-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Robin H. Johnson wrote:
> On Wed, May 27, 2009 at 01:45:24PM -0500, Dale wrote:
>> Is there something besides a captcha that can be used?  I hate those
>> things because they make no sense to me.  I usually just give up when I
>> encounter one of these and try three or four times with no success.  The
>> ones that look like broken glass or something are the ones I don't even
>> try anymore.  I can't get past one of those.
> recaptcha [1] is very common at this point, offloads the problem to an
> external service, supports visually-challenged users, and includes it's
> own detection of brute forcing from IP addresses and subnets.
> 
> If that's not acceptable to you, I'll just deploy calculus-captcha.
> calculus-captcha is best viewed on this page here:
> http://random.irb.hr/signup.php
> (reload a few times to see the fun they had in qualifying questions).

The reCAPTCHA page mentions[1] that simple text recognition (with minimal
distortion) is easy to do with computer programs. Given that the
calculus-captcha are non-distorted LaTeX'ed formulas we should therefore
probably assume that computers can read those formulas. They only seem to have
very few kinds of questions (zeros of small polynomials, differentiation of some
trigonometric functions (only cos and sin), arithmetic), all of which are
extremely simple especially for a program[1]. If this CAPTCHA becomes widespread
someone WILL break it.

On the other hand I like that reCAPTCHA puts your answers to use for automatic
digitizations of books. Unfortunately their "Stop spam, read books" message
doesn't make this very clear unless you already know.

Marijn

[1]:http://recaptcha.net/captcha.html

- --
If you cannot read my mind, then listen to what I say.

Marijn Schouten (hkBst), Gentoo Lisp project, Gentoo ML
<http://www.gentoo.org/proj/en/lisp/>, #gentoo-{lisp,ml} on FreeNode
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.0.11 (GNU/Linux)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org

iEYEARECAAYFAkodvLMACgkQp/VmCx0OL2zK/QCgmt+/RincRzXtmuGNTxsE4Yd+
wo8An2zcFsPPaxpzbB75lYlnFCAg1o8q
=glct
-----END PGP SIGNATURE-----