数字签名

package com.test;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.security.Key;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.Signature;

public class Sign {

	/**
	 * @param args
	 */
	public static void main(String[] args) throws Exception {
		Sign sign = new Sign();
		sign.sign();
		sign.verify();
	}

	public void sign() throws Exception{
		KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
		KeyPair keyPair = kpg.generateKeyPair();
		PublicKey publicKey = keyPair.getPublic();
		PrivateKey privateKey = keyPair.getPrivate();

		Signature sign = Signature.getInstance("SHA1withRSA");
		sign.initSign(privateKey);
		sign.update("测试数据".getBytes());
		byte[] data = sign.sign();

		saveKey(publicKey, "sign_publicKey");
		saveData(data, "sign_data");

	}

	public void verify() throws Exception{

		PublicKey publicKey = (PublicKey)readKey("sign_publicKey");

		Signature sign = Signature.getInstance("SHA1withRSA");
		sign.initVerify(publicKey);
		sign.update("测试数据".getBytes());

		byte[] data = readData("sign_data");

		boolean rs = sign.verify(data);

		System.out.println(rs);

	}


	public void saveData(byte[] data, String fileName) throws Exception{
		FileOutputStream fos = new FileOutputStream(fileName);
		ObjectOutputStream oos = new ObjectOutputStream(fos);
		oos.writeObject(data);
		oos.close();
		fos.close();
	}

	public void saveKey(Key key, String fileName) throws Exception{
		FileOutputStream fos = new FileOutputStream(fileName);
		ObjectOutputStream oos = new ObjectOutputStream(fos);
		oos.writeObject(key);
		oos.close();
		fos.close();
	}

	public Key readKey(String fileName) throws Exception{
		FileInputStream fis = new FileInputStream(fileName);
		ObjectInputStream ois = new ObjectInputStream(fis);
		Key privateKey = (Key)ois.readObject();
		return privateKey;
	}

	public byte[] readData(String fileName) throws Exception{
		FileInputStream fis = new FileInputStream(fileName);
		ObjectInputStream ois = new ObjectInputStream(fis);
		byte[] data = (byte[])ois.readObject();
		return data;
	}
}