Utils.java

/**
 * Clase de Utilidades para Cifrado AES
 * 
 * Autor: alejanf2885
 * Github: https://github.com/alejanf2885
 */

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Base64;

public class Utils {

    public static SecretKey generateKey(int n) throws NoSuchAlgorithmException {
        KeyGenerator keyGen = KeyGenerator.getInstance("AES");
        keyGen.init(n);
        return keyGen.generateKey();
    }

    public static String encrypt(String data, SecretKey key) throws Exception {
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        byte[] iv = new byte[16];
        SecureRandom random = new SecureRandom();
        random.nextBytes(iv);
        IvParameterSpec ivSpec = new IvParameterSpec(iv);
        cipher.init(Cipher.ENCRYPT_MODE, key, ivSpec);
        byte[] encryptedData = cipher.doFinal(data.getBytes());
        byte[] encryptedDataWithIv = new byte[iv.length + encryptedData.length];
        System.arraycopy(iv, 0, encryptedDataWithIv, 0, iv.length);
        System.arraycopy(encryptedData, 0, encryptedDataWithIv, iv.length, encryptedData.length);
        return Base64.getEncoder().encodeToString(encryptedDataWithIv);
    }

    public static String decrypt(String encryptedData, SecretKey key) throws Exception {
        byte[] encryptedDataWithIv = Base64.getDecoder().decode(encryptedData);
        byte[] iv = new byte[16];
        byte[] encryptedBytes = new byte[encryptedDataWithIv.length - iv.length];
        System.arraycopy(encryptedDataWithIv, 0, iv, 0, iv.length);
        System.arraycopy(encryptedDataWithIv, iv.length, encryptedBytes, 0, encryptedBytes.length);
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        IvParameterSpec ivSpec = new IvParameterSpec(iv);
        cipher.init(Cipher.DECRYPT_MODE, key, ivSpec);
        byte[] decryptedData = cipher.doFinal(encryptedBytes);
        return new String(decryptedData);
    }
}