--- Comment #6 from Amgine <> ---
(In reply to shashank jaiswal from comment #4)
> As per the above points :
> I have proposed the idea on
> * An arbitary(or properly indexed/sorted)image taken from mediaWiki
> Database, split into (n x m) matrix using GD and then images are rotated and
> then set as Captcha image. A spam bot may need to validation it for (n*m)!
> times. Incase if n>3 & m>3 => Total number of combinations possible would be
> more than (3*3)! = 362880 clearly image captcha Validation for more than
> 362880 times.
> * The CAPTCHA is automatically created from big pools of image files from
> mediawiki. There won't be any manual selection of images or other types of
> extra human work.
> * Proper indexing of Image files from mediawiki can be done which can be
> region based local image if required.
> * Yes it's Non-discriminatory to users depending on their
> language.(Multilingual)
> * Usable in a mobile context:
>     This can be pretty much interactive for touchscreen phone users.
>     For other phones we can go with simpler ones like "Simple Image based
> Captcha with numbers or alpha-Numeric multi-Case character written on it
> along with some lines and similar effects using GD".
> Thanks.

js-based game captchas (Are You A Human) are most-easily solved by
reverse-engineering the js and determining how it decides you've solved it.
XRumer includes several modules to solve a few hundred of them. The other
method is to hire out the game-playing to subcontractors.

With the image rotations, you will need to determine which images with known
humans have a high rate of failure to identify the correct orientation, and
remove them from the pool. As far as I am aware this quality assurance step
cannot be automated. (One possible method for distributing this task is to ask
all logins to optionally identify 'up' for an image, and those which are
auto-confirmed accounts and choose to answer can be assumed to be human.
Figuring out how to do this task before and after user login should be quite
the challenge.) 

Likewise, I believe you will need to add quality monitoring to any other
captcha method. Selecting random images from the millions of files available on
Commons may seem like an easy solution, but it will result in contextually
inneffective problems: the goal of the captcha is to let humans in easily, not
to keep bots out. If the humans do not get through easily, the site will not be
used and the purpose for the captcha is lost.

The captcha may be non-discriminatory based on language, but does it work for
someone who cannot see a full spectrum of color? Almost all photo effects which
cause distortion of the initial image will be exceptionally difficult for
people with even mild levels of dyslexia. I can introduce you to several
wikimedians with degrees of visual impairment who will be unable to solve
several of your proposed captchas.

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