Rotate Image Captcha for phpBB 3.0.6
As soon as I heard the news that phpBB 3.0.6 was going to support CAPTCHA plugins, I was excited. I have enjoyed experimenting with CAPTCHAs, but was unimpressed with the way the system was initially designed for phpBB3. Rather than easily uploading to a folder, CAPTCHAs needed to dive into the core CAPTCHA generation code to insert themselves, and it was rather hackish. With the plugin system, all that is needed is the upload of a few files to control the CAPTCHA, the ACP, and the registration screen and you’re done.
So, I finally have gotten around to creating an initial version of an idea that intrigued me a while ago. Google was experimenting with a CAPTCHA where users needed to rotate a picture upright in order to prove they were not a bot. While this solution would take more time than I intended to spend, I realized I could simplify the idea, and let users chose the upright image rather than rotate it themselves. While not as strong against bots, a simple 4×4 grid would still give a 1/256 random chance of being correct, and a .4 guessing percentage is nothing to sneeze at.
So where else do I want to go with this? Well, observant testers will realize that there is a Yahoo! API key field in the ACP. This does nothing at the moment, but hopefully in the future will provide a way for admins to easily grab images from Flickr for use in their CAPTCHA. That is one of the greatest weaknesses for image based CAPTCHAs; if everyone has the same library of images, bots will load that library and have no problem. With the ability to grab uploaded, unique, images a bot would need to download all photos on Flickr in order to find the one that matches. If they can do that, then we really are in trouble. 
Use of this CAPTCHA is rather simple. Images uploaded to the includes/captcha/plugins/imgrotate folder will be resized and used in CAPTCHAs immediately. Only jpeg images are supported at the moment, and I have not decided whether to support more. 4 example images are included in this release, for easy testing, but in the final release will not be included for reasons above.
I hope people find this useful, and I would appreciate any comments you have about the project.
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download: Rotate Image Captcha for phpBB 3.0.6 v0.1 (321.71KB) added: 15/06/2009 clicks: 144 description: A CAPTCHA that has users select the upright image from a set of images in order to determine if they are human. This is an initial release with basic functionality, but limited in features and design |