Encrypt Decrypt message using AES-128 CBC in java (with example)

Leave a Comment / By Yogesh / July 6, 2016

Given a message, We would like to encrypt & decrypt plain/cipher text using AES CBC algorithm in java. We will perform following operations:

Generate symmetric key using AES-128.
Generate initialization vector used for CBC (Cipher Block Chaining).
Encrypt message using symmetric key and initialization vector.
Decrypt the encrypted message using symmetric key and initialization vector.

Program to encrypt & decrypt message in java:

Given encryption key & initialization vector.
We will use AES algorithm to encrypt & decrypt input text.
CryptoMngr is used generate cipher text from plain text & vice versa.

package org.learn;
 
import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
 
public class CryptoMngr {
     
    public static String ALGORITHM = "AES";
    private static String AES_CBS_PADDING = "AES/CBC/PKCS5Padding";
 
    public static byte[] encrypt(final byte[] key, final byte[] IV, final byte[] message) throws Exception {
        return CryptoMngr.encryptDecrypt(Cipher.ENCRYPT_MODE, key, IV, message);
    }
 
    public static byte[] decrypt(final byte[] key, final byte[] IV, final byte[] message) throws Exception {
        return CryptoMngr.encryptDecrypt(Cipher.DECRYPT_MODE, key, IV, message);
    }
 
    private static byte[] encryptDecrypt(final int mode, final byte[] key, final byte[] IV, final byte[] message)
            throws Exception {
        final Cipher cipher = Cipher.getInstance(AES_CBS_PADDING);
        final SecretKeySpec keySpec = new SecretKeySpec(key, ALGORITHM);
        final IvParameterSpec ivSpec = new IvParameterSpec(IV);
        cipher.init(mode, keySpec, ivSpec);
        return cipher.doFinal(message);
    }
}

CryptoMngrClient Class: CryptoMngrClient class will generate random input message and will invoke CryptoMngr to encrypt & decrypt input message.

package org.learn;
 
import java.util.Base64;
import java.util.UUID;
 
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
 
public class CryptoMngrClient {
 
    private static int AES_128 = 128;
 
    public static void main(String[] args) throws Exception {
         
        KeyGenerator keyGenerator = KeyGenerator.getInstance(CryptoMngr.ALGORITHM);
        keyGenerator.init(AES_128);
        //Generate Key
        SecretKey key = keyGenerator.generateKey();
        //Initialization vector
        SecretKey IV = keyGenerator.generateKey();
 
        String randomString = UUID.randomUUID().toString().substring(0, 16);
        System.out.println("1. Message to Encrypt: " + randomString);
         
        byte[] cipherText = CryptoMngr.encrypt(key.getEncoded(), IV.getEncoded(), randomString.getBytes());
        System.out.println("2. Encrypted Text: " + Base64.getEncoder().encodeToString(cipherText));
         
        byte[] decryptedString = CryptoMngr.decrypt(key.getEncoded(), IV.getEncoded(), cipherText);
        System.out.println("3. Decrypted Message : " + new String(decryptedString));
    }
}

Program output to encrypt & decrypt to / from plain text is java:

Message to Encrypt: d6d0c0d9-a53c-42
Encrypted Text: hdZSyZiTq8t0FCifdgH0mqw0inpyZKLdGpbRgKjPUdA=
Decrypted Message : d6d0c0d9-a53c-42