This class in PHP can be used as a simple method of authentication. It uses the MD5 of a string as secret and can be easily bookmarked. It doesn't uses cookies, session or login/password combo, just a single secret passed by URL.

Example: http://example.org/file.php?key=7315a012ecad1059a3634f8be1347846

In this case, 7315a012ecad1059a3634f8be1347846 is the MD5 of my password: "MySecretPassword".

Source Code

All source code is online here.

How to use it

<?php

 require_once('SimpleAuth.class.php');

 $simpleAuth = new SimpleAuth('MySecretPassword');

 /**
  * Valid URLs:
  * http://example.org/file.php?key=7315a012ecad1059a3634f8be1347846
  * http://example.org/file.php?key=MySecretPassword
  */
 if ($simpleAuth->isValid()) {
   // Secure Zone
 } else {
   // Wrong Password
 }

 /**
  * Show MD5 key, valid URL:
  * http://example.org/file.php?key=MySecretPassword&help
  */
 if ($simpleAuth->isValid() && isset($_GET['help'])) {
    echo $simpleAuth->getSecret(); // Show MD5 key
 }

?>