CNS Lab Exercise -6

6. Write a JAVA program to implement the Rijndael algorithm logic.

import javax.crypto.Cipher;

import javax.crypto.KeyGenerator;

import javax.crypto.SecretKey;

import java.util.Base64;

import java.util.Scanner;

public class RijndaelAES {

    public static void main(String[] args) throws Exception {

        Scanner sc = new Scanner(System.in);

        // User input plaintext

        System.out.print("Enter Plain Text: ");

        String plaintext = sc.nextLine();

        // Step 1: Generate AES Key (128-bit)

        KeyGenerator keyGen = KeyGenerator.getInstance("AES");

        keyGen.init(128);

        SecretKey secretKey = keyGen.generateKey();

        // Step 2: Encryption

        Cipher cipher = Cipher.getInstance("AES");

        cipher.init(Cipher.ENCRYPT_MODE, secretKey);

        byte[] encryptedBytes = cipher.doFinal(plaintext.getBytes());

        // Convert encrypted bytes to Base64 for display

        String encryptedText = Base64.getEncoder().encodeToString(encryptedBytes);

        // Step 3: Decryption

        cipher.init(Cipher.DECRYPT_MODE, secretKey);

        byte[] decryptedBytes = cipher.doFinal(encryptedBytes);

        String decryptedText = new String(decryptedBytes);

        // Output

        System.out.println("\n----- OUTPUT -----");

        System.out.println("Plain Text  : " + plaintext);

        System.out.println("Encrypted   : " + encryptedText);

        System.out.println("Decrypted   : " + decryptedText);

    }

}

Output:

Enter Plain Text: hi 

----- OUTPUT -----

Plain Text  : hi 

Encrypted   : dmZUHhpls3tEe6mr0SNITw==

Decrypted   : hi