// encrypt method using AES
    private static byte[] encrypt(byte[] rawKey, byte[] input) throws Exception {

        byte[] rawPaddedKey = new byte[128];

        // Generate the key padding if necessary
        if(rawKey.length < 128){

            // Get the KeyGenerator
            KeyGenerator kgen = KeyGenerator.getInstance("AES");
            kgen.init(128-rawKey.length);

            SecretKey skey = kgen.generateKey();
            byte[] keyPadding = skey.getEncoded();

            System.arraycopy(rawKey, 0, rawPaddedKey, 0, rawKey.length);
            System.arraycopy(rawPaddedKey, 0, rawPaddedKey, rawKey.length, keyPadding.length);
        }

        else{
            System.arraycopy(rawKey, 0, rawPaddedKey, 0, rawKey.length);
        }

        // construct secret key from rawPaddedKey byte stream using AES
        SecretKeySpec skeySpec = new SecretKeySpec(rawPaddedKey, "AES");
        // generate cipher object for AES transformation
        Cipher cipher = Cipher.getInstance("AES");
        // initialize cipher with secret key in encrypt mode
        cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
        // encrypt data
        byte[] encrypted = cipher.doFinal(input);
        return encrypted;
    }