[hashcash] Re: Idea for alternative hashcash/antispam implementation.

The only negative thing I can come up with at the moment is that it
requires an SMTP-protocol update in order to work.

Which, unfortunately, is a very large point against it. Namely, it appears to require all legitimate senders to update their MTAs to support the newly modified protocol. Therefore, you might as well replace SMTP wholesale, which we already know isn't going to happen.

Another question worth asking is: What does it save versus checking hashcash after receiving the message? Bandwidth and a bit of storage is the answer, but neither of those are expensive resources in most of today's Internet (at the MTA level, not necessarily client level).

However much we'd like it to be, hashcash by itself does not make an anti-spam scheme. Initially at least, the best places for it to work are as a false-positive mitigator (in conjunction with a content filter or DNSBL) and/or an introducer (in conjunction with a whitelist). I have in development a scheme which explicitly combines both of these approaches, and Eric has something broadly similar in CAMRAM.

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from:     Jonathan "Chromatix" Morton
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