/**
* Construct a group session for sending messages.
*
* @param senderKeyName The (groupId, senderId, deviceId) tuple. In this case, 'senderId' should be the caller.
* @return A SenderKeyDistributionMessage that is individually distributed to each member of the group.
*/
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 (InvalidKeyIdException e)
{
throw new Exception(e.Message);
}
catch (InvalidKeyException e)
{
throw new Exception(e.Message);
}
}
}
/**
* 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, 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 (InvalidKeyException e)
{
throw new InvalidMessageException(e);
}
catch (InvalidKeyIdException e)
{
throw new InvalidMessageException(e);
}
}
}
