FC: Dorothy Denning on "geo-encryption": Tracking people by their locations

[Declan McCullagh <declan () well com>]

A paper from 1996 by Dorothy Denning and Peter F. MacDoran:
 "Location-Based Authentication: Grounding Cyberspace for Better Security"
 http://www.cs.georgetown.edu/~denning/infosec/Grounding.txt

An excerpt:
>  The location signature is virtually impossible to forge at the required
> accuracy.  This is because the GPS observations at any given time are
> essentially unpredictable to high precision due to subtle satellite
> orbit perturbations, which are unknowable in real-time, and intentional
> signal instabilities (dithering) imposed by the U.S.  Department of
> Defense selective availability (SA) security policy.  Further, because a
> signature is invalid after five milliseconds, the attacker cannot spoof
> the location by replaying an intercepted signature, particularly when it
> is bound to the message (e.g., through a checksum or digital signature).
> Continuous authentication provides further protection against such
> attacks.

Below is a discussion from cypherpunks. Time magazine article:
http://www.time.com/time/magazine/article/0,9171,1101011126-184999,00.html

-Declan

********

From: John Young <jya () pipeline com>
Subject: Denning's Geo-crypto
Date: Thu, 22 Nov 2001 11:06:21 -0800

Time Magazine, November 26, 2001:

Denning's pioneering a new field she calls geo-encryption.
Working with industry, Denning has developed a way to keep
information undecipherable until it reaches its location, as
determined by GPS satellites. Move studios, for example,
have been afraid to release films digitally for the same reasons
record companies hate Napster: once loose on the Internet,
there's little to stop someone from posting the latest blockbuster
DVD on the Web for all to see and download. With Denning's
system, however, only subscribers in specified locations --
such as movie theaters -- would be able to unscramble the
data. The technology works as well for national security
as it does for Harry Potter. Coded messages that the State
Department sends to its embassies, for example, could only
be deciphered in the embassy buildings themselves, greatly
reducing the risk of interception.

For now, Denning says, terrorists "may want to bring down
the power grid or the finance system, but it's still easier to
blow up a building." If she's right, it's due in large part to her.

********

From: Peter Wayner <pcw2 () flyzone com>
Subject: Re: Denning's Geo-crypto
Date: Thu, 22 Nov 2001 12:23:29 -0500

At 11:06 AM -0800 11/22/01, John Young wrote:
>Time Magazine, November 26, 2001:

This is a fascinating idea, but problematic. The simplest approach
is easy to spoof. Let's say that you encrypt the data with the GPS coordinates
X. The software takes GPS coordinates from a GPS receiver and tries
to decrypt the data using these coordinates. Only someone at the
right place would be able to figure it out.

Naturally, this could be spoofed by replacing the GPS receiver
with one that spits out the right coordinates.

A better system might rely upon the signals from the satellites
themselves. The signals let the GPS receiver measure the
time the signal took to travel from the satellite to the receiver.
Knowing the distance from three or more satellites makes it
possible to triangulate and come up with the real location.

A more sophisticated system would encrypt the data with
these signals themselves. It might take the data coming from
satellites 1,2 and 3 at one particular instant. Only a person
in the right location would see the right values at that particular instant.

But I think this could be spoofed by time shifting the signals using
a TIVO-like mechanism. If you're not in the right location you
could pretend to be in another.

Maybe they have a more complicated mechanism. Or maybe
this is just FUD.

-Peter

********
From: Steve Schear <schear () lvcm com>
Subject: Re: Denning's Geo-crypto
To: John Young <jya () pipeline com>, cypherpunks () lne com
Date: Thu, 22 Nov 2001 09:38:35 -0800

At 11:06 AM 11/22/2001 -0800, you wrote:
>Time Magazine, November 26, 2001:
>
>Denning's pioneering a new field she calls geo-encryption.
>Working with industry, Denning has developed a way to keep
>information undecipherable until it reaches its location, as
>determined by GPS satellites. Move studios, for example,
>have been afraid to release films digitally for the same reasons
>record companies hate Napster: once loose on the Internet,
>there's little to stop someone from posting the latest blockbuster
>DVD on the Web for all to see and download. With Denning's
>system, however, only subscribers in specified locations --
>such as movie theaters -- would be able to unscramble the
>data. The technology works as well for national security
>as it does for Harry Potter. Coded messages that the State
>Department sends to its embassies, for example, could only
>be deciphered in the embassy buildings themselves, greatly
>reducing the risk of interception.
>
>For now, Denning says, terrorists "may want to bring down
>the power grid or the finance system, but it's still easier to
>blow up a building." If she's right, it's due in large part to her.

I believe several patents have been filed for something along this line
(e.g. tamper resistant GPS-smart cards).  Mostly to enable casino to
satisfy state regulators that their clients are in permitted geographic
locales.

steve

********

From: John Young <jya () pipeline com>
Subject: Denning on Denning's Geo-crypto
Date: Fri, 23 Nov 2001 12:29:49 -0800

--

Date: Fri, 23 Nov 2001 08:38:13 -0800
To: John Young <jya () pipeline com>
From: Dorothy Denning <denning () cs georgetown edu>
Subject: Re: Geo-encryption

We don't have anything yet we are giving out to the public, but no,
it isn't related to the CoinCard (which I hadn't even heard of).

********

From: "Trei, Peter" <ptrei () rsasecurity com>
Subject: RE: Denning's Geo-crypto
Date: Mon, 26 Nov 2001 11:35:51 -0500

Curious. 4-5 years ago Denning and another associate (I
forget who, it's in the archives :-) tried to market an authentication
scheme which purported to authenticate the location of a remote
user using GPS.

The idea was that the user's machine would pick up the
aggregate analog GPS signal available at it's location
(either the regular, non-classified version or the
high-precision classified signals), and transmit it to
the server, which would use it to work out the
location of the user - a user who was located at
'Pentagon, third ring, fourth floor, Army segment'
would be accorded different privilieges than one whose
location decoded as 'Presidential Palace, Baghdad'.

I and several other list subscribers pointed out numerous
issues. Among them were:

1. GPS signals don't work well in buildings of substantial
construction, and the chance of them working at all in a
TEMPEST shielded building are about zip.

2. There are numerous DOS attacks available - the GPS
signals are easily jammed. One amusing approach would
be to use GPS test equipment to generate signals
appropriate for a different location (eg, Pyongyang) and
beam them at the site to be DOS'd.

4. Conversely, an  attacker could use the same test equipment
to make it look like he's in the Pentagon, when he's actually
in Kandahar.

5. GPS is based on the relative time delays of signals from
different satellites. Since network lag of hundreds of
milliseconds must be accepted, anyone who can see
the same set of satellites as the location to be spoofed
can separate the signals from the different satellites,
modify the lags appropriately, and remix to generate a
spoofed analog signal.

--------
I sent these concerns to Denning, who replied that she
would address them only under NDA, which I declined to
enter.

This sounds an awful lot like old wine in new bottles. Many
of the same concerns arise.

Peter Trei
Disclaimer: The above represents only my personal
opinions.

********




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