Decrypting AES encrypted in C# with crypto-js - cryptojs

Question

I am encrypting a string with AES in C# like this :
public static byte[] KeyFromString(string key, int keyBits)// keyBits is 128, 192, or 256.
{
byte[] keyBinary = Encoding.UTF8.GetBytes(key);
byte[] b = new byte[keyBits / 8];
for (int i = 0, j = 0; i < b.Length && j < keyBinary.Length; i++, j++)
{
b[i] = keyBinary[j];
}
return b;
}
public static string encrypt(string key, string input)
{
byte[] inputBytes = System.Text.Encoding.ASCII.GetBytes(input);
byte[] keyBytes = KeyFromString(key, 256);
byte[] encrypted = null;
using (RijndaelManaged rijAlg = new RijndaelManaged())
{
rijAlg.Mode = CipherMode.CBC;
rijAlg.Padding = PaddingMode.PKCS7;
rijAlg.KeySize = 256;
rijAlg.Key = keyBytes;
rijAlg.IV = new byte[rijAlg.IV.Length]; //use empty IV
using(var encryptor = rijAlg.CreateEncryptor())
{
encrypted = encryptor.TransformFinalBlock(inputBytes, 0, inputBytes.Length);
}
}
var res = Convert.ToBase64String(encrypted);
return res;
}
And I want to decrypt ciphered text in javascript, I tryed with crypto-js :
var iv = [];
for (var i = 0 ; i < 16 ; i++) iv.push(0); //empty IV
var options = { keySize: 256 / 8, mode: CryptoJS.mode.CBC, iv: iv, padding: CryptoJS.pad.Pkcs7 };
var decrypted = CryptoJS.AES.decrypt(cipheredtext, key, options);
var decryptedText = decrypted.toString(CryptoJS.enc.Utf8);
The decrypted text I got is empty. I tried multiple changes in encoding, key size, etc
I can use another javascript Library if needed

Answer 1

Perhaps CryptoJS docs don't mention this explicitly enough, but in order for the crypto algorithm of your choice (AES in your case) to use the exact key and IV you provide they must be passed in as a CJS type WordArray.
One way to get the word arrays is to use parse methods of an encoding of your choice:
var iv = CryptoJS.enc.Hex.parse("HEX ENCODING OF THE KEY");
var key = CryptoJS.enc.Hex.parse("HEX ENCODING OF THE IV");
after that, all you do should work fine.
Hope someone finds this useful Took me a while to figure this out a couple of days ago.