I think I reached this WWW-09 paper (What’s Up CAPTCHA? A CAPTCHA Based On Image Orientation) through one of those google research’s blogs. Anyways, how I got it or how I read it is immaterial at the moment. What is making me write this post is the general idea of the paper. Its so simple and pleasing to hear – ofcourse, I am not belittling anybody’s imagination and technological competence. I am just saying – once its published, now, the idea appears like – “Oh! thats so obvious! why didn’t anybody try this before google?”. As usual, eh? 😉
So, it is about using image based CAPTCHAs, instead of text based ones. Language independence and freedom from text entry are stated as the conveniences. Ofcourse, to me image based captcha is more appealing and interesting – atleast to imagine. The motivation? Spam bots are becoming over intelligent in understanding text captchas. To minimize their effects, systems are complicating text captchas by twisting letters, increasing noise in the captcha etc, to make the job difficult for machines. Result – they became irritating to humans as well (I was one of those who got so irritated seeing some of those new generation captchas). Hence, CAPTCHAs got a new direction in trying image orientation.
Three basic tenets of captcha include – easy for humans to solve, hard for machines to solve and being easier to generate and evaluate. Now, using these, the problem is to work on image captchas. With the case of image captchas, choosing the right set of images is again an issue since some images can be oriented by machines easily (Eg: using face recognition etc). Some cannot be properly oriented even by humans, since theres no way of judging one to be the right orientation (Eg: Abstract art).
To summarize, the whole process can be summarized as:
1. Having an image orientation detection and understanding mechanism system firstly.
2. Then, picking up only selective set of images, by removing the computer detectable images from the list.
2. Removing even those images which are difficult for humans to orient.
Now that your system is ready – this is how its used.
1. You give an image for the user to orient.
2. Like text captchas, you give him access to next level only after he has oriented it to the right direction.
Google conducted 2 usability studies regarding this – A viability study and a happiness study, whose purposes can be understood by their names.
I felt its an interesting social experiment and worth sharing my thoughts on it at my blog. Waiting to see it live soon… 🙂
Details of the paper can be seen here.