Java实现MD5加密解密类

java 4 2016-02-29 13:03
女装

Java实现MD5加密以及解密类,附带测试类,具体见代码。

MD5加密解密类——MyMD5Util,代码如下

package com.zyg.security.md5;

import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Arrays;

public class MyMD5Util {
 
 private static final String HEX_NUMS_STR="0123456789ABCDEF";
 private static final Integer SALT_LENGTH = 12;
 
 /** 
  * 将16进制字符串转换成字节数组 
  * @param hex 
  * @return 
  */
 public static byte[] hexStringToByte(String hex) {
  int len = (hex.length() / 2);
  byte[] result = new byte[len];
  char[] hexChars = hex.toCharArray();
  for (int i = 0; i < len; i++) {
   int pos = i * 2;
   result[i] = (byte) (HEX_NUMS_STR.indexOf(hexChars[pos]) << 4 
       | HEX_NUMS_STR.indexOf(hexChars[pos + 1]));
  }
  return result;
 }

 
 /**
  * 将指定byte数组转换成16进制字符串
  * @param b
  * @return
  */
 public static String byteToHexString(byte[] b) {
  StringBuffer hexString = new StringBuffer();
  for (int i = 0; i < b.length; i++) {
   String hex = Integer.toHexString(b[i] & 0xFF);
   if (hex.length() == 1) {
    hex = '0' + hex;
   }
   hexString.append(hex.toUpperCase());
  }
  return hexString.toString();
 }
 
 /**
  * 验证口令是否合法
  * @param password
  * @param passwordInDb
  * @return
  * @throws NoSuchAlgorithmException
  * @throws UnsupportedEncodingException
  */
 public static boolean validPassword(String password, String passwordInDb)
   throws NoSuchAlgorithmException, UnsupportedEncodingException {
  //将16进制字符串格式口令转换成字节数组
  byte[] pwdInDb = hexStringToByte(passwordInDb);
  //声明盐变量
  byte[] salt = new byte[SALT_LENGTH];
  //将盐从数据库中保存的口令字节数组中提取出来
  System.arraycopy(pwdInDb, 0, salt, 0, SALT_LENGTH);
  //创建消息摘要对象
  MessageDigest md = MessageDigest.getInstance("MD5");
  //将盐数据传入消息摘要对象
  md.update(salt);
  //将口令的数据传给消息摘要对象
  md.update(password.getBytes("UTF-8"));
  //生成输入口令的消息摘要
  byte[] digest = md.digest();
  //声明一个保存数据库中口令消息摘要的变量
  byte[] digestInDb = new byte[pwdInDb.length - SALT_LENGTH];
  //取得数据库中口令的消息摘要
  System.arraycopy(pwdInDb, SALT_LENGTH, digestInDb, 0, digestInDb.length);
  //比较根据输入口令生成的消息摘要和数据库中消息摘要是否相同
  if (Arrays.equals(digest, digestInDb)) {
   //口令正确返回口令匹配消息
   return true;
  } else {
   //口令不正确返回口令不匹配消息
   return false;
  }
 }


 /**
  * 获得加密后的16进制形式口令
  * @param password
  * @return
  * @throws NoSuchAlgorithmException
  * @throws UnsupportedEncodingException
  */
 public static String getEncryptedPwd(String password)
   throws NoSuchAlgorithmException, UnsupportedEncodingException {
  //声明加密后的口令数组变量
  byte[] pwd = null;
  //随机数生成器
  SecureRandom random = new SecureRandom();
  //声明盐数组变量
  byte[] salt = new byte[SALT_LENGTH];
  //将随机数放入盐变量中
  random.nextBytes(salt);

  //声明消息摘要对象
  MessageDigest md = null;
  //创建消息摘要
  md = MessageDigest.getInstance("MD5");
  //将盐数据传入消息摘要对象
  md.update(salt);
  //将口令的数据传给消息摘要对象
  md.update(password.getBytes("UTF-8"));
  //获得消息摘要的字节数组
  byte[] digest = md.digest();

  //因为要在口令的字节数组中存放盐,所以加上盐的字节长度
  pwd = new byte[digest.length + SALT_LENGTH];
  //将盐的字节拷贝到生成的加密口令字节数组的前12个字节,以便在验证口令时取出盐
  System.arraycopy(salt, 0, pwd, 0, SALT_LENGTH);
  //将消息摘要拷贝到加密口令字节数组从第13个字节开始的字节
  System.arraycopy(digest, 0, pwd, SALT_LENGTH, digest.length);
  //将字节数组格式加密后的口令转化为16进制字符串格式的口令
  return byteToHexString(pwd);
 }
}

测试类——Client,代码如下:

package com.zyg.security.md5;

import java.io.UnsupportedEncodingException;
import java.security.NoSuchAlgorithmException;
import java.util.HashMap;
import java.util.Map;

public class Client {
 private static Map users = new HashMap();
 
 public static void main(String[] args){
  String userName = "zyg";
  String password = "123";
  registerUser(userName,password);
  
  userName = "changong";
  password = "456";
  registerUser(userName,password);
  
  String loginUserId = "zyg";
  String pwd = "1232";
  try {
   if(loginValid(loginUserId,pwd)){
    System.out.println("欢迎登陆!!!");
   }else{
    System.out.println("口令错误,请重新输入!!!");
   }
  } catch (NoSuchAlgorithmException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (UnsupportedEncodingException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } 
 }
 
 /**
  * 注册用户
  * 
  * @param userName
  * @param password
  */
 public static void registerUser(String userName,String password){
  String encryptedPwd = null;
  try {
   encryptedPwd = MyMD5Util.getEncryptedPwd(password);
   
   users.put(userName, encryptedPwd);
   
  } catch (NoSuchAlgorithmException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (UnsupportedEncodingException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
 }
 
 /**
  * 验证登陆
  * 
  * @param userName
  * @param password
  * @return
  * @throws UnsupportedEncodingException 
  * @throws NoSuchAlgorithmException 
  */
 public static boolean loginValid(String userName,String password) 
    throws NoSuchAlgorithmException, UnsupportedEncodingException{
  String pwdInDb = (String)users.get(userName);
  if(null!=pwdInDb){ // 该用户存在
    return MyMD5Util.validPassword(password, pwdInDb);
  }else{
   System.out.println("不存在该用户!!!");
   return false;
  }
 }
}
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