[tlug] CAPTCHA on keitai

["Stephen J. Turnbull" <stephen@example.com>]

Dave M G writes:

 > I ask because a lot of CAPTCHAs I've seen are seemingly a little too 
 > large for a lot of keitai screens, and the ones that do fit are 
 > potentially to easy to crack.

All captcha protection is theoretically easy to crack.  Remember, a
computer will happily try three or four or five times if the captcha
is difficult; a human will not.  So even rather poor OCR will
eventually get a match, and your system is toast.

I think the best way to treat captchas is to assume that for a while
even a trivial catcha will do fine.  (They do work in practice, after
all.)  But keep looking for a better way to do it.  (They *will* get
broken -- I've seen at least two scripts that claim excellent results
based on common FLOSS components.)