class KeyAgreementProtocolTest extends BrambleTestCase {
 	@Test
 	public void testBobProtocol() throws Exception {
 		// set up
-		Payload theirPayload = new Payload(ALICE_COMMIT, null);
-		Payload ourPayload = new Payload(BOB_COMMIT, null);
+		Payload theirPayload = new Payload(aliceCommit, null);
+		Payload ourPayload = new Payload(bobCommit, null);
 		KeyPair ourKeyPair = new KeyPair(ourPubKey, null);
-		SecretKey sharedSecret = TestUtils.getSecretKey();
-		SecretKey masterSecret = TestUtils.getSecretKey();
+		SecretKey sharedSecret = getSecretKey();
+		SecretKey masterSecret = getSecretKey();
 
 		KeyAgreementProtocol protocol =
 				new KeyAgreementProtocol(callbacks, crypto, payloadEncoder,
@@ -143,45 +149,50 @@ public class KeyAgreementProtocolTest extends BrambleTestCase {
 		context.checking(new Expectations() {{
 			// Helpers
 			allowing(payloadEncoder).encode(ourPayload);
-			will(returnValue(BOB_PAYLOAD));
+			will(returnValue(bobPayload));
 			allowing(payloadEncoder).encode(theirPayload);
-			will(returnValue(ALICE_PAYLOAD));
+			will(returnValue(alicePayload));
 			allowing(ourPubKey).getEncoded();
-			will(returnValue(BOB_PUBKEY));
+			will(returnValue(bobPubKeyBytes));
+			allowing(crypto).getAgreementKeyParser();
+			will(returnValue(keyParser));
 
 			// Bob receives Alice's public key
 			oneOf(transport).receiveKey();
-			will(returnValue(ALICE_PUBKEY));
+			will(returnValue(alicePubKeyBytes));
 			oneOf(callbacks).initialRecordReceived();
+			oneOf(keyParser).parsePublicKey(alicePubKeyBytes);
+			will(returnValue(alicePubKey));
 
 			// Bob verifies Alice's public key
-			oneOf(crypto).deriveKeyCommitment(ALICE_PUBKEY);
-			will(returnValue(ALICE_COMMIT));
+			oneOf(crypto).deriveKeyCommitment(alicePubKey);
+			will(returnValue(aliceCommit));
 
 			// Bob sends his public key
-			oneOf(transport).sendKey(BOB_PUBKEY);
+			oneOf(transport).sendKey(bobPubKeyBytes);
 
 			// Bob computes shared secret
-			oneOf(crypto).deriveSharedSecret(ALICE_PUBKEY, ourKeyPair, false);
+			oneOf(crypto).deriveSharedSecret(SHARED_SECRET_LABEL, alicePubKey,
+					ourKeyPair, false);
 			will(returnValue(sharedSecret));
 
 			// Bob receives Alices's confirmation record
 			oneOf(transport).receiveConfirm();
-			will(returnValue(ALICE_CONFIRM));
+			will(returnValue(aliceConfirm));
 
 			// Bob verifies Alice's confirmation record
-			oneOf(crypto).deriveConfirmationRecord(sharedSecret, ALICE_PAYLOAD,
-					BOB_PAYLOAD, ALICE_PUBKEY, ourKeyPair, false, true);
-			will(returnValue(ALICE_CONFIRM));
+			oneOf(crypto).deriveConfirmationRecord(sharedSecret, alicePayload,
+					bobPayload, alicePubKey, ourKeyPair, false, true);
+			will(returnValue(aliceConfirm));
 
 			// Bob sends his confirmation record
-			oneOf(crypto).deriveConfirmationRecord(sharedSecret, ALICE_PAYLOAD,
-					BOB_PAYLOAD, ALICE_PUBKEY, ourKeyPair, false, false);
-			will(returnValue(BOB_CONFIRM));
-			oneOf(transport).sendConfirm(BOB_CONFIRM);
+			oneOf(crypto).deriveConfirmationRecord(sharedSecret, alicePayload,
+					bobPayload, alicePubKey, ourKeyPair, false, false);
+			will(returnValue(bobConfirm));
+			oneOf(transport).sendConfirm(bobConfirm);
 
 			// Bob computes master secret
-			oneOf(crypto).deriveMasterSecret(sharedSecret);
+			oneOf(crypto).deriveKey(MASTER_SECRET_LABEL, sharedSecret);
 			will(returnValue(masterSecret));
 		}});
 
@@ -192,8 +203,8 @@ public class KeyAgreementProtocolTest extends BrambleTestCase {
 	@Test(expected = AbortException.class)
 	public void testAliceProtocolAbortOnBadKey() throws Exception {
 		// set up
-		Payload theirPayload = new Payload(BOB_COMMIT, null);
-		Payload ourPayload = new Payload(ALICE_COMMIT, null);
+		Payload theirPayload = new Payload(bobCommit, null);
+		Payload ourPayload = new Payload(aliceCommit, null);
 		KeyPair ourKeyPair = new KeyPair(ourPubKey, null);
 
 		KeyAgreementProtocol protocol =
@@ -204,26 +215,31 @@ public class KeyAgreementProtocolTest extends BrambleTestCase {
 		context.checking(new Expectations() {{
 			// Helpers
 			allowing(ourPubKey).getEncoded();
-			will(returnValue(ALICE_PUBKEY));
+			will(returnValue(alicePubKeyBytes));
+			allowing(crypto).getAgreementKeyParser();
+			will(returnValue(keyParser));
 
 			// Alice sends her public key
-			oneOf(transport).sendKey(ALICE_PUBKEY);
+			oneOf(transport).sendKey(alicePubKeyBytes);
 
 			// Alice receives a bad public key
 			oneOf(callbacks).connectionWaiting();
 			oneOf(transport).receiveKey();
-			will(returnValue(BAD_PUBKEY));
+			will(returnValue(badPubKeyBytes));
 			oneOf(callbacks).initialRecordReceived();
+			oneOf(keyParser).parsePublicKey(badPubKeyBytes);
+			will(returnValue(badPubKey));
 
 			// Alice verifies Bob's public key
-			oneOf(crypto).deriveKeyCommitment(BAD_PUBKEY);
-			will(returnValue(BAD_COMMIT));
+			oneOf(crypto).deriveKeyCommitment(badPubKey);
+			will(returnValue(badCommit));
 
 			// Alice aborts
 			oneOf(transport).sendAbort(false);
 
 			// Alice never computes shared secret
-			never(crypto).deriveSharedSecret(BAD_PUBKEY, ourKeyPair, true);
+			never(crypto).deriveSharedSecret(SHARED_SECRET_LABEL, badPubKey,
+					ourKeyPair, true);
 		}});
 
 		// execute
@@ -233,8 +249,8 @@ public class KeyAgreementProtocolTest extends BrambleTestCase {
 	@Test(expected = AbortException.class)
 	public void testBobProtocolAbortOnBadKey() throws Exception {
 		// set up
-		Payload theirPayload = new Payload(ALICE_COMMIT, null);
-		Payload ourPayload = new Payload(BOB_COMMIT, null);
+		Payload theirPayload = new Payload(aliceCommit, null);
+		Payload ourPayload = new Payload(bobCommit, null);
 		KeyPair ourKeyPair = new KeyPair(ourPubKey, null);
 
 		KeyAgreementProtocol protocol =
@@ -245,22 +261,26 @@ public class KeyAgreementProtocolTest extends BrambleTestCase {
 		context.checking(new Expectations() {{
 			// Helpers
 			allowing(ourPubKey).getEncoded();
-			will(returnValue(BOB_PUBKEY));
+			will(returnValue(bobPubKeyBytes));
+			allowing(crypto).getAgreementKeyParser();
+			will(returnValue(keyParser));
 
 			// Bob receives a bad public key
 			oneOf(transport).receiveKey();
-			will(returnValue(BAD_PUBKEY));
+			will(returnValue(badPubKeyBytes));
 			oneOf(callbacks).initialRecordReceived();
+			oneOf(keyParser).parsePublicKey(badPubKeyBytes);
+			will(returnValue(badPubKey));
 
 			// Bob verifies Alice's public key
-			oneOf(crypto).deriveKeyCommitment(BAD_PUBKEY);
-			will(returnValue(BAD_COMMIT));
+			oneOf(crypto).deriveKeyCommitment(badPubKey);
+			will(returnValue(badCommit));
 
 			// Bob aborts
 			oneOf(transport).sendAbort(false);
 
 			// Bob never sends his public key
-			never(transport).sendKey(BOB_PUBKEY);
+			never(transport).sendKey(bobPubKeyBytes);
 		}});
 
 		// execute
@@ -270,10 +290,10 @@ public class KeyAgreementProtocolTest extends BrambleTestCase {
 	@Test(expected = AbortException.class)
 	public void testAliceProtocolAbortOnBadConfirm() throws Exception {
 		// set up
-		Payload theirPayload = new Payload(BOB_COMMIT, null);
-		Payload ourPayload = new Payload(ALICE_COMMIT, null);
+		Payload theirPayload = new Payload(bobCommit, null);
+		Payload ourPayload = new Payload(aliceCommit, null);
 		KeyPair ourKeyPair = new KeyPair(ourPubKey, null);
-		SecretKey sharedSecret = TestUtils.getSecretKey();
+		SecretKey sharedSecret = getSecretKey();
 
 		KeyAgreementProtocol protocol =
 				new KeyAgreementProtocol(callbacks, crypto, payloadEncoder,
@@ -283,49 +303,54 @@ public class KeyAgreementProtocolTest extends BrambleTestCase {
 		context.checking(new Expectations() {{
 			// Helpers
 			allowing(payloadEncoder).encode(ourPayload);
-			will(returnValue(ALICE_PAYLOAD));
+			will(returnValue(alicePayload));
 			allowing(payloadEncoder).encode(theirPayload);
-			will(returnValue(BOB_PAYLOAD));
+			will(returnValue(bobPayload));
 			allowing(ourPubKey).getEncoded();
-			will(returnValue(ALICE_PUBKEY));
+			will(returnValue(alicePubKeyBytes));
+			allowing(crypto).getAgreementKeyParser();
+			will(returnValue(keyParser));
 
 			// Alice sends her public key
-			oneOf(transport).sendKey(ALICE_PUBKEY);
+			oneOf(transport).sendKey(alicePubKeyBytes);
 
 			// Alice receives Bob's public key
 			oneOf(callbacks).connectionWaiting();
 			oneOf(transport).receiveKey();
-			will(returnValue(BOB_PUBKEY));
+			will(returnValue(bobPubKeyBytes));
 			oneOf(callbacks).initialRecordReceived();
+			oneOf(keyParser).parsePublicKey(bobPubKeyBytes);
+			will(returnValue(bobPubKey));
 
 			// Alice verifies Bob's public key
-			oneOf(crypto).deriveKeyCommitment(BOB_PUBKEY);
-			will(returnValue(BOB_COMMIT));
+			oneOf(crypto).deriveKeyCommitment(bobPubKey);
+			will(returnValue(bobCommit));
 
 			// Alice computes shared secret
-			oneOf(crypto).deriveSharedSecret(BOB_PUBKEY, ourKeyPair, true);
+			oneOf(crypto).deriveSharedSecret(SHARED_SECRET_LABEL, bobPubKey,
+					ourKeyPair, true);
 			will(returnValue(sharedSecret));
 
 			// Alice sends her confirmation record
-			oneOf(crypto).deriveConfirmationRecord(sharedSecret, BOB_PAYLOAD,
-					ALICE_PAYLOAD, BOB_PUBKEY, ourKeyPair, true, true);
-			will(returnValue(ALICE_CONFIRM));
-			oneOf(transport).sendConfirm(ALICE_CONFIRM);
+			oneOf(crypto).deriveConfirmationRecord(sharedSecret, bobPayload,
+					alicePayload, bobPubKey, ourKeyPair, true, true);
+			will(returnValue(aliceConfirm));
+			oneOf(transport).sendConfirm(aliceConfirm);
 
 			// Alice receives a bad confirmation record
 			oneOf(transport).receiveConfirm();
-			will(returnValue(BAD_CONFIRM));
+			will(returnValue(badConfirm));
 
 			// Alice verifies Bob's confirmation record
-			oneOf(crypto).deriveConfirmationRecord(sharedSecret, BOB_PAYLOAD,
-					ALICE_PAYLOAD, BOB_PUBKEY, ourKeyPair, true, false);
-			will(returnValue(BOB_CONFIRM));
+			oneOf(crypto).deriveConfirmationRecord(sharedSecret, bobPayload,
+					alicePayload, bobPubKey, ourKeyPair, true, false);
+			will(returnValue(bobConfirm));
 
 			// Alice aborts
 			oneOf(transport).sendAbort(false);
 
 			// Alice never computes master secret
-			never(crypto).deriveMasterSecret(sharedSecret);
+			never(crypto).deriveKey(MASTER_SECRET_LABEL, sharedSecret);
 		}});
 
 		// execute
@@ -335,10 +360,10 @@ public class KeyAgreementProtocolTest extends BrambleTestCase {
 	@Test(expected = AbortException.class)
 	public void testBobProtocolAbortOnBadConfirm() throws Exception {
 		// set up
-		Payload theirPayload = new Payload(ALICE_COMMIT, null);
-		Payload ourPayload = new Payload(BOB_COMMIT, null);
+		Payload theirPayload = new Payload(aliceCommit, null);
+		Payload ourPayload = new Payload(bobCommit, null);
 		KeyPair ourKeyPair = new KeyPair(ourPubKey, null);
-		SecretKey sharedSecret = TestUtils.getSecretKey();
+		SecretKey sharedSecret = getSecretKey();
 
 		KeyAgreementProtocol protocol =
 				new KeyAgreementProtocol(callbacks, crypto, payloadEncoder,
@@ -348,43 +373,48 @@ public class KeyAgreementProtocolTest extends BrambleTestCase {
 		context.checking(new Expectations() {{
 			// Helpers
 			allowing(payloadEncoder).encode(ourPayload);
-			will(returnValue(BOB_PAYLOAD));
+			will(returnValue(bobPayload));
 			allowing(payloadEncoder).encode(theirPayload);
-			will(returnValue(ALICE_PAYLOAD));
+			will(returnValue(alicePayload));
 			allowing(ourPubKey).getEncoded();
-			will(returnValue(BOB_PUBKEY));
+			will(returnValue(bobPubKeyBytes));
+			allowing(crypto).getAgreementKeyParser();
+			will(returnValue(keyParser));
 
 			// Bob receives Alice's public key
 			oneOf(transport).receiveKey();
-			will(returnValue(ALICE_PUBKEY));
+			will(returnValue(alicePubKeyBytes));
 			oneOf(callbacks).initialRecordReceived();
+			oneOf(keyParser).parsePublicKey(alicePubKeyBytes);
+			will(returnValue(alicePubKey));
 
 			// Bob verifies Alice's public key
-			oneOf(crypto).deriveKeyCommitment(ALICE_PUBKEY);
-			will(returnValue(ALICE_COMMIT));
+			oneOf(crypto).deriveKeyCommitment(alicePubKey);
+			will(returnValue(aliceCommit));
 
 			// Bob sends his public key
-			oneOf(transport).sendKey(BOB_PUBKEY);
+			oneOf(transport).sendKey(bobPubKeyBytes);
 
 			// Bob computes shared secret
-			oneOf(crypto).deriveSharedSecret(ALICE_PUBKEY, ourKeyPair, false);
+			oneOf(crypto).deriveSharedSecret(SHARED_SECRET_LABEL, alicePubKey,
+					ourKeyPair, false);
 			will(returnValue(sharedSecret));
 
 			// Bob receives a bad confirmation record
 			oneOf(transport).receiveConfirm();
-			will(returnValue(BAD_CONFIRM));
+			will(returnValue(badConfirm));
 
 			// Bob verifies Alice's confirmation record
-			oneOf(crypto).deriveConfirmationRecord(sharedSecret, ALICE_PAYLOAD,
-					BOB_PAYLOAD, ALICE_PUBKEY, ourKeyPair, false, true);
-			will(returnValue(ALICE_CONFIRM));
+			oneOf(crypto).deriveConfirmationRecord(sharedSecret, alicePayload,
+					bobPayload, alicePubKey, ourKeyPair, false, true);
+			will(returnValue(aliceConfirm));
 
 			// Bob aborts
 			oneOf(transport).sendAbort(false);
 
 			// Bob never sends his confirmation record
-			never(crypto).deriveConfirmationRecord(sharedSecret, ALICE_PAYLOAD,
-					BOB_PAYLOAD, ALICE_PUBKEY, ourKeyPair, false, false);
+			never(crypto).deriveConfirmationRecord(sharedSecret, alicePayload,
+					bobPayload, alicePubKey, ourKeyPair, false, false);
 		}});
 
 		// execute

briar-api/src/main/java/org/briarproject/briar/api/introduction/IntroductionConstants.java

@@ -86,4 +86,44 @@ public interface IntroductionConstants {
 	int TASK_ACTIVATE_CONTACT = 1;
 	int TASK_ABORT = 2;
 
+	/**
+	 * Label for deriving the shared secret.
+	 */
+	String SHARED_SECRET_LABEL =
+			"org.briarproject.briar.introduction/SHARED_SECRET";
+
+	/**
+	 * Label for deriving Alice's key binding nonce from the shared secret.
+	 */
+	String ALICE_NONCE_LABEL =
+			"org.briarproject.briar.introduction/ALICE_NONCE";
+
+	/**
+	 * Label for deriving Bob's key binding nonce from the shared secret.
+	 */
+	String BOB_NONCE_LABEL =
+			"org.briarproject.briar.introduction/BOB_NONCE";
+
+	/**
+	 * Label for deriving Alice's MAC key from the shared secret.
+	 */
+	String ALICE_MAC_KEY_LABEL =
+			"org.briarproject.briar.introduction/ALICE_MAC_KEY";
+
+	/**
+	 * Label for deriving Bob's MAC key from the shared secret.
+	 */
+	String BOB_MAC_KEY_LABEL =
+			"org.briarproject.briar.introduction/BOB_MAC_KEY";
+
+	/**
+	 * Label for signing the introduction response.
+	 */
+	String SIGNING_LABEL =
+			"org.briarproject.briar.introduction/RESPONSE_SIGNATURE";
+
+	/**
+	 * Label for MACing the introduction response.
+	 */
+	String MAC_LABEL = "org.briarproject.briar.introduction/RESPONSE_MAC";
 }

briar-core/src/main/java/org/briarproject/briar/introduction/IntroduceeManager.java

@@ -50,7 +50,11 @@ import static org.briarproject.bramble.api.data.BdfDictionary.NULL_VALUE;
 import static org.briarproject.briar.api.introduction.IntroduceeProtocolState.AWAIT_REQUEST;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.ACCEPT;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.ADDED_CONTACT_ID;
+import static org.briarproject.briar.api.introduction.IntroductionConstants.ALICE_MAC_KEY_LABEL;
+import static org.briarproject.briar.api.introduction.IntroductionConstants.ALICE_NONCE_LABEL;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.ANSWERED;
+import static org.briarproject.briar.api.introduction.IntroductionConstants.BOB_MAC_KEY_LABEL;
+import static org.briarproject.briar.api.introduction.IntroductionConstants.BOB_NONCE_LABEL;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.CONTACT;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.CONTACT_ID_1;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.EXISTS;
@@ -60,6 +64,7 @@ import static org.briarproject.briar.api.introduction.IntroductionConstants.INTR
 import static org.briarproject.briar.api.introduction.IntroductionConstants.LOCAL_AUTHOR_ID;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.MAC;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.MAC_KEY;
+import static org.briarproject.briar.api.introduction.IntroductionConstants.MAC_LABEL;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.MESSAGE_ID;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.MESSAGE_TIME;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.NAME;
@@ -76,7 +81,9 @@ import static org.briarproject.briar.api.introduction.IntroductionConstants.REMO
 import static org.briarproject.briar.api.introduction.IntroductionConstants.REMOTE_AUTHOR_IS_US;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.ROLE;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.ROLE_INTRODUCEE;
+import static org.briarproject.briar.api.introduction.IntroductionConstants.SHARED_SECRET_LABEL;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.SIGNATURE;
+import static org.briarproject.briar.api.introduction.IntroductionConstants.SIGNING_LABEL;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.STATE;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.STORAGE_ID;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.TASK;
@@ -89,7 +96,6 @@ import static org.briarproject.briar.api.introduction.IntroductionConstants.TYPE
 import static org.briarproject.briar.api.introduction.IntroductionConstants.TYPE_ABORT;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.TYPE_ACK;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.TYPE_RESPONSE;
-import static org.briarproject.briar.api.introduction.IntroductionManager.CLIENT_ID;
 
 @Immutable
 @NotNullByDefault
@@ -98,9 +104,6 @@ class IntroduceeManager {
 	private static final Logger LOG =
 			Logger.getLogger(IntroduceeManager.class.getName());
 
-	static final String SIGNING_LABEL_RESPONSE =
-			CLIENT_ID.getString() + "/RESPONSE";
-
 	private final MessageSender messageSender;
 	private final DatabaseComponent db;
 	private final ClientHelper clientHelper;
@@ -288,8 +291,7 @@ class IntroduceeManager {
 
 	@Nullable
 	private BdfDictionary performTasks(Transaction txn,
-			BdfDictionary localState)
-			throws FormatException, DbException {
+			BdfDictionary localState) throws FormatException, DbException {
 
 		if (!localState.containsKey(TASK) || localState.get(TASK) == NULL_VALUE)
 			return null;
@@ -306,22 +308,21 @@ class IntroduceeManager {
 			}
 
 			// figure out who takes which role by comparing public keys
-			byte[] publicKeyBytes = localState.getRaw(OUR_PUBLIC_KEY);
-			byte[] theirEphemeralKey = localState.getRaw(E_PUBLIC_KEY);
-			int comp = Bytes.COMPARATOR.compare(new Bytes(publicKeyBytes),
-					new Bytes(theirEphemeralKey));
+			byte[] ourPublicKeyBytes = localState.getRaw(OUR_PUBLIC_KEY);
+			byte[] theirPublicKeyBytes = localState.getRaw(E_PUBLIC_KEY);
+			int comp = Bytes.COMPARATOR.compare(new Bytes(ourPublicKeyBytes),
+					new Bytes(theirPublicKeyBytes));
 			boolean alice = comp < 0;
 
 			// get our local author
 			LocalAuthor author = identityManager.getLocalAuthor(txn);
 
 			SecretKey secretKey;
-			byte[] privateKeyBytes = localState.getRaw(OUR_PRIVATE_KEY);
+			byte[] ourPrivateKeyBytes = localState.getRaw(OUR_PRIVATE_KEY);
 			try {
 				// derive secret master key
-				secretKey =
-						deriveSecretKey(publicKeyBytes, privateKeyBytes, alice,
-								theirEphemeralKey);
+				secretKey = deriveSecretKey(ourPublicKeyBytes,
+						ourPrivateKeyBytes, alice, theirPublicKeyBytes);
 				// derive MAC keys and nonces, sign our nonce and calculate MAC
 				deriveMacKeysAndNonces(localState, author, secretKey, alice);
 			} catch (GeneralSecurityException e) {
@@ -410,34 +411,36 @@ class IntroduceeManager {
 		return null;
 	}
 
-	private SecretKey deriveSecretKey(byte[] publicKeyBytes,
-			byte[] privateKeyBytes, boolean alice, byte[] theirPublicKey)
-			throws GeneralSecurityException {
+	private SecretKey deriveSecretKey(byte[] ourPublicKeyBytes,
+			byte[] ourPrivateKeyBytes, boolean alice,
+			byte[] theirPublicKeyBytes) throws GeneralSecurityException {
 		// parse the local ephemeral key pair
 		KeyParser keyParser = cryptoComponent.getAgreementKeyParser();
-		PublicKey publicKey;
-		PrivateKey privateKey;
+		PublicKey ourPublicKey;
+		PrivateKey ourPrivateKey;
 		try {
-			publicKey = keyParser.parsePublicKey(publicKeyBytes);
-			privateKey = keyParser.parsePrivateKey(privateKeyBytes);
+			ourPublicKey = keyParser.parsePublicKey(ourPublicKeyBytes);
+			ourPrivateKey = keyParser.parsePrivateKey(ourPrivateKeyBytes);
 		} catch (GeneralSecurityException e) {
 			if (LOG.isLoggable(WARNING)) {
 				LOG.log(WARNING, e.toString(), e);
 			}
 			throw new RuntimeException("Our own ephemeral key is invalid");
 		}
-		KeyPair keyPair = new KeyPair(publicKey, privateKey);
+		KeyPair ourKeyPair = new KeyPair(ourPublicKey, ourPrivateKey);
+		PublicKey theirPublicKey =
+				keyParser.parsePublicKey(theirPublicKeyBytes);
 
-		// The master secret is derived from the local ephemeral key pair
+		// The shared secret is derived from the local ephemeral key pair
 		// and the remote ephemeral public key
-		return cryptoComponent
-				.deriveMasterSecret(theirPublicKey, keyPair, alice);
+		return cryptoComponent.deriveSharedSecret(SHARED_SECRET_LABEL,
+				theirPublicKey, ourKeyPair, alice);
 	}
 
 	/**
 	 * Derives nonces, signs our nonce and calculates MAC
 	 * <p>
-	 * Derives two nonces and two mac keys from the secret master key.
+	 * Derives two nonces and two MAC keys from the shared secret key.
 	 * The other introducee's nonce and MAC key are added to the localState.
 	 * <p>
 	 * Our nonce is signed with the local author's long-term private key.
@@ -448,21 +451,23 @@ class IntroduceeManager {
 	private void deriveMacKeysAndNonces(BdfDictionary localState,
 			LocalAuthor author, SecretKey secretKey, boolean alice)
 			throws FormatException, GeneralSecurityException {
-		// Derive two nonces and a MAC key from the secret master key
-		byte[] ourNonce =
-				cryptoComponent.deriveSignatureNonce(secretKey, alice);
-		byte[] theirNonce =
-				cryptoComponent.deriveSignatureNonce(secretKey, !alice);
-		SecretKey macKey = cryptoComponent.deriveMacKey(secretKey, alice);
-		SecretKey theirMacKey = cryptoComponent.deriveMacKey(secretKey, !alice);
+		// Derive two nonces and MAC keys from the shared secret key
+		byte[] ourNonce = cryptoComponent.deriveKeyBindingNonce(
+				alice ? ALICE_NONCE_LABEL : BOB_NONCE_LABEL, secretKey);
+		byte[] theirNonce = cryptoComponent.deriveKeyBindingNonce(
+				alice ? BOB_NONCE_LABEL : ALICE_NONCE_LABEL, secretKey);
+		SecretKey ourMacKey = cryptoComponent.deriveKey(
+				alice ? ALICE_MAC_KEY_LABEL : BOB_MAC_KEY_LABEL, secretKey);
+		SecretKey theirMacKey = cryptoComponent.deriveKey(
+				alice ? BOB_MAC_KEY_LABEL : ALICE_MAC_KEY_LABEL, secretKey);
 
 		// Save the other nonce and MAC key for the verification
 		localState.put(NONCE, theirNonce);
 		localState.put(MAC_KEY, theirMacKey.getBytes());
 
 		// Sign our nonce with our long-term identity public key
-		byte[] sig = cryptoComponent
-				.sign(SIGNING_LABEL_RESPONSE, ourNonce, author.getPrivateKey());
+		byte[] sig = cryptoComponent.sign(SIGNING_LABEL, ourNonce,
+				author.getPrivateKey());
 
 		// Calculate a MAC over identity public key, ephemeral public key,
 		// transport properties and timestamp.
@@ -472,7 +477,7 @@ class IntroduceeManager {
 		BdfList toMacList = BdfList.of(author.getPublicKey(),
 				publicKeyBytes, tp, ourTime);
 		byte[] toMac = clientHelper.toByteArray(toMacList);
-		byte[] mac = cryptoComponent.mac(macKey, toMac);
+		byte[] mac = cryptoComponent.mac(MAC_LABEL, ourMacKey, toMac);
 
 		// Add MAC and signature to localState, so it can be included in ACK
 		localState.put(OUR_MAC, mac);
@@ -486,7 +491,7 @@ class IntroduceeManager {
 		byte[] key = localState.getRaw(PUBLIC_KEY);
 
 		// Verify the signature
-		if (!cryptoComponent.verify(SIGNING_LABEL_RESPONSE, nonce, key, sig)) {
+		if (!cryptoComponent.verify(SIGNING_LABEL, nonce, key, sig)) {
 			LOG.warning("Invalid nonce signature in ACK");
 			throw new GeneralSecurityException();
 		}
@@ -506,7 +511,7 @@ class IntroduceeManager {
 		long timestamp = localState.getLong(TIME);
 		BdfList toMacList = BdfList.of(pubKey, ePubKey, tp, timestamp);
 		byte[] toMac = clientHelper.toByteArray(toMacList);
-		byte[] calculatedMac = cryptoComponent.mac(macKey, toMac);
+		byte[] calculatedMac = cryptoComponent.mac(MAC_LABEL, macKey, toMac);
 		if (!Arrays.equals(mac, calculatedMac)) {
 			LOG.warning("Received ACK with invalid MAC");
 			throw new GeneralSecurityException();

briar-core/src/test/java/org/briarproject/briar/introduction/IntroduceeManagerTest.java

@@ -53,6 +53,7 @@ import static org.briarproject.briar.api.introduction.IntroductionConstants.INTR
 import static org.briarproject.briar.api.introduction.IntroductionConstants.LOCAL_AUTHOR_ID;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.MAC;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.MAC_KEY;
+import static org.briarproject.briar.api.introduction.IntroductionConstants.MAC_LABEL;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.MAC_LENGTH;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.MESSAGE_ID;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.MESSAGE_TIME;
@@ -66,6 +67,7 @@ import static org.briarproject.briar.api.introduction.IntroductionConstants.ROLE
 import static org.briarproject.briar.api.introduction.IntroductionConstants.ROLE_INTRODUCEE;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.SESSION_ID;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.SIGNATURE;
+import static org.briarproject.briar.api.introduction.IntroductionConstants.SIGNING_LABEL;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.STATE;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.STORAGE_ID;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.TIME;
@@ -74,7 +76,6 @@ import static org.briarproject.briar.api.introduction.IntroductionConstants.TYPE
 import static org.briarproject.briar.api.introduction.IntroductionConstants.TYPE_ACK;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.TYPE_REQUEST;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.TYPE_RESPONSE;
-import static org.briarproject.briar.introduction.IntroduceeManager.SIGNING_LABEL_RESPONSE;
 import static org.hamcrest.Matchers.array;
 import static org.hamcrest.Matchers.samePropertyValuesAs;
 import static org.junit.Assert.assertFalse;
@@ -266,7 +267,7 @@ public class IntroduceeManagerTest extends BriarTestCase {
 		);
 
 		context.checking(new Expectations() {{
-			oneOf(cryptoComponent).verify(SIGNING_LABEL_RESPONSE, nonce,
+			oneOf(cryptoComponent).verify(SIGNING_LABEL, nonce,
 					introducee2.getAuthor().getPublicKey(), sig);
 			will(returnValue(false));
 		}});
@@ -296,7 +297,7 @@ public class IntroduceeManagerTest extends BriarTestCase {
 		state.put(SIGNATURE, sig);
 
 		context.checking(new Expectations() {{
-			oneOf(cryptoComponent).verify(SIGNING_LABEL_RESPONSE, nonce,
+			oneOf(cryptoComponent).verify(SIGNING_LABEL, nonce,
 					publicKeyBytes, sig);
 			will(returnValue(true));
 		}});
@@ -330,7 +331,8 @@ public class IntroduceeManagerTest extends BriarTestCase {
 					BdfList.of(publicKeyBytes, ePublicKeyBytes, tp, time));
 			will(returnValue(signBytes));
 			//noinspection unchecked
-			oneOf(cryptoComponent).mac(with(samePropertyValuesAs(macKey)),
+			oneOf(cryptoComponent).mac(with(MAC_LABEL),
+					with(samePropertyValuesAs(macKey)),
 					with(array(equal(signBytes))));
 			will(returnValue(mac));
 		}});
@@ -343,14 +345,15 @@ public class IntroduceeManagerTest extends BriarTestCase {
 					BdfList.of(publicKeyBytes, ePublicKeyBytes, tp, time));
 			will(returnValue(signBytes));
 			//noinspection unchecked
-			oneOf(cryptoComponent).mac(with(samePropertyValuesAs(macKey)),
+			oneOf(cryptoComponent).mac(with(MAC_LABEL),
+					with(samePropertyValuesAs(macKey)),
 					with(array(equal(signBytes))));
 			will(returnValue(TestUtils.getRandomBytes(MAC_LENGTH)));
 		}});
 		try {
 			introduceeManager.verifyMac(state);
 			fail();
-		} catch(GeneralSecurityException e) {
+		} catch (GeneralSecurityException e) {
 			// expected
 		}
 		context.assertIsSatisfied();

briar-core/src/test/java/org/briarproject/briar/introduction/IntroductionIntegrationTest.java

@@ -56,21 +56,25 @@ import javax.inject.Inject;
 import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_PUBLIC_KEY_LENGTH;
 import static org.briarproject.bramble.test.TestPluginConfigModule.TRANSPORT_ID;
 import static org.briarproject.briar.api.client.MessageQueueManager.QUEUE_STATE_KEY;
+import static org.briarproject.briar.api.introduction.IntroductionConstants.ALICE_MAC_KEY_LABEL;
+import static org.briarproject.briar.api.introduction.IntroductionConstants.ALICE_NONCE_LABEL;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.E_PUBLIC_KEY;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.GROUP_ID;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.MAC;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.MAC_KEY;
+import static org.briarproject.briar.api.introduction.IntroductionConstants.MAC_LABEL;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.NAME;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.NONCE;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.PUBLIC_KEY;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.SESSION_ID;
+import static org.briarproject.briar.api.introduction.IntroductionConstants.SHARED_SECRET_LABEL;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.SIGNATURE;
+import static org.briarproject.briar.api.introduction.IntroductionConstants.SIGNING_LABEL;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.TIME;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.TRANSPORT;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.TYPE;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.TYPE_REQUEST;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.TYPE_RESPONSE;
-import static org.briarproject.briar.introduction.IntroduceeManager.SIGNING_LABEL_RESPONSE;
 import static org.briarproject.briar.test.BriarTestUtils.assertGroupCount;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
@@ -635,7 +639,7 @@ public class IntroductionIntegrationTest
 		// adapt outgoing message queue to removed message
 		Group g2 = introductionGroupFactory
 				.createIntroductionGroup(contact2From0);
-		decreaseOutgoingMessageCounter(ch, g2.getId(), 1);
+		decreaseOutgoingMessageCounter(ch, g2.getId());
 
 		// allow visitor to modify response
 		boolean earlyAbort = visitor.visit(response);
@@ -746,34 +750,33 @@ public class IntroductionIntegrationTest
 		// create keys
 		KeyPair keyPair1 = crypto.generateSignatureKeyPair();
 		KeyPair eKeyPair1 = crypto.generateAgreementKeyPair();
-		byte[] ePublicKeyBytes1 = eKeyPair1.getPublic().getEncoded();
 		KeyPair eKeyPair2 = crypto.generateAgreementKeyPair();
-		byte[] ePublicKeyBytes2 = eKeyPair2.getPublic().getEncoded();
 
 		// Nonce 1
-		SecretKey secretKey =
-				crypto.deriveMasterSecret(ePublicKeyBytes2, eKeyPair1, true);
-		byte[] nonce1 = crypto.deriveSignatureNonce(secretKey, true);
+		SecretKey sharedSecret = crypto.deriveSharedSecret(SHARED_SECRET_LABEL,
+				eKeyPair2.getPublic(), eKeyPair1, true);
+		byte[] nonce1 = crypto.deriveKeyBindingNonce(ALICE_NONCE_LABEL,
+				sharedSecret);
 
 		// Signature 1
-		byte[] sig1 = crypto.sign(SIGNING_LABEL_RESPONSE, nonce1,
+		byte[] sig1 = crypto.sign(SIGNING_LABEL, nonce1,
 				keyPair1.getPrivate().getEncoded());
 
 		// MAC 1
-		SecretKey macKey1 = crypto.deriveMacKey(secretKey, true);
+		SecretKey macKey1 = crypto.deriveKey(ALICE_MAC_KEY_LABEL, sharedSecret);
 		BdfDictionary tp1 = BdfDictionary.of(new BdfEntry("fake", "fake"));
 		long time1 = clock.currentTimeMillis();
 		BdfList toMacList = BdfList.of(keyPair1.getPublic().getEncoded(),
-				ePublicKeyBytes1, tp1, time1);
+				eKeyPair1.getPublic().getEncoded(), tp1, time1);
 		byte[] toMac = clientHelper.toByteArray(toMacList);
-		byte[] mac1 = crypto.mac(macKey1, toMac);
+		byte[] mac1 = crypto.mac(MAC_LABEL, macKey1, toMac);
 
 		// create only relevant part of state for introducee2
 		BdfDictionary state = new BdfDictionary();
 		state.put(PUBLIC_KEY, keyPair1.getPublic().getEncoded());
 		state.put(TRANSPORT, tp1);
 		state.put(TIME, time1);
-		state.put(E_PUBLIC_KEY, ePublicKeyBytes1);
+		state.put(E_PUBLIC_KEY, eKeyPair1.getPublic().getEncoded());
 		state.put(MAC, mac1);
 		state.put(MAC_KEY, macKey1.getBytes());
 		state.put(NONCE, nonce1);
@@ -786,16 +789,16 @@ public class IntroductionIntegrationTest
 		// replace ephemeral key pair and recalculate matching keys and nonce
 		KeyPair eKeyPair1f = crypto.generateAgreementKeyPair();
 		byte[] ePublicKeyBytes1f = eKeyPair1f.getPublic().getEncoded();
-		secretKey =
-				crypto.deriveMasterSecret(ePublicKeyBytes2, eKeyPair1f, true);
-		nonce1 = crypto.deriveSignatureNonce(secretKey, true);
+		sharedSecret = crypto.deriveSharedSecret(SHARED_SECRET_LABEL,
+				eKeyPair2.getPublic(), eKeyPair1f, true);
+		nonce1 = crypto.deriveKeyBindingNonce(ALICE_NONCE_LABEL, sharedSecret);
 
 		// recalculate MAC
-		macKey1 = crypto.deriveMacKey(secretKey, true);
+		macKey1 = crypto.deriveKey(ALICE_MAC_KEY_LABEL, sharedSecret);
 		toMacList = BdfList.of(keyPair1.getPublic().getEncoded(),
 				ePublicKeyBytes1f, tp1, time1);
 		toMac = clientHelper.toByteArray(toMacList);
-		mac1 = crypto.mac(macKey1, toMac);
+		mac1 = crypto.mac(MAC_LABEL, macKey1, toMac);
 
 		// update state with faked information
 		state.put(E_PUBLIC_KEY, ePublicKeyBytes1f);
@@ -970,12 +973,12 @@ public class IntroductionIntegrationTest
 
 	}
 
-	private void decreaseOutgoingMessageCounter(ClientHelper ch, GroupId g,
-			int num) throws FormatException, DbException {
+	private void decreaseOutgoingMessageCounter(ClientHelper ch, GroupId g)
+			throws FormatException, DbException {
 		BdfDictionary gD = ch.getGroupMetadataAsDictionary(g);
 		LOG.warning(gD.toString());
 		BdfDictionary queue = gD.getDictionary(QUEUE_STATE_KEY);
-		queue.put("nextOut", queue.getLong("nextOut") - num);
+		queue.put("nextOut", queue.getLong("nextOut") - 1);
 		gD.put(QUEUE_STATE_KEY, queue);
 		ch.mergeGroupMetadata(g, gD);
 	}