From: bureau42 Anonymous Remailer <nobody@bureau42.ml.org>
Date: Thu, 9 Oct 1997 05:53:05 +0800
To: cypherpunks@toad.com
Subject: Re: Secure phone
Message-ID: <YEGLY2IAZdGVHR5WT9gjbA==@bureau42.ml.org>
MIME-Version: 1.0
Content-Type: text/plain



John Deters wrote:
> At 12:44 PM 10/7/97 -0700, Eric Blossom you wrote:
> >I wrote:
> >> Therefore, man-in-the-middle can be more precisely described as an
> >> unauthenticated end-point problem.  Therefore, without authentication,
> >> there is no defense (yet) against MITM attacks.

> >I concur from the theoretical point of view.

> It would be easy enough to "trick" the MITM into exposing their existance
> anyway, just by using digits that come up in conversation. 

> A sudden dropout of sound (or "accidental" loss of
> connection) while the MITM recognizes the trap and tries to backpedal will
> be instantly noticed.  Human protocols are resilient, whereas mathematical
> protocols are precise.

Speaking from a practical standpoint, since I have been the target of
a variety of electronic surveillance for over a quarter of a century,
the Man-in-the-Middle rarely operates so well that there are not a
number of small anomalies that one cannot spot in the quality and/or
flow of the service they are receiving. On the other hand, they rarely
screw up so badly as to make it glaringly obvious what they are doing.

The main thing, when one has reason to believe that quality or technical
problems may be the result of MITM, is to take subtle actions such as
the one suggested above, in order to force the MITM to adjust on-the-fly
to situations that you create in order to monitor the monitor.
  e.g. - "Call me in 5 minutes at 555-PAY-PHONE for the secret code."
    If you already have a shill using that pay phone to monitor sudden
  anomalies in the function, fine, but it is ususally sufficient to
  take a call at the phone in five minutes, and the results of a quick
  patch will be noticeable.
     - "Do you have a radio playing, or something?"
    Hi-tech MITMs use a white-noise system designed to provide a cover
  for noise from their equipment, and a statement such as the above will
  invariably cause them to adjust it, usually resulting in a greater
  clarity or greater fuzziness on the line.

  Similar analysis of one's email, particularly if you have several
recipients who can send you full feedback on timing/routing, etc., can
reveal consistent differences between letters to your mom, and your
death threats against the King (as well as letter to your mom which
contain death threats against the King).

  Bottom line: If you are sending something worthy of being monitored,
then your actions and methodologies should reflect the belief that
you *are* being monitored.

  Please destroy your hard drive after reading this post.

TruthMonger