AES encryption using Java and decryption using Javascript

Question

I am making an application which needs Java based AES Encryption and JavaScript based decryption. I am using the following code for encryption as a basic form.

public class AESencrp {

  private static final String ALGO = "AES";
  private static final byte[] keyValue = 
      new byte[] { 'A', 'b', 'c', 'd', 'e', 'f', 'g',
      'h', 'i', 'j', 'k','l', 'm', 'n', 'o', 'p'};

  public static String encrypt(String Data) throws Exception {
    Key key = generateKey();
    Cipher c = Cipher.getInstance(ALGO);
    c.init(Cipher.ENCRYPT_MODE, key);
    byte[] encVal = c.doFinal(Data.getBytes());
    String encryptedValue = new BASE64Encoder().encode(encVal);
    return encryptedValue;
  }


  private static Key generateKey() throws Exception {
    Key key = new SecretKeySpec(keyValue, ALGO);
    return key;
  }
}

The JavaScript that I am trying to use to decrypt is

<script src="http://crypto-js.googlecode.com/svn/tags/3.1.2/build/rollups/aes.js">   </script>

var decrypted = CryptoJS.AES.decrypt(encrypted,"Abcdefghijklmnop").toString(CryptoJS.enc.Utf8);

But the JavaScript decryption is not working. I am new to this, could someone tell me a way to solve without changing the Java code block ?

I tried Base-64 decoding my text like this:

var words  = CryptoJS.enc.Base64.parse(encrKey);
var base64 = CryptoJS.enc.Base64.stringify(words);
var decrypted = CryptoJS.AES.decrypt(base64, "Abcdefghijklmnop");
alert("dec :" +decrypted);

but still no good.

I tried the solution suggested below to resolve possible padding issue but its not giving any solution.

var key = CryptoJS.enc.Base64.parse("QWJjZGVmZ2hpamtsbW5vcA==");
var decrypt = CryptoJS.AES.decrypt( encrKey, key, { mode: CryptoJS.mode.ECB,padding: CryptoJS.pad.Pkcs7 } );

alert("dec :" +decrypt);

Solution 1

1. Your Java code uses the 128-bit AES key while your JavaScript code uses the 256-bit AES key.

2. Your Java code uses the "Abcdefghijklmnop".getBytes() as the actual key value, while your JavaScript code uses the "Abcdefghijklmnop" as the passphrase from which the actual key is derived.

3. The default transformation for Java AES is AES/ECB/PKCS5Padding, while default transformation for CryptoJS is AES/CBC/PKCS7Padding.

One way to fix your example is to fix the JavaScript side:

// this is Base64 representation of the Java counterpart
// byte[] keyValue = new byte[] { 'A', 'b', 'c', 'd', 'e', 'f', 'g',
//                'h', 'i', 'j', 'k','l', 'm', 'n', 'o', 'p'};
// String keyForJS = new BASE64Encoder().encode(keyValue);
var base64Key = "QWJjZGVmZ2hpamtsbW5vcA==";
console.log( "base64Key = " + base64Key );

// this is the actual key as a sequence of bytes
var key = CryptoJS.enc.Base64.parse(base64Key);
console.log( "key = " + key );

// this is the plain text
var plaintText = "Hello, World!";
console.log( "plaintText = " + plaintText );

// this is Base64-encoded encrypted data
var encryptedData = CryptoJS.AES.encrypt(plaintText, key, {
    mode: CryptoJS.mode.ECB,
    padding: CryptoJS.pad.Pkcs7
});
console.log( "encryptedData = " + encryptedData );

// this is the decrypted data as a sequence of bytes
var decryptedData = CryptoJS.AES.decrypt( encryptedData, key, {
    mode: CryptoJS.mode.ECB,
    padding: CryptoJS.pad.Pkcs7
} );
console.log( "decryptedData = " + decryptedData );

// this is the decrypted data as a string
var decryptedText = decryptedData.toString( CryptoJS.enc.Utf8 );
console.log( "decryptedText = " + decryptedText );

Solution 2

For Java and JavaScript to able to inter operate, it is essential that no defaults are used while creating Key or the Cipher. The iteration count, key length, padding, salt and IV should all be the same.

Reference: https://github.com/mpetersen/aes-example

Sample code below:

Encrypting String in Java:

    String keyValue = "Abcdefghijklmnop";     
    SecretKeyFactory factory =   SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
    KeySpec spec = new PBEKeySpec(keyValue.toCharArray(), hex("dc0da04af8fee58593442bf834b30739"),
        1000, 128);

    Key key = new SecretKeySpec(factory.generateSecret(spec).getEncoded(), "AES");
    Cipher c = Cipher.getInstance(“AES/CBC/PKCS5Padding”);
    c.init(Cipher.ENCRYPT_MODE, key, new IvParameterSpec(hex("dc0da04af8fee58593442bf834b30739")));

    byte[] encVal = c.doFinal("The Quick Brown Fox Jumped over the moon".getBytes());
    String base64EncodedEncryptedData = new String(Base64.encodeBase64(encVal));
    System.out.println(base64EncodedEncryptedData);

}

Decrypting the same string in JavaScript:

var iterationCount = 1000;
var keySize = 128;
var encryptionKey  ="Abcdefghijklmnop";
var dataToDecrypt = "2DZqzpXzmCsKj4lfQY4d/exg9GAyyj0hVK97kPw5ZxMFs3jQiEQ6LLvUsBLdkA80" //The base64 encoded string output from Java;
var iv = "dc0da04af8fee58593442bf834b30739"
var salt = "dc0da04af8fee58593442bf834b30739"

var aesUtil = new AesUtil(keySize, iterationCount);
var plaintext =  aesUtil.decrypt(salt, iv, encryptionKey, dataToDecrypt);
console.log(plaintext);

**//AESUtil - Utility class for CryptoJS**
var AesUtil = function(keySize, iterationCount) {
 this.keySize = keySize / 32;
 this.iterationCount = iterationCount;
};

AesUtil.prototype.generateKey = function(salt, passPhrase) {
  var key = CryptoJS.PBKDF2(passPhrase, CryptoJS.enc.Hex.parse(salt),
  { keySize: this.keySize, iterations: this.iterationCount });
  return key;
}

AesUtil.prototype.decrypt = function(salt, iv, passPhrase, cipherText) {
  var key = this.generateKey(salt, passPhrase);
  var cipherParams = CryptoJS.lib.CipherParams.create({
    ciphertext: CryptoJS.enc.Base64.parse(cipherText)
  });
  var decrypted = CryptoJS.AES.decrypt(cipherParams,key,
  { iv: CryptoJS.enc.Hex.parse(iv) });
  return decrypted.toString(CryptoJS.enc.Utf8);
 }
}

Comments

[rkj]

Nope, still not working. Are you sure that your "var decrypt" is correct because I think the key should be in UTF-8 format. Anyway I tried it but didnt work.

[Oleg Estekhin]

Your question now contains CryptoJS.AES.decrypt( encrKey, key, ...) near the end, and it seems that you are trying to decrypt the key with key, which meaningless. The first parameter should be the encrypted data in base64.

[rkj]

Thats just the naming convention that I was following. The first parameter is indeed the encrypted data.

[Oleg Estekhin]

Try jsfiddle.net/pKNzV (the output is in the console) and try to encode the same data in Java and in that example. And do not forget to use the same key (use new BASE64Encoder().encode(keyValue) in Java to get the base64Key value for JS)

[rkj]

Its working !! Actually I was implementing the javascript using cordova and phonegap and there was an issue regarding the scripts not being downloaded. Once I downloaded the original script in the source code it statred working.

[Achyut]

@OlegEstekhin I tried doing what solution you have proposed but its not working for me. I have used the same java code and converted the Key to to Base64 for JS using the code String keyForJS = Base64.encodeBase64(keyValue).toString(); Now in you fiddle, if i give the generated key and generated encrypted value from Java, it does not decrypt the text. Can you please help

[Achyut]

@OlegEstekhin Can you try a fiddle which takes the input from a Java output and then decrypt it. I have a similar issue here - stackoverflow.com/questions/26315885/…