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[nycphp-talk] easily defeating captchas using automated imageanalysis

inforequest 1j0lkq002 at sneakemail.com
Tue Nov 2 16:33:09 EST 2004


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Original Message:
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you know if there is a way to make the test there is a way to break it ;)

-- 
Joseph Crawford Jr.
Codebowl Solutions
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Actually, it is not quite that simple. The point of a captcha was to get
past that observation (if a system built it, a system can beat it). The
Captcha was to be a turing test.. something that only a human could solve. 

The most obvous flaw with the graphic captcha was that it was visual, and
therefore *specific* --which by definition made it "discriminatory" --
against the visually impaired -- and also solveable. It is the use of
machines to implement the test that causes it to be machine crackable.

Think about typed print (typefaces) vs. cursive (script handwriting). Why
wasn't the captcha created using cursive? That would have made it
infinitely harder to crack for machines, but I bet most humans could solve
a cursive captcha as well as some of the graphic ones I have seen. Of
course it is really hard to make a machine write human-style cursive --
perhaps equally as hard as it is to make a machine that can read
human-style cursive?

Where there is a will there is a way... this is simply not a turing test. 

What wouldit take to build a massive Internet database of cursive words,
collected continuously and used for captchas? Universal pen input,
probably. until then, what do we have?

-=john andrews









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