des.java

采用RSA公秘钥体制和MD5签名算法的安全通信

import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.KeyGenerator;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKey;


public class DES {
    private  Cipher cipher = null;
    private  SecretKey key = null;
    public DES(){
  	  try {
			KeyGenerator kpg = KeyGenerator.getInstance("DES");
			SecureRandom random = new SecureRandom();
			kpg.init(random);
			key = kpg.generateKey();
		} catch (NoSuchAlgorithmException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} ;
    }
    public SecretKey getSecretKey(){
  	  return this.key;
    }
    public void setSecretKey(SecretKey key){
  	  this.key = key;
    }
    public byte[] encrpty(byte[] msg){
  	  byte[] result = null;
  	  try {
  		cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");
			cipher.init(Cipher.ENCRYPT_MODE, key);
			if(msg.length==8192){
				result = cipher.doFinal(msg);
			}
			else{
				result = cipher.doFinal(msg);
			}
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		//  System.out.println(result.length);
  	  return result;
  }
    public byte[] decrpty(byte[] msg){
  	  byte[] result = null;
  	  try {
  		  cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");
			cipher.init(Cipher.DECRYPT_MODE, key);
			if(msg.length==8200){
				result = cipher.doFinal(msg);
			}
			else {
				result = cipher.doFinal(msg);
			}
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
  	  return result;
    }
}