Since it is widely know that the captcha implementations used by Yahoo, Microsoft, and Google can be broken by computers with a fairly high success rate (around 20-30%), I have been throwing around ideas in my head about a new captcha implementation. However, I don't have a workable or complete idea. I think I need to browse some math sites until something dawns on me.
The problem is that I need a method to generate patterns that can't be easily recognized by computers but is recognizable by humans.
Perhaps we should have some sort of captcha contest on DonationCoder to see who can come up with the best implementation? Also, let's get a list of new/innovative captcha implementations going so we can see what has been done.