Java Security SealedObject save to file

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectOutputStream;
import java.security.PublicKey;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SealedObject;
import javax.crypto.SecretKey;
import javax.security.cert.X509Certificate;

///*from  ww  w.  j  a va  2  s.  c o m*/
public class Main {
   public static void main(String args[]) throws Exception {
      String alg = "DES", target = "Hello World!";

      PublicKey pub = X509Certificate.getInstance(new FileInputStream("test.cer")).getPublicKey();
      Cipher cipher = Cipher.getInstance(pub.getAlgorithm());
      cipher.init(Cipher.ENCRYPT_MODE, pub);
      KeyGenerator kg = KeyGenerator.getInstance(alg);
      SecretKey sk = kg.generateKey();
      SealedObject so = new SealedObject(sk.getEncoded(), cipher);
      ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("key"));
      oos.writeObject(so);

      cipher = Cipher.getInstance(alg);
      cipher.init(Cipher.ENCRYPT_MODE, sk);
      so = new SealedObject(target, cipher);
      oos = new ObjectOutputStream(new FileOutputStream("data"));
      oos.writeObject(so);
      oos.close();
   }
}