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Authoring/Development - Tools of the Trade: reCAPTCHA
A CAPTCHA (Completely Automated Turing Test To Tell Computers and Humans
Apart) is an application that tries to tell the difference between a human
and a computer. These applications are widely used
to help prevent spam because it will prevent junk e-mail programs called
spam bots to send messages or fill out forms. However, it will allow
human users to proceed in sending the e-mail or fill out
the form. A CAPTCHA presents the user with a couple different words or
character strings that the user then has to then retype into a text field.
If the user is human, this request does not pose
a problem. On the other hand, if the user is a spam bot, then it will not
be able to "read" the CAPTCHA and will be stopped in its tracks.
reCAPTCHA is a CAPTCHA program that does not display random words or
character strings but instead presents words that assist in the digitizing
of physical books. reCAPTCAHA also conforms to Section
508 in the United States by providing an audio version of reCAPTCHA for
visually-impaired individuals.
You can implement reCAPTCHA on your site by following the instructions
below:
- Visit (http://recaptcha.net/)
- Sign-up for a
reCAPTCHA account (it's free)
- Enter the domain name you
wish to use
- Write down your public and private key
- Log into your Web hosting account via SSH
- Run the command
"cp /usr/www/cgi-bin/recaptcha_formmail.pl ." in the directory where your Web site's files reside
- Open the file up and set $PRIVATE_KEY to the
private key you were given
- Set up your formmail form as described in
our formmail article with the following two changes
- Call your edited
version of recaptcha_formmail.pl instead of
/cgi-sys/formmail.pl (in the form action)
- Insert the sample code given
at recaptcha.net and include your public key as instructed by
recaptcha.net (in the HTML of your form page)
More information on implementing reCAPTCHA on your site can be found on
reCAPTCHA's resources page: http://recaptcha.net/resources.html
The Perl, PHP, Ruby, and Python interfaces to reCAPTCHA mentioned on this
resource page are now installed on all pair Networks servers for your use.
Please provide
feedback on this article.
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