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Geo-Encryption: Global Copyright Defense?
An Anonymous Coward writes: "CIO Insight has a story on the copyright-protection scheme devised by Georgetown professor Dorothy Denning. Geo-encryption uses GPS technology to keep information scrambled until it reaches a precise location anywhere in the world. Denning has started a new company, GeoCodex, to capitalize on the technology." I can't wait for the Crypto-Gram article about this one..
From a design point of view, it's simple. You have a gps, and some compuiter that will give you some data (i.e., a decription key) when the gps detects that you're at a specific position in space. The really, really hard part is making the device tamperproof.
It has not only to resist to direct attacks trying to get to the data, it also has to deal with jamming of the gps signals, or more specifically putting the device in a faraday cage and sending it signals imitating the gps satellites in the appropriate position. Too bad the article has zero information on their methods.
Oh well, let's hope a followup article by Schneier (who also considers the tamperproofing critical) will be more detailed on the technical side.
OG.
This is only how to defeat the system... I don't even mention what consumers will think of it... how would {RI,MP}AA justify licensing the material to a physical coordinates rather than a paying customer? It is not likely to work. GPS does not work inside buildings, BTW, and very few people go in a park to watch DVDs :-)
It was around 100 meters in any direction from your current location. And yes, it was by the U.S. government to prevent people from bombing the White House. As if a bomb big enough, off by 100 meters, would actually miss the white house.
They removed it sometime last year, I believe. With 9-11, there are rumors they may impose the restriction again, but that's assuming any primary threats have missiles capable of using GPS.
This restriction would pose little or no problem to people using it for the purposes this article describes. GPS correction is available through a "post-processing" method. You position a GPS base station at a known location. If you take samples at exactly the same time from different locations, those locations are off by exactly the same error vector. So, you simply compare the base station samples to the base station position to get the error vector, and apply this error vector to the roaming samples to get your almost-exact position.
I say almost exact because signals are disrupted by various things. Light and sound are waves; they move at a constant speed as long as the travel medium doesn't change. As a consequence, like sound, light is affected by the doppler effect. It usually isn't significant, but can throw your results off nonetheless.
Clouds, rain, snow, buildings, etc. can also affect the results, as well as the SNR (signal to noise ratio -- measures the amount of readable data to background noise). If the SNR is high, it's unlikely the results will be thrown off significantly. All these problems are virtually unavoidable unless the weather is clear, you have a high channel capacity on your GPS device (8 is usually good, I think available satellites above the horizon range from about 8-11, high on elevated terrain), and there are few if any buildings around.
You need at least n+1 satellites in reach to get nth-dimensional results. So, for planar (2d) positions (latitude/longitude, or azimuth or whatever) you need 3 satellites, and 4 for spatial (3d, 2d + a z-position, your elevation).
The more satellites, the more precise your results are. If the base station is within 500 metres away, and you have real-time correction (which would still help with climate problems), you can get sub-centimetre accuracy.
> How do you store the location in the media file in such a way that it can't be changed? How do you prevent players from being manufactured that don't look at the location.
Because it's encrypted, with the GPS location being the key, or at least part of it. So it's not like you can just ignore a location header and get at the text file: you need to pass your GPS location into a decryption algorithm that will decrypt the scrambled data into a readable file.
Of course, this can be an additional layer added onto existing methods of asymmetric encryption. As GPS units become more precise, we might even begin to have a "decryption tile" or square in bedrooms so that each resident has their own decryption key accurate to that specific square foot of space.
Someone stole your laptop? They're going to have to break into your house, steal a key to your room, and stand on your decryption square just to decrypt any of your files. Sounds like an interesting acrobatic scene for Mission Impossible 3.
"A good conspiracy is an unprovable one." -Conspiracy Theory
Another important defect of this system is that in modern society most people live in cities, and as such the keys are not randomly distributed, but very much clustered. To find a movie key, for example, one just needs to try GPS locations of few big cities (SF, LA, NYC etc.) to hit the paydirt.
But likely, this key search won't be needed at all, because whoever posts the material on Usenet will put the necessary serialz ^W GPS code into the accompanying note. The only problem is to apply the key to get the raw contents, and that is not too difficult because all the strength of the crypto is in the key, not in the algorithm.
Some juicy bites from her publications:
..My conclusion is that modern encryption is predominately a privacy
Is Encryption Speech? A Cryptographer's Perspective
enhancing technology rather than speech. Although encryption might be
regarded as a manner of speech, it is unlike other methods in that it
contributes nothing to communication.
One implication of this interpretation is that regulation of encryption
would not violate the First Amendment. Another is that restrictions on
the use of encryption could not be used as a basis for prohibiting the
use of an obscure foreign language or any other ordinary language.
Testimony Before U.S. House of Representatives, May 3, 1994.
"..The Clipper Chip and associated key escrow system is a technically
sound approach for ensuring the security and privacy of electronic
communications. Clipper's SKIPJACK encryption algorithm provides
strong cryptographic security, and the key escrow system includes
extensive safeguards to protect against unauthorized use of keys. The
more advanced chip, Capstone, further provides all the cryptographic
functionality needed for information security on the National
Information Infrastructure."
And there's even more, go and see by yourself. I'm really waiting for the comments from the cryptograhical community on this systems..
V.
Do a google search for 'Denning GPS'.
First hit that comes up is a 1996 paper Location-based Authentication: Grounding cyberspace for better security, by Dorothy E. Denning and Peter F. MacDoran. Reading the paper, the idea looks to be that by knowing the location of a computer user one can define whether they are authorised to perform a particular action.
This makes marginal sense (if somebody who isn't in a bank office is playing with computer codes then they're probably not really permitted to play with them). However, to me this article reads like, 'Hey, if I mention copyright protection, I'll get funding'. And the whole idea reads like that - after all, for the person in the above example to perform an unauthorised action on bank accounts, they must already have broken through the protection placed around the system. Simply adding another authentication isn't going to magically fix that problem (hey, you want me to tell the system I'm in the White House? OK. It's no different to telling the system that I'm Bob, financial manager).
As for the use of said technology to control music distribution... what?!. If this woman is 'America's Cyberwarrior' then... be afraid. Very afraid. I'm sorry to say it, but whilst there are some very valid uses for GPS technology (something like HP's Cooltown project, mobile computing in general, augmented reality, etc), I don't think this is it.
On the one side, it's valid to argue that including un-spoofable - if that's a word - location data in all internet communication would help in some cases (finding malicious hackers, absolving the innocent) but given that it also destroys the whole concept of anonymity, it's plain not worth it. Location information has to be optional. This is just another step in the 'media programs phoning home'/WinXP DRM direction, and it's not a good one.
If I sound irritated, it's because I am; I have no idea what Denning's politics are or whether the spin on this story is merely unfortunate, but the article linked to in this story (somewhat unlike the paper) sounds like something the EFF will eventually find themselves fighting.
I particularly like the part of that paper marked 'privacy considerations', where they note "The use of location signatures has the potential of being used to track
the physical locations of individuals."
Their solution?
"Access to [this information] should be strictly limited." And, um, "Privacy can also be protected by using and retaining only that information which is needed for a particular application." Or you can "opt-out" of giving your information, although of course "some actions may be prohibited if location is not supplied".
You mean the MPAA/RIAA are only going to retain as much information on me as they need for marketing purposes, and I can opt out if I don't mind never listening to another RIAA-produced CD? Thank you, Denning and MacDoran.