import java.io.*;
import java.security.*;
import javax.crypto.*;
import javax.crypto.spec.*;

public class DesTest
{
   public static void main(String args[]) throws Exception                                     
   {                                                                                           
      String msg="pozdrowienia od cioci";                                                      
                                                                                               
      String passwd="tajnehaslo";                                                              
      byte[] b=passwd.getBytes();                                                              
                                                                                               
                                                                                               
                                                                                               
      //-- generowanie klucza --                                                               
         System.out.println("tworzy generator kluczy");                                        
      KeyGenerator kgen = KeyGenerator.getInstance("DES");                                     
      kgen.init(new java.security.SecureRandom(b));                                            
                                                                                               
      System.out.println("generuje klucz");                                                    
      SecretKey key = kgen.generateKey();                                                      
                                                                                               
                                                                                               
                                                                                               
      //-- szyfrowanie --                                                                      
         System.out.println("tworzy obiekt klasy Cipher");                                     
      javax.crypto.Cipher c1 = javax.crypto.Cipher.getInstance("DES");                         
                                                                                               
      System.out.println("inicjuje cipher do szyfrowania");                                    
      c1.init(Cipher.ENCRYPT_MODE,key);                                                        
                                                                                               
      ObjectOutputStream out;                                                                  
      out=new ObjectOutputStream(new CipherOutputStream(new FileOutputStream("plik.txt"),c1)); 
      out.writeObject(msg);                                                                    
      out.flush();                                                                             
      out.close();                                                                             
                                                                                               
                                                                                               
                                                                                               
      //-- deszyfrowanie --                                                                    
         System.out.println("tworzy obiekt klasy Cipher");                                     
      javax.crypto.Cipher c2 = javax.crypto.Cipher.getInstance("DES");                         
                                                                                               
      System.out.println("inicjuje cipher do deszyfrowania");                                  
      c2.init(Cipher.DECRYPT_MODE,key);                                                        
                                                                                               
      ObjectInputStream in;                                                                    
      in=new ObjectInputStream(new CipherInputStream(new FileInputStream("plik.txt"),c2));     
      String str=(String)in.readObject();                                                      
      in.close();                                                                              
                                                                                               
      System.out.println("\n-- "+str+" --\n");                                                 
   }                                                                                           
}