Clueless service restrictions (was RE: Anti-spam System Idea)

Tue Feb 17 23:56:17 UTC 2004

Steve,

--On 17 February 2004 17:28 -0500 "Steven M. Bellovin" 
<smb at research.att.com> wrote:

> In almost all circumstances, authentication is useful for one of two
> things: authorization or retribution.  But who says you need
> "authorization" to send email?  Authorized by whom?  On what criteria?

Authorized by the recipient or some delegee thereof, using whatever
algorithms and heuristics they chose. But based on data the authenticity of
which they can determine without it being trivially forgeable, and without
it being mixed up with the transport protocol. IE in much the same way as
say PGP, or BGP.

> Attempts to define "official" ISPs leads very quickly to the walled
> garden model -- you have to be part of the club to be able to send mail
> to its members, but the members themselves have to enforce good
> behavior by their subscribers.

I never said anything about "official" ISPs. I am attempting to draw an
analogy (and note the difference) between SMTP as currently deployed, and
the way this same problem has been solved many times for other well known
protocols.

We do not have an official BGP authorization repository. Or an official PGP
authorization repository. We just have people we chose to trust, and people
they in turn chose to trust. Take BGP (by which I mean eBGP) as the case in
point: It seems to be general held opinion that the one-and-only canonical
central repository for routes does not work well. The trust relationship is
important, and we expect some transitivity (no pun intended) in the trust
relationshipa to apply. And many end-users in the BGP case - i.e. stub
networks - chose to "outsource" their their trust to their upstream; when
they don't like how their upstream manages their routes, they move
provider. BGP allows me (in commonly deployed form) to run a relatively
secure protocol between peers, and deploy (almost) universal end-to-end
connectivity for IP packets in a manner that does not necessarily involve
end users in needing to know anything about it bar "if the routing doesn't
work, I move providers"; and IP packets do not flow "through" BGP, they
flow in manners prescribed by BGP. Replace BGP by "a mail authorization
protocol" and "IP packets" by "emails" in the foregoing; if the statement
still holds, we are getting there (without reverting to bangpaths &
pathalias). Oh, and people keep mentioning settlement and how it might fix
everything - people said the same about BGP (i.e. IP peering) - may be, may
be not - the market seems to have come up with all sorts of ingenious
solutions for BGP.

Alex