<?php
/*
 * Ourphp - CMS建站系统
 * Copyright (C) 2014 ourphp.net
 * 开发者：哈尔滨伟成科技有限公司
*/
if(!defined('OURPHPNO')){exit('no!');}

function authcode($string, $operation = 'DECODE', $key = '', $expiry = 0) {  
    $ckey_length = 4;  
    $key = md5($key ? $key : C('AU_KEY'));  
    $keya = md5(substr($key, 0, 16));  
    $keyb = md5(substr($key, 16, 16));  
    $keyc = $ckey_length ? ($operation == 'DECODE' ? substr($string, 0, $ckey_length): substr(md5(microtime()), -$ckey_length)) : '';  
    $cryptkey = $keya.md5($keya.$keyc);  
    $key_length = strlen($cryptkey);  
    $string = $operation == 'DECODE' ? base64_decode(substr($string, $ckey_length)) : sprintf('%010d', $expiry ? $expiry + time() : 0).substr(md5($string.$keyb), 0, 16).$string;  
    $string_length = strlen($string);  
    $result = '';  
    $box = range(0, 255);  
    $rndkey = array();  
    for($i = 0; $i <= 255; $i++) {  
        $rndkey[$i] = ord($cryptkey[$i % $key_length]);  
    }  
    for($j = $i = 0; $i < 256; $i++) {  
        $j = ($j + $box[$i] + $rndkey[$i]) % 256;  
        $tmp = $box[$i];  
        $box[$i] = $box[$j];  
        $box[$j] = $tmp;  
    }  
    for($a = $j = $i = 0; $i < $string_length; $i++) {  
        $a = ($a + 1) % 256;  
        $j = ($j + $box[$a]) % 256;  
        $tmp = $box[$a];  
        $box[$a] = $box[$j];  
        $box[$j] = $tmp;  
        $result .= chr(ord($string[$i]) ^ ($box[($box[$a] + $box[$j]) % 256]));  
    }  
    if($operation == 'DECODE') {  
        if((substr($result, 0, 10) == 0 || substr($result, 0, 10) - time() > 0) && substr($result, 10, 16) == substr(md5(substr($result, 26).$keyb), 0, 16)) {  
            return substr($result, 26);  
        } else {  
            return '';  
        }  
    } else {  
        return $keyc.str_replace('=', '', base64_encode($result));  
    }  
}
?>