I keep seeing hysterical reports that Bill Gates wants to impose e-mail postage to stop spam. A quick Feedster search for "gates spam postage", for example, turned up 90 posts. Most of these are based on this CNN/AP story .
Unfortunately, virtually all of the articles and commentary miss the point: Microsoft's not calling for people to pay money for postage. Instead, they're floating the idea of using a hashcash-like system that requires the sender to perform a calculation (something like a hash of the message plus the sender's address, with some additional crypto thrown in) before sending the message. The MS Research system (described somewhat here) uses a similar idea: if you require a certain amount of computation to send messages, that raises the cost to people who send out millions of messages, i.e. spammers. (Interestingly, the BBC article says that Cynthia Dwork, who first floated the idea of computational-postage systems in 1992, is now working at Microsoft Research. Her original paper, here, makes for interesting reading).
Now, here's the part that most people are missing in all the "Bill Gates wants my postage" kerfuffle. If the message doesn't have a valid hashcash token, it can be passed through a normal spam filter. . In other words, if it has "postage" (which is created by burning a few CPU-seconds on the sender's machine), it can be directly accepted (or not), but if it doesn't have "postage" it gets the full proctologist's treatment with SpamAssassin, the Exchange IMF, or whatever. (n.b. Ecto's spellchecker recognized "proctologist's"-- pretty cool, huh?) This is exactly analogous to what we all do with postal mail: if I get something that was mailed bulk rate (thus lacking "postage"), it's much more likely to get canned.
Microsoft is not suggesting that we pay actual cash for any of this (although these guys, and others, are). Calm down, everybody. Considering that there aren't any viable micropayments systems (and yes, I include Peppercoin in that dismissal), the idea of requiring actual micropayments for email is laughable, and no one knows that better than MS. However, a hashcash-like system is a useful adjunct to (not replacement for) other filtering systems. In fact, there's already at least one hashcash implementation, FirePay.Posted by Paul at March 11, 2004 03:39 PM
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