java 之 加密解密学习示例

package com.ethan.security;import java.io.ByteArrayInputStream;import java.io.ByteArrayOutputStream;import java.io.FileInputStream;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.InvalidKeyException;import java.security.Key;import java.security.NoSuchAlgorithmException;import javax.crypto.BadPaddingException;import javax.crypto.Cipher;import javax.crypto.IllegalBlockSizeException;import javax.crypto.KeyGenerator;import javax.crypto.NoSuchPaddingException;import javax.crypto.SecretKey;public class SecretKeyTest {/** * 对称加密---------------》密钥对密钥 * key secretKey   * 非对称加密----------------->公钥  私钥 * publicKey/PrivateKey * @param args * @throws ClassNotFoundException  * @throws IOException  * @throws BadPaddingException  * @throws IllegalBlockSizeException  * @throws NoSuchPaddingException  * @throws NoSuchAlgorithmException  * @throws InvalidKeyException  */public static void main(String[] args) throws InvalidKeyException, NoSuchAlgorithmException, NoSuchPaddingException, IllegalBlockSizeException, BadPaddingException, IOException, ClassNotFoundException {// TODO Auto-generated method stub//secretEncrypt();secretDecrypt();}public static void secretEncrypt() {//加密类try {Cipher cipher = Cipher.getInstance("AES");//密钥SecretKey key = KeyGenerator.getInstance("AES").generateKey();//得到密钥//1->加密 2->解密 用常量 英文单词表示数字cipher.init(Cipher.ENCRYPT_MODE,key);//把密钥 key写入文件FileOutputStream fos = new FileOutputStream("ethan_secret.key");ObjectOutputStream oosSecretKey = new ObjectOutputStream(fos);oosSecretKey.writeObject(key);fos.close();//把加密结果也写进文件//填充数据cipher.update("aaa".getBytes());byte[] results = cipher.doFinal();System.out.println(new String(results));FileOutputStream fosData = new FileOutputStream("ethan_data.data");fosData.write(results);fosData.close();/* * 直接加密 一句话 * cipher.doFinal("aaa".getBytes()); *//*//解密cipher.init(Cipher.DECRYPT_MODE, key);System.out.println(new String(cipher.doFinal(results)));*/} catch(Exception e) {e.printStackTrace();}}private static void secretDecrypt() throws NoSuchAlgorithmException, NoSuchPaddingException, IOException, ClassNotFoundException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException {//AES 加密的一种算法Cipher cipher = Cipher.getInstance("AES");FileInputStream fisKey = new FileInputStream("ethan_secret.key");ObjectInputStream oisKey = new ObjectInputStream(fisKey);//读取到 Key 对象 Key-----------is interfaceKey key = (Key) oisKey.readObject(); oisKey.close();fisKey.close();cipher.init(Cipher.DECRYPT_MODE, key);//拿到 要解密的内容FileInputStream fisDat = new FileInputStream("ethan_data.data");//ByteArrayInputStream bais = new ByteArrayInputStream(arg0)ByteArrayOutputStream baos = new ByteArrayOutputStream();copyStream(fisDat,baos);/* * 第二种 read 数据的方法 * byte[] src = new byte[1024]; *int len = fisDat.read(src); * int total = 0; * 下边不能是  while(len!=-1)因为如果read(byte[],offset,len) len=0了，则return 0; * 不等于-1，则进入死循环 * while(total<src.length) { * total += len; * 从total处 开始接着读 到 src.length-total * len = fisDat.read(src,total,src.length-total); *   * } *  * byte[] result = cipher.doFinal(src); * fisDat.close(); */byte[] result = cipher.doFinal(baos.toByteArray());//记得关闭流fisDat.close();baos.close();System.out.println(new String(result));}private static void copyStream(InputStream ips,OutputStream ops) {byte[] buffer = new byte[1024];int len = 0;try {while((len=ips.read(buffer))!=-1) {ops.write(buffer,0,len);}} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}

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