At 12:59 PM 10/11/00 -0400, Marcel Popescu wrote:
Real-To: "Marcel Popescu"
An interesting idea has surfaced on the freenet-chat list: is it possible to build a program that creates some sort of a puzzle, whose answer the generating computer knows (and can verify), but which can only be answered by a human being, not by a computer? [Additional requirement: it should be easy for the human to answer the puzzle.]
My proposal was to randomly create an image, which should be 1) easily recognizable by a human (say the image of a pet), but 2) complex enough so that no known algorithm could "reverse-engineer" this. [You need a randomly-generated image because otherwise one could build a large database of all the possible images and the correct answers.] Background information would also be very useful - see http://www.digitalblasphemy.com/userg/images/969403123.shtml - it's easy for a human being to identify the animal in the picture, but (AFAIK) impossible to write a program to do the same thing.
I don't follow the other list you mentioned, so I don't know what the actual problem to solve is - my guess is that this is an anti-bot protection measure, intended to make sure that only human participants can engage in a conversation. If that's the problem - or if it's similar - you'll also need to make the puzzle difficult enough that it's hard to brute-force or solve statistically - let's say you provide the other party with 20 images, 19 cats and 1 dog, and ask them to identify the dog. What keeps a bot from answering the question 20 times? Let's assume the first arms-race countermeasure prevents answering the question more than once by generating puzzles on-the-fly from known cat and dog images - so the bot just picks an answer randomly, and keeps doing that until they hit. Can God create a rock so big he can't lift it? I think you're barking up the wrong tree, thinking about "known algorithms" and such - just like with crypto, the real way in isn't to attack the strong front door, but to just go around it. This sounds like maybe it's essentially a credentialling/ID problem, where you're generating credentials on the fly based on a short-form Turing test. Can you restate the problem so that instead of a Turing test it's a more familiar multi-channel authentication process? (e.g., require new participants to have "introductions" from existing participants, track introductions, and remove the access for accounts found to be bots, or found to have introduced bots .. or similar.) -- Greg Broiles gbroiles@netbox.com