Develop Reference

the problem of crypting data by C# on the server side and encrypting it by CryptoJS on the client side

I got stuck also a bit lost in C# and CryptoJS differences.i have two server side
functions to encrypt data by AES256 bit as follows;
public string EncryptText_PBKDF2(string input, string password)
{
// Get the bytes of the strings
byte[] bytesToBeEncrypted = Encoding.UTF8.GetBytes(input);
byte[] passwordBytes = Encoding.UTF8.GetBytes(password);
// Hash the password with SHA256 for AES key
passwordBytes = SHA256.Create().ComputeHash(passwordBytes);
byte[] bytesEncrypted = AES_Encrypt_PBKDF2(bytesToBeEncrypted, passwordBytes);
string result = Convert.ToBase64String(bytesEncrypted);
return result;
}
private byte[] AES_Encrypt_PBKDF2(byte[] bytesToBeEncrypted, byte[] passwordBytes)
{
byte[] encryptedBytes = null;
byte[] saltBytes = new byte[] { 0, 0, 0, 0, 0, 0, 0, 0 };
using (MemoryStream ms = new MemoryStream())
{
aes.KeySize = 256;
aes.BlockSize = 128;
aes.IV = MD5.Create().ComputeHash(passwordBytes);//16 byte
var PBKDF2_key = new Rfc2898DeriveBytes(passwordBytes, saltBytes, 1000);
aes.Key = PBKDF2_key.GetBytes(aes.KeySize / 8);//32 byte
aes.Mode = CipherMode.CBC;
using (var cs = new CryptoStream(ms, aes.CreateEncryptor(aes.Key, aes.IV), CryptoStreamMode.Write))
{
cs.Write(bytesToBeEncrypted, 0, bytesToBeEncrypted.Length);
cs.Close();
}
encryptedBytes = ms.ToArray();
}
return encryptedBytes;
}
then i send it to view by a controller action;
string res = aesIsl.EncryptText_PBKDF2("my text", "my key");
ViewBag.Crypted1 = res;
on the client side i get it from a hidden field
<div id="crypted"><input id="hidden1" data-enc="#ViewBag.Crypted1" type="hidden" /></div>
and decrypt it by crypto-js library(i have 4 attempts indicated on top of them)
here is my decrypting function and attempts:
function AesleDesifrele_PBKDF2(ciphertext, pwd) {
var salt = "0000000000000000";
var iv = CryptoJS.MD5(CryptoJS.SHA256(CryptoJS.enc.Utf8.parse(pwd)));
//these are my attempts to decrypt
//ATTEMPT #1:
//returning object contains a word array but converting it to utf8 string
//causes "Malformed UTF-8 data" error
console.log(CryptoJS.AES.decrypt(ciphertext, pwd).toString(CryptoJS.enc.Utf8));
//ATTEMPT #2
var key = CryptoJS.PBKDF2(
CryptoJS.enc.Utf8.parse(pwd).toString(CryptoJS.enc.Utf8),
CryptoJS.enc.Hex.parse(salt),
{ keySize: 128 / 32, iterations: 1000 }
);
var decrypted = CryptoJS.AES.decrypt(
ciphertext,
key,
{ iv: iv }
);
//returning object contains a word array but converting it to utf8 string
//causes "Malformed UTF-8 data" error
console.log(decrypted.toString(CryptoJS.enc.Utf8));
//ATTEMPT #3
var raw = base64UrlDecode(ciphertext);
var iv1 = CryptoJS.lib.WordArray.create(CryptoJS.MD5(CryptoJS.SHA256(CryptoJS.enc.Utf8.parse(pwd))));;
var salt1 = CryptoJS.lib.WordArray.create(CryptoJS.enc.Hex.parse(salt));
var key1 = generateKey(pwd, salt1);
var ciphertextWords = CryptoJS.lib.WordArray.create(raw.words.slice(128 / 32 + 128 / 32));
var cipherParams = CryptoJS.lib.CipherParams.create({ ciphertext: ciphertextWords });
var plaintextArray = CryptoJS.AES.decrypt(
cipherParams,
key1,
{ iv: iv1 }
);
console.log(CryptoJS.enc.Utf8.stringify(plaintextArray));
//returning object contains a word array but converting it to utf8 string
//returns nothing
//ATTEMPT #4
var iv2 = CryptoJS.MD5(CryptoJS.SHA256(CryptoJS.enc.Utf8.parse(pwd)));
var Pass = CryptoJS.enc.Utf8.parse(pwd);
var Salt = CryptoJS.enc.Utf8.parse(salt);
var key256Bits1000Iterations = CryptoJS.PBKDF2(Pass.toString(CryptoJS.enc.Utf8), Salt, { keySize: 256 / 32, iterations: 1000 });
var cipherParams = CryptoJS.lib.CipherParams.create({
ciphertext: CryptoJS.enc.Base64.parse(ciphertext)
});
var decrypted = CryptoJS.AES.decrypt(cipherParams, key256Bits1000Iterations, { mode: CryptoJS.mode.CBC, iv: iv2, padding: CryptoJS.pad.Pkcs7 });
console.log(decrypted.toString(CryptoJS.enc.Utf8));
//returning object contains a word array but converting it to utf8 string
//returns nothing
}
this is the function to generate key for CryptoJs decrypt
function generateKey(secret, salt) {
return CryptoJS.PBKDF2(
secret,
salt,
{
keySize: this.keySize / 32, // size in Words
iterations: 1000,
hasher: CryptoJS.algo.SHA256
}
);
}
this is the conversion function i use
function base64UrlDecode(str) {
return CryptoJS.enc.Base64.parse(str.replace(/\-/g, '+').replace(/\_/g, '/'));
}
even though i control params on the client(cyphertext,password,IV and the salt) are exactly the same with the server,CryptoJS.decrypt returns nothing without any error.i guess i miss converting something to another in order C# to be compatible with CryptoJs.
any advice welcomes.
thanks in advance.

Encoding in RSA in C# for Symfony(PHP) [duplicate]

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 text is decrypted! I started working from this example: Decrypt PHP encrypted string in C#
Here's the text (JSON) that I am encrypting (sensitive information removed):
{"DisplayName":"xxx", "Username": "yyy", "EmailAddress":"zzz"}
So I login to the C# app which creates/encodes the cookie from stored Key and IV and then redirects to the PHP app which is supposed to decrypt/read the cookie. When I decrypt the cookie, it comes out like this:
{"DisplayName":"xxx","F�A ;��HP=D�������4��z����ť���k�#E���R�j�5�\�t. t�D��"
UPDATE: i've gotten a little bit further and this is now the result
string(96) "{"DisplayName":"xxx","Username":"yyy","EmailAddress"�)ق��-�J��k/VV-v� �9�B`7^"
As you can see, it starts decrypting it, but then gets messed up...
When Decrypt the string it comes out correct (with padding, which I have a function to remove padding), but if I change the test string by one character I get garbage again:
B�nHL�Ek �¿?�UΣlO����OЏ�M��NO/�f.M���Lƾ�CC�Y>F��~�qd�+
Here's the c# code I use to generate the random Key and IV:
UPDATE: I'm just using static key/IV for now, here they are:
Key: lkirwf897+22#bbtrm8814z5qq=498j5
IV: 741952hheeyy66#cs!9hjv887mxx7#8y
RijndaelManaged symmetricKey = new RijndaelManaged();
symmetricKey.BlockSize = 256;
symmetricKey.KeySize = 256;
symmetricKey.Padding = PaddingMode.Zeros;
symmetricKey.Mode = CipherMode.CBC;
string key = Convert.ToBase64String(symmetricKey.Key);
string IV = Convert.ToBase64String(symmetricKey.IV);
I then save the key and IV to a database to be retrieved later for encoding/decoding.
This is the full 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,
//FeedbackSize = 256
};
var key = Encoding.ASCII.GetBytes(prm_key);
var IV = Encoding.ASCII.GetBytes(prm_iv);
//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,
//FeedbackSize = 256
};
var key = Encoding.ASCII.GetBytes(prm_key);
var IV = Encoding.ASCII.GetBytes(prm_iv);
//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,
//FeedbackSize = 256
};
rj.GenerateKey();
rj.GenerateIV();
key = Convert.ToBase64String(rj.Key);
IV = Convert.ToBase64String(rj.IV);
}
}
Here's the PHP code I am using to decrypt the data:
function decryptRJ256($key,$iv,$string_to_decrypt)
{
$string_to_decrypt = base64_decode($string_to_decrypt);
$rtn = mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $key, $string_to_decrypt, MCRYPT_MODE_CBC, $iv);
//$rtn = rtrim($rtn, "\0\4");
$rtn = unpad($rtn);
return($rtn);
}
function unpad($value)
{
$blockSize = mcrypt_get_block_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_CBC);
//apply pkcs7 padding removal
$packing = ord($value[strlen($value) - 1]);
if($packing && $packing < $blockSize){
for($P = strlen($value) - 1; $P >= strlen($value) - $packing; $P--){
if(ord($value{$P}) != $packing){
$packing = 0;
}//end if
}//end for
}//end if
return substr($value, 0, strlen($value) - $packing);
}
$ky = 'lkirwf897+22#bbtrm8814z5qq=498j5'; // 32 * 8 = 256 bit key
$iv = '741952hheeyy66#cs!9hjv887mxx7#8y'; // 32 * 8 = 256 bit iv
$enc = $_COOKIE["MyCookie"];
$dtext = decryptRJ256($ky, $iv, $enc);
var_dump($dtext);
I am a little unsure about this part, because all of the example code I've seen simply passes in the base64 encoded string directly to the decryptor, but in my example, I have to base64_decode it before I pass it otherwise I get the error that the key and IV are not the correct length.
UPDATE: I'm using ASCII keys in the format needed by PHP. If I generate keys from the RijndaelManaged class they dont work on the PHP side, but I can use keys that are known to work on PHP side and use them in the RijndaelManaged C# side.
Please let me know if I left out any pertinent information. TIA!

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
<?php
function decryptRJ256($key,$iv,$encrypted)
{
//PHP strips "+" and replaces with " ", but we need "+" so add it back in...
$encrypted = str_replace(' ', '+', $encrypted);
//get all the bits
$key = base64_decode($key);
$iv = base64_decode($iv);
$encrypted = base64_decode($encrypted);
$rtn = mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $key, $encrypted, MCRYPT_MODE_CBC, $iv);
$rtn = unpad($rtn);
return($rtn);
}
//removes PKCS7 padding
function unpad($value)
{
$blockSize = mcrypt_get_block_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_CBC);
$packing = ord($value[strlen($value) - 1]);
if($packing && $packing < $blockSize)
{
for($P = strlen($value) - 1; $P >= strlen($value) - $packing; $P--)
{
if(ord($value{$P}) != $packing)
{
$packing = 0;
}
}
}
return substr($value, 0, strlen($value) - $packing);
}
?>
<pre>
<?php
$enc = $_COOKIE["MyCookie"];
$ky = ""; //INSERT THE KEY GENERATED BY THE C# CLASS HERE
$iv = ""; //INSERT THE IV GENERATED BY THE C# CLASS HERE
$json_user = json_decode(decryptRJ256($ky, $iv, $enc), true);
var_dump($json_user);
?>

Since the string is partially OK, but there is gibberish at the end it would suggest a padding problem within the encryption which expects exact blocks of 256 bytes. I suggest setting the padding as PKCS7 (PaddingMode.PKCS7) instead of Zeros on the C# side which PHP will understand without issues (as it's the default mode on that parser).
Edit: Oops, I did not notice that you had the following in your PHP:
$enc = $_COOKIE["MyCookie"];
This is the caveat. PHP is likely not getting the encrypted data as-is and is running some urldecode sanitizing. You should print this variable to see that it really matches what is being sent from the C# code.
Edit2:
Convert the whitespaces to missing + characters from the cookie by adding this:
str_replace(' ', '+', $enc);

Port AES encryption code to WinRT

I need to port this code (console application in c#):
Decrypt PHP encrypted string in C#
to WinRT code. I have:
class Crypto{const string Key = "lkirwf897+22#bbtrm8814z5qq=498j5";
const string IV = "741952hheeyy66#cs!9hjv887mxx7#8y";
public static string Encrypt(string login)
{
var input = CryptographicBuffer.ConvertStringToBinary(login, BinaryStringEncoding.Utf8);
var key1 = CryptographicBuffer.ConvertStringToBinary(Key, BinaryStringEncoding.Utf8);
var iv = CryptographicBuffer.ConvertStringToBinary(IV, BinaryStringEncoding.Utf8);
var encryptor = SymmetricKeyAlgorithmProvider.OpenAlgorithm(SymmetricAlgorithmNames.AesCbcPkcs7);
var key2 = encryptor.CreateSymmetricKey(key1);
var encrypted = CryptographicEngine.Encrypt(key2, input, iv);
return CryptographicBuffer.ConvertBinaryToString(BinaryStringEncoding.Utf8, encrypted);
}
public static string Decrypt(string LoginToDecode)
{
var input = CryptographicBuffer.ConvertStringToBinary(LoginToDecode, BinaryStringEncoding.Utf8);
var key1 = CryptographicBuffer.ConvertStringToBinary(Key, BinaryStringEncoding.Utf8);
var iv = CryptographicBuffer.ConvertStringToBinary(IV, BinaryStringEncoding.Utf8);
var decryptor = SymmetricKeyAlgorithmProvider.OpenAlgorithm(SymmetricAlgorithmNames.AesCbcPkcs7);
var key2 = decryptor.CreateSymmetricKey(key1);
var decrypted = CryptographicEngine.Decrypt(key2, input, iv);
return CryptographicBuffer.ConvertBinaryToString(BinaryStringEncoding.Utf8, decrypted);
}}
I have an error in the last line of the Encrypt function:
Additional information: No mapping for the Unicode character exists in the target multi-byte code page.
I would like to get the same result like in topic above. This solution can be correct without error?
UPDATE
I removed the error. Code is:
class Crypto{const string Key = "lkirwf897+22#bbtrm8814z5qq=498j5";
const string IV = "741952hheeyy66#cs!9hjv887mxx7#8y";
public static string Encrypt(string login)
{
var input = CryptographicBuffer.ConvertStringToBinary(login, BinaryStringEncoding.Utf8);
var key1 = CryptographicBuffer.ConvertStringToBinary(Key, BinaryStringEncoding.Utf8);
var iv = CryptographicBuffer.ConvertStringToBinary(IV, BinaryStringEncoding.Utf8);
var encryptor = SymmetricKeyAlgorithmProvider.OpenAlgorithm(SymmetricAlgorithmNames.AesCbcPkcs7);
var key2 = encryptor.CreateSymmetricKey(key1);
var encrypted = CryptographicEngine.Encrypt(key2, input, iv);
return CryptographicBuffer.EncodeToBase64String(encrypted);
}
public static string Decrypt(string LoginToDecode)
{
var input = CryptographicBuffer.DecodeFromBase64String(LoginToDecode);
var key1 = CryptographicBuffer.ConvertStringToBinary(Key, BinaryStringEncoding.Utf8);
var iv = CryptographicBuffer.ConvertStringToBinary(IV, BinaryStringEncoding.Utf8);
var decryptor = SymmetricKeyAlgorithmProvider.OpenAlgorithm(SymmetricAlgorithmNames.AesCbcPkcs7);
var key2 = decryptor.CreateSymmetricKey(key1);
var decrypted = CryptographicEngine.Decrypt(key2, input, iv);
return CryptographicBuffer.ConvertBinaryToString(BinaryStringEncoding.Utf8, decrypted);
}
}}
But the result of this code it's not the same like from topic above. I need this because I have to communicate with php server.
UPDATE#2
Ok, I learned that in WinRT can I use only 128AES. So, I changed PHP script:
function decryptRJ128($key,$iv,$string_to_decrypt){
$string_to_decrypt = base64_decode($string_to_decrypt);
$rtn = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $key, $string_to_decrypt, MCRYPT_MODE_CBC, $iv);
$rtn = rtrim($rtn, "\0\4");
return($rtn);}
function encryptRJ128($key,$iv,$string_to_encrypt){ $rtn = mcrypt_encrypt(MCRYPT_RIJNDAEL_128, $key, $string_to_encrypt, MCRYPT_MODE_CBC, $iv); $rtn = base64_encode($rtn); return($rtn);}
And for
password = "Asd"
Key = "lkirwf897+22#bbt" it's must be 16bit
IV = "741952hheeyy66#c"
I have in c# "eSy8m8ygN7rtC80DMdGOUQ==". I need this in PHP.

Well, here's my solution.
In C# code I need to merge two byte array before encode it into base64.
/* PHP */
$key = '12345678abcdefgh';
$text = "d9e978bc7ca9179f0d51e91521d41d8d";
$iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC);
$iv = mcrypt_create_iv($iv_size);
$iv = '87654321hgfedcba'; //Just to test
$encrypted = mcrypt_encrypt(MCRYPT_RIJNDAEL_128, $key, $text, MCRYPT_MODE_CBC, $iv);
$encrypted = base64_encode($iv.$encrypted);
$decryptedd = base64_decode($encrypted);
$iv_dec = substr($decryptedd, 0, $iv_size);
$decrypted = substr($decryptedd, $iv_size);
$decrypted = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $key, $decrypted, MCRYPT_MODE_CBC, $iv_dec);
echo 'Key: '.$key.'<br />';
echo 'Text: '.$text.'<br />';
echo 'IV: '.$iv.' (Size: '.$iv_size.')<br />';
echo 'Encrypted: '.$encrypted.'<br />';
echo 'IV decrypted: '.$iv_dec.'<br />';
echo 'Decrypted: '.$decrypted.'<br />';
And here is C# code:
var input = CryptographicBuffer.ConvertStringToBinary("d9e978bc7ca9179f0d51e91521d41d8d", BinaryStringEncoding.Utf8);
var key = CryptographicBuffer.ConvertStringToBinary("12345678abcdefgh", BinaryStringEncoding.Utf8);
var iv = CryptographicBuffer.ConvertStringToBinary("87654321hgfedcba", BinaryStringEncoding.Utf8);
var encryptor = SymmetricKeyAlgorithmProvider.OpenAlgorithm(SymmetricAlgorithmNames.AesCbc);
byte[] a = iv.ToArray();
byte[] b = CryptographicEngine.Encrypt(encryptor.CreateSymmetricKey(key), input, iv).ToArray();
byte[] c = new byte[a.Length + b.Length];
Buffer.BlockCopy(a, 0, c, 0, a.Length);
Buffer.BlockCopy(b, 0, c, a.Length, b.Length);
var result = Convert.ToBase64String(c);

C# <-> PHP dynamic AES key exchange

I want to make an encrypted communication system with a dynamic key exchange between C# and PHP. At the moment I have a working encrypt/decrypt PHP <-> PHP and C# <-> C# but it's not working PHP <-> C# for some reason. The problem is that the C# code decrypted string generates a longer output than the PHP would expect, but the data is the same when viewing the output as a simple string. E.g a string "daa" sent from C# to PHP, decrypted length is 28, which is not what is supposed to be. Same goes with the string sent from PHP to C#, I get a compiler error ArgumentException: length
C# code:
public static string EncryptTest(string input)
{
string key = "256 bit key (32 char)";
input = Md5Sum(input).Substring(0, 4) + input;
var encoding = new UTF8Encoding();
var Key = encoding.GetBytes(key);
byte[] encrypted;
byte[] result;
using (var rj = new RijndaelManaged())
{
try
{
rj.Padding = PaddingMode.PKCS7;
rj.Mode = CipherMode.CBC;
rj.KeySize = 256;
rj.BlockSize = 256;
rj.Key = Key;
rj.GenerateIV();
using (ICryptoTransform encryptor = rj.CreateEncryptor())
{
using (MemoryStream ms = new MemoryStream())
{
using (CryptoStream cs = new CryptoStream(ms, encryptor, CryptoStreamMode.Write))
{
using (StreamWriter writer = new StreamWriter(cs))
{
writer.Write(input);
}
}
encrypted = ms.ToArray();
result = new byte[rj.BlockSize / 8 + encrypted.Length];
// Result is built as: IV (plain text) + Encrypted(data)
Array.Copy(rj.IV, result, rj.BlockSize / 8);
Array.Copy(encrypted, 0, result, rj.BlockSize / 8, encrypted.Length);
}
}
}
finally
{
rj.Clear();
}
}
return Convert.ToBase64String(result);
}
public static string DecryptTest(string input)
{
string key = "256 bit key (32 char)";
byte[] data = Convert.FromBase64String(input);
if (data.Length < 32)
return null;
var encoding = new UTF8Encoding();
var Key = encoding.GetBytes(key);
using (RijndaelManaged aes = new RijndaelManaged())
{
aes.Padding = PaddingMode.PKCS7;
aes.Mode = CipherMode.CBC;
aes.KeySize = 256;
aes.BlockSize = 256;
aes.Key = Key;
// Extract the IV from the data first.
byte[] iv = new byte[aes.BlockSize / 8];
Array.Copy(data, iv, iv.Length);
aes.IV = iv;
// The remainder of the data is the encrypted data we care about.
byte[] encryptedData = new byte[data.Length - iv.Length];
Array.Copy(data, iv.Length, encryptedData, 0, encryptedData.Length);
using (ICryptoTransform decryptor = aes.CreateDecryptor())
{
using (MemoryStream ms = new MemoryStream(encryptedData))
{
using (CryptoStream cs = new CryptoStream(ms, decryptor, CryptoStreamMode.Read))
{
using (StreamReader reader = new StreamReader(cs))
{
string output = reader.ReadToEnd();
if (output.Length < 4)
return null;
string dataHash = output.Substring(0, 4);
string dataInput = output.Substring(4);
string dataInputHash = Md5Sum(dataInput).Substring(0, 4);
if (dataHash != dataInputHash)
return null;
return dataInput;
}
}
}
}
}
}
private static string Md5Sum(string strToEncrypt)
{
UTF8Encoding ue = new UTF8Encoding();
byte[] bytes = ue.GetBytes(strToEncrypt);
MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider();
byte[] hashBytes = md5.ComputeHash(bytes);
string hashString = "";
for (int i = 0; i < hashBytes.Length; i++)
{
hashString += Convert.ToString(hashBytes[i], 16).PadLeft(2, '0');
}
return hashString.PadLeft(32, '0');
}
PHP code:
$key = "256 bit key (32 char)";
function iv()
{
$iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_CBC);
return mcrypt_create_iv($iv_size, MCRYPT_RAND);
}
function encrypt($data, $key32)
{
# Prepend 4-chars data hash to the data itself for validation after decryption
$data = substr(md5($data), 0, 4).$data;
# Prepend $iv to decrypted data
$iv = iv();
$enc = $iv.mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $key32, $data, MCRYPT_MODE_CBC, $iv);
return base64_encode($enc);
}
function decrypt($data, $key32)
{
$data = base64_decode($data);
if ($data === false || strlen($data) < 32)
return null;
$iv = substr($data, 0, 32);
$encrypted = substr($data, 32);
$decrypted = rtrim(mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $key32, $encrypted, MCRYPT_MODE_CBC, $iv), "\0");
if ($decrypted === false || is_null($decrypted) || strlen($decrypted) < 4)
return null;
$dataHash = substr($decrypted, 0, 4);
$data = substr($decrypted, 4);
if (substr(md5($data), 0, 4) !== $dataHash)
return null; // it breaks here, md5 sum is not correct because of the length
return $data;
}

PHP / mcrypt is not using PKCS#7 padding, it uses zero padding of 0..n bytes where n is the block size.
To PKCS#7-pad the plaintext before encryption, use:
$pad = $blockSize - (strlen($data) % $blockSize);
$pdata = $data . str_repeat(chr($pad), $pad);
to unpad the plaintext after decryption simply perform:
$pad = ord($pdata[strlen($pdata) - 1]);
$data = substr($pdata, 0, strlen($pdata) - $pad);
PKCS#7 is now the ad hoc standard for padding. Zero padding is non-deterministic; it may alter the plaintext if the plaintext ends with zero's itself.

C# Encryption to PHP Decryption

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 text is decrypted! I started working from this example: Decrypt PHP encrypted string in C#
Here's the text (JSON) that I am encrypting (sensitive information removed):
{"DisplayName":"xxx", "Username": "yyy", "EmailAddress":"zzz"}
So I login to the C# app which creates/encodes the cookie from stored Key and IV and then redirects to the PHP app which is supposed to decrypt/read the cookie. When I decrypt the cookie, it comes out like this:
{"DisplayName":"xxx","F�A ;��HP=D�������4��z����ť���k�#E���R�j�5�\�t. t�D��"
UPDATE: i've gotten a little bit further and this is now the result
string(96) "{"DisplayName":"xxx","Username":"yyy","EmailAddress"�)ق��-�J��k/VV-v� �9�B`7^"
As you can see, it starts decrypting it, but then gets messed up...
When Decrypt the string it comes out correct (with padding, which I have a function to remove padding), but if I change the test string by one character I get garbage again:
B�nHL�Ek �¿?�UΣlO����OЏ�M��NO/�f.M���Lƾ�CC�Y>F��~�qd�+
Here's the c# code I use to generate the random Key and IV:
UPDATE: I'm just using static key/IV for now, here they are:
Key: lkirwf897+22#bbtrm8814z5qq=498j5
IV: 741952hheeyy66#cs!9hjv887mxx7#8y
RijndaelManaged symmetricKey = new RijndaelManaged();
symmetricKey.BlockSize = 256;
symmetricKey.KeySize = 256;
symmetricKey.Padding = PaddingMode.Zeros;
symmetricKey.Mode = CipherMode.CBC;
string key = Convert.ToBase64String(symmetricKey.Key);
string IV = Convert.ToBase64String(symmetricKey.IV);
I then save the key and IV to a database to be retrieved later for encoding/decoding.
This is the full 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,
//FeedbackSize = 256
};
var key = Encoding.ASCII.GetBytes(prm_key);
var IV = Encoding.ASCII.GetBytes(prm_iv);
//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,
//FeedbackSize = 256
};
var key = Encoding.ASCII.GetBytes(prm_key);
var IV = Encoding.ASCII.GetBytes(prm_iv);
//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,
//FeedbackSize = 256
};
rj.GenerateKey();
rj.GenerateIV();
key = Convert.ToBase64String(rj.Key);
IV = Convert.ToBase64String(rj.IV);
}
}
Here's the PHP code I am using to decrypt the data:
function decryptRJ256($key,$iv,$string_to_decrypt)
{
$string_to_decrypt = base64_decode($string_to_decrypt);
$rtn = mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $key, $string_to_decrypt, MCRYPT_MODE_CBC, $iv);
//$rtn = rtrim($rtn, "\0\4");
$rtn = unpad($rtn);
return($rtn);
}
function unpad($value)
{
$blockSize = mcrypt_get_block_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_CBC);
//apply pkcs7 padding removal
$packing = ord($value[strlen($value) - 1]);
if($packing && $packing < $blockSize){
for($P = strlen($value) - 1; $P >= strlen($value) - $packing; $P--){
if(ord($value{$P}) != $packing){
$packing = 0;
}//end if
}//end for
}//end if
return substr($value, 0, strlen($value) - $packing);
}
$ky = 'lkirwf897+22#bbtrm8814z5qq=498j5'; // 32 * 8 = 256 bit key
$iv = '741952hheeyy66#cs!9hjv887mxx7#8y'; // 32 * 8 = 256 bit iv
$enc = $_COOKIE["MyCookie"];
$dtext = decryptRJ256($ky, $iv, $enc);
var_dump($dtext);
I am a little unsure about this part, because all of the example code I've seen simply passes in the base64 encoded string directly to the decryptor, but in my example, I have to base64_decode it before I pass it otherwise I get the error that the key and IV are not the correct length.
UPDATE: I'm using ASCII keys in the format needed by PHP. If I generate keys from the RijndaelManaged class they dont work on the PHP side, but I can use keys that are known to work on PHP side and use them in the RijndaelManaged C# side.
Please let me know if I left out any pertinent information. TIA!

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
<?php
function decryptRJ256($key,$iv,$encrypted)
{
//PHP strips "+" and replaces with " ", but we need "+" so add it back in...
$encrypted = str_replace(' ', '+', $encrypted);
//get all the bits
$key = base64_decode($key);
$iv = base64_decode($iv);
$encrypted = base64_decode($encrypted);
$rtn = mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $key, $encrypted, MCRYPT_MODE_CBC, $iv);
$rtn = unpad($rtn);
return($rtn);
}
//removes PKCS7 padding
function unpad($value)
{
$blockSize = mcrypt_get_block_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_CBC);
$packing = ord($value[strlen($value) - 1]);
if($packing && $packing < $blockSize)
{
for($P = strlen($value) - 1; $P >= strlen($value) - $packing; $P--)
{
if(ord($value{$P}) != $packing)
{
$packing = 0;
}
}
}
return substr($value, 0, strlen($value) - $packing);
}
?>
<pre>
<?php
$enc = $_COOKIE["MyCookie"];
$ky = ""; //INSERT THE KEY GENERATED BY THE C# CLASS HERE
$iv = ""; //INSERT THE IV GENERATED BY THE C# CLASS HERE
$json_user = json_decode(decryptRJ256($ky, $iv, $enc), true);
var_dump($json_user);
?>

Since the string is partially OK, but there is gibberish at the end it would suggest a padding problem within the encryption which expects exact blocks of 256 bytes. I suggest setting the padding as PKCS7 (PaddingMode.PKCS7) instead of Zeros on the C# side which PHP will understand without issues (as it's the default mode on that parser).
Edit: Oops, I did not notice that you had the following in your PHP:
$enc = $_COOKIE["MyCookie"];
This is the caveat. PHP is likely not getting the encrypted data as-is and is running some urldecode sanitizing. You should print this variable to see that it really matches what is being sent from the C# code.
Edit2:
Convert the whitespaces to missing + characters from the cookie by adding this:
str_replace(' ', '+', $enc);