PHP 数据加密

<?php

/**
 *
 * 加密
 *
 */

function lock_url($txt, $key = "aiteng") {
    $chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-=+";
    $nh = rand(0, 64);
    $ch = $chars[$nh];
    $mdKey = md5($key . $ch);
    $mdKey = substr($mdKey, $nh % 8, $nh % 8 + 7);
    $txt = base64_encode($txt);
    $tmp = '';
    $i = 0;
    $j = 0;
    $k = 0;
    for ($i = 0; $i < strlen($txt); $i++) {
        $k = $k == strlen($mdKey) ? 0 : $k;
        $j = ($nh + strpos($chars, $txt[$i]) + ord($mdKey[$k++])) % 64;
        $tmp.= $chars[$j];
    }
    return urlencode($ch . $tmp);
}

/**
 *
 * 解密
 *
 */
function unlock_url($txt, $key = "aiteng") {
    $txt = urldecode($txt);
    $chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-=+";
    $ch = $txt[0];
    $nh = strpos($chars, $ch);
    $mdKey = md5($key . $ch);
    $mdKey = substr($mdKey, $nh % 8, $nh % 8 + 7);
    $txt = substr($txt, 1);
    $tmp = '';
    $i = 0;
    $j = 0;
    $k = 0;
    for ($i = 0; $i < strlen($txt); $i++) {
        $k = $k == strlen($mdKey) ? 0 : $k;
        $j = strpos($chars, $txt[$i]) - $nh - ord($mdKey[$k++]);
        while ($j < 0) $j+= 64;
        $tmp.= $chars[$j];
    }
    return base64_decode($tmp);
}
?>