I submit that if Joe Lunchbox is not spamming, he is unlikely to need to change his habits regarding having his machine available
Mostly unrelated to this, but something's just occurred to me. Probably I'm being really stupid, but ... for the receiving MTA to know that the
----- Original Message ----- From: "Paul Walker" <paul@black-sun.demon.co.uk> Subject: Re: A Trial Balloon to Ban Email? problem
has been processed properly, it would have to know the answer. How does it know what the answer should be?
That one's easy. Use a problem that is not in P but is in NP. To make it clearer to most people, use a problem that can be verified cheaply, but that can't be solved cheaply. Since it's only everyone's computer Minesweeper is an example of such a problem. Once a solution has been found it is easy enough to verify that it is correct (all bombs marked, all non-bomb places revealed), but it can be prohibitively expensive to compute a large grid. Other common examples include jigsaw puzzles, digits of pi, etc. More functional puzzles for this purpose are NP-complete problems; e.g. traveling salesman, Hamiltonian cycle, SAT, etc. Right now another couple of good examples would be discrete logarithm, and integer factoring. In all these cases verifying the solution is cheap (generally travelling the path in the NP-complete problems, or computing the values in the DL and IF). Verifying that the puzzle is valid is only slightly more difficult, but retaining an active list of problems would solve the issue (but open up the possibility of DOS attacks). Basically it's a fairly easily solved problem. Joe