<?php
require_once 'Crypt/HMAC.php';

$hash = new Crypt_HMAC('SECRETKEY', 'sha1');

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