学步园

       最近在做一个android项目，用到非对称加密，java的实现如下：

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 javax.crypto.Cipher;

public class Encryption {
	
	public static void main(String[] args) throws Exception {
		PublicEnrypt();
		privateDecrypt();
		}
	/*
	 * 公钥加密
	 */
	private static void PublicEnrypt()throws Exception {
		Cipher cipher =Cipher.getInstance("RSA");
		//实例化Key
		KeyPairGenerator keyPairGenerator=KeyPairGenerator.getInstance("RSA");
		//获取一对钥匙
		KeyPair keyPair=keyPairGenerator.generateKeyPair();
		//获得公钥
		Key publicKey=keyPair.getPublic();
		//获得私钥 
		Key privateKey=keyPair.getPrivate();
		//用公钥加密
		cipher.init(Cipher.ENCRYPT_MODE, publicKey);
		byte [] result=cipher.doFinal("天天向上".getBytes("UTF-8"));
		//将Key写入到文件
		saveKey(privateKey,"csc_private.key");
		//加密后的数据写入到文件
		saveData(result,"public_encryt.dat");
	}
	
	/*
	 * 私钥解密
	 */
	private static void privateDecrypt() throws Exception {
		Cipher cipher=Cipher.getInstance("RSA");
		//得到Key
		Key privateKey=readKey("csc_private.key");
		//用私钥去解密
		cipher.init(Cipher.DECRYPT_MODE, privateKey);
		//读数据源
		byte [] src =readData("public_encryt.dat");
		//得到解密后的结果
		byte[] result=cipher.doFinal(src);
		//二进制数据要变成字符串需解码
		System.out.println(new String(result,"UTF-8"));
	}

	private static void saveData(byte[] result, String fileName) throws Exception {
		FileOutputStream fosData=new FileOutputStream(fileName);
		fosData.write(result);
		fosData.close();
	}
	public static void saveKey(Key key,String fileName)throws Exception{
		FileOutputStream fosKey=new FileOutputStream(fileName);
		ObjectOutputStream oosSecretKey =new ObjectOutputStream(fosKey);
		oosSecretKey.writeObject(key);
		oosSecretKey.close();
		fosKey.close();
	}
	private static Key readKey(String fileName) throws Exception {
		FileInputStream fisKey=new FileInputStream(fileName);
		ObjectInputStream oisKey =new ObjectInputStream(fisKey);
		Key key=(Key)oisKey.readObject();
		oisKey.close();
		fisKey.close();
		return key;
	}
	private static byte[] readData(String filename) throws Exception {
		FileInputStream fisDat=new FileInputStream(filename);
		byte [] src=new byte [fisDat.available()];
		int len =fisDat.read(src);
		int total =0;
		while(total<src.length){
			total +=len;
			len=fisDat.read(src,total,src.length-total);
		}
		fisDat.close();
		return src;
	}
}