Re: CAPTCHA image validation in web form

[Pete Helgren <Pete@xxxxxxxxxx>]

I guess I misread that post but the more I think about it, the better 
the idea seems to me.  You could have 7 images, generated in random 
order and that followed by the statement that says: "Click on the image 
of the boat" and allow the selection.  If it is correct, perhaps 
challenge them with a second randomly generated set of images with a 
second statement. 

If the answer is incorrect, generate a new set of images and a new 
statement: "Click on the image of the Cat".  Correct selections are 
verified at the server with a few seconds delay to avoid a brute force 
attack.

I also thought the discussion about image sizes and characteristics to 
be interesting as well.  With some randomness in colors, images, sizes 
and resolutions, you could probably have a small number of images that 
could be manipulated into a large number or variants making an automated 
method of guessing correctly difficult to accomplish.

Interesting discussion.

Pete


Nathan Andelin wrote:
> > From: Pete Helgren
> > Couldn't you generate random placement and valid responses each
> > time and store them on the server?  So, boat may be in the first position
> > the first time and then in the 4th position the second time, etc.
> >     
>
> Well, the example that Guillermo posted had just 1 image displayed.  And the challenge was to select the appropriate description from 7 radio group options; only one of which would be correct.
>
> But I think you hit upon a key to a strong captcha.  The number of options should be large.  And the challenge for the client should be random.
>
> It's a lot of work to catalog a large number of images of familiar people, places, and things; along with appropriate descriptions.
>
> But the random idea seems like a good lead.  I've been looking at the CEERAN0 api, and calling it from RPG to come up with a procedure for generating random numbers within a parameter range - like give me a random number between 5 and 8, for example.  Or, give me a number between 1 and 100.  I think I'll add something like that to my toolkit because it seems like something that could be useful for captcha and other things.
>
> Nathan.
>
>
>       
>