Casual Ideas for Software Development

Image-Based Bot Detector is a variant of image-based CAPTCHAs that uses human ability to recognize a distorted region on the image he never seen before. Licence Copyright (c) 2007, Mykola Tarasyuk All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: * Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. * Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. * The name of the copyright holder may not be used to endorse or promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF ME...

Demo project that illustrates the idea of the image-based CAPTCHA . The code overview The proposed image-based CAPTCHA control works in such a way: a visitor sees a picture with a distorted part and he has to click elsewhere in the anomalous region boundaries. The point he clicks on will be marked with a red spot. The control fulfils a double functionality, it renders its HTML content and forms the picture itself. It has two child controls: an image, and a hidden field that serves to store coordinates of the visitor's chosen point. The image URL forms by adding the special parameter to the currently requested URL. When the request to this new URL comes, the control interrupts the usual process of page loading and writes the image as a byte array in the response. protected override void OnInit(EventArgs e) { if (HttpContext.Current.Request[queryKey] != null) DrawImage(); ..... } private void DrawImage() { Bitmap bitmap; //the image creation goes here ...

The brief overview of the most known implementations Carnegie Mellon's PIX CAPTCHA - the so called "naming images CAPTCHA" - the user sees a few pictures, and has to select a word that is appropriate to all the shown pictures. The main problem of this type of CAPTCHAs is misspelling while writing the answer, and synonyms for the answer-word (for example: dog, hound, pooch). In the described case, this is solved by means of transferring all the variants of the answer to the client side. Oli Warner's KittenAuth - in order to prove his humanity, the visitor has to select all animals of a specified species among the proposed pictures. But, the limited number of pictures allows to recreate the picture base manually. Microsoft's Asirra - in outline, it is similar to KittenAuth - the user has to distinguish cats from dogs - but, it works with an extremely large array of pictures (photos of homeless animals from the specialized site), and a reconstruction of the pictur...