AESEncryption.java

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import java.util.Base64;
import java.util.Scanner;

public class AESEncryption {

    // Encrypt text using AES algorithm
    public static String encrypt(String plainText, SecretKey key) throws Exception {
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.ENCRYPT_MODE, key);
        byte[] encryptedBytes = cipher.doFinal(plainText.getBytes());
        return Base64.getEncoder().encodeToString(encryptedBytes);
    }

    // Decrypt text using AES algorithm
    public static String decrypt(String encryptedText, SecretKey key) throws Exception {
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.DECRYPT_MODE, key);
        byte[] decodedBytes = Base64.getDecoder().decode(encryptedText);
        byte[] decryptedBytes = cipher.doFinal(decodedBytes);
        return new String(decryptedBytes);
    }

    public static void main(String[] args) throws Exception {
        Scanner scanner = new Scanner(System.in);

        System.out.println("=== AES Encryption & Decryption Demo ===");
        System.out.print("Enter text to encrypt: ");
        String text = scanner.nextLine();

        // Generate AES key (128-bit)
        KeyGenerator keyGen = KeyGenerator.getInstance("AES");
        keyGen.init(128);
        SecretKey secretKey = keyGen.generateKey();

        // Encrypt
        String encryptedText = encrypt(text, secretKey);
        System.out.println("Encrypted text: " + encryptedText);

        // Decrypt
        String decryptedText = decrypt(encryptedText, secretKey);
        System.out.println("Decrypted text: " + decryptedText);

        // Print key for reference
        System.out.println("Secret Key (Base64): " + Base64.getEncoder().encodeToString(secretKey.getEncoded()));

        scanner.close();
    }
}