java安全-非对称加密/解密(附源码实现)
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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