From: "Timothy C. May" <tcmay@got.net>
Date: Sat, 9 Nov 1996 17:58:35 -0800 (PST)
To: cypherpunks@toad.com
Subject: Re: Another possible remailer attack?
In-Reply-To: <Pine.BSF.3.91.961109134348.182B-100000@bitbucket.edmweb.com>
Message-ID: <v03007800aeaae66a770f@[207.167.93.63]>
MIME-Version: 1.0
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At 2:34 PM -0800 11/9/96, Steve Reid wrote:
...
>You want to know if Dimitri is the person regularly posting these
>messages. So, you use your powers as ISP to block his access to all
>remailers. If the public messages suddenly stop then you can be reasonably
>certain that Dimitri was sending them.

I'm not following something...just how to your "powers as ISP" affect a
remailer in, say, Holland, or one for that matter on another ISP? (As a
matter of fact, I expect the "compliance rate" with your request would be
something less than 10%.)

>I expect this would work even against DC nets.

One presumption about nodes in DC-nets is that they are even more
crypto-savvy than routine mixes, so I doubt even more strongly than nodes
in a DC-Net would obey your recommendations to source-block any particular
user from entering the DC-net.

(And all your hypothetical "Dimitri" has to do is to use a remailer outside
the DC-net to anonymize his identity, or to use Unix/Sendmail hacks to
obscure the name, etc.)

On the larger issue of foiling remailer networks by analyzing message
sent--message received statistics, this is never going to go away
completely. Just as the Nazis could isolate spy transmitters by selectively
turning off electricity to different neigborhoods, so, too, can various
in-out correlations be analyzed to deduce _probable_ sources of some
messages. Given enough traffic. A SIGINT problem similar to submarine
warfare Bayesian statistics problems.

-Tim May

"The government announcement is disastrous," said Jim Bidzos,.."We warned IBM
that the National Security Agency would try to twist their technology."
[NYT, 1996-10-02]
We got computers, we're tapping phone lines, I know that that ain't allowed.
---------:---------:---------:---------:---------:---------:---------:----
Timothy C. May              | Crypto Anarchy: encryption, digital money,
tcmay@got.net  408-728-0152 | anonymous networks, digital pseudonyms, zero
W.A.S.T.E.: Corralitos, CA  | knowledge, reputations, information markets,
Higher Power: 2^1,257,787-1 | black markets, collapse of governments.
"National borders aren't even speed bumps on the information superhighway."