ServiceStack.HmacUtils.Verify C# (CSharp) Method

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

            if (authEncryptedBytes == null || authEncryptedBytes.Length == 0)
                throw new ArgumentException("Encrypted Message Required!", nameof(authEncryptedBytes));

            using (var hmac = CreateHashAlgorithm(authKey))
            {
                var sentTag = new byte[KeySizeBytes];
                //Calculate Tag
                var calcTag = hmac.ComputeHash(authEncryptedBytes, 0, authEncryptedBytes.Length - sentTag.Length);
                const int ivLength = AesUtils.BlockSizeBytes;

                //return false if message length is too small
                if (authEncryptedBytes.Length < sentTag.Length + ivLength)
                    return false;

                //Grab Sent Tag
                Buffer.BlockCopy(authEncryptedBytes, authEncryptedBytes.Length - sentTag.Length, sentTag, 0, sentTag.Length);

                //Compare Tag with constant time comparison
                var compare = 0;
                for (var i = 0; i < sentTag.Length; i++)
                    compare |= sentTag[i] ^ calcTag[i];

                //return false if message doesn't authenticate
                if (compare != 0)
                    return false;
            }

            return true; //Haz Success!
        }

        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);
            }
        }