From: jim bell <jimbell@pacifier.com>
Date: Thu, 11 Apr 1996 08:28:58 +0800
To: cypherpunks@toad.com
Subject: Re: No matter where you go, there they are.
Message-ID: <m0u74QI-0008yEC@pacifier.com>
MIME-Version: 1.0
Content-Type: text/plain


At 08:41 AM 4/10/96 -0400, Perry E. Metzger wrote:
>
>Anonymous writes:
>> 
>> Location-based System Delivers User
>> Authentication Breakthrough
>> 
>> By Dorothy E. Denning and Peter F. MacDoran
>> Copyright(c), 1996 - Computer Security Institute - All Rights Reserved
>> Top - Help
>> 
>
>A bunch of us heard about this a while back, and I was in on an
>exchange between several people including Phil Karn and Dorothy
>Denning. The gist of it is that Denning et al believe they have
>something -- and they are smart people -- but all the smart people who
>understand both GPS and crypto think its total bunk and not at all
>hard to fake being anywhere at all. I would say that I go with the
>latter.

The latter is far closer to the truth.  First off, GPS signals can be faked. 
 In fact, there are commercial boxes sold that generate a full synthetic 
constellation of GPS signals; these boxes are usually intended to simulate 
motion of a vehicle when the GPS unit under test is actually stuck in a 
laboratory or factory floor.  If such a box were connected to an amplifier 
of a few tens or hundreds of milliwatts, it would be possible to park near a 
potential target and deny him service by making it look like his signal came 
from anywhere else around the world.  (Military boxes would detect this 
because of A/S, however.)  

And if you had a receiver at some specific location at 
which you intend to appear to be connected at, it is likely that full data 
describing the motions of the satellites could be supplied to any other 
location on the Internet needing well under 14,400 bps.

Jim Bell
jimbell@pacifier.com