/// <summary>
/// Construct a group session for sending messages.
/// </summary>
/// <param name="senderKeyName">The (groupId, senderId, deviceId) tuple. In this case, 'senderId' should be the
/// caller.</param>
/// <returns>A SenderKeyDistributionMessage that is individually distributed to each member of the group.</returns>
public SenderKeyDistributionMessage create(SenderKeyName senderKeyName)
{
lock (GroupCipher.LOCK)
{
try
{
SenderKeyRecord senderKeyRecord = senderKeyStore.loadSenderKey(senderKeyName);
if (senderKeyRecord.isEmpty())
{
senderKeyRecord.setSenderKeyState(KeyHelper.generateSenderKeyId(),
0,
KeyHelper.generateSenderKey(),
KeyHelper.generateSenderSigningKey());
senderKeyStore.storeSenderKey(senderKeyName, senderKeyRecord);
}
SenderKeyState state = senderKeyRecord.getSenderKeyState();
return(new SenderKeyDistributionMessage(state.getKeyId(),
state.getSenderChainKey().getIteration(),
state.getSenderChainKey().getSeed(),
state.getSigningKeyPublic()));
}
catch (Exception e) when(e is InvalidKeyIdException || e is InvalidKeyException)
{
throw new Exception(e.Message);
}
}
}
/// <summary>
/// Encrypt a message.
/// </summary>
/// <param name="paddedPlaintext">The plaintext message bytes, optionally padded.</param>
/// <returns>Ciphertext.</returns>
/// <exception cref="NoSessionException"></exception>
public byte[] encrypt(byte[] paddedPlaintext)
{
lock (LOCK)
{
try
{
SenderKeyRecord record = senderKeyStore.loadSenderKey(senderKeyId);
SenderKeyState senderKeyState = record.getSenderKeyState();
SenderMessageKey senderKey = senderKeyState.getSenderChainKey().getSenderMessageKey();
byte[] ciphertext = getCipherText(senderKey.getIv(), senderKey.getCipherKey(), paddedPlaintext);
SenderKeyMessage senderKeyMessage = new SenderKeyMessage(senderKeyState.getKeyId(),
senderKey.getIteration(),
ciphertext,
senderKeyState.getSigningKeyPrivate());
senderKeyState.setSenderChainKey(senderKeyState.getSenderChainKey().getNext());
senderKeyStore.storeSenderKey(senderKeyId, record);
return(senderKeyMessage.serialize());
}
catch (InvalidKeyIdException e)
{
throw new NoSessionException(e);
}
}
}
/// <summary>
/// Decrypt a SenderKey group message.
/// </summary>
/// <param name="senderKeyMessageBytes">The received ciphertext.</param>
/// <param name="callback">A callback that is triggered after decryption is complete, but before the updated
/// session state has been committed to the session DB. This allows some implementations to store the committed
/// plaintext to a DB first, in case they are concerned with a crash happening between the time the session
/// state is updated but before they're able to store the plaintext to disk.</param>
/// <returns>Plaintext</returns>
/// <exception cref="LegacyMessageException"></exception>
/// <exception cref="InvalidMessageException"></exception>
/// <exception cref="DuplicateMessageException"></exception>
/// <exception cref="NoSessionException"></exception>
public byte[] decrypt(byte[] senderKeyMessageBytes, DecryptionCallback callback)
{
lock (LOCK)
{
try
{
SenderKeyRecord record = senderKeyStore.loadSenderKey(senderKeyId);
if (record.isEmpty())
{
throw new NoSessionException("No sender key for: " + senderKeyId);
}
SenderKeyMessage senderKeyMessage = new SenderKeyMessage(senderKeyMessageBytes);
SenderKeyState senderKeyState = record.getSenderKeyState(senderKeyMessage.getKeyId());
senderKeyMessage.verifySignature(senderKeyState.getSigningKeyPublic());
SenderMessageKey senderKey = getSenderKey(senderKeyState, senderKeyMessage.getIteration());
byte[] plaintext = getPlainText(senderKey.getIv(), senderKey.getCipherKey(), senderKeyMessage.getCipherText());
callback.handlePlaintext(plaintext);
senderKeyStore.storeSenderKey(senderKeyId, record);
return(plaintext);
}
catch (Exception e) when(e is InvalidKeyException || e is InvalidKeyIdException)
{
throw new InvalidMessageException(e);
}
}
}
/// <summary>
/// Construct a group session for receiving messages from senderKeyName.
/// </summary>
/// <param name="senderKeyName">The (groupId, senderId, deviceId) tuple associated with the SenderKeyDistributionMessage.</param>
/// <param name="senderKeyDistributionMessage">A received SenderKeyDistributionMessage.</param>
public void process(SenderKeyName senderKeyName, SenderKeyDistributionMessage senderKeyDistributionMessage)
{
lock (GroupCipher.LOCK)
{
SenderKeyRecord senderKeyRecord = senderKeyStore.loadSenderKey(senderKeyName);
senderKeyRecord.addSenderKeyState(senderKeyDistributionMessage.getId(),
senderKeyDistributionMessage.getIteration(),
senderKeyDistributionMessage.getChainKey(),
senderKeyDistributionMessage.getSignatureKey());
senderKeyStore.storeSenderKey(senderKeyName, senderKeyRecord);
}
}