PHP MCRYPT_RIJNDAEL_128 encryption in C #

Question

I am trying to rewrite this function in C #. but c # output doesn't match php

PHP version

// Encrypt data using AES128-cbc function encrypt($data, $key, $iv) { $cipher = mcrypt_module_open(MCRYPT_RIJNDAEL_128, '', 'cbc', ''); mcrypt_generic_init($cipher, $key, $iv); $multipass = mcrypt_generic($cipher, $data); mcrypt_generic_deinit($cipher); return $multipass; } 

C # Version

 public static string encrypt(string encryptionString, string iv, string key) { byte[] clearTextBytes = Encoding.UTF8.GetBytes(encryptionString); var rijn = SymmetricAlgorithm.Create(); rijn.KeySize = 128; rijn.Mode = CipherMode.CBC; var ms = new MemoryStream(); var cs = new CryptoStream(ms, rijn.CreateEncryptor(Encoding.UTF8.GetBytes(key), Encoding.UTF8.GetBytes(iv)), CryptoStreamMode.Write); cs.Write(clearTextBytes, 0, clearTextBytes.Length); cs.Close(); var tmp = Encoding.UTF8.GetString(ms.ToArray()); return tmp; } 

Answer 1

Encrypt / decrypt using PHP:

 class Cipher { private $key, $iv; function __construct() { $this->key = "edrtjfjfjlldldld"; $this->iv = "56666852251557009888889955123458"; } function encrypt($text) { $block = mcrypt_get_block_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_CBC); $padding = $block - (strlen($text) % $block); $text .= str_repeat(chr($padding), $padding); $crypttext = mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $this->key, $text, MCRYPT_MODE_CBC, $this->iv); return base64_encode($crypttext); } function decrypt($input) { $dectext = mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $this->key, base64_decode($input), MCRYPT_MODE_CBC, $this->iv); return $dectext; } } 

Encryption / Decryption using C #:

 public class RijndaelSimple { const string iv = "56666852251557009888889955123458"; const string key = "edrtjfjfjlldldld"; static public String EncryptRJ256(string plainText) { var encoding = new UTF8Encoding(); var Key = encoding.GetBytes(key); var IV = encoding.GetBytes(iv); byte[] encrypted; using (var rj = new RijndaelManaged()) { try { rj.Padding = PaddingMode.PKCS7; rj.Mode = CipherMode.CBC; rj.KeySize = 256; rj.BlockSize = 256; rj.Key = Key; rj.IV = IV; var ms = new MemoryStream(); using (var cs = new CryptoStream(ms, rj.CreateEncryptor(Key, IV), CryptoStreamMode.Write)) { using (var sr = new StreamWriter(cs)) { sr.Write(plainText); sr.Flush(); cs.FlushFinalBlock(); } encrypted = ms.ToArray(); } } finally { rj.Clear(); } } return Convert.ToBase64String(encrypted); } static public String DecryptRJ256(string input) { byte[] cypher = Convert.FromBase64String(input); var sRet = ""; var encoding = new UTF8Encoding(); var Key = encoding.GetBytes(key); var IV = encoding.GetBytes(iv); using (var rj = new RijndaelManaged()) { try { rj.Padding = PaddingMode.PKCS7; rj.Mode = CipherMode.CBC; rj.KeySize = 256; rj.BlockSize = 256; rj.Key = Key; rj.IV = IV; var ms = new MemoryStream(cypher); using (var cs = new CryptoStream(ms, rj.CreateDecryptor(Key, IV), CryptoStreamMode.Read)) { using (var sr = new StreamReader(cs)) { sRet = sr.ReadLine(); } } } finally { rj.Clear(); } } return sRet; } } 

Answer 2

Two problems with C # code.

• You should not encode the contents of your MemoryStream in UTF8. The output of the CryptoStream is binary and will not be correctly converted. Either return a byte[] , or if you really want a string, encode the output to Hex or Base64.

• You need to set padding mode via rijn.Padding = PaddingMode.Zeros; . Although not explicitly stated, PHP populates data up to the size of the block using 0. The default padding for SymmetricAlgorithm is PKCS7.

Also note that the signatures of your PHP and C # methods are different. The order of the parameters for your PHP function is data, key, iv , and the C # method is data, iv, key . If you still have a problem after the changes listed above, it is possible that your IV and key are canceled when you call your encryption method in C #.