Knablart-CAPTCHA v. 0.6:
  a stylish off-line B/W CAPTCHA picture generator in C++/QT3 and a
  cookieless, databaseless, AJAX aware checking system in PHP

Copyright (C) 2003-2007 by Jarno Elonen <elonen@iki.fi>.
Licensed under GNU Lesser General Public License (LGPL).
See LGPL.txt for details.

Quickstart:
  + install
    + PHP with mcrypt, db4 and CLI support ('php' executable)
    + imagemagick
    + g++
    + QT3 and qmake
  + run ./build-all.sh and wait forever as it generates 5000 images
  + If everything went right, you should now have a
    "captcha.db" of about 7MB worth of CAPTCHA images.
    They should also be in pic-generator/generated/ as separate GIFs
  + Edit config.inc appropriately
    + Check your installation path
    + Change the encryption key. Don't use the default!
  + Put the whole thing under some web directory and try out usage-example.php.
    + Don't forget to copy .htaccess, too! Otherwise the DB and your
      encryption key will be world-accessible!

How it works:
  + Off-line preparation:
    + Creates a large enough amount of challenge pictures (gifs)
      with a C++/QT3 program (QT4 probably won't work)
    + Puts them into a DBA (default: db4) file
  + On-line:
    + Creates HTML and Javascript for the challenge with one PHP call
      (see usage-example.php).
    + Sends an encrypted version of the correct answer and a timestamp
      along with the form code in a "type=hidden" field.
      + This makes and HTTP session management unnecessary.
      + Points the <img> tag to a PHP script that decrypts the answer
        field and fetches the correct image data from the DBA file.
    + If Javascript is enabled, checks user's answer AJAX-style
      (immediately by a Javascript HTTP request) and displays
      "OK" or "Wrong" even before the user hits Submit. Failure
      results in a 2-3 second delay.
    + When checking the answer (on HTTP server side), decrypts the
      correct answer and fails expired (time configurable) challenges
      to prevent reuse.

Some options:
  + Localization strings: config.inc
  + The PHP dba driver used for the pics: config.inc
  + Number of generated pics. See: pic-generator/build-and-gen.sh
