How to decrypt in Java strings that have been encrypted using JS crypto

This is how you can encrypt/decrypt in JS and Java using Crypto and javax.crypto respectively.

If you don't care about interoperability of different environment, you can get started pretty quickly using createCypher(algorithm, password) in your JS code, but it is not very portable as you don't know how raw key and initialization vector is derived from the password.

Changing the JS code to use createCipheriv(algorithm, key, iv) instead, will give you a portable encryption/decryption:

    encryptString : function encryptString(str, encryptionKey, iv) {
        var cipher = crypto.createCipheriv('aes-128-cbc', encryptionKey, iv);
        var cipherText = cipher.update(str, 'binary', 'base64');
        var cipherTextRemaining = cipher.final('base64');
        return cipherText + cipherTextRemaining;
    },

    decryptString : function decryptString(str, encryptionKey, iv) {
        var desipher = crypto.createDecipheriv('aes-128-cbc', encryptionKey, iv);
        var desipherText = desipher.update(str, 'base64', 'binary');
        var desipherTextRemaining = desipher.final('binary');
        return desipherText + desipherTextRemaining;
    },

This is the equivalent Java code that does the same thing:

public static String encryptString(String clearText, byte[] key, byte[] initialVector) throws Exception
{
    Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
    SecretKeySpec secretKeySpecy = new SecretKeySpec(key, "AES");
    IvParameterSpec ivParameterSpec = new IvParameterSpec(initialVector);
    cipher.init(Cipher.ENCRYPT_MODE, secretKeySpecy, ivParameterSpec);
    byte[] encrypted = cipher.doFinal(clearText.getBytes());
    return new String(Base64.encodeBase64(encrypted, false));
}

public static String decryptString(String cipherText, byte[] key, byte[] initialVector) throws Exception
{
    Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
    SecretKeySpec secretKeySpecy = new SecretKeySpec(key, "AES");
    IvParameterSpec ivParameterSpec = new IvParameterSpec(initialVector);
    cipher.init(Cipher.DECRYPT_MODE, secretKeySpecy, ivParameterSpec);
    return new String(cipher.doFinal(Base64.decodeBase64(cipherText)));
}

We had a similar problem. So what we wanted is to encrypt the voucherCode in Java side and send it to front end side. Encryption needed to make the voucher code secure.

Now on front end, a third party java script library requires this voucherCode, such that it should be able to retrieve the actual voucherCode by decryption it.

So here is what we have done

On java side

import javax.xml.bind.DatatypeConverter;

    public class Controller{

     @RequestMapping("voucherCode")
     public String getVoucherCode{
       String voucherCode = voucherService.getVoucherCode()
             return  DatatypeConverter.printBase64Binary(voucherCode.getBytes("UTF-8"))

}
    }

So if we have voucher code as 50%OFF then the above code will send NTAlT0ZG as encoded value for 50%OFF.

Now once we have the encoded value on front end. In javascript we can get the original value by using

window.atob("NTAlT0ZG") // this will return 50%OFF

So this way we can have the enncryption/decryption hand in hand between java and java script.

window object provides two methods for encrypt and decrypt

 window.btoa("50%OFF") // returns NTAlT0ZG
    window.atob("NTAlT0ZG") // return original value as "50%OFF"