Why can't java decrypt CryptoJS encrypted data?

Question

I have function for decrypting in Java as such

public String decrypt() throws Exception {
        SecretKey secretKey = getSecretKey("o9szYIOq1rRMiouNhNvaq96lqUvCekxR");

        Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
        cipher.init(Cipher.DECRYPT_MODE, secretKey);
        return new String(cipher.doFinal(base64Decode("ASDASDADS")));
    }

public SecretKey getSecretKey(String secretKey) throws Exception {
        byte[] decodeSecretKey = base64Decode(secretKey);
        return new SecretKeySpec(decodeSecretKey, 0, decodeSecretKey.length, "AES");
    }

I tried to encrypt the data using CryptoJS as such

  function aesEncrypt(data, secretKey) {
    var encrypted = CryptoJS.AES.encrypt(data, secretKey, {
    mode: CryptoJS.mode.ECB,
    padding: CryptoJS.pad.Pkcs7
    });

    var ciphertext = encrypted.ciphertext.toString();

    var wordArray = CryptoJS.enc.Utf8.parse(ciphertext);
    var base64 = CryptoJS.enc.Base64.stringify(wordArray);
    return base64
  }
  //call the function
  aesEncrypt('Test' , 'o9szYIOq1rRMiouNhNvaq96lqUvCekxR');

When I send the request to JAVA API I get

Given final block not properly padded. Such issues can arise if a bad key is used during decryption

I even tried with forge library. It does not work either.

function aesEncrypt(data, secretKey) {
    var cipher = forge.cipher.createCipher('AES-ECB', secretKey)

    cipher.start()
    cipher.update(forge.util.createBuffer(data))
    cipher.finish()

    return forge.util.encode64(cipher.output.data)
  }

The difference I see between the two is from forge, when I output the data i.e console.log(cipher.output.data) . I get

uJ@^$¿EÅKÖé1ÙN¢cÖúpxÇÅÂëv¥qè9Ï/¨§È5æý»¸,À¿ "y§¯:ßñ[®

Michael Fehr Michael Fehr · Accepted Answer · 2020-09-29T21:45:38

Please find below a code pair that uses Javascript to en- and decrypt a string with static key in ECB mode. The Java code is taking the ciphertext (= output of encryption function) from Javascript and decrypts the Base64 encoded ciphertext.

Security warning: Both codes are UNSECURE as they use the ECB mode and static encryption key.

Javascript output (see live example with this link: https://playcode.io/682378)

plaintext: Test
ciphertext: oNP8t53ZTi1WUptGCDh5NQ==
decryptedtext: Test

Java output:

ciphertextFromJavascript: oNP8t53ZTi1WUptGCDh5NQ==
decrypted: Test

Javascript code:

// *** Security warning **
// DO NOT USE THIS CODE IN PRODUCTION AS IT IS UNSECURE
// it uses ECB mode and static key

var plaintext = 'Test';
console.log('plaintext: ', plaintext);

/**
 * Encryption
 * @param word
 * @returns {*}
 */
function encrypt(word){
    const keyBase64 = "o9szYIOq1rRMiouNhNvaq96lqUvCekxR";
    var key = CryptoJS.enc.Base64.parse(keyBase64);
    var srcs = CryptoJS.enc.Utf8.parse(word);
    var encrypted = CryptoJS.AES.encrypt(srcs, key, {mode:CryptoJS.mode.ECB,padding: CryptoJS.pad.Pkcs7});
    return encrypted.toString();
}
 
/**
   * Decrypt
 * @param word
 * @returns {*}
 */
function decrypt(word){
    const keyBase64 = "o9szYIOq1rRMiouNhNvaq96lqUvCekxR";
    var key = CryptoJS.enc.Base64.parse(keyBase64);
    var decrypt = CryptoJS.AES.decrypt(word, key, {mode:CryptoJS.mode.ECB,padding: CryptoJS.pad.Pkcs7});
    return CryptoJS.enc.Utf8.stringify(decrypt).toString();
}

var ciphertext = encrypt(plaintext);
console.log('ciphertext: ', ciphertext);
var decryptedtext = decrypt(ciphertext);
console.log('decryptedtext: ', decryptedtext);

Java code:

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import java.util.Base64;

public class Main {
    public static void main(String[] args) throws Exception {
        System.out.println("Why can't java decrypt CryptoJS encrypted data ?");
        String ciphertextFromJavascript = "oNP8t53ZTi1WUptGCDh5NQ==";
        System.out.println("ciphertextFromJavascript: " + ciphertextFromJavascript);
        System.out.println("decrypted: " + decrypt(ciphertextFromJavascript));
    }
    public static String decrypt(String ciphertext) throws Exception {
        SecretKey secretKey = getSecretKey("o9szYIOq1rRMiouNhNvaq96lqUvCekxR");
        Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
        cipher.init(Cipher.DECRYPT_MODE, secretKey);
        return new String(cipher.doFinal(Base64.getDecoder().decode(ciphertext)));
        //return new String(cipher.doFinal(base64Decode("ASDASDADS")));
    }

    public static SecretKey getSecretKey(String secretKey) throws Exception {
        byte[] decodeSecretKey = Base64.getDecoder().decode(secretKey);
        //byte[] decodeSecretKey = base64Decode(secretKey);
        return new SecretKeySpec(decodeSecretKey, 0, decodeSecretKey.length, "AES");
    }
}

Why can't java decrypt CryptoJS encrypted data?

1 Answers