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Aes Decryption in .net 5

I have below code written in .net framework to decrypt encrypted text and it is working fine.
private static string MD5(string testString)
{
byte[] asciiBytes = ASCIIEncoding.ASCII.GetBytes(testString);
byte[] hashedBytes = MD5CryptoServiceProvider.Create().ComputeHash(asciiBytes);
string hashedString = BitConverter.ToString(hashedBytes).Replace("-", "").ToLower();
return hashedString;
}
public static string DecryptString(string cypherText, string encryptionKey)
{
byte[] cipherTextBytes = Convert.FromBase64String(cipherText);
byte[] key = ASCIIEncoding.ASCII.GetBytes(MD5(encryptionKey));
if (key == null || key.Length <= 0)
throw new ArgumentNullException("key");
string plaintext;
using (var rijAlg = new RijndaelManaged())
{
rijAlg.BlockSize = 256;
rijAlg.Key = key;
rijAlg.Mode = CipherMode.CBC;
rijAlg.Padding = PaddingMode.Zeros;
rijAlg.IV = ASCIIEncoding.ASCII.GetBytes(MD5(MD5(_encryptionKey)));
ICryptoTransform decryptor = rijAlg.CreateDecryptor(rijAlg.Key, rijAlg.IV);
using (var msDecrypt = new MemoryStream(cipherTextBytes))
using (var csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
using (var srDecrypt = new StreamReader(csDecrypt))
plaintext = srDecrypt.ReadToEnd();
}
return plaintext;
}
Above code never worked and was returning some junk characters when the code was migrated to .net 5. With some research and help from fellow community member I got the below updated code that works.
public static string DecryptUsingBouncyCastle(string cypherText, string keyString)
{
byte[] key = ASCIIEncoding.ASCII.GetBytes(MD5(keyString));
byte[] cipherTextBytes = Convert.FromBase64String(cypherText);
if (key == null || key.Length <= 0)
throw new ArgumentNullException("key");
var ivStringBytes = ASCIIEncoding.ASCII.GetBytes(MD5(MD5(keyString)));
var engine = new RijndaelEngine(256);
var blockCipher = new CbcBlockCipher(engine);
var cipher = new PaddedBufferedBlockCipher(blockCipher, new ZeroBytePadding());
var keyParam = new KeyParameter(key);
var keyParamWithIV = new ParametersWithIV(keyParam, ivStringBytes, 0, ivStringBytes.Length);
cipher.Init(false, keyParamWithIV);
var outputBytes = new byte[cipher.GetOutputSize(cipherTextBytes.Length)];
var length = cipher.ProcessBytes(cipherTextBytes, outputBytes, 0);
length += cipher.DoFinal(outputBytes, length);
var resultText = Encoding.UTF8.GetString(outputBytes, 0, length);
return resultText;
}
I was cautioned that AES should be preferred over Rijndael with 256 bits block size. With that in mind I tried to write the decrypt method using AES but I could not succeed. It is not throwing any error but returning some garbage text.
public static string DecryptStringFromAES(string cypherText, string keyString)
{
byte[] key = ASCIIEncoding.ASCII.GetBytes(MD5(keyString));
byte[] cipherText = Convert.FromBase64String(cypherText);
if (key == null || key.Length <= 0)
throw new ArgumentNullException("key");
string plaintext;
using (var aes = Aes.Create())
{
aes.BlockSize = 128;
aes.Key = key;
aes.Mode = CipherMode.CBC;
aes.Padding = PaddingMode.Zeros;
aes.IV = new byte[16];
ICryptoTransform decryptor = aes.CreateDecryptor(aes.Key, aes.IV);
using (var msDecrypt = new MemoryStream(cipherText))
using (var csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
using (var srDecrypt = new StreamReader(csDecrypt))
plaintext = srDecrypt.ReadToEnd();
}
return plaintext;
}
I am not an expert in Cryptography and I don't really know what is wrong in the above code. My job demanded this task to decrypt some encrypted information from Active Directory. Encryption is done by some other process and I can't share the encryption key and don't have test code as we don't have a test environment.
Appreciate if someone could look at the code and see if I messed up anything with that code and suggest any correction that could possibly fix the issue. Thanks in advance.

C# encrypt/decrypt methods which are equivalent to PHP7 openssl

I have the following lines in a PHP 7 program encrypting/decrypting data:
$key = base64_decode("mykey===");
$iv = substr(hash('sha256', "myiv======"), 0, 16);
printf(base64_encode(openssl_encrypt("hello", "aes-256-cbc", $key, OPENSSL_RAW_DATA, $iv)));
printf("<br>");
printf(openssl_decrypt(base64_decode("2XJxQXSbPuJ9LMsZ/FESGw=="), "aes-256-cbc", $key, OPENSSL_RAW_DATA, $iv));
This is working, PHP decrypts "hello" to "2XJxQXSbPuJ9LMsZ/FESGw==" and vice versa. However I'm trying to decrypt and encrypt the same data (from a Database) with C# but can't seem to figure it out. I used the following method for decryption (C#):
private string aes_decrypt(string cipherText, string key, string iv)
{
RijndaelManaged aes = new RijndaelManaged();
aes.KeySize = 256;
aes.BlockSize = 128;
aes.Mode = CipherMode.CBC;
aes.Padding = PaddingMode.None;
aes.Key = Convert.FromBase64String(key);
aes.IV = Encoding.UTF8.GetBytes(iv);
if (aes.Key.Length < 32)
{
var paddedkey = new byte[32];
Buffer.BlockCopy(aes.Key, 0, paddedkey, 0, aes.Key.Length);
aes.Key = paddedkey;
}
var decrypt = aes.CreateDecryptor();
byte[] xBuff = null;
using (var ms = new MemoryStream())
{
using (var cs = new CryptoStream(ms, decrypt, CryptoStreamMode.Write))
{
byte[] xXml = Convert.FromBase64String(cipherText);
cs.Write(xXml, 0, xXml.Length);
}
xBuff = ms.ToArray();
}
String Output = Encoding.UTF8.GetString(xBuff);
return Output;
}
But a call to this method:
string encryptionkey = "mykey===";
string encryptioniv = GenerateSHA256String("myiv======").Substring(0, 16);
string str = aes_decrypt("2XJxQXSbPuJ9LMsZ/FESGw==", encryptionkey, encryptioniv);
Console.WriteLine(#str);
returns: HellO++++??????+
The encryption method doesnt seem to work either (referenced online and modified):
private static String EncryptIt(String s, string akey, string aIV)
{
String result;
byte[] key = Convert.FromBase64String(akey);
byte[] IV = Encoding.UTF8.GetBytes(aIV);
RijndaelManaged rijn = new RijndaelManaged();
rijn.Mode = CipherMode.CBC;
rijn.Padding = PaddingMode.PKCS7;
rijn.KeySize = 256;
rijn.BlockSize = 128;
using (MemoryStream msEncrypt = new MemoryStream())
{
using (ICryptoTransform encryptor = rijn.CreateEncryptor(key, IV))
{
using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
{
using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
{
swEncrypt.Write(s);
}
}
}
result = Convert.ToBase64String(msEncrypt.ToArray());
}
rijn.Clear();
return result;
}
A call to this method: EncryptIt("hello", encryptionkey, encryptioniv); returns ul0axDR0WWGcpeijPRNusg== and not 2XJxQXSbPuJ9LMsZ/FESGw== which was generated by PHP. Anyone knows what's wrong here?
For reference, I used these methods with the IV, they are working without errors:
private string GenerateSHA256String(string inputString)
{
SHA256 sha256 = SHA256Managed.Create();
byte[] bytes = Encoding.UTF8.GetBytes(inputString);
byte[] hash = sha256.ComputeHash(bytes);
return GetStringFromHash(hash);
}
private string GetStringFromHash(byte[] hash)
{
StringBuilder result = new StringBuilder();
for (int i = 0; i < hash.Length; i++)
{
result.Append(hash[i].ToString("X2"));
}
return result.ToString();
}

Old question, but I ran into this again recently.
When using PHP 7.2 openssl_decrypt/openssl_encrypt padding as OPENSSL_RAW_DATA, it only worked for me when the chsarp AES padding was set to PaddingMode.PKCS7.
The original post has PaddingMode.None for decrypt and PaddingMode.PKCS7 for encrypt.

PHP Encryption and C# Decryption [Rijndael]

I use RJ256 to login, since the return string is fairly small, it works (PHP gives encrypted string and C# needs to decrypt).
The data gets decrypted and fully works. Although, now I am transferring a 79KB string from PHP (Encrypted) to C# (Needs to Decrypt) and I get this error:
http://i.imgur.com/M4sgEct.png
This error only happens when the string is a bit larger than normally.
Here is my PHP code to encrypt:
private function _encrypt($data)
{
$iv = "sfhfskfsusfdsfd79fd8s79sdf789f79";
$key = "da4b9237bacccdf1";
// to append string with trailing characters as for PKCS7 padding scheme
$block = mcrypt_get_block_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_CBC);
$padding = $block - (strlen($data) % $block);
$data .= str_repeat(chr($padding), $padding);
$crypttext = mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $key, $data, MCRYPT_MODE_CBC, $iv);
// this is not needed here
//$crypttext = urlencode($crypttext);
return base64_encode($crypttext);
}
Here is my C# Code to decrypt:
public static dynamic DecryptRJ256(string cypher, bool isJson = true, bool getBytes = false)
{
string sRet;
var encoding = new UTF8Encoding();
var key = encoding.GetBytes("da4b9237bacccdf1");
var iv = encoding.GetBytes("sfhfskfsusfdsfd79fd8s79sdf789f79");
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(Decode(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();
}
}
// ReSharper disable once AssignNullToNotNullAttribute
return (isJson ? JsonConvert.DeserializeObject<dynamic>(sRet) : (getBytes ? Encoding.UTF8.GetBytes(sRet) : (dynamic)sRet));
}
How can I make it work?

How about this:
public static byte[] DecryptRJ256(string prm_key, string prm_iv, string prm_text_to_decrypt)
{
var sEncryptedString = prm_text_to_decrypt;
var myRijndael = new RijndaelManaged();
myRijndael.Padding = PaddingMode.Zeros;
myRijndael.Mode = CipherMode.CBC;
myRijndael.KeySize = 256;
myRijndael.BlockSize = 256;
byte[] key;
byte[] IV;
key = Encoding.ASCII.GetBytes(prm_key);
IV = Encoding.ASCII.GetBytes(prm_iv);
var decryptor = myRijndael.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 (System.Text.Encoding.ASCII.GetString(fromEncrypt))
return fromEncrypt;
}

Encrypting using C# AES encryption & decryption from these PHP codes

I am facing some issues in AES encryption using PHP and decode the same using C #. My reference site.
Here is the PHP code:
function encrypt_string($input, $key)
{
$iv = mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC), MCRYPT_RAND);
return preg_replace('/=/', "", base64_encode($iv . mcrypt_encrypt(MCRYPT_RIJNDAEL_128, hash("sha256", $key, true), $input, MCRYPT_MODE_CBC, $iv)));
}
function decrypt_string($input, $key)
{
$input .= "=";
$data = base64_decode($input);
$iv = substr($data, 0, mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC));
return rtrim(mcrypt_decrypt(MCRYPT_RIJNDAEL_128,hash('sha256', $key, true),substr($data, mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC)),MCRYPT_MODE_CBC,$iv),"\0");
}
Here is C# code that I tried:
private static byte[] sha256_data(string input)
{
SHA256 hash = SHA256Managed.Create();
Encoding encode = Encoding.UTF8;
return hash.ComputeHash(encode.GetBytes(input));
}
private string encode_data(string data, string key)
{
byte[] buff;
RijndaelManaged rij = new RijndaelManaged();
rij.BlockSize = 256;
rij.KeySize = 256;
rij.GenerateIV();
rij.Key = sha256_data(key);
rij.Mode = CipherMode.CBC;
ICryptoTransform encoder = rij.CreateEncryptor(rij.Key, rij.IV);
using (MemoryStream mem = new MemoryStream())
{
using (CryptoStream crypt = new CryptoStream(mem, encoder, CryptoStreamMode.Write))
{
byte[] temp = Encoding.UTF8.GetBytes(data);
crypt.Write(temp, 0, temp.Length);
}
buff = mem.ToArray();
}
return Convert.ToBase64String(result);
}
private string decode_data(string input, string key)
{
RijndaelManaged rij = new RijndaelManaged();
rij.KeySize = 256;
rij.BlockSize = 256;
rij.Key = sha256_data(key);
rij.GenerateIV();
rij.Mode = CipherMode.CBC;
rij.Padding = PaddingMode.PKCS7;
ICryptoTransform decrypter = rij.CreateDecryptor();
byte[] buff;
using (MemoryStream mem = new MemoryStream())
{
using (CryptoStream cstream = new CryptoStream(mem, decrypter, CryptoStreamMode.Write))
{
byte[] data = Convert.FromBase64String(input);
cstream.Write(data, 0, data.Length);
}
buff = mem.ToArray();
}
return Encoding.UTF8.GetString(buff);
}
What am i doing wrong?

when you decode you must parse the IV that was used for encoding not generate a new one.

PHP mcrypt_encrypt to .NET

I have almost lost my hair, mind and everything else! I have been trying to convert this PHP function to C#:
function encrypt_decrypt($action, $string) {
$output = false;
$key = 'My strong secret key';
// initialization vector
$iv = md5(md5($key));
$output = mcrypt_encrypt(MCRYPT_RIJNDAEL_256, md5($key), $string, MCRYPT_MODE_CBC, $iv);
$output = bin2hex($output);
return $output;
}
I have been working with Rijandel Class:
function encrypt_decrypt(string password) {
UTF8Encoding encoding = new UTF8Encoding();
// For consistency with PHP function, MD5Encrypt applies MD5 encryption and does a bin2hex
byte[] Key = Encoding.ASCII.GetBytes(MD5Encrypt(password).ToLower());
byte[] IV = Encoding.ASCII.GetBytes(MD5Encrypt(MD5Encrypt(password).ToLower()).ToLower());
RijndaelManaged rj = new RijndaelManaged();
rj.BlockSize = 256;
rj.KeySize = 256;
rj.Key = Key;
rj.IV = IV;
rj.Mode = CipherMode.CBC;
MemoryStream ms = new MemoryStream();
using (CryptoStream cs = new CryptoStream(ms, rj.CreateEncryptor(Key, IV), CryptoStreamMode.Write))
{
using (StreamWriter sw = new StreamWriter(cs))
{
sw.Write(message);
sw.Close();
}
cs.Close();
}
byte[] encoded = ms.ToArray();
string output = "";
foreach (var ele in encoded)
{
output += ele.ToString("X2");
}
return output;
}
I have been validating the output of the PHP code with that from the C# code and they do not match. (http://writecodeonline.com/php/). Any feedback would be appreciated.

There are multiple issues to be kept in mind while doing this like converting binary, checking encoding and padding issues. Since we cannot see your complete code we are helpless in this case. Check this tutorial for further info: http://blog.djekldevelopments.co.uk/?p=334

Try this instead:
using (RijndaelManaged myRijndael = new RijndaelManaged())
{
myRijndael.Key = Encoding.UTF8.GetBytes(password);
string strIv16 = "\x0\x0\x0\x0\x0\x0\x0\x0\x0\x0\x0\x0\x0\x0\x0\x0";
myRijndael.IV = Encoding.UTF8.GetBytes(strIv16);
// Encrypt the string to an array of bytes.
byte[] encrypted = EncryptStringToBytes(message, myRijndael.Key, myRijndael.IV);
string output = Convert.ToBase64String(encrypted);
}