From: m5@vail.tivoli.com (Mike McNally)
Date: Tue, 28 Dec 93 12:02:34 PST
To: cypherpunks@toad.com
Subject: GPS and security
Message-ID: <9312282001.AA24981@vail.tivoli.com>
MIME-Version: 1.0
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CBS's "60 Minutes" had a "Oooh Scarey" segment about the Global
Positioning System last Sunday.  The scarey part is, according to 60
Minutes, that any old terrorist government can now put together
accurate guided missles and wreak death and destruction upon our
homeland.  The crux of the problem is that the system broadcasts out
positioning information to one and all indiscriminately, and according
to the show there's no way we can stop it.

Because my mind is regularly exposed to wild conspiracy theories and
all sorts of crazed paranoiac ravings (i.e., I read Usenet), I started
thinking that this is rather unlikely.  I speculated that the
government may in fact have designed the satellite systems so that
they could be told to do several things in case of national emergency:

*	Shut down (probably possible; they may have actually mentioned
this on the show).  Problem is that lots of friendlies may grow to
rely on the data for life-critical things, like guiding commercial
airliners.

*	Shut down normal transmission and begin strongly encrypted
transmission.  No mention of this; apparently, the satellites were
originally designed with some sort of weak system that made the data
difficult to use for high-accuracy purposes, but that's been defeated
(by the FAA or someone contracted thereto).

*	Enter into a bogus-cleartext with encrypted subchannel mode,
where the plaintext is slyly made to be wrong, but using some
subchannel encrypted "good stuff" is still available.


I don't know much about how this system works, so I don't know whether
any of my thoughts are relevant.  It's probably most likely that the
government indeed blasted these things up into space without
considering using encryption technology to enhance security.

--
Mike McNally : m5@tivoli.com : Day Laborer : Tivoli Systems : Austin, TX
------------------------------------------------------------------------
Remember that all experimentation does not produce extrapolated results.
                                                           - k. pisichko