/*
* Copyright (c) 2004 ???. All Rights Reserved.
* Download by http://www.codefans.net
* Version 1.0 , Created on 2004-3-10
*
*/
/**
* @author Devon
*/
import java.security.*;
import java.security.spec.*;
import javax.crypto.*;
public class PairKeyExample {
public static void main(String argv[]) {
try {
String algorithm = "RSA"; //定义加密算法,可用 DES,DESede,Blowfish
String message = "张三，你好，我是李四";
//产生张三的密钥对(keyPairZhang)
KeyPairGenerator keyGeneratorZhang =
KeyPairGenerator.getInstance(algorithm); //指定采用的算法
keyGeneratorZhang.initialize(1024); //指定密钥长度为1024位
KeyPair keyPairZhang = keyGeneratorZhang.generateKeyPair(); //产生密钥对
System.out.println("生成张三的公钥对");
// 张三生成公钥(publicKeyZhang)并发送给李四,这里发送的是公钥的数组字节
byte[] publicKeyZhangEncode = keyPairZhang.getPublic().getEncoded();
//通过网络或磁盘等方式,把公钥编码传送给李四
//李四接收到张三编码后的公钥,将其解码
KeyFactory keyFacoryLi = KeyFactory.getInstance(algorithm); //得到KeyFactory对象
X509EncodedKeySpec x509KeySpec =
new X509EncodedKeySpec(publicKeyZhangEncode); //公钥采用X.509编码
PublicKey publicKeyZhang = keyFacoryLi.generatePublic(x509KeySpec); //将公钥的KeySpec对象转换为公钥
System.out.println("李四成功解码,得到张三的公钥");
//李四用张三的公钥加密信息，并发送给李四
Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding"); //得到Cipher对象
cipher.init(Cipher.ENCRYPT_MODE, publicKeyZhang); //用张三的公钥初始化Cipher对象
byte[] cipherMessage = cipher.doFinal(message.getBytes()); //得到加密信息
System.out.println("加密后信息：" + new String(cipherMessage));
System.out.println("加密完成，发送给李四...");
//张三用自己的私钥解密从李四处收到的信息
cipher.init(Cipher.DECRYPT_MODE, keyPairZhang.getPrivate()); //张三用其私钥初始化Cipher对象
byte[] originalMessage = cipher.doFinal(cipherMessage); //得到解密后信息
System.out.println("张三收到信息，解密后为：" + new String(originalMessage));
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
