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How to decrypt AES with crypto-js from C#

I am trying to decrypt a value that is encrypted with AES in backend with C#.
The decryption part will happen in the front end with Angular (using crypto-js )
The problem that I am having is that I'm always getting an empty string as the result of the decryption.
I don't know what am I doing wrong. Am I missing some sort of configuration?
My C# code to Encrypt looks like this:
//
EncryptAES("XEMFkT92UtR1VJI8kU8XQJALk98GGEFM", "random text to encrypt");
public static string EncryptAES(string passPhrase, string plainText)
{
byte[] iv = Generate256BitsOfRandomEntropy();
byte[] temp;
byte[] array;
using (Aes aes = Aes.Create())
{
byte[] salt = Generate256BitsOfRandomEntropy();
Rfc2898DeriveBytes pdb = new Rfc2898DeriveBytes(passPhrase, salt, 100);
aes.Key = pdb.GetBytes(32);
aes.KeySize = 256;
aes.Padding = PaddingMode.PKCS7;
aes.Mode = CipherMode.CBC;
aes.IV = iv;
ICryptoTransform encryptor = aes.CreateEncryptor(aes.Key, aes.IV);
using (MemoryStream memoryStream = new MemoryStream())
{
using (CryptoStream cryptoStream = new CryptoStream((Stream)memoryStream, encryptor, CryptoStreamMode.Write))
{
using (StreamWriter streamWriter = new StreamWriter((Stream)cryptoStream, Encoding.UTF8))
{
streamWriter.Write(plainText);
}
temp = memoryStream.ToArray();
array = salt.Concat(iv).Concat(temp).ToArray();
cryptoStream.Flush();
encryptor.Dispose();
}
}
}
return Convert.ToBase64String(array);
}
//Random byte[] generator
private static byte[] Generate256BitsOfRandomEntropy()
{
var randomBytes = new byte[16];
using (var rngCsp = new RNGCryptoServiceProvider())
{
rngCsp.GetBytes(randomBytes);
}
return randomBytes;
}
The decryption part in the.ts file is:
//The param "key" will be same as the C# code: XEMFkT92UtR1VJI8kU8XQJALk98GGEFM
//The param "toDecrypt" will the the Base64 returned by the service in C#
decryptAES(key: string, toDecrypt: string) {
var data = Buffer.from(toDecrypt, 'base64');
var salt = data.slice(0, 16); //first 16 bytes to get the salt
var iv = data.slice(16, 32);// next 16 bytes to get the IV
const wordArrayIV = CryptoJS.lib.WordArray.create(Array.from(iv));
const wordArraySalt = CryptoJS.lib.WordArray.create(Array.from(salt))
var keyPBKDF2 = CryptoJS.PBKDF2(key, wordArraySalt, {
keySize: 256 / 32,
iterations: 100
});
var decrypted = CryptoJS.AES.decrypt(toDecrypt, keyPBKDF2,
{
mode: CryptoJS.mode.CBC,
padding: CryptoJS.pad.Pkcs7,
iv: wordArrayIV
});
//Return empty string
return decrypted.toString();
}

In the C# code, the key derived with PBKDF2 is not used, but a randomly generated key. This is because when the key size is set, a new key is implicitly generated.
As fix simply remove the setting of the key size, i.e. the line aes.KeySize = 256 (the key size is implicitly set when the key is set).
...
aes.Key = pdb.GetBytes(32);
//aes.KeySize = 256; // Fix: remove
//aes.Padding = PaddingMode.PKCS7; // default
//aes.Mode = CipherMode.CBC; // default
aes.IV = iv;
...
In addition, there are several issues in the CryptoJS code: First, the Buffers are incorrectly converted to WordArrays, so that IV and salt are wrong.
Also, the ciphertext is not taken into account when separating and is furthermore passed incorrectly to AES.decrypt().
And the decrypted data is hex encoded, but should be UTF-8 decoded.
function decryptAES(key, toDecrypt) {
var data = CryptoJS.enc.Base64.parse(toDecrypt);
var wordArraySalt = CryptoJS.lib.WordArray.create(data.words.slice(0, 4)); // Fix: Array -> WordArray conversion
var wordArrayIV = CryptoJS.lib.WordArray.create(data.words.slice(4, 8)); // Fix: Array -> WordArray conversion
var wordArrayCt = CryptoJS.lib.WordArray.create(data.words.slice(8)); // Fix: Consider ciphertext
var keyPBKDF2 = CryptoJS.PBKDF2(key, wordArraySalt, {keySize: 256 / 32, iterations: 100});
var decrypted = CryptoJS.AES.decrypt({ciphertext: wordArrayCt}, keyPBKDF2, {iv: wordArrayIV}); // Fix: Pass ciphertext as CipherParams object
return decrypted.toString(CryptoJS.enc.Utf8); // Fix: UTF-8 decode
}
var decrypted = decryptAES('XEMFkT92UtR1VJI8kU8XQJALk98GGEFM', '4YI4unJecVXvvNQVgBsdUwrr7rlwcImDb7t1LT88UO0w8BdFpOp5PLsu6PRJ+eCeKB01rWdVVrGMLj7tOi3KHg==');
console.log(decrypted);
<script src="https://cdnjs.cloudflare.com/ajax/libs/crypto-js/4.1.1/crypto-js.min.js"></script>
Note that the ciphertext in above code was generated with the fixed C# code.
Regarding vulnerabilities: An iteration count of 100 in key derivation with PBKDF2 is generally too small.

How to decrypt a Rijndael 128 encrypted text

I'm trying to decrypt a Rijndael-128 encrypted cipher, these are the values:
Cipher: "QfJzZ9V6Jm43jYPiVaXP9mu+f88S/JC24saHbOMxxC8="
Key: "45744855535472525844494538555934",
Mode: CBC
Result should be: "abcd#1234"
This website seems to decrypt the cipher just fine:
https://codebeautify.org/encrypt-decrypt
I'm trying to do the same thing in C# with absolutely no luck, what am I missing here?
class Program
{
static void Main(string[] args)
{
var text = Decrypt("QfJzZ9V6Jm43jYPiVaXP9mu+f88S/JC24saHbOMxxC8=", Convert.FromBase64String("45744855535472525844494538555934"));
}
public static string Decrypt(string Text, byte[] keyBytes)
{
var textBytes = Convert.FromBase64String(Text);
var rijKey = new RijndaelManaged();
rijKey.IV = textBytes.Take(rijKey.BlockSize / 8).ToArray();
rijKey.Padding = PaddingMode.None;
rijKey.Mode = CipherMode.CBC;
var decryptor = rijKey.CreateDecryptor(keyBytes, rijKey.IV);
var memoryStream = new MemoryStream(textBytes);
var cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read);
var pTextBytes = new byte[textBytes.Length];
var decryptedByteCount = cryptoStream.Read(pTextBytes, 0, pTextBytes.Length);
memoryStream.Close();
cryptoStream.Close();
string plainText = Encoding.UTF8.GetString(pTextBytes, 0, decryptedByteCount);
return plainText;
}
}

The problem with your code is this line:
rijKey.GenerateIV();
You need the original IV. You can't just use a random one.
If you go to the site you linked to, each time you press encrypt with the key and text you have given, you get a different encrypted text (because a random IV is used). The web page must be prepending the random IV used to encrypt to the encrypted text (or less likely, the web page is storing it), which is why it can then decrypt the encrypted text.
[Your code also needs using statements.]
Is it possible to NOT use the IV when implementing Rijndael decryption?
How to Use Rijndael ManagedEncryption with C#

Example code PHP / C# AES encryption - random IV

I found an implementation for AES encryption/decryption that's supposed to work in PHP and C#:
https://odan.github.io/2017/08/10/aes-256-encryption-and-decryption-in-php-and-csharp.html
However, in this example, the IV is always 0, which is not good.
So, as the author suggests, I use the openssl_random_pseudo_bytes() function:
$ivlen = openssl_cipher_iv_length($method);
$iv = openssl_random_pseudo_bytes($ivlen);
However, the problem now is, that I have to store the IV somewhere so that the C# app can use it for decryption. My idea was to base64_encode it and prepend it to the encrypted message with ":" separating both, so that I can simply split the string, then base64 decode it in C# and can use the IV. However, this does not work. This is the code:
public string DecryptString(string cipherText, byte[] key, byte[] iv)
{
// Instantiate a new Aes object to perform string symmetric encryption
Aes encryptor = Aes.Create();
encryptor.Mode = CipherMode.CBC;
// Set key and IV
byte[] aesKey = new byte[32];
Array.Copy(key, 0, aesKey, 0, 32);
encryptor.Key = aesKey;
encryptor.IV = iv;
// Instantiate a new MemoryStream object to contain the encrypted bytes
MemoryStream memoryStream = new MemoryStream();
// Instantiate a new encryptor from our Aes object
ICryptoTransform aesDecryptor = encryptor.CreateDecryptor();
// Instantiate a new CryptoStream object to process the data and write it to the
// memory stream
CryptoStream cryptoStream = new CryptoStream(memoryStream, aesDecryptor, CryptoStreamMode.Write);
// Will contain decrypted plaintext
string plainText = String.Empty;
try {
// Convert the ciphertext string into a byte array
byte[] cipherBytes = Convert.FromBase64String(cipherText);
// Decrypt the input ciphertext string
cryptoStream.Write(cipherBytes, 0, cipherBytes . Length);
// Complete the decryption process
cryptoStream.FlushFinalBlock();
// Convert the decrypted data from a MemoryStream to a byte array
byte[] plainBytes = memoryStream.ToArray();
// Convert the decrypted byte array to string
plainText = Encoding.ASCII.GetString(plainBytes, 0, plainBytes.Length);
} finally {
// Close both the MemoryStream and the CryptoStream
memoryStream.Close();
cryptoStream.Close();
}
// Return the decrypted data as a string
return plainText;
}
And this is how I try to call the function with the IV prepended to the encrypted message:
private void btnDecrypt_Click(object sender, EventArgs e)
{
string encrypted = txtEncrypted.Text;
string password = txtPW.Text;
string[] temp = encrypted.Split(":".ToCharArray());
string iv_str = temp[0];
encrypted = temp[1];
SHA256 mySHA256 = SHA256Managed.Create();
byte[] key = mySHA256.ComputeHash(Encoding.ASCII.GetBytes(password));
iv_str = Encoding.Default.GetString(Convert.FromBase64String(iv_str));
byte[] iv = Encoding.ASCII.GetBytes(iv_str);
txtDecrypted.Text = this.DecryptString(encrypted, key, iv);
}
Doesn't work. It decrypts something, but that's just gibberish and not the message I encrypted in PHP.
I think it has to do with the IV somehow.

#Topaco:
Thank you very much... now I see what my mistake was. It works now with generated IV.
By the way, two more questions on the strength of the encryption:
Is it ok to use the following function to generate an IV (GenerateIV() for some reason won't work):
byte[] iv = new byte[16];
Random rnd = new Random();
rnd.NextBytes(iv);
I added a randomly generated salt to the password of the user, so that the key is a hash from the user password and a salt. I also prepend the salt, together with the now randomly generated IV, to the message. Then for the decryption process I use the prepended salt and the key the user enters. Works so far. But does it weaken the encryption? No, right?
Thank you very much.
// Edit: Code format doesn't work, don't know why.

Trying to decrypt a string using AES Managed

I am trying to write code to decrypt a string.
I was given an equivalent in python and I am trying to create the same in . NET
Python:
//Initialization vector is just a string of 16 null bytes
iv = '\x00' * 16
//Create new AES object using the key and init vector
aes = AES.new(key, AES.MODE_CBC, iv)
//Decrypt password and remove padding
result = aes.decrypt(myString).rstrip('\x0b\x08\x07')
return result
Here is my attempt:
byte[] iv = new byte[16];
byte[] rawPlaintext = Convert.FromBase64String("MyBase64String");
byte[] key = // Read from common source
using (Aes aes = new AesManaged())
{
aes.Padding = PaddingMode.None;
aes.KeySize = 128; // in bits
aes.Key = new byte[128 / 8]; // 16 bytes for 128 bit encryption
aes.IV = new byte[128 / 8]; // AES needs a 16-byte IV
// Should set Key and IV here. Good approach: derive them from
// a password via Cryptography.Rfc2898DeriveBytes
byte[] cipherText = key;
byte[] plainText = iv;
using (MemoryStream ms = new MemoryStream())
{
using (CryptoStream cs = new CryptoStream(ms, aes.CreateEncryptor(), CryptoStreamMode.Write))
{
cs.Write(rawPlaintext, 0, rawPlaintext.Length);
}
cipherText = ms.ToArray();
}
using (MemoryStream ms = new MemoryStream())
{
using (CryptoStream cs = new CryptoStream(ms, aes.CreateDecryptor(), CryptoStreamMode.Write))
{
cs.Write(cipherText, 0, cipherText.Length);
}
plainText = ms.ToArray();
}
string s = System.Text.Encoding.Unicode.GetString(plainText);
Console.WriteLine(s);
}
It doesn't appear to be working for the result is a string of symbols.
Possible issues:
- I see a mode of CBC getting set. I'm not sure where that equivalent setting would be. I've tried to play with the PaddingMode.
- Could my iv byte[] be causing the issue? Is the default null or 0?
EDIT:
- From what I am reading AesManaged uses AES in CBC mode so that should be a non-issue.

Try replacing this:
string s = System.Text.Encoding.Unicode.GetString(plainText);
to:
string s = System.Text.Encoding.UTF8.GetString(plainText);

Decrypted data with usage of TripleDESCryptoServiceProvider has additonal characters

I am facing with problem when decrypting data with usage of TripleDESCryptoServiceProvider. The problem is that decrypted value contains beside of original value some additional, strange characters at the end
Per instance if I provide "rastko" to be encrypted, I will get later with decryption something like this "rastko⥊㮶". For other values it could be different number of 'dummy' characters or in some cases I will get exact value.
Then, I saw that for all encrypted data byte array size is divisible by 8. It looks like any provided data is rounded on value that is divisible by 8. Only in case when original encoded value is divisible by 8, decryption will retrieve appropriate value.
Here are methods that I am using :
public static byte[] EncryptPassword(string password, out byte[] cryptoKey, out byte[] cryptoIV)
{
try
{
UnicodeEncoding unicodeEncoding = new UnicodeEncoding();
byte[] unicodePassword = unicodeEncoding.GetBytes(password);
byte[] encryptedPassword;
using (TripleDESCryptoServiceProvider tripleDes = new TripleDESCryptoServiceProvider())
{
tripleDes.Key = GetCryptoKey();
tripleDes.Mode = CipherMode.CBC;
tripleDes.Padding = PaddingMode.PKCS7;
cryptoKey = tripleDes.Key;
cryptoIV = tripleDes.IV;
using (MemoryStream memoryStream = new MemoryStream())
{
ICryptoTransform cryptoTransform = tripleDes.CreateEncryptor();
using (
CryptoStream cryptoStream = new CryptoStream(memoryStream, cryptoTransform, CryptoStreamMode.Write))
{
cryptoStream.Write(unicodePassword, 0, unicodePassword.Length);
////cryptoStream.FlushFinalBlock();
}
encryptedPassword = memoryStream.ToArray();
}
}
return encryptedPassword;
}
catch (Exception ex)
{
throw new Exception("Password encryption failed !", ex);
}
}
public static string DecryptPassword(byte[] encryptedPassword, byte[] cryptoKey, byte[] cryptoIV)
{
try
{
UnicodeEncoding unicodeEncoding = new UnicodeEncoding();
string readablePassword;
using (TripleDESCryptoServiceProvider tripleDes = new TripleDESCryptoServiceProvider())
{
tripleDes.Key = cryptoKey;
tripleDes.IV = cryptoIV;
tripleDes.Mode = CipherMode.CBC;
tripleDes.Padding = PaddingMode.PKCS7;
// Create a new MemoryStream using the passed
// array of encrypted data.
using (MemoryStream memoryStream = new MemoryStream(encryptedPassword))
{
// Create crypto transform that defines the basic operations of cryptographic transformations.
ICryptoTransform cryptoTransform = tripleDes.CreateDecryptor();
// Create a CryptoStream using the MemoryStream and the passed key and initialization vector (IV).
using (CryptoStream decryptoStream = new CryptoStream(memoryStream, cryptoTransform, CryptoStreamMode.Write))
{
decryptoStream.Write(encryptedPassword, 0, encryptedPassword.Length);
///decryptoStream.FlushFinalBlock();
}
byte[] decryptedPassword = memoryStream.ToArray();
//Convert the buffer into a string and return it.
readablePassword = unicodeEncoding.GetString(decryptedPassword, 0, decryptedPassword.Length);
}
}
return readablePassword;
}
catch (Exception ex)
{
throw new Exception("Password decryption failed !", ex);
}
}
private static byte[] GetCryptoKey()
{
UnicodeEncoding unicodeEncoding = new UnicodeEncoding();
string plainKey = "rastkoisajev2310982josipasenera153";
byte[] encodedKey = unicodeEncoding.GetBytes(plainKey);
// Prepares 192 bit key
byte[] preparedKey = new byte[24];
Array.Copy(encodedKey, preparedKey, 24);
return preparedKey;
}
Here is sample test invocation :
private static void CryptoTest()
{
string password = "rastko";
byte[] cryptoKey;
byte[] cryptoIV;
byte[] encryptedPassword = Crypto.EncryptPassword(password, out cryptoKey, out cryptoIV);
string decryptedPAssword = Crypto.DecryptPassword(encryptedPassword, cryptoKey, cryptoIV);
}
I have not good experience with security. What I see is that IV vector is 8byte size and as I found it is related to BlockSize, that is 8times greater then IV size. TripleDESCryptoServiceProvider for IV vector is using 8byte value. I can not change this.
Could you please tell me what I have to do or did I wrote something wrongly ?

DES is a 64 bit block cypher. Any text that does not divide cleanly into 64 bit (=8 byte) blocks needs to be padded to make up a whole number of blocks. You need to set padding for encryption and decryption. If you have control of both ends then use PKCS#5 padding to encrypt and decrypt. If you only have control over the decryption end, then ask the encrypting end what padding they are using and expect that.

Note that encrypting a password is normally not the way to go. Use PBKDF2 instead. Don't confuse passwords and keys!
Try to make sure that your CryptoStreams get closed or flushed:
http://msdn.microsoft.com/en-us/library/system.security.cryptography.cryptostream.flushfinalblock.aspx
If you don't then the padding/unpadding will likely not be performed, and you get trash instead.

After detail investigation I have found the solution for my problem.
I have changed a little bit decryption logic.
Instead of this part in DecryptPassword method :
// Create a CryptoStream using the MemoryStream and the passed key and initialization vector (IV).
using (CryptoStream decryptoStream = new CryptoStream(memoryStream, cryptoTransform, CryptoStreamMode.Write))
{
decryptoStream.Write(encryptedPassword, 0, encryptedPassword.Length);
///decryptoStream.FlushFinalBlock();
}
byte[] decryptedPassword = memoryStream.ToArray();
//Convert the buffer into a string and return it.
readablePassword = unicodeEncoding.GetString(decryptedPassword, 0, decryptedPassword.Length);
}
I am now using the Read logic from CryptoStream and then I am just removing nullable characters. It is like this now :
// Create a CryptoStream using the MemoryStream and the passed key and initialization vector (IV).
using (CryptoStream decryptoStream = new CryptoStream(memoryStream, cryptoTransform, CryptoStreamMode.Read))
{
// Create buffer to hold the decrypted data.
byte[] fromEncrypt = new byte[encryptedPassword.Length];
decryptoStream.Read(fromEncrypt, 0, fromEncrypt.Length);
//Convert the buffer into a string and return it.
readablePassword = unicodeEncoding.GetString(fromEncrypt);
readablePassword = readablePassword.Replace("\0", string.Empty);
}
This works perfectly for me ! Thank you all for your time.