java安全-对称/非对称的加密和解密（付源代码）

对称加密/解密
密和解密使用相同的密钥，有代表性的有DES、Blowfish、TEA、Base64。对称加密解密的特点是运算相对非对称加密解密简单、速度块，主要应用于需要加密大量数据的场合，例如游戏的资源文件加密。

非对称加密/解密。
加密和解密使用不同的密钥（公钥/私钥），有代表性的有RSA、DSA、ElGamal和ECDSA。非对称加密/解密的安全性是基于复杂数学难题，特点是运算复杂、速度慢，主要应用于金融、军事等重大机密的系统。

代码演示：

package com.naxsu.security;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.OutputStream;
import java.security.Key;
import java.security.KeyPair;
import java.security.KeyPairGenerator;

import javax.crypto.Cipher;
import javax.crypto.CipherOutputStream;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.PBEParameterSpec;

/**
 * 对称/非对称加密与解密
 */
public class SecretKeyTest {
	public static void main(String[] args) throws Exception {
//		 secretEncrypt();
//		 secretDecrypt();

//		 secretEncryptByPass();
//		 secretDecryptByPass();

		publicEncrypt();
		privateDecrypt();
	}
	
	/**
	 * 对称加密，随机产生密钥
	 * @throws Exception
	 */
	private static void secretEncrypt() throws Exception {
		// Cipher：为加密和解密提供密码功能
		Cipher cipher = Cipher.getInstance("AES");
		// 生成密钥
		SecretKey key = KeyGenerator.getInstance("AES").generateKey();

		/*
		 * 小知识： 由于key是一个对象，要把它写到文件中，所在要用ObjectOutputStream.writeObject()
		 * 要用这个方法，这个类必须实现Serializable接口进行持久化进行对象保存，Object-->硬盘-->Object
		 */

		// 把密钥保存到secret.key文件中
		saveKey(key, "secret.key");
		// 根据密钥把cipher初始化为加密模式
		cipher.init(Cipher.ENCRYPT_MODE, key);
		// cipher.update("aaa".getBytes());
		// cipher.update("aaa".getBytes());
		// byte[] results = cipher.doFinal();

		// 对aaa进行加密操作
		byte[] results = cipher.doFinal("aaa".getBytes());
		System.out.println(new String(results));

		// 把加密后的字符串存放到data.txt中
		saveData(results, "data.txt");
	}

	/**
	 * 对称解密，读取存放密钥的文件获取密钥，然后根据密钥来解密
	 * @throws Exception
	 */
	private static void secretDecrypt() throws Exception {
		Cipher cipher = Cipher.getInstance("AES");
		// 读取存放密钥的secret.key文件
		Key key = readKey("secret.key");
		// 根据密钥把cipher初始化为解密模式
		cipher.init(Cipher.DECRYPT_MODE, key);
		// 读取data.txt文件，获取要解密的内容
		byte[] src = readData("data.txt");
		// 解密
		byte[] result = cipher.doFinal(src);
		System.out.println(new String(result));
	}

	/**
	 * 根据密码进行对称加密
	 * @throws Exception
	 */
	private static void secretEncryptByPass() throws Exception {
		Cipher cipher = Cipher.getInstance("PBEWithMD5AndDES");
		SecretKey key = SecretKeyFactory.getInstance("PBEWithMD5AndDES")
				.generateSecret(new PBEKeySpec("12345678".toCharArray()));
		PBEParameterSpec parameterSpec = new PBEParameterSpec(new byte[] { 1,
				2, 3, 4, 5, 6, 7, 8 }, 1000);
		cipher.init(Cipher.ENCRYPT_MODE, key, parameterSpec);

		byte[] results = cipher.doFinal("aaa".getBytes());
		System.out.println(new String(results));

		saveData(results,"data.txt");
	}

	/**
	 * 根据密码进行对称解密
	 * @throws Exception
	 */
	private static void secretDecryptByPass() throws Exception {
		Cipher cipher = Cipher.getInstance("PBEWithMD5AndDES");
		SecretKey key = SecretKeyFactory.getInstance("PBEWithMD5AndDES")
				.generateSecret(new PBEKeySpec("12345678".toCharArray()));
		PBEParameterSpec parameterSpec = new PBEParameterSpec(new byte[] { 1,
				2, 3, 4, 5, 6, 7, 8 }, 1000);
		cipher.init(Cipher.DECRYPT_MODE, key, parameterSpec);

		byte[] src = readData("data.txt");

		// 解密
		byte[] result = cipher.doFinal(src);
		System.out.println(new String(result));
	}

	/**
	 * 根据公钥进行非对称加密
	 * @throws Exception
	 */
	private static void publicEncrypt() throws Exception {
		Cipher cipher = Cipher.getInstance("RSA");
		KeyPairGenerator kPairGenerator = KeyPairGenerator.getInstance("RSA");
		KeyPair keyPair = kPairGenerator.generateKeyPair();
		Key publicKey = keyPair.getPublic();
		Key privateKey = keyPair.getPrivate();
		cipher.init(Cipher.ENCRYPT_MODE, publicKey);
		byte[] result = cipher.doFinal("那些事儿".getBytes("UTF-8"));

		saveKey(privateKey, "secret2.key");
		saveData(result, "data2.txt");
	}

	/**
	 * 根据私钥进行非对称解密
	 * @throws Exception
	 */
	private static void privateDecrypt() throws Exception{
		Cipher cipher = Cipher.getInstance("RSA");
		Key privateKey = readKey("secret2.key");
		cipher.init(Cipher.DECRYPT_MODE, privateKey);
		
		//方法1：
//		byte[] src = readData("data2.txt");
//		byte[] result=cipher.doFinal(src);
//		System.err.println(new String(result,"UTF-8"));
		
		//方法2：
//		FileInputStream fis = new FileInputStream("data2.txt");
//		CipherInputStream cis = new CipherInputStream(fis, cipher);
//		//简单处理一下
//		byte[] buf = new byte[1024];
//		int len = cis.read(buf);
//		System.out.println(new String(buf,0,len,"UTF-8"));
		
		//方法3：
		FileInputStream fis = new FileInputStream("data2.txt");
		FileOutputStream fos = new FileOutputStream("result.txt");
		CipherOutputStream cos = new CipherOutputStream(fos, cipher);
		copyStream(fis, cos);
		cos.close();
		fos.close();
		fis.close();
	}

	/**
	 * 把输入流拷贝到输出流
	 * @param is
	 * @param os
	 * @throws IOException
	 */
	private static void copyStream(InputStream is, OutputStream os)
			throws IOException {
		byte[] buf = new byte[1024];
		int len = is.read(buf);
		while (len != -1) {
			os.write(buf, 0, len);
			len = is.read(buf);
		}
	}

	/**
	 * 把key保存到文件中
	 * @param key
	 * @param fileName
	 * @throws FileNotFoundException
	 * @throws IOException
	 */
	private static void saveKey(Key key, String fileName)
			throws FileNotFoundException, IOException {
		FileOutputStream fosKey = new FileOutputStream(fileName);
		ObjectOutputStream oos = new ObjectOutputStream(fosKey);
		oos.writeObject(key);
		oos.close();
		fosKey.close();
	}
	
	/**
	 * 把二进制数据保存到文件中
	 * @param results
	 * @param fileName
	 * @throws FileNotFoundException
	 * @throws IOException
	 */
	private static void saveData(byte[] results, String fileName)
			throws FileNotFoundException, IOException {
		FileOutputStream fosData = new FileOutputStream(fileName);
		fosData.write(results);
		fosData.close();
	}
	
	/**
	 * 从文件中获取key
	 * @param fileName
	 * @return
	 * @throws FileNotFoundException
	 * @throws IOException
	 * @throws ClassNotFoundException
	 */
	private static Key readKey(String fileName) throws FileNotFoundException, IOException,
			ClassNotFoundException {
		FileInputStream fisKey = new FileInputStream(fileName);
		ObjectInputStream oisKey = new ObjectInputStream(fisKey);
		Key key = (Key) oisKey.readObject();
		oisKey.close();
		fisKey.close();
		return key;
	}
	
	/**
	 * 从文件中读取二进制数据
	 * @param fileName
	 * @return
	 * @throws FileNotFoundException
	 * @throws IOException
	 */
	private static byte[] readData(String fileName) throws FileNotFoundException, IOException {
		FileInputStream fisData = new FileInputStream(fileName);
		// 方法1：把输入流拷贝到输出流，再把 输出流转换为byte数组
		// ByteArrayOutputStream baos = new ByteArrayOutputStream();
		// copyStream(fisData, baos);
		// byte[] src = baos.toByteArray();
		// 方法2：用available()方法来读取
		// available()：返回可以不受阻塞地从此输入流中读取（或跳过）的估计剩余字节数。
		byte[] src = new byte[fisData.available()];
		int len = fisData.read(src);
		int total = 0;
		while (total < src.length) {
			total += len;
			len = fisData.read(src, total, src.length - total);
		}

		fisData.close();
		// baos.close();
		return src;
	}
}

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