C# Encryption to PHP Decryption

Question

I\'m trying to encrypt some (cookie) data in C# and then decrypt it in PHP. I have chosen to use Rijndael encryption. I\'ve almost got it working, except only part of the te

Answer 1

For posterity I'm placing the fully completed solution here.

C# Encryption Class

public static class Encryption
{
    public static string Encrypt(string prm_text_to_encrypt, string prm_key, string prm_iv)
    {
        var sToEncrypt = prm_text_to_encrypt;

        var rj = new RijndaelManaged()
        {
            Padding = PaddingMode.PKCS7,
            Mode = CipherMode.CBC,
            KeySize = 256,
            BlockSize = 256,
        };

        var key = Convert.FromBase64String(prm_key);
        var IV = Convert.FromBase64String(prm_iv);

        var encryptor = rj.CreateEncryptor(key, IV);

        var msEncrypt = new MemoryStream();
        var csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write);

        var toEncrypt = Encoding.ASCII.GetBytes(sToEncrypt);

        csEncrypt.Write(toEncrypt, 0, toEncrypt.Length);
        csEncrypt.FlushFinalBlock();

        var encrypted = msEncrypt.ToArray();

        return (Convert.ToBase64String(encrypted));
        }

    public static string Decrypt(string prm_text_to_decrypt, string prm_key, string prm_iv)
    {

        var sEncryptedString = prm_text_to_decrypt;

        var rj = new RijndaelManaged()
        {
            Padding = PaddingMode.PKCS7,
            Mode = CipherMode.CBC,
            KeySize = 256,
            BlockSize = 256,
        };

        var key = Convert.FromBase64String(prm_key);
        var IV = Convert.FromBase64String(prm_iv);

        var decryptor = rj.CreateDecryptor(key, IV);

        var sEncrypted = Convert.FromBase64String(sEncryptedString);

        var fromEncrypt = new byte[sEncrypted.Length];

        var msDecrypt = new MemoryStream(sEncrypted);
        var csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read);

        csDecrypt.Read(fromEncrypt, 0, fromEncrypt.Length);

        return (Encoding.ASCII.GetString(fromEncrypt));
        }

    public static void GenerateKeyIV(out string key, out string IV)
    {
        var rj = new RijndaelManaged()
        {
            Padding = PaddingMode.PKCS7,
            Mode = CipherMode.CBC,
            KeySize = 256,
            BlockSize = 256,
        };
        rj.GenerateKey();
        rj.GenerateIV();

        key = Convert.ToBase64String(rj.Key);
        IV = Convert.ToBase64String(rj.IV);
    }
}

PHP Decryption Snippet

= strlen($value) - $packing; $P--)
        {
            if(ord($value{$P}) != $packing)
            {
                $packing = 0;
            }
        }
    }

    return substr($value, 0, strlen($value) - $packing); 
}
?>