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Re: reCAPTCHA implementation problems

From: Gez Lemon <gez.lemon@gmail.com>
Date: Mon, 16 Jul 2007 19:00:39 +0100
Message-ID: <e2a28a920707161100x3fe77083mcfb3bd4b71ea27e@mail.gmail.com>
To: "Ben Maurer" <bmaurer@andrew.cmu.edu>
Cc: "Al Gilman" <Alfred.S.Gilman@ieee.org>, wai-xtech@w3.org, "Colin McMillen" <mcmillen@cs.cmu.edu>

Hi Ben,

On 16/07/07, Ben Maurer <bmaurer@andrew.cmu.edu> wrote:
<quote>
Well, if they disable images, they're screwed with CAPTCHAs anyways --
they won't be able to see the images. A blind, dialup user trying to save
bandwidth would still be able to use the CAPTCHA because they'd see the
psudo-alt text.
</quote>

Not at all. Presumably, the CAPTCHA won't have alt text, or any robot
would be able to answer it. People who deliberately disable all images
can enable any image they like, providing they know it's there - so
would choose to display the CAPTCHA image to solve it.

The technique you described used CSS for a functional link ("get a new
challenge"). If the text is moved off the screen and replaced with an
image, someone with CSS enabled but images disabled would have no idea
that there was text there that has been removed. You asked if there
were any issues with that approach, and that is an issue.

Gez


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Received on Monday, 16 July 2007 18:00:45 GMT

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