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Re: comments? hashcash based MTA filtering

1999-02-22 13:41:56
Date: Fri, 19 Feb 1999 23:48:50 GMT
From: Adam Back <aba(_at_)dcs(_dot_)ex(_dot_)ac(_dot_)uk>

I have a proposal for another class of filtering criteria: filtering
on the basis of a token which consumes CPU time to produce as a method
to throttle systematic abuse.

I am requesting comments from this group because it seems the closest
match of IETF topic to "technical solutions to UBE".  I am open to
comments as to how best to progress this technical solution.

We are not trying to solve the spam problem.  That said, I like
hashcash.  Adding a test for a hashcash value is trivial.  But getting
Sieve out there is a large amount of work in itself.

The originator is required to send with email a costly to compute
token bound to that resource name.  Example: Coyote emails Roadrunner,
he computes a hash collision on "roadrunner(_at_)birdseed(_dot_)org".
runs a MTA filter rejecting mail without hashcash postage.

The problem with this is that it means the amount of computational power 
that a mailing list costs is rather high.

Tim Showalter <tjs+(_at_)andrew(_dot_)cmu(_dot_)edu>