private byte[] decrypt(SessionState sessionState, WhisperMessage ciphertextMessage)
{
if (!sessionState.hasSenderChain())
{
throw new InvalidMessageException("Uninitialized session!");
}
if (ciphertextMessage.getMessageVersion() != sessionState.getSessionVersion())
{
throw new InvalidMessageException($"Message version {ciphertextMessage.getMessageVersion()}, but session version {sessionState.getSessionVersion()}");
}
uint messageVersion = ciphertextMessage.getMessageVersion();
ECPublicKey theirEphemeral = ciphertextMessage.getSenderRatchetKey();
uint counter = ciphertextMessage.getCounter();
ChainKey chainKey = getOrCreateChainKey(sessionState, theirEphemeral);
MessageKeys messageKeys = getOrCreateMessageKeys(sessionState, theirEphemeral,
chainKey, counter);
/* ciphertextMessage.verifyMac(messageVersion,
sessionState.getRemoteIdentityKey(),
sessionState.getLocalIdentityKey(),
messageKeys.getMacKey());*/
byte[] plaintext = getPlaintext(messageVersion, messageKeys, ciphertextMessage.getBody());
sessionState.clearUnacknowledgedPreKeyMessage();
return plaintext;
}