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. Ideas? Mark --- All inventions or works of authorship original to me, herein and past, are placed irrevocably in the public domain, and may be used or modified for any purpose, without permission, attribution, or notification.