On Sat, 13 Dec 1997, Adam Back wrote: [...]
(Hashcash is a way of proving that the sender has consumed a tunable amount of CPU time. The verification process consumes negligible CPU time. This allows us to require the would be spammer to spend say 20 seconds per mail, which will slow him down considerably, over his current tactics of 1000 long Bcc lists allowing him to hand off spamming tasks to mail servers.) [...]
Sounds like a headache to me: people use wildly different machines to handle their e-mail. Some places use 25 MHz '486 machines, others use 300 MHz Pentium-IIs, a difference of 1-2 orders of magnitude? Collision search is also easy to parallelize over a network, so the load can be shared using, say, 50 Pentium-II 300MHz PCs, costing less than $100,000 (we don't need lots of disk or memory, just a fast CPU). Here's at least three orders of magnitude for you. The '486 may be used by a school, while the 50 Pentium-II machines are owned by Spamford W., Esq. Now we're faced with a dilemma: we either limit the school's outgoing e-mail capacity severely, or Spamford will keep on sending spam. For every thousand messages the school sends Spamford can send a million. The risk: starting a CPU arms race. Ge' Ge' Weijers Voice: (614)326 4600 Progressive Systems, Inc. FAX: (614)326 4601 2000 West Henderson Rd. Suite 400 Columbus, OH 43220 http://www.Progressive-Systems.com