This proposal doesn't require a new protocol. An ESMTP extension would
do just fine. I think we should kill two birds with one stone:
implement an extension in which the receiving server picks 2 primes of
sufficient length, multiplies them, and asks the sending server to
factor them.
I proposed something like this ("...it could be as simply as passing
the sender a product of primes, etc. and demanding that he factor
them before accepting the message. ") not quite a year ago in message
https://www1.ietf.org/mail-archive/working-
groups/asrg/current/msg00989.html
There apparently is some reason why this solution won't work, however
(I'm not sure what the issue was, but I received private replies that
insisted that the solution was unworkable, and the proposal itself
was generally ignored).
"SMTP clients and servers MUST support the original HELO mechanisms as a
fallback." - rfc2821
So you can expect objections to proposals based on extensions.
And besides, the penny black stuff aims (I've I've read it right) to set a
problem which isn't purely CPU (or math co-processor) bound. However, all
proof-of-work schemes have the drawback that they assume "work" is
expensive for the spammer. This assumption is invalidated if the spammer
commands a large numder of slave machines. Or buys a crypto card.
I think that's a fair summary, I'm sure anything I've missed can be found
in the archive.
--
_______________________________________________
Asrg mailing list
Asrg(_at_)ietf(_dot_)org
https://www1.ietf.org/mailman/listinfo/asrg