/**
* Decrypt a SenderKey group message.
*
* @param senderKeyMessageBytes The received ciphertext.
* @param 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.
* @return Plaintext
* @throws LegacyMessageException
* @throws InvalidMessageException
* @throws DuplicateMessageException
*/
public byte[] Decrypt(byte[] senderKeyMessageBytes, IDecryptionCallback 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);
}
}
}
/**
* Encrypt a message.
*
* @param paddedPlaintext The plaintext message bytes, optionally padded.
* @return Ciphertext.
* @throws NoSessionException
*/
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);
}
}
}
