/*
 * Unrestricted security policy files for Java JRE need to be installed from Oracle for 256 keys to work
 */
package com.mycompany.mavenproject1;

import java.security.SecureRandom;
import java.security.Security;

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

import java.util.Base64;
import java.util.Arrays;

import org.bouncycastle.jce.provider.BouncyCastleProvider;

public class Main {

    private static final int keyLength = 32;
    private static final SecureRandom random = new SecureRandom();
    
    private static SecretKey key;
    private static byte[] iv;

    public static void main(String [] args) throws Exception {
        Security.addProvider(new BouncyCastleProvider());
        
        String plaintext = "hello world";
        byte [] ciphertext = encrypt(plaintext);
        String recoveredPlaintext = decrypt(ciphertext);

        System.out.println(recoveredPlaintext);
    }
    
    private static void printByteArr(byte[] arr) {
        System.out.print("[");
        for (int i = 0; i < arr.length; i++) {
            System.out.printf(i == 0 ? "%d" : ",%d", (arr[i] & 0xFF));
        }
        System.out.println("]");
    }

    private static byte [] encrypt(String plaintext) throws Exception {
        key = generateKey();

        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS7Padding");
        String ivStr = "0123456789abcdef";
        iv = ivStr.getBytes("US-ASCII");
        cipher.init(Cipher.ENCRYPT_MODE, key, new IvParameterSpec(iv));
        
        System.out.println(
                Base64.getEncoder().withoutPadding()
                    .encodeToString(key.getEncoded())
        );
        printByteArr(iv);
        return cipher.doFinal(plaintext.getBytes());
    }

    private static String decrypt(byte [] ciphertext) throws Exception {
        printByteArr(ciphertext);
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS7Padding");
        cipher.init(Cipher.DECRYPT_MODE, key, new IvParameterSpec(iv));
        return new String(cipher.doFinal(ciphertext));
    }

    private static SecretKey generateKey() throws Exception {
        byte[] keyBytes = new byte[keyLength];
        random.nextBytes(keyBytes);
        SecretKeySpec keySpec = new SecretKeySpec(keyBytes, "AES");
        return keySpec;
    }

    private static IvParameterSpec generateIV(Cipher cipher) throws Exception {
        byte [] ivBytes = new byte[cipher.getBlockSize()];
        random.nextBytes(ivBytes);
        return new IvParameterSpec(ivBytes);
    }
}