tripledes encryption not yielding same results in PHP and C#

Question

When I encrypt with C# I get arTdPqWOg6VppOqUD6mGITjb24+x5vJjfAufNQ4DN7rVEtpDmhFnMeJGg4n5y1BN

static void Main(string[] args)
{
    Encoding byteEncoder = Encoding.Default;

    String key = "ShHhd8a08JhJiho98ayslcjh";
    String message = "Let us meet at 9 o'clock at the secret place.";

    String encryption = Encrypt(message, key, false);
    String decryption = Decrypt(encryption , key, false);

    Console.WriteLine("Message: {0}", message);
    Console.WriteLine("Encryption: {0}", encryption);
    Console.WriteLine("Decryption: {0}", decryption);
}

public static string Encrypt(string toEncrypt, string key, bool useHashing)
{
    byte[] keyArray;
    byte[] toEncryptArray = UTF8Encoding.UTF8.GetBytes(toEncrypt);

    if (useHashing)
    {
        MD5CryptoServiceProvider hashmd5 = new MD5CryptoServiceProvider();
        keyArray = hashmd5.ComputeHash(UTF8Encoding.UTF8.GetBytes(key));
    }
    else
        keyArray = UTF8Encoding.UTF8.GetBytes(key);

    TripleDESCryptoServiceProvider tdes = new TripleDESCryptoServiceProvider();
    tdes.Key = keyArray;
    tdes.Mode = CipherMode.ECB;
    tdes.Padding = PaddingMode.PKCS7;

    ICryptoTransform cTransform = tdes.CreateEncryptor();
    byte[] resultArray = cTransform.TransformFinalBlock(toEncryptArray, 0, toEncryptArray.Length);

    return Convert.ToBase64String(resultArray, 0, resultArray.Length);
}

public static string Decrypt(string toDecrypt, string key, bool useHashing)
{
    byte[] keyArray;
    byte[] toEncryptArray = Convert.FromBase64String(toDecrypt);

    if (useHashing)
    {
        MD5CryptoServiceProvider hashmd5 = new MD5CryptoServiceProvider();
        keyArray = hashmd5.ComputeHash(UTF8Encoding.UTF8.GetBytes(key));
    }
    else
        keyArray = UTF8Encoding.UTF8.GetBytes(key);

    TripleDESCryptoServiceProvider tdes = new TripleDESCryptoServiceProvider();
    tdes.Key = keyArray;
    tdes.Mode = CipherMode.ECB;
    tdes.Padding = PaddingMode.PKCS7;

    ICryptoTransform cTransform = tdes.CreateDecryptor();
    byte[] resultArray = cTransform.TransformFinalBlock(toEncryptArray, 0, toEncryptArray.Length);

    return UTF8Encoding.UTF8.GetString(resultArray);
}

When I encrypt with PHP I get: arTdPqWOg6VppOqUD6mGITjb24+x5vJjfAufNQ4DN7rVEtpDmhFnMVM+W/WFlksR

    <?php
        $key = "ShHhd8a08JhJiho98ayslcjh";
        $input = "Let us meet at 9 o'clock at the secret place.";

        $td = mcrypt_module_open('tripledes', '', 'ecb', '');
        $iv = mcrypt_create_iv (mcrypt_enc_get_iv_size($td), MCRYPT_RAND);
        mcrypt_generic_init($td, $key, $iv);
        $encrypted_data = mcrypt_generic($td, $input);
        mcrypt_generic_deinit($td);
        mcrypt_module_close($td);

        echo base64_encode($encrypted_data);
    ?>

I don't know enough about cryptography to figure out why. Any ideas? Thanks.

Answer 1

Peter is right. PHP just pads with zeros, while you're using PKCS#7 in the C# code. Here's some code that should do it right:

function pkcs7_pad($text, $blocksize)
{
    $pad = $blocksize - (strlen($text) % $blocksize);
    return $text . str_repeat(chr($pad), $pad);
}

$input = pkcs7_pad("Let us meet at 9 o'clock at the secret place.", 16);

Alternatively, you should be able to put this in your C# code:

tdes.Padding = PaddingMode.Zeros;

and also have it work (albeit slightly less securely).