字符串加密和解密的方法

/**
 * @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);