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.

---------- From: John Young[SMTP:jya@pipeline.com] Sent: Thursday, November 22, 2001 2:06 PM To: cypherpunks@lne.com Subject: Denning's Geo-crypto

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.