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Q: Website account creation pictures of messed up text ( Answered,   2 Comments )
Subject: Website account creation pictures of messed up text
Category: Computers > Graphics
Asked by: hmetz-ga
List Price: $15.00
Posted: 12 Aug 2006 23:55 PDT
Expires: 11 Sep 2006 23:55 PDT
Question ID: 755469
When you go to create a web account on some websites they have a
picture with letters and numbers and other markings, and they want you
to type what you see into a box to prove that your not a computer.
What is that called and why can't OCR reconize it?
Subject: Re: Website account creation pictures of messed up text
Answered By: sycophant-ga on 13 Aug 2006 00:41 PDT

The technology you're talking about is called CAPTCHA (Completely
Automated Public Turing test to tell Computers and Humans Apart).

The idea, obviously, is that only humans can decipher the text in the
image due to complicating factors such as distortion, low contrast and
background noise. Common web bots have no method for dealing with it
at all, and basic OCR systems are unable to decode the text at all.

However in practice most CAPTCHA systems can be defeated with
specifically tuned OCR systems. But most systems will defeat most
traditional OCR techniques so they remain largely effective. By
targeting a specific CAPTCHA system with a specific OCR routine it is
possible to attain a very high recognition rate - higher in fact than
many humans can manage.

This technology is very well documented in the following Wikipedia entry:

Subject: Re: Website account creation pictures of messed up text
From: the_sniff-ga on 30 Sep 2006 03:20 PDT
One of the projects intended to defeating CAPTCHAs is
Subject: Re: Website account creation pictures of messed up text
From: nabeelzeeshan-ga on 15 Oct 2006 17:39 PDT
that process is called 'Word Verification' .. was that what you wanted to know?

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