/*
 * Copyright (c) 2004 ???. All Rights Reserved.
 *
 * Version 1.0 , Created on 2004-3-10
 *
 */

/**
 * @author Devon
 */

 /**
  *  如何產(chǎn)生和保存密鑰
  */

import java.security.*;
import java.security.spec.*;
import javax.crypto.*;
import java.io.*;

public class KeyGeneratorExample {
	public static void main(String[] args)	{
		try{
		   //產(chǎn)生單鑰加密的密鑰(myKey)
			KeyGenerator keyGenerator = KeyGenerator.getInstance("DESede"); //采用DESede算法
			keyGenerator.init(168); //選擇DESede算法,密鑰長(zhǎng)度為112位或168位
			Key myKey = keyGenerator.generateKey(); //生成密鑰
			System.out.println("得到單鑰加密密鑰");

			//產(chǎn)生雙鑰的密鑰對(duì)(keyPair)
			KeyPairGenerator keyPairGenerator=KeyPairGenerator.getInstance("RSA"); //采用RSA算法
			keyPairGenerator.initialize(1024); //指定密鑰長(zhǎng)度為1024位
			KeyPair keyPair = keyPairGenerator.generateKeyPair();  //生成密鑰對(duì)
			System.out.println("生成張三的公鑰對(duì)");

			//保存公鑰的字節(jié)數(shù)組
			File f = new File("publicKey.dat");  //保存公鑰到文件publicKey.dat
			FileOutputStream fout = new FileOutputStream(f);
			fout.write(keyPair.getPublic().getEncoded()); //得到公鑰的字節(jié)數(shù)組
			fout.close();  //關(guān)閉文件輸出流
			System.out.println("保存公鑰到文件: "+f.getAbsolutePath());

			//用Java對(duì)象序列化保存私鑰,通常應(yīng)對(duì)私鑰加密后再保存
			ObjectOutputStream oout = new ObjectOutputStream(new FileOutputStream("privateKey.dat")); //保存私鑰到文件privateKey.dat
			oout.writeObject(keyPair.getPrivate()); //序列化私鑰
			oout.close();  //關(guān)閉輸出流
			System.err.println("保存私鑰到: privateKey.dat");

			//從文件中得到公鑰編碼的字節(jié)數(shù)組
			FileInputStream fin = new FileInputStream("publicKey.dat");  //打天publicKey.dat
			ByteArrayOutputStream baout = new ByteArrayOutputStream();  //用于寫入文件的字節(jié)流
			int aByte = 0;
			while ((aByte = fin.read())!= -1)  //從文件讀取一個(gè)字節(jié)
			{
			   baout.write(aByte);   //寫入一個(gè)字節(jié)
			}
			fin.close();  //關(guān)閉文件輸入流
			byte[] keyBytes = baout.toByteArray();  //得到公鑰的字節(jié)數(shù)組
			baout.close();  //關(guān)閉字節(jié)數(shù)組輸出流

			//從字節(jié)數(shù)組解碼公鑰
			X509EncodedKeySpec x509KeySpec =new X509EncodedKeySpec(keyBytes);
			KeyFactory keyFactory = KeyFactory.getInstance("RSA");  //指定算法RSA,得到一個(gè)KeyFactory的實(shí)例
			PublicKey pubKey = keyFactory.generatePublic(x509KeySpec);  //解碼公鑰
            System.out.println("從文件中成功得到公鑰");
		}catch (Exception ex){ex.printStackTrace();
		}
	}
}