DES.java

import javax.crypto.SecretKey;
import javax.crypto.Cipher;

/**
 * DES is a wrapper class which allows encryption/decryption using the DES block cipher
 */

public class DES {

    /**
     * encrypts plaintext given as a byte array
     * @param ptBytes plaintext given as byte array
     * @param key secret key
     * @return returns byte array containing the ciphertext
     */
    public static byte [] encrypt(byte[] ptBytes, SecretKey key) throws Exception 
    {
        Cipher cipher = Cipher.getInstance("DES/ECB/NoPadding");
        cipher.init(Cipher.ENCRYPT_MODE, key);
        return cipher.doFinal(ptBytes);
    }

     /**
     * decrypts ciphertext given as a byte array
     * @param ctBytes ciphertext given as byte array
     * @param key secret key
     * @return returns byte array containing the plaintext
     */
    public static byte [] decrypt(byte[] ctBytes, SecretKey key) throws Exception 
    {
        Cipher cipher = Cipher.getInstance("DES/ECB/NoPadding");
        cipher.init(Cipher.DECRYPT_MODE, key);
        return cipher.doFinal(ctBytes);
    }
}