<?php
define('SECRETKEY', 'quis custodiet ipsos custodes');

if (isset($_COOKIE['stamp'])) {
    if ($_COOKIE['stamp'] == sha1($_COOKIE['data'] . SECRETKEY)) {
        echo "Validated!\n";
    } else {
        echo "<blink>Not validated</blink>";
    }
} else {
    $_COOKIE['data'] = '00110100011';
    $_COOKIE['stamp'] = sha1($_COOKIE['data'] . SECRETKEY);
}
?>