php 简单加密/解密类

<?php
/**
 * 精简版加密/解密类
 * @author 布衣 QQ 780998900
 * @packge SimpleTools
 * @link http://commoner.cn 布衣博客
 * @copyright http://commoner.cn
 */
class SimpleCrypt{
    /**
     * 密钥
     * 越复杂越好，但字符串长度会整加
     * @var String
     */
    private static $key = 'jdkhvxdicstui';
    /**
     * 用于生成随机字符串
     * @var array
     */
    private static $word = array('a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','v','u','w','x','y','z','A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','V','U','W','X','Y','Z');
    
    /**
     * 加密算法
     * @param $str 需要加密的字符串
     * @return String 加密后的字符串
     */
    public static function encode($str){
        
        //首次加密
        $str = base64_encode($str);
        //计算字符串长度
        $str_num = mb_strlen($str);
        //取一半长度
        $half = ceil($str_num / 2);
        //获取前半和后半字符串
        $head_str = substr($str , 0 , $half);
        $end_str = substr($str , $half , $str_num);
        //计算前半和后半加密次数
        $head_loop_num = $half < 50 ? ceil($half / 5) : ceil($half / 10);
        $end_loop_num = $str_num > 200 ? ceil($str_num / 10) : ceil($str_num /8);
        //生成随机字符串
        $head_rand_loop_num = ($head_loop_num * 10) - $head_loop_num;
        $end_rand_loop_num = ($end_loop_num + $head_loop_num) * 10 - $end_loop_num;
        $head_rand_str = null;
        $end_rand_str = null;
        //前半部分随机字符串
        for($i = 0 ; $i < $head_rand_loop_num ; $i++){
            $head_rand_str .= self::$word[rand(0 , 51) ];
        }
        //后半部分随机字符串
        for($i = 0 ; $i < $end_rand_loop_num ; $i++){
            $end_rand_str .= self::$word[rand(0 , 51)];
        }
        //前半部分内容加密
        for($i = 0 ; $i < $head_loop_num ; $i++){
            $head_str = base64_encode($head_str);
        }
        //撕毁变量
        unset($i);
        //后半部分内容加密
        for($i = 0 ; $i < $end_loop_num ; $i++){
            $end_str = base64_encode($end_str);
        }
        //合并
        $implode_str = $head_rand_str . $head_str . self::$key . base64_encode($head_loop_num) . self::$key . base64_encode($end_loop_num) . self::$key . $end_str . $end_rand_str;
        
        $result = base64_encode($implode_str);
        //以后继续，先返回
        return $result;
    }
    
    /**
     * 解密算法
     * @param $str 需解密的字符串
     * @return String 解密后字符串
     */
    public static function decode($str){
        
        //获取加密信息
        $get = explode(self::$key , base64_decode($str));
        $head_str = $get[0];
        $end_str = $get[3];
        $head_loop_num = base64_decode($get[1]);
        $end_loop_num = base64_decode($get[2]);
        //去除随机字符串的算法
        $head_rand_num = ($head_loop_num * 10) - $head_loop_num;
        $end_rand_num = ($end_loop_num + $head_loop_num) * 10 - $end_loop_num;
        //去除随机字符串，获取原文
        $head_str = substr($head_str , $head_rand_num , strlen($head_str));
        $end_str = substr($end_str , 0 , strlen($end_str) - $end_rand_num);
        //解密前半部分
        for($i = 0 ; $i < $head_loop_num ; $i++){
            $head_str = base64_decode($head_str);
        }
        //撕毁变量
        unset($i);
        //解密后半部分
        for($i = 0 ; $i < $end_loop_num ; $i++){
            $end_str = base64_decode($end_str);
        }
        //合并并解密
        $result = base64_decode($head_str . $end_str);
        
        return $result;
    }
}
?>