Non-image CAPTCHAs for AppEngine
In this lab, I want to experiment with some ideas for implementing non-image CAPTCHAs for, but not limited, to AppEngine. At the time of this writing, 11-06-2008, if you search for AppEngine Captcha on Google, likely you would find the following article in the top spot and not much else after that. This is a great solution that leverages the reCaptcha service and a well written article. But the problem I have found is that the images from reCaptcha are really hard for human to tell what it is. So I am conducting here a couple of experiments, and the results that I come up with are two potential solutions: the first one requires that JavaScript must be enabled, and the second does not.
Clearly, the first one is more "sexy", suitable for the so called Web 2.0, but would not function on browsers where JavaScript is disabled. The second one works more universally, but is not as appealing, and might be easier to be defeated by spam bots than the first.
Read the reference article.