PHP <--> .NET Encryption

[TheServant]

Hi all,
I am really struggling with this and I have tried so many things I feel like I'm just chasing my tail.

Trying to have a matching encryption service in my .NET application and a PHP server, but no matter what I do, I can't seem to get these to agree, even when I use the same Key and IV. Any help would be greatly appreciated I you can see the inconsistency!

PHP

         function pad($string, $blocksize = 32)
        {
            $len = strlen($string);
            $pad = $blocksize - ($len % $blocksize);
            $string .= str_repeat(chr($pad), $pad);
            return $string;
        }
        function encrypt($string)
        {
            $key = base64_decode("/RczyqV95+E4dC/owOzv1tncb5X2n+tzehoxdarJPmc=");
            $iv = base64_decode("MFo4Fm64Y+58oZ2lOQ1bqT+P9WgdirhG9CkPAubwI1E=");
            return base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $key, $this->pad($string), MCRYPT_MODE_CBC, $iv));
        }

C#

        private static SymmetricAlgorithm GetAlgorithm(SecureString password)
        {
            SymmetricAlgorithm algorithm = new RijndaelManaged();
            algorithm.KeySize = 256;
            algorithm.BlockSize = 256;
            algorithm.Mode = CipherMode.CBC;
            algorithm.Padding = PaddingMode.PKCS7;
            algorithm.Key = Convert.FromBase64String("/RczyqV95+E4dC/owOzv1tncb5X2n+tzehoxdarJPmc=");
            algorithm.IV = Convert.FromBase64String("MFo4Fm64Y+58oZ2lOQ1bqT+P9WgdirhG9CkPAubwI1E=");
        }
 
        public static string EncryptString(string clearText, string password)
        {
            SymmetricAlgorithm algorithm = GetAlgorithm(password);
            byte[] clearBytes = Encoding.Unicode.GetBytes(clearText);
            MemoryStream ms = new MemoryStream();
            CryptoStream cs = new CryptoStream(ms, algorithm.CreateEncryptor(), CryptoStreamMode.Write);
            cs.Write(clearBytes, 0, clearBytes.Length);
            cs.Close();
            return Convert.ToBase64String(ms.ToArray());
        }

And my test code:

            var input = "test";
 
            using (WebClient client = new WebClient())
            {
                byte[] response = client.UploadValues("[PHP script which takes $_POST val and returns encrypted byte array]", new NameValueCollection()
                {
                { "test", input },
                });
                Console.WriteLine(Encoding.Default.GetString(response));
            }
 
            var encrypted = [Relavent Class].EncryptString(input);
            Console.WriteLine(encrypted);

Which returns basically the two encryptions (which I want to be the same):

QrWFHlhzOsVRTD7wqEyGcnfb1PvMl6ZR8p9ES5SR0Tw=
oGX2FLLQJuC0y8KvDKFWxiS3b6XLIU+60EYtNe0PExw=

[Frinavale]

You may need to consider using a 3rd party component to do the encryption that you can utilize in your C# code and in your PHP code.

I'm sorry but I don't think you are going to ever going to produce the same output attempting to use two different technologies like this.

It has been a long time since I've done much with encryption but I'm pretty sure that the .NET stuff generates their keys based based on inner workings of it's won code and that is going to be different than the stuff that PHP does.

If you use a 3rd party component I think that you'll have more luck with this.

[TheServant]

Thanks Frin. I ended up deleting the lot and starting over. I did get it working, and I have a feeling it had something to do with the order I did the base64 encoding. It's spread over several files now, and don't have time to post, but it was not very different to the above.
** I also just noticed that the default blocksize for the PHP pad function did not match that of C#, which would have also prevented it from functioning properly.

[Frinavale]

I'm glad you got it working!