<?php
function auth_encrypt($txt, $key)
{
    srand((double)microtime() * 1000000);
    $encrypt_key = md5(rand(0, 32000));
    $ctr = 0;
    $tmp = '';
    for($i = 0;$i < strlen($txt); $i++)
    {
        $ctr = $ctr == strlen($encrypt_key) ? 0 : $ctr;
        $tmp .= $encrypt_key[$ctr] . ($txt[$i] ^ $encrypt_key[$ctr++]);
    } 
    return base64_encode(auth_key($tmp, $key));
} 

function auth_decrypt($txt, $key)
{
    $txt = auth_key(base64_decode($txt), $key);
    $tmp = '';
    for ($i = 0;$i < strlen($txt); $i++)
    {
        $md5 = $txt[$i];
        $tmp .= $txt[++$i] ^ $md5;
    } 
    return $tmp;
} 

function auth_key($txt, $encrypt_key)
{
    $encrypt_key = md5($encrypt_key);
    $ctr = 0;
    $tmp = '';
    for($i = 0; $i < strlen($txt); $i++)
    {
        $ctr = $ctr == strlen($encrypt_key) ? 0 : $ctr;
        $tmp .= $txt[$i] ^ $encrypt_key[$ctr++];
    } 
    return $tmp;
} 

?>