public ActionResult Encrypt(string plainText)
        {
            ViewBag.PlainText = plainText;
            byte[] encryptedBytes     = AESCrypto.AES_EncryptString(plainText);
            string encryptedHexString = CryptoHelper.ConvertByteArrayToHexString(encryptedBytes);

            ViewBag.EncryptedHexString = encryptedHexString + "&HMacToken=" + GenerateHMac(encryptedHexString);
            return(View("Index"));
        }