AES/CBC/PKCS5PADDING - Java/Javascript (Encryption & Decryption)

0000.md

AES/CBC/PKCS5PADDING - Java/Javascript (Encryption & Decryption)

AESUtil.java

package com.ashish.crypto;

import java.util.Base64;

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

public class AESUtil {

  public static void main(String args[]) throws Exception {
    byte[] cipherText = encrypt("Testing AES/CBC/PKCS5PADDING stuff from Java and with JavaScript - some random text".getBytes(), "ABCDEFGHIJKLMNOPQRSTUVWXYZ123456".getBytes()); // 32 length Key
    System.out.println(new String(cipherText));
    byte[] origText = decrypt(new String(cipherText).getBytes(), "ABCDEFGHIJKLMNOPQRSTUVWXYZ123456".getBytes());
    System.out.println(new String(origText));
  }

  public static byte[] encrypt(byte[] plainTextData, byte[] secretKey) throws Exception {
    try {
      String iv = new String(secretKey).substring(0, 16);

      Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING");

      byte[] dataBytes = plainTextData;
      int plaintextLength = dataBytes.length;
      byte[] plaintext = new byte[plaintextLength];
      System.arraycopy(dataBytes, 0, plaintext, 0, dataBytes.length);

      SecretKeySpec keyspec = new SecretKeySpec(secretKey, "AES");
      IvParameterSpec ivspec = new IvParameterSpec(iv.getBytes());

      cipher.init(Cipher.ENCRYPT_MODE, keyspec, ivspec);
      byte[] encrypted = cipher.doFinal(plaintext);

      return new String(Base64.getEncoder().encode(encrypted)).getBytes();

    } catch (Exception e) {
      e.printStackTrace();
      return null;
    }
  }

  public static byte[] decrypt(byte[] cipherTextData, byte[] secretKey) throws Exception {
    try {
      String iv = new String(secretKey).substring(0, 16);

      byte[] encrypted = Base64.getDecoder().decode(cipherTextData);

      Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING");
      SecretKeySpec keyspec = new SecretKeySpec(secretKey, "AES");
      IvParameterSpec ivspec = new IvParameterSpec(iv.getBytes());

      cipher.init(Cipher.DECRYPT_MODE, keyspec, ivspec);

      byte[] original = cipher.doFinal(encrypted);
      String originalString = new String(original);
      return originalString.getBytes();
    } catch (Exception e) {
      e.printStackTrace();
      return null;
    }
  }
}

AESUtil.js

var secretkey = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ123456'; //Length 32
var key = CryptoJS.enc.Utf8.parse(secretkey);
var iv = CryptoJS.enc.Utf8.parse(secretkey.substring(0, 16));

/*-- Encryption --*/
var cipherText = CryptoJS.AES.encrypt("Testing AES/CBC/PKCS5PADDING stuff from Java and with JavaScript - some random text", key, {
    iv: iv,
    mode: CryptoJS.mode.CBC,
    padding: CryptoJS.pad.Pkcs7
}).toString();
console.log(cipherText);

/*-- Decryption --*/
var decrypted = CryptoJS.AES.decrypt("RQ/SEoGFF9IHmiMNbo/vlPTHuPWCGgDeEK5ZZBZjk/Kh5AIdgmVEeD42gciaK7gDKMP9odpjjZB/PGjebwpYSLzvEONS2jUiDtGPj7C0iNexmK5v5Gw9C8jsvqJdlmVK", key, {
    iv: iv,
    mode: CryptoJS.mode.CBC,
    padding: CryptoJS.pad.Pkcs7
});
console.log(decrypted.toString(CryptoJS.enc.Utf8));

I am not exactly sure what is the issue you are facing.
Can you share the input and the expected output.

In case you want to convert it to NodeJS, then you can find that code here:
https://github.com/kcak11/kcak11-api/blob/master/functions/routes/Crypto.js

Just for your awareness, the code does a RSA+AES Encryption and this is the output after encryption & decryption with your input at https://crypto.kcak11.com:

It does the following:

1. Client creates a random encryption key i.e. (rek)
2. Client encrypts (rek) with RSA Public Key (obtained via jwks.json endpoint) to get encrypted key i.e. (ekey)
3. Client encrypts the actual data using AES algorithm with the random encryption key i.e. (rek) to get encrypted data i.e. (edata)
4. Client then sends both (ekey) & (edata) to the server.
5. The server has the RSA Private Key, so it decrypts (ekey) using the RSA Private Key to get the original encryption key i.e. (rek)
6. Next the server uses AES algorithm to decrypt the (edata) with (rek) --> which gives the original data.

work like charm