java实现字符串非对称加密（私钥加密，公钥解密并对比)

/**
 * @author cyw  创建日期: 2010-11-25
 */
package com.bean;

import java.security.InvalidKeyException;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.Signature;
import java.security.SignatureException;

public class P14_02 {

 private KeyPair key = null; //公钥和私钥对
 Signature sig = null;
 public P14_02() throws NoSuchAlgorithmException
 {
  //形成DSA公钥对
  KeyPairGenerator kgen = KeyPairGenerator.getInstance("DSA");
  kgen.initialize(1024);
  //生成公钥和私钥对
  key = kgen.generateKeyPair();
  //实例化signature,用于指定数字签名，指定用DSA算法
  sig = Signature.getInstance("DSA");
 }
 
 public byte[] jiami(String msg) throws InvalidKeyException,SignatureException   //私钥加密
 {
  byte[] msgBytes = msg.getBytes();
  //得到私钥
  PrivateKey privateKey = key.getPrivate();
  //用私钥来初始化数字签名对象
  sig.initSign(privateKey);
  //对msgBytes 进行数字签名
  sig.update(msgBytes);
  //完成签名后，将放入字节数组signatureBytes
  byte[] signatureBytes = sig.sign();
  return signatureBytes;
 }
 
 public boolean yanzheng(String msg,byte[] signatureBytes) throws InvalidKeyException,SignatureException
 {
  //使用公钥验证
  PublicKey publicKey = key.getPublic();
  sig.initVerify(publicKey);
  byte[] msgBytes2 = msg.getBytes();
  //对msgBytes2 重新进行数字签名
  sig.update(msgBytes2);
  return sig.verify(signatureBytes);
  
 }
 
 public static void main(String[] args) throws Exception{
  String msg = "我是一条数据";
  System.out.println("原文是："+msg);
  
  P14_02 p14_02 = new P14_02();
  byte[] signatureBytes = p14_02.jiami(msg);
  //下边两行没有实际用处，是显示加密后的字符串用的

  String signature1 = new String(signatureBytes);
  System.out.println("签名是："+signature1);
  //
  boolean a = p14_02.yanzheng(msg,signatureBytes);
  if(a)
  {
   System.out.println("验证成功");
  }
  else
  {
   System.out.println("验证失败");  
  }

 }