PHP加密解密算法

/**
  * 加密函数
  * [url=home.php?mod=space&uid=952169]@Param[/url] mixed $txt 需要加密的数据
  * @param string $key 密钥
  * [url=home.php?mod=space&uid=155549]@Return[/url] string 返回加密结果
  */
 function encrypt($txt, $key = ''){
    if (empty($txt)) return $txt;
    if (is_array($txt)) $txt = serialize($txt);
    if (empty($key)) $key = md5('MD5_KEY');
    $chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_.";
    $ikey ="-x6g6ZWm2G9g_vr0Bo.pOq3kRIxsZ6rm";
    $nh1 = rand(0,64);
    $nh2 = rand(0,64);
    $nh3 = rand(0,64);
    $ch1 = $chars{$nh1};
    $ch2 = $chars{$nh2};
    $ch3 = $chars{$nh3};
    $nhnum = $nh1 + $nh2 + $nh3;
    $knum = 0;$i = 0;
    while(isset($key{$i})) $knum +=ord($key{$i++});
    $mdKey = substr(md5(md5(md5($key.$ch1).$ch2.$ikey).$ch3),$nhnum%8,$knum%8 + 16);
    $txt = base64_encode(time().'_'.$txt);
    $txt = str_replace(array('+','/','='),array('-','_','.'),$txt);
    $tmp = '';
    $j=0;$k = 0;
    $tlen = strlen($txt);
    $klen = strlen($mdKey);
    for ($i=0; $i<$tlen; $i++) {
        $k = $k == $klen ? 0 : $k;
        $j = ($nhnum+strpos($chars,$txt{$i})+ord($mdKey{$k++}))%64;
        $tmp .= $chars{$j};
    }
    $tmplen = strlen($tmp);
    $tmp = substr_replace($tmp,$ch3,$nh2 % ++$tmplen,0);
    $tmp = substr_replace($tmp,$ch2,$nh1 % ++$tmplen,0);
    $tmp = substr_replace($tmp,$ch1,$knum % ++$tmplen,0);
    return $tmp;
 }
 /**
  * 解密函数
  * @param string $txt 需要解密的字符串
  * @param string $key 密匙
  * @return string 字符串类型的返回结果
  */
 function decrypt($txt, $key = '', $ttl = 0){
    if (empty($txt)) return $txt;
    if (empty($key)) $key = md5('MD5_KEY');
    $chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_.";
    $ikey  = "-x6g6ZWm2G9g_vr0Bo.pOq3kRIxsZ6rm";
    $knum  = 0;$i = 0;
    $tlen  = @strlen($txt);
    while(isset($key{$i})) $knum +=ord($key{$i++});
    $ch1 = @$txt{$knum % $tlen};
    $nh1 = strpos($chars,$ch1);
    $txt = @substr_replace($txt,'',$knum % $tlen--,1);
    $ch2 = @$txt{$nh1 % $tlen};
    $nh2 = @strpos($chars,$ch2);
    $txt = @substr_replace($txt,'',$nh1 % $tlen--,1);
    $ch3 = @$txt{$nh2 % $tlen};
    $nh3 = @strpos($chars,$ch3);
    $txt = @substr_replace($txt,'',$nh2 % $tlen--,1);
    $nhnum = $nh1 + $nh2 + $nh3;
    $mdKey = substr(md5(md5(md5($key.$ch1).$ch2.$ikey).$ch3),$nhnum % 8,$knum % 8 + 16);
    $tmp = '';
    $j = 0; $k = 0;
    $tlen = @strlen($txt);
    $klen = @strlen($mdKey);
    for ($i=0; $i<$tlen; $i++) {
        $k = $k == $klen ? 0 : $k;
        $j = strpos($chars,$txt{$i})-$nhnum - ord($mdKey{$k++});
        while ($j<0) $j+=64;
        $tmp .= $chars{$j};
    }
    $tmp = str_replace(array('-','_','.'),array('+','/','='),$tmp);
    $tmp = trim(base64_decode($tmp));
    if (preg_match("/\d{10}_/s",substr($tmp,0,11))){
        if ($ttl > 0 && (time() - substr($tmp,0,11) > $ttl)){
            $tmp = null;
        }else{
            $tmp = substr($tmp,11);
        }
    }
    //解密出来后先反序列化看是否是一个数组信息
    $res = unserialize($tmp);
    if($res){
        return $res;
    }else{
        return $tmp;
    }
}