DES算法要求有一个可信任的随机数源

import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class PasswordEncryption {
    private static final String PASSWORD_CRYPT_KEY = "_hrwps20090716pass_";

    private final static String DES = "DES";

    /**
     * 
     * 加密
     * 
     * @param src
     *            数据源
     * 
     * @param key
     *            密钥，长度必须是8的倍数
     * 
     * @return 返回加密后的数据
     * 
     * @throws Exception
     * 
     */

       public static byte[] encrypt(byte[] src, byte[] key) throws Exception {
      
       // DES算法要求有一个可信任的随机数源
       
        SecureRandom sr = new SecureRandom();
       
        // 从原始密匙数据创建DESKeySpec对象
       
        DESKeySpec dks = new DESKeySpec(key);
       
        // 创建一个密匙工厂，然后用它把DESKeySpec转换成
       
        // 一个SecretKey对象
       
        SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(DES);
       
        SecretKey securekey = keyFactory.generateSecret(dks);
       
        // Cipher对象实际完成加密操作
       
        Cipher cipher = Cipher.getInstance(DES);
       
        // 用密匙初始化Cipher对象
       
        cipher.init(Cipher.ENCRYPT_MODE, securekey, sr);
       
        // 现在，获取数据并加密
       
        // 正式执行加密操作
       
        return cipher.doFinal(src);
       
       }
      
       /**
        * 
        * 解密
        * 
        * @param src
        *            数据源
        * 
        * @param key
        *            密钥，长度必须是8的倍数
        * 
        * @return 返回解密后的原始数据
        * 
        * @throws Exception
        * 
        */
      
       public static byte[] decrypt(byte[] src, byte[] key) throws Exception {
      
        // DES算法要求有一个可信任的随机数源
       
        SecureRandom sr = new SecureRandom();
       
        // 从原始密匙数据创建一个DESKeySpec对象
       
        DESKeySpec dks = new DESKeySpec(key);
       
        // 创建一个密匙工厂，然后用它把DESKeySpec对象转换成
       
        // 一个SecretKey对象
       
        SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(DES);
       
        SecretKey securekey = keyFactory.generateSecret(dks);
       
        // Cipher对象实际完成解密操作
       
        Cipher cipher = Cipher.getInstance(DES);
       
        // 用密匙初始化Cipher对象
       
        cipher.init(Cipher.DECRYPT_MODE, securekey, sr);
       
        // 现在，获取数据并解密
       
        // 正式执行解密操作
       
        return cipher.doFinal(src);
      
       }
      
       /**
        * 
        * 密码解密
        * 
        * @param data
        * 
        * @return
        * 
        * @throws Exception
        * 
        */
      
       public final static String decrypt(String data) {
      
       try {
      
        return new String(decrypt(hex2byte(data.getBytes()), PASSWORD_CRYPT_KEY.getBytes()));
      
       } catch (Exception e) {
      
       }
      
       return null;
      
       }
      
       /**
        * 
        * 密码加密
        * 
        * @param password
        * 
        * @return
        * 
        * @throws Exception
        * 
        */
      
       public final static String encrypt(String password) {
      
       try {
      
       return byte2hex(encrypt(password.getBytes(), PASSWORD_CRYPT_KEY
       .getBytes()));
       } catch (Exception e) {
      
       }
      
       return null;
      
       }
      
       /**
        * 
        * 二行制转字符串
        * 
        * @param b
        * 
        * @return
        * 
        */
      
       public static String byte2hex(byte[] b) {
      
        String hs = "";
       
        String stmp = "";
       
        for (int n = 0; n  < b.length; n++) {
       
        stmp = (java.lang.Integer.toHexString(b[n] & 0XFF));
       
        if (stmp.length() == 1)
       
        hs = hs + "0" + stmp;
       
        else
       
        hs = hs + stmp;
       
        }
       
        return hs.toUpperCase();
       
       }
        
       public static byte[] hex2byte(byte[] b) {
       
        if ((b.length % 2) != 0)   
       
        throw new IllegalArgumentException("长度不是偶数");
       
        byte[] b2 = new byte[b.length / 2];
       
        for (int n = 0; n  < b.length; n += 2) {
       
        String item = new String(b, n, 2);
       
        b2[n / 2] = (byte) Integer.parseInt(item, 16);
       
       }
      
       return b2;  
       }
   
    /**
     * 获得一个随机的加密密码
     * @param minLen:密码的最小长度
     * @param maxLen:密码的最大长度
     * @return
     */
    public String getRandomEncryptPassword(int minLen,int maxLen){
        String randPassword="";
        String randChar="abcdefghijklmnopqrstuvwxyz1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ";
        int randNum=(int)(Math.random()*(maxLen-minLen+1))+minLen;  //密码的随机长度(minLen<=length<=maxLen)
        for(int i=0;i<randNum;i++){
            int randCharIndex=(int)(Math.random()*randChar.length());
            randPassword=randPassword+randChar.charAt(randCharIndex);
        }
        String encryptPassword=this.encrypt(randPassword);
        return encryptPassword;
    }
//    public ActionForward doUserPasswordChange(ActionMapping mapping, ActionForm form,
//            HttpServletRequest request, HttpServletResponse response) {
//       
//        String password=request.getParameter("oldpass");
//        String newPassword=request.getParameter("confirmPassword");
//        TSmUser userLogin=(TSmUser) request.getSession().getAttribute("loginUser");
//        PasswordEncryption passWordEncry = new PasswordEncryption();
//        if(!userLogin.getUserPassword().equals(passWordEncry.encrypt(password.trim()))){
//            request.getSession().setAttribute("msgs", "校验输入的旧密码错误");
//            return mapping.findForward("change");
//        }else if(userLogin.getUserPassword().equals(passWordEncry.encrypt(newPassword.trim()))){
//            request.getSession().setAttribute("msgs", "输入的新密码于旧密码相同");
//            return mapping.findForward("change");
//        }else{
//            userLogin.setUserPassword(passWordEncry.encrypt(newPassword.trim()));
//            try{
//            tsmuserImpl.update(userLogin);
//            }catch(Exception e){
//                request.getSession().setAttribute("msgs", "修改密码失败");
//                return mapping.findForward("change");
//            }
//            return mapping.findForward("success");
//        }
//    }
   
    public static void main(String[] args) {
        String s=PasswordEncryption.decrypt("4094D62D6C8C89C7");
        System.out.println(s);
    }

}