On Thu, 15 May 2003, Nomen Nescio wrote:
Zero Knowledge in the Cave
There is a cave with a large entry room. From this room lead two passageways, 1 and 2. Each of 1 and 2 branches into a myriad of smaller passages, twisting and turning through the massive rock formation. The passageways go on for miles and have never been fully explored. ... 1. How could you have done things differently, to produce a tape that would be convincing to others?
Flip a coin each time you called out which entrace you wanted him to come out of. Couldn't have been predetermined that way. Plus, since he's hidden in the cave, he can't see you proving to the camera this is random and therefore doesn't know you've foiled his intent.
2. What counter-measures and conditions could the explorer have put in place to prevent you from getting a convincing tape in this manner?
Claiming it was a loaded coin after he hears about it? :-) He could force you to write down your list of tunnels in advance, and you must call off the list in order. Each time he correctly leaves the right tunnel, you must show him the list to prove that you haven't faked the list or changed the order. You know he didn't see the list beforehand, you're convinced, people watching your tape don't know he didn't see the list beforehand, and won't be. There's probably a much easier way of doing that, I imagine. -- jordan wiens --------------------------------------------------------------------- The Cryptography Mailing List Unsubscribe by sending "unsubscribe cryptography" to majordomo@metzdowd.com