Denning's Geo-crypto

Peter Wayner pcw2 at flyzone.com
Thu Nov 22 09:23:29 PST 2001


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



>
>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.





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