Question

I am using this example that Brett gave:

Encrypt and decrypt a string

And doing this:

public static bool VerifyLicenseKey(string applicationGuid)
{
  Console.WriteLine("G: " + applicationGuid);
  var appSettings = AppSettings.GetInstance();
  if (appSettings == null)
  {
    return false;
  }
  var hwinfo = HardwareInfo.GetHardwareSerial();
  Console.WriteLine("h: " + hwinfo);
  Console.WriteLine("a: " + applicationGuid);
  var currentSerial = Crypto.EncryptStringAES(hwinfo, applicationGuid);
  Console.WriteLine("c: " + currentSerial);
  Console.WriteLine("o: " + appSettings.LicenseSerialNumber);
  if (currentSerial == appSettings.LicenseSerialNumber)
  {
    return true;
  }
  return false;
}

}

The GetHardwareSerial and applicationGuid are coming back the same every time but when I call the EncryptStringAES it is not.

Am I using the wrong class? Is it not suppose to be the same each time?

If not, does someone have a better example where the encryted values are the same?

Answer 1

The algorithm you’re referring to uses the RijndaelManaged class and it seems to be using the default value for its IV property which is (quite rightly) automatically set to a new random value whenever you create a new instance (see documentation).

Hence, you’ll get a different result every time. (You’ll find more about the purpose of the IV on Wikipedia, for example.)