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 <jyaat_private> 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 <pcw2at_private> 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 <schearat_private> Subject: Re: Denning's Geo-crypto To: John Young <jyaat_private>, cypherpunksat_private 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 <jyaat_private> 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 <jyaat_private> From: Dorothy Denning <denningat_private> 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" <ptreiat_private> 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. ******** ------------------------------------------------------------------------- POLITECH -- Declan McCullagh's politics and technology mailing list You may redistribute this message freely if you include this notice. Declan McCullagh's photographs are at http://www.mccullagh.org/ To subscribe to Politech: http://www.politechbot.com/info/subscribe.html This message is archived at http://www.politechbot.com/ -------------------------------------------------------------------------
This archive was generated by hypermail 2b30 : Tue Nov 27 2001 - 08:55:17 PST