ServiceStack.HmacUtils.DecryptAuthenticated C# (CSharp) Метод

        public static byte[] DecryptAuthenticated(byte[] authEncryptedBytes, byte[] cryptKey)
        {
            if (cryptKey == null || cryptKey.Length != KeySizeBytes)
                throw new ArgumentException($"CryptKey needs to be {KeySize} bits", nameof(cryptKey));

            //Grab IV from message
            var iv = new byte[AesUtils.BlockSizeBytes];
            Buffer.BlockCopy(authEncryptedBytes, 0, iv, 0, iv.Length);

            using (var aes = AesUtils.CreateSymmetricAlgorithm())
            {
                using (var decrypter = aes.CreateDecryptor(cryptKey, iv))
                using (var decryptedStream = new MemoryStream())
                {
                    using (var decrypterStream = new CryptoStream(decryptedStream, decrypter, CryptoStreamMode.Write))
                    using (var writer = new BinaryWriter(decrypterStream))
                    {
                        //Decrypt Cipher Text from Message
                        writer.Write(
                            authEncryptedBytes,
                            iv.Length,
                            authEncryptedBytes.Length - iv.Length - KeySizeBytes);
                    }

                    return decryptedStream.ToArray();
                }
            }
        }
    }

        public TResponse Send <TResponse>(string httpMethod, object request)
        {
            byte[] cryptKey, authKey, iv;
            AesUtils.CreateCryptAuthKeysAndIv(out cryptKey, out authKey, out iv);

            try
            {
                var encryptedMessage = CreateEncryptedMessage(request, request.GetType().Name, cryptKey, authKey, iv, httpMethod);
                var encResponse      = Client.Send(encryptedMessage);

                var authEncryptedBytes = Convert.FromBase64String(encResponse.EncryptedBody);

                if (!HmacUtils.Verify(authEncryptedBytes, authKey))
                {
                    throw new Exception("Invalid EncryptedBody");
                }

                var decryptedBytes = HmacUtils.DecryptAuthenticated(authEncryptedBytes, cryptKey);

                var responseJson = decryptedBytes.FromUtf8Bytes();
                var response     = responseJson.FromJson <TResponse>();

                return(response);
            }
            catch (WebServiceException ex)
            {
                throw DecryptedException(ex, cryptKey, authKey);
            }
        }