Java實現MD5加密解密類

Java實現MD5加密以及解密類，附帶測試類，具體見代碼。

MD5加密解密類——MyMD5Util,代碼如下

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;

/**
* 將16進制字符串轉換成字節數組
* @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;
}

/**
* 將指定byte數組轉換成16進制字符串
* @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();
}

/**
* 驗證口令是否合法
* @param password
* @param passwordInDb
* @return
* @throws NoSuchAlgorithmException
* @throws UnsupportedEncodingException
*/
public static boolean validPassword(String password, String passwordInDb)
throws NoSuchAlgorithmException, UnsupportedEncodingException {
//將16進制字符串格式口令轉換成字節數組
byte[] pwdInDb = hexStringToByte(passwordInDb);
//聲明鹽變量
byte[] salt = new byte[SALT_LENGTH];
//將鹽從數據庫中保存的口令字節數組中提取出來
System.arraycopy(pwdInDb, 0, salt, 0, SALT_LENGTH);
//創建消息摘要對象
MessageDigest md = MessageDigest.getInstance("MD5");
//將鹽數據傳入消息摘要對象
md.update(salt);
//將口令的數據傳給消息摘要對象
md.update(password.getBytes("UTF-8"));
//生成輸入口令的消息摘要
byte[] digest = md.digest();
//聲明一個保存數據庫中口令消息摘要的變量
byte[] digestInDb = new byte[pwdInDb.length - SALT_LENGTH];
//取得數據庫中口令的消息摘要
System.arraycopy(pwdInDb, SALT_LENGTH, digestInDb, 0, digestInDb.length);
//比較根據輸入口令生成的消息摘要和數據庫中消息摘要是否相同
if (Arrays.equals(digest, digestInDb)) {
//口令正確返回口令匹配消息
return true;
} else {
//口令不正確返回口令不匹配消息
return false;
}
}

/**
* 獲得加密後的16進制形式口令
* @param password
* @return
* @throws NoSuchAlgorithmException
* @throws UnsupportedEncodingException
*/
public static String getEncryptedPwd(String password)
throws NoSuchAlgorithmException, UnsupportedEncodingException {
//聲明加密後的口令數組變量
byte[] pwd = null;
//隨機數生成器
SecureRandom random = new SecureRandom();
//聲明鹽數組變量
byte[] salt = new byte[SALT_LENGTH];
//將隨機數放入鹽變量中
random.nextBytes(salt);

//聲明消息摘要對象
MessageDigest md = null;
//創建消息摘要
md = MessageDigest.getInstance("MD5");
//將鹽數據傳入消息摘要對象
md.update(salt);
//將口令的數據傳給消息摘要對象
md.update(password.getBytes("UTF-8"));
//獲得消息摘要的字節數組
byte[] digest = md.digest();

//因為要在口令的字節數組中存放鹽，所以加上鹽的字節長度
pwd = new byte[digest.length + SALT_LENGTH];
//將鹽的字節拷貝到生成的加密口令字節數組的前12個字節，以便在驗證口令時取出鹽
System.arraycopy(salt, 0, pwd, 0, SALT_LENGTH);
//將消息摘要拷貝到加密口令字節數組從第13個字節開始的字節
System.arraycopy(digest, 0, pwd, SALT_LENGTH, digest.length);
//將字節數組格式加密後的口令轉化為16進制字符串格式的口令
return byteToHexString(pwd);
}
}

測試類——Client,代碼如下：

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("歡迎登陸！！！");
}else{
System.out.println("口令錯誤，請重新輸入！！！");
}
} catch (NoSuchAlgorithmException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

/**
* 注冊用戶
*
* @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();
}
}

/**
* 驗證登陸
*
* @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){ // 該用戶存在
return MyMD5Util.validPassword(password, pwdInDb);
}else{
System.out.println("不存在該用戶！！！");
return false;
}
}
}

Java 8 中 HashMap 的性能提升 http://www.linuxidc.com/Linux/2014-04/100868.htm

Java 8 的 Nashorn 引擎 http://www.linuxidc.com/Linux/2014-03/98880.htm

Java 8簡明教程 http://www.linuxidc.com/Linux/2014-03/98754.htm