Captcha, also known as Completely Automated Public Turing test, is a program
used to distinguish between a human and a bot. You might have used Captcha while
filling an online form or posting comments on a blog. Just to refresh your
memory, these are images containg numbers or words that you are asked to enter
in a box. This is to verify that a human is filling the form and not a bot. The
captcha images are designed in such a way that it is hard for computer programs
to read them. Captchas are used to preventing against bots registering on a
website, protecting spam comments in blogs, preventing brute force attacks on a
website to bypass authentication, etc. reCAPTCHA is one such captcha provider,
which we will talk about in this article.
Humans solve around 60 million CAPTCHAs every day and so reCAPTCHA decided to
utilize such efforts to the process of digitizing books. These books are first
scanned and photographic images are then changed into text through OCR. Now OCR
doesn't read all images, so somebody needs to enter them. reCAPTCHA sends these
words as captcha images to users. To ensure proper authentication, correct
answers of first word of reCAPTCHA are known, while OCR cannot read correctly
the second word.
Applies To: Webmasters
USP: Deploying Captcha to protect your
MediaWiki against spam
Primary Link: http://recaptcha.net/
Google Keywords: Captcha,Mediawiki
Using reCAPTCHA with MediaWiki
To get started you need to acquire Public and Private Keys from reCAPTCHA's
website. To do this, simply register your domain name on reCAPTCHA's website and
it will automatically generate keys for you.
|In reCAPTCHA, you are asked to
enter two words for authentication unlike other captchas.
Once you have acquired the keys from reCAPTCHA's website, download its
Mediawiki extension from http://code.google. com/p/recaptcha /downloads/list?q=MW-Latest.
Now simply unzip this file and upload it to extensions directory of Mediawiki.
Now open MediaWiki's LocalSettings.php file and add following lines to it.
$recaptcha_private_key = ' ';
$recaptcha_public_key = ' ';
Here between single codes enter Public and Private Key which you acquired
earlier from reCAPTCHA's website. Now open 'Create account page' of MediaWiki.
You will see a reCAPTCHA image with the create account form. In case a user
cannot see the image, he can click on 'Get an Audio challenge' and it will play
an audio file, which will have eight numbers. The users will be asked to enter
those numbers. reCAPTCHA also comes with plug-ins for Joomla, phpBB and other
applications which can be found on its website.