MessageDigest 加密和解密2

package com.drawthink.platform.util;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * MD5类:加密
 */
public class MD5Util {
    //获取字符串的MD5串
    public static String Md5(//
            String plainText //原字符串
    ) {
        if (plainText == null) {
            return null;
        }
        StringBuffer buf = new StringBuffer();
        try {
            MessageDigest md = MessageDigest.getInstance("MD5");
            md.update(plainText.getBytes());
            md.reset();
            byte b[] = md.digest();
            int i;
            for (int offset = ; offset < b.length; offset++) {
                i = b[offset];
                if (i < ) {
                    i += ;
                }
                if (i < ) {
                    buf.append("");
                }
                buf.append(Integer.toHexString(i));
            }
        } catch (NoSuchAlgorithmException ex) {
            ex.printStackTrace();
        }
        return buf.toString();
    }
}

-------------------解密---------------------------
package com.drawthink.platform.util;

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 = ;

    /**
    * 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() / );
        byte[] result = new byte[len];
        char[] hexChars = hex.toCharArray();
        for (int i = ; i < len; i++) {
            int pos = i * ;
            result[i] = (byte) (HEX_NUMS_STR.indexOf(hexChars[pos]) <<
            | HEX_NUMS_STR.indexOf(hexChars[pos + ]));
        }
        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 = ; i < b.length; i++) {
             String hex = Integer.toHexString(b[i] & 0xFF);
             if (hex.length() == ) {
                 hex = '' + 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, , salt, , 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, , 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, , pwd, , 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, , 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);
     }

     //测试方法
     public static void main(String[] args) {
        try {
            String password = "5a105e8b9d40e1329780d62ea2265d8a";
            boolean encryptedPwd = MyMD5Util.validPassword(password,password);
            System.out.println(encryptedPwd);
        } catch (NoSuchAlgorithmException | UnsupportedEncodingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}