> > My understanding of the system is that they have one known word (ie
> > dictionary) and one unknown word (from book) person enters 
> known word 
> > for auth, and that gains them access, unknown word if it 
> agrees with 3 
> > other people is then used for the text.
> 
> I am not following you here. At point 0 a program cuts a 
> piece of book text image from a larger page and makes it into 
> a Captcha (warps it etc). It may first try to OCR it and end 
> up with 5 guesses for a word. Then it will serve the next 5 
> Captcha requests using the warped picture and one of the 5 words each.
> That gives the turks 20% success chances at the first try but 
> none of them know it and neither does the computer that 
> prepared the question. 


You get shown 2 words.  The server knows what the first one is, the second
is cut from the book it's processing.  The person 'solving' the captcha see
something like:

Green /\/\33T

The solution is 'Green Meet', you need to at least get 'Green' right to
proceed.  Your guess for the second part gets logged.  Tally 10 results, 8
match, so the unknown word is 'Meet'.

The next captcha may be '/\/\33T C@t', since 'Meet' is now known, but 'C@t'
isn't.

I love how forums have captchas on their search pages now.  Actually I
don't, it's bloody annoying.

Tony

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist