public Packet MessageDecrypt(Packet outer)
{
byte[] remoteKeyData = outer.Body.Take(21).ToArray();
byte[] ivData = outer.Body.Skip(21).Take(4).ToArray();
byte[] innerEncryptedData = outer.Body.Skip(25).Take(outer.Body.Length - 29).ToArray();
// Decode the body
ECKeyPair remoteEphemeralKeys = ECKeyPair.LoadKeys(SecNamedCurves.GetByName("secp160r1"), remoteKeyData, null);
var idAgreement = ECDHAgree(remoteEphemeralKeys.PublicKey, Key.PrivateKey);
var agreedHash = Helpers.SHA256Hash(Helpers.ToByteArray(idAgreement, 20));
var aesKey = Helpers.FoldOnce(agreedHash);
// Pad out the IV
byte[] aesIV = new byte[16];
Array.Clear(aesIV, 0, 16);
Buffer.BlockCopy(ivData, 0, aesIV, 0, 4);
// Decrypt it
var cipher = new BufferedBlockCipher(new SicBlockCipher(new AesFastEngine()));
var parameters = new ParametersWithIV(new KeyParameter(aesKey), aesIV);
cipher.Init(false, parameters);
byte[] decryptedBody = new byte[innerEncryptedData.Length];
var offset = cipher.ProcessBytes(innerEncryptedData, decryptedBody, 0);
cipher.DoFinal(decryptedBody, offset);
Packet outPacket = Packet.DecodePacket(decryptedBody);
return(outPacket);
}
public void LoadKeys(byte[] publicKeyData, byte[] privateKeyData)
{
Key = ECKeyPair.LoadKeys(SecNamedCurves.GetByName("secp160r1"), publicKeyData, privateKeyData);
}
