Triple encryption does not give identical results in PHP and C #

Question

When I encrypt using 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 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 do not know enough about cryptography to understand why. Any ideas? Thanks.

Answer 1

Peter is right. PHP just prepares zeros while you use PKCS # 7 in C # code. Here is the 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 can put this in your C # code:

 tdes.Padding = PaddingMode.Zeros; 

and also work (albeit a little less reliably).

Answer 2

I don’t know PHP, and I didn’t parse your C # code either, but since most of the encrypted string is the same, maybe adding data is the difference? Maybe PHP uses a different mode than PaddingMode.PKCS7 used in C # code? (That would be a comment if I could comment ...)

Answer 3

As a note: if you use ECB, you do not need IV. In fact, using the ECB in most cases is a security risk, so you really need to use something else, for example. CBC that uses IV. IV - a random, unclassified value with the same size as the size of the encryption block (8 bytes for 3DES). A new IV must be created for each message, and the decryptor must know the IV that the encryption side used. In practice, IV is sent with an encrypted message.