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Path: utzoo!watmath!clyde!burl!ulysses!allegra!mouton!karn
From: karn@mouton.UUCP
Newsgroups: net.ham-radio
Subject: Re: Packet Radio Vax access
Message-ID: <185@mouton.UUCP>
Date: Fri, 19-Oct-84 21:08:45 EDT
Article-I.D.: mouton.185
Posted: Fri Oct 19 21:08:45 1984
Date-Received: Sun, 21-Oct-84 14:07:50 EDT
References: <2257@pur-ee.UUCP>
Organization: Bell Communications Research, Inc
Lines: 34

I too have been thinking a lot about using packet radio for high speed
remote access to a Unix system. The problem of broadcasting your Unix
password all over two meters is a real one, but there are ways the
problem could be solved with public key cryptosystems.  The current
sentiment among the legal eagles is that such a scheme would NOT violate
the prohibition against "codes and ciphers" in the amateur service
because it is intended as a authentication scheme and not to hide
information.  There is ample precedent for authentication schemes, e.g.,
repeater autopatch and control codes.

The regular traffic would still have to be transmitted in the clear, of
course, and this would provide "spoofing" opportunities for a bad guy.
It would only take one spurious packet of the form "rm -rf *"
from some clown and even though the protocol might recover from the
unsolicited acknowledgement, the higher-level damage would obviously be done.
About the only thing that could prevent this would be a public key
authentication scheme on each and every packet.

Another clever (non-encryption) scheme for protecting radio communications
links is in use by the military.  It works on the fact that the atmosphere
has widely varying attenuation with frequency, and in particular at
frequencies near 60 GHz the atmosphere is virtually opaque due to oxygen
absorption lines.  Secure point-to-point radio systems use frequency-agile
transmitters which operate as high up on this absorption curve as possible
while still being received at the intended recipient.  If an enemy tries
to intercept the beam somewhere farther along, atmospheric noise
and attenuation will make the signal useless.

You're probably best off using a laser (infrared, so to not attract
attention.)  It has the additional advantage of not needing a license,
and not being subject to the amateur rule restrictions against business use.

Phil