How to decrypt a cryptojs AES encrypted message at the java server side?

Question

I have the following cryptojs based javascript encryption/decryption functions which works perfectly fine.

I use a random salt, random iv value and a specific password while encrypting the message using cryptpjs. I reuse the same salt, iv and the password to generate the key while decrypting the encrypted message.

This part works well..

function  encrypt(){
  var salt = CryptoJS.lib.WordArray.random(128/8);
  var iv = CryptoJS.lib.WordArray.random(128/8);
  console.log('salt  '+ salt );
  console.log('iv  '+ iv );
  var key128Bits = CryptoJS.PBKDF2("Secret Passphrase", salt, { keySize: 128/32 }); 
  console.log( 'key128Bits '+ key128Bits);
  var key128Bits100Iterations = CryptoJS.PBKDF2("Secret Passphrase", salt, { keySize: 128/32, iterations: 100 });
  console.log( 'key128Bits100Iterations '+ key128Bits100Iterations);
  var encrypted = CryptoJS.AES.encrypt("Message", key128Bits100Iterations, { iv: iv, mode: CryptoJS.mode.CBC, padding: CryptoJS.pad.Pkcs7  });
  console.log('encrypted   '+ encrypted  );
}

function  decrypt(){
  var salt = CryptoJS.enc.Hex.parse("4acfedc7dc72a9003a0dd721d7642bde");
  var iv = CryptoJS.enc.Hex.parse("69135769514102d0eded589ff874cacd");
  var encrypted = "PU7jfTmkyvD71ZtISKFcUQ==";
  console.log('salt  '+ salt );
  console.log('iv  '+ iv );
  var key = CryptoJS.PBKDF2("Secret Passphrase", salt, { keySize: 128/32, iterations: 100 });
  console.log( 'key '+ key);
  var decrypt = CryptoJS.AES.decrypt(encrypted, key, { iv: iv, mode: CryptoJS.mode.CBC, padding: CryptoJS.pad.Pkcs7 });
  var ddd = decrypt.toString(CryptoJS.enc.Utf8); 
  console.log('ddd '+ddd);
} 

But the issue starts when I try to decrypt the same encrypted text at the java server side. I want the encrypted message to be decrypted by my java server code. Here is the Java code that I wrote:

public static void main(String args[]) throws Exception{
  String password = "Secret Passphrase";
  String salt = "4acfedc7dc72a9003a0dd721d7642bde";
  String iv = "69135769514102d0eded589ff874cacd";
  String encrypted = "PU7jfTmkyvD71ZtISKFcUQ==";
  byte[] saltBytes = salt.getBytes(); //hexStringToByteArray(salt);
  byte[] ivBytes = iv.getBytes();//hexStringToByteArray(iv);
  IvParameterSpec ivParameterSpec = new IvParameterSpec(ivBytes);        
  SecretKeySpec sKey = (SecretKeySpec) generateKeyFromPassword(password, saltBytes);
  System.out.println( decrypt( encrypted , sKey ,ivParameterSpec));
}

public static SecretKey generateKeyFromPassword(String password, byte[] saltBytes) throws GeneralSecurityException {

  KeySpec keySpec = new PBEKeySpec(password.toCharArray(), saltBytes, 100, 128/32);
  SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
  SecretKey secretKey = keyFactory.generateSecret(keySpec);
  return new SecretKeySpec(secretKey.getEncoded(), "AES");
}

public static String decrypt(String encryptedData, SecretKeySpec sKey, IvParameterSpec ivParameterSpec) throws Exception {

  Cipher c = Cipher.getInstance("AES");
  c.init(Cipher.DECRYPT_MODE, sKey, ivParameterSpec);
  byte[] decordedValue = new BASE64Decoder().decodeBuffer(encryptedData);
  byte[] decValue = c.doFinal(decordedValue);
  String decryptedValue = new String(decValue);
  return decryptedValue;
}

But I get the following exception:

Exception breakpoint: SecretKeySpec.java:96, java.lang.IllegalArgumentException, Empty key
Exception in thread "main" java.lang.IllegalArgumentException: Empty key
at javax.crypto.spec.SecretKeySpec.<init>(SecretKeySpec.java:96)

I have no idea what I should do

Answer 1

This part of your code is wrong:

KeySpec keySpec = new PBEKeySpec(password.toCharArray(), saltBytes, 100, 128/32);
//->---------------------------------------------------------------------^^^^^^^

The 128/32 value is erroneous. You need either 128, 192 or 256. Currently you have the equivalent of 4, which seems to result in no output at all from the PBKDF2 function.

Also, in Java you should use DatatypeConverter.parseHexBinary(), or similar, to convert hex into bytes. Currently you are just calling getBytes() which isn't right.

Finally, you need to specify CBC mode and PKCS#5 padding in order to match your Javascript code. So change the line to:

Cipher c = Cipher.getInstance("AES/CBC/PKCS5Padding");