In the case of micromint I agree, there still has to be a centralised mint, so one can reasonably make a direct economic comparison with blind signature based coins or whatever and do the cost benefit analysis and decide which scheme to use (micromint may be cheaper per coin after the large initial investment has been recovered); however with hashcash it's major advantage is that it doesn't require any infrastructure.

Having a centralised e-cash bank issuing coins (or a group of banks with inter-bank clearing) is a highly non-trivial task when you're talking about micropayments that are expected to be attached to every email. The volume alone is staggering. And it's not clear what the

Adam

While it's true that some infrastructure is required for a value-based stamp (as opposed to destruction-of-value proof of work stamps), that infrastructure is also useful for many other purposes: the same mints that handle email stamps can also handle bearer instruments for game tokens, site passes, subscriptions, deeds, shares, and good old fashioned loot/money/cash. It also provides an opportunity for a clever entrepreneur to make money by running a self-sustaining service; this financial incentive can be a powerful factor in getting things done. Also, a value-based stamp bought for cash can also be acquired by consumers through side channels. Perhaps an ISP can purchase huge batches at steep discounts and redistribute them to users as a service; they can be given away as promotions; perhaps a spammer or advertiser could throw in email coupons as an incentive to read, or grocery stores could print them on the backs of receipts. As a very-low-value but useful token, it would be a prime target for commercial vectors. Again, a clever entrepreneur can come up with hundreds of angles. I believe that micropayments get stuck in the millicent ghetto because even a few million transactions at low value is probably not worth the effort. But the market for email stamps could be in the billions of transactions per day, and maybe that would be worth the effort. Patrick http://lucrative.thirdhost.com/ --------------------------------------------------------------------- The Cryptography Mailing List Unsubscribe by sending "unsubscribe cryptography" to majordomo@metzdowd.com