DES.java

import java.util.*;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.KeyGenerator;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;

import java.io.*;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.spec.InvalidKeySpecException;

class DES{
    public static void main(String[] args) throws IOException, NoSuchAlgorithmException, InvalidKeyException, InvalidKeySpecException, NoSuchPaddingException, IllegalBlockSizeException, BadPaddingException {
        
        //String we we want to encrypt
        String  message="This is a confidential message.";
        byte[] myMessage =message.getBytes(); //string to byte array as DES works on bytes

        //If you want to use your own key
        // SecretKeyFactory MyKeyFactory = SecretKeyFactory.getInstance("DES");
        // String Password = "My Password";
        // byte[] mybyte =Password.getBytes();
        // DESKeySpec myMaterial = new DESKeySpec(mybyte);
        // SecretKey myDESKey = MyKeyFactory.generateSecret(myMaterial);

        //Generating Key
        KeyGenerator Mygenerator = KeyGenerator.getInstance("DES");
        SecretKey myDesKey = Mygenerator.generateKey();

        //initializing crypto algorithm
        Cipher myCipher = Cipher.getInstance("DES");

        //setting encryption mode
        myCipher.init(Cipher.ENCRYPT_MODE, myDesKey);
        byte[] myEncryptedBytes=myCipher.doFinal(myMessage);
        

        //setting decryption mode
        myCipher.init(Cipher.DECRYPT_MODE, myDesKey);
        byte[] myDecryptedBytes=myCipher.doFinal(myEncryptedBytes);

        //print message in byte format
        //System.out.println(Arrays.toString(myEncryptedBytes));
        //System.out.println(Arrays.toString(myDecryptedBytes));

        String encrypteddata=new String(myEncryptedBytes);
        String decrypteddata=new String(myDecryptedBytes);

        System.out.println("Message : "+ Arrays.toString(myMessage));
        System.out.println("Encrypted - "+ encrypteddata);
        System.out.println("Decrypted Message - "+ decrypteddata);
    }
}