Webseite von Michael Rennecke

define(KEY, "Ich bin ein Key");
define(IV, "KlyV6gxG3MOPzlfuj8azF6sKKTnsdsiN58i0zjHA0EU=");
 
function Crypt($plaintext){
    $td = mcrypt_module_open('rijndael-256', '', 'ofb', '');
 
    $iv = base64_decode(IV);
    $ks = mcrypt_enc_get_key_size($td);
 
     /* Create key */
    $key = substr(md5(KEY), 0, $ks);
 
    /* Intialize encryption */
    mcrypt_generic_init($td, $key, $iv);
 
    /* Encrypt data */
    $encrypted = mcrypt_generic($td, $plaintext);
 
    /* Terminate decryption handle and close module */
    mcrypt_generic_deinit($td);
    mcrypt_module_close($td);
 
    return base64_encode($encrypted);
}
 
function Decrypt($chiffre){
    $td = mcrypt_module_open('rijndael-256', '', 'ofb', '');
 
    $iv = base64_decode(IV);
    $ks = mcrypt_enc_get_key_size($td);
 
     /* Create key */
    $key = substr(md5(KEY), 0, $ks);
 
    $chiffre = base64_decode($chiffre);
    mcrypt_generic_init($td, $key, $iv);
    $plaintext = mdecrypt_generic($td, $chiffre);
 
    mcrypt_generic_deinit($td);
    mcrypt_module_close($td);
 
    return $plaintext;
}
 
function draw_captcha_form(){
    .....
    $time = time() + 60*30;
    $captchaSolution = "Test"
    echo "\t\n\tBitte Captcha lösen<br/>\n";
    // erzeuge ein Captcha
    echo "\t\n";
    echo "\t" . '
<input name="captvalue" id="captvalue" value="" size="40" tabindex="4" type="text"/>' . "\n";
    echo "\t"    . '
<input name="captcha" value="'. Crypt($time . "~" . $captchaSolution . "~" . $REMOTE_ADDR) . '" type="hidden"/>' . "\n";
}
 
function check_post($) {
    ....
    $captcha = $_POST['captvalue'];
    list($timeOld, $secret, $addr) = explode('~',Decrypt($_POST['captcha']));
    ....
    if($timeOld <= time()){
            echo "Deine Zeit ist abgelaufen";
            return;
    }
    if($addr != $REMOTE_ADDR){
            echo "Falsche IP";
            return;
    }
    if($secret != $captcha){
            echo "Falsches Captcha";
            return;
    }
    .....
}