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Encryption Security

Authentication Via Geographical Location? 159

Posted by Cliff from the where-am-I-now? dept.
RudeDude asks: " While reading Cryptonomicon I became a bit paranoid about encryption and digital signatures but it has me thinking a bit as well. I'm trying to visualize a way to prove my physical location in a cryptographically strong way and I can't think of one. My digital signature proves who I am, but wouldn't it be nice if I could also give proof of my physical location at a given time stamp? I've thought of only a few things that would be very hardware dependent, etc. but what I really think would be cool would be something that is as strong as digital signatures. Some sort of GPS/MD5 signature that a third party could confirm so that it would be impossible to spoof my location. " This question has been asked a bit by people looking to restrict services to various countries, but currently one can't be sure if the IP a person is using is really the location from which the connection is being made. Would a system like the one described above be a possible answer?

"This is mostly just a thought experiment, but I am curious to see what other Slashdot readers could maybe dream up. In my opinion (and I'm sure many others as well) my current meatspace coordinates usually mean much less than my network 'location' does, but I can think of many times where proving my meatspace location could be just as important as proof of identity."
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Confirming Geographical Location over the Internet? More

Confirming Geographical Location over the Internet?

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  • Authorities.... (Score:1)

    by Anonymous Coward
    We currently have certificate authorities that vouch for the person... Acknowledging that he is who he says he is...

    Why not location authorities that say "we are reasonably sure this person is who he says he is, and he was at this location at this date/time".

    "How does the LA (location authority) know where ou are, pictures would be good. Go to the "Location Authority", stop and get your picture taken.

    Then you would have a certificate that said "I was in Paris on Nov 11/2000" You could use that for tourist tax refunds, or whatever.

    This could even work for trucks... The location authority has a camera set up at a roadside location. As the truck goes by a picture is taken and datestamped, and now you can prove that that truck was at that location at that time.
  • As a former empolyee at ARIN, and a current employee at the RIPE NCC, we get this question with fairly regular frequency. My short answer is always, "It can't be done." The long answer is, well longer.

    The fundamental problem with using IP to establish location is that IP was designed to seperate physical topology from network topology. In other words, you're not supposed to know where hosts are at.

    There are three main reasons in my experience why people want to do this:

    • Marketing. Companies want to do targetted advertisements and such. Using source IP is a bad way to do this - though there are some companies who use DNS tricks to do this with some success.
    • Legal Protection. Because of bogus laws in various locations around the world (Virginia, Afghanistan, wherever), companies want to avoid sending certain data to certain places. However, this almost always is mainly intended as a CYA (or "good faith" in legal circles), rather than to actually solve the problem.
    • Curiousity. Networking people do tend to have a certain amount of natural inquisitiveness. That's why they look at HTTP logs, for instance - not just to see where the best pron is.
    Any even mildly determined individual can cross national boundaries with ease. Use telnet/ssh into a machine in another location. Also, ISP's transit data between countries (lots of countries in eastern Europe and the middle east use satallite downlinks with bases in North America, for instance).

    There was a Spatial Relation BOF at the IETF in Australia this spring, but I don't know how that work is progressing. I expect that voluntary location is a solvable problem. You can also pinpoint someone's farthest possible location with simple speed of light calculations. Anything else I expect is either impossible or intractable.

    Shane

  • Ah, at last we're getting it right! Using the notion of spacetime coordinates really nails an event.

    Now, whether this is politically good or bad I'll leave to those more savvy in that arena.
  • I frequently have to give a landline number rather than a mobile number, if nothing else but to prove I am who I say I am - and I am where I say I am.

    Not to mention that the killer app for WAP and bluetooth and the whole "mobile internet" thing will be mobility based.

    If you can prove where you are, your provider can use that information to be able to return information based on your locale.

  • You don't have to have it embedded in your skin - you simply have to provide a piece of information only you would know, such as your PGP/GPG private key

    And what if I log in over a secure connection during the bank robery to prove that I was at home then? I could even use the X10 connection to flip the lights on and off so my neighbors could vouch for me.

  • I just found a flaw in my own plan. The location is based on the difference between the arrival times of the signals, not the contents of the signals per-se. It would still be possible for someone to record the encrypted messages from the satellites and misrepresent when these were received by the GPS, thus misrepresenting their location.

    I still like having the encryption in the satellites because it is very hard to tamper with. A scheme where the encryption is done in the receiver seems easier to break. There's a better solution but I can't quite think of it right now.

    As for the usefulness of this, I hope this can be a tool for people to prove their whereabouts, but that it never becomes a requirement for anything.
  • Even assuming the picture can't be modified, all you proved was you were at Paris on or after that day.

    -David T. C.

  • We seem to be doing fine with IPv4 combined with NAT. Ugly, but it works. IPv6 seems to be suffering from a combination of second-system effect, and too many cooks.

    The geographical features in particular show that the people who built it haven't taken the Internet and what it represents to heart.

    Inside IPv6 is a small, easy-to-implement protocol waiting to get out. Hopefully someone will notice.

  • Yet another reason not to adopt IPv6.

  • It only proves that someone/thing that had access to your secret key has signed it. This is an important distinction that most people fail to make.
  • Other than implanting a homing beacon in your skull, I can't think of a way to "prove" anything. Anything else is subject to tampering or transmission.

    I heard a rumor that satelite phone occationally wake up and broadcast their position the the satellites, even when they are not in use. Any truth to that?
  • So a GPS reciever can be faked into reporting a specific destination when it has no other data to go on. But that doesn't mean that a GPS reciever sitting next to it and listening to N satellites for real GPS data would believe your GPS' report of its location. And wouldn't millitary-grade GPS systems have a way of figuring out what GPS datastreams are "real" and which are fake?

    My understanding of how GPS works (yes, probably another poorly informed slashdot poster) is that the GPS satellites send out clocking information and some other magic that allows recievers to triangulate to determine position. If you're trying to authenticate your location via GPS AND the system you're trying to authenticate to has its own independant system of GPS data verification, wouldn't the authenticatee be able to pass raw GPS data to the authentication system for verification?

    I guess what I'm getting at: Is there anything in the GPS datastream that is unique enough over a short timespan that an authenticator with its own GPS information feed could use to at least verify the GPS information it receives? Of course this might mean having compromisable GPS authenticator "field offices" that have access to some high percentage of GPS satellites so you know the information being passed to you is valid, but hey, it could be one of the few .com opportunities left..

  • On a similar thread I would like a method of timestamping that couldn't be spoofed. For example I would like to be able to record when I came up with a certain idea or make a prediction like "Linux will have X market share by date Y" and then be able to prove that I did it on a certain date. I can already see one problem with the potential solution. I'm reminded of an episode of the US T.V. show "Cheers!" where the main character Sam finds out he's going to sleep with the main female character, Rebecca I think. He pulls a piece of paper from his pocket and reads it,

    "Today, April 23rd 1982, I will sleep with Rebecca"

    Someone replies,

    "That's amazing! How did you know that?"

    He replies,

    "Simple, I make a new one every day."

    For example you have to make sure that someone can't just sign multiple documents saying that "Nader will win", "Bush will win", "Gore will win" etc..

    So, how do you prove that you signed something on a particular date? Does it require a third party? I don't like the idea of a centralized third party. Perhaps some sort of system where the time/date was verified by several timeservers in different countries run by various groups so you could be pretty sure that the system wasn't compromised.

    Any thoughts?
  • Unless you happen to be on AOL?

    I would suspect that AOL also suballocates its IP addresses, and probably gets its European IP addresses from the European pool.

    I'll buy the hit about connecting long distance to your ISP though!
  • Your credit cards number could be used to validate your (general) location. As it is Visa, Amex etc have records of each transaction - this includes the business name. This could be easily expanded to also include the location.

    For these records one could then determine the 'average' shopping location (ignoring on-line purchases) and the last shopping location...

    Mobile phones could also be used - the phone companies (can) know the current location of the phone and have details of its owner... You just need them to give access to the data...

  • Back when iCraveTV was litigated, they promised to return with better security, implemented with the help of www.bordercontrol.com [bordercontrol.com]. Try it out, it's pretty exact (at least with the country).

    However, all this will be useless if you use a bouncer or a web proxy at a different location. Any location information on the Internet can be spoofed with the current technology. I'm not sure if IPv6 will change anything, so far I haven't noticed any location-specific header field in the specs.

  • I'm waving now.
    Do a couple of jumping-jacks.
    Yeah, ok, you're there, third window
    from the left.
    Good. Can you send me the software,
    then?
  • Gah, plain old text still removes GT & LT symbols. Serves me right for not previewing. Should have read:

    <person1> I'm waving now.
    <person2> Do a couple of jumping-jacks.
    <person2> Yeah, ok, you're there, third window from the left.
    <person1> Good. Can you send me the software, then?

  • Re:GPS (Score:1)

    by jbf ( 30261 )
    there are still ways of making non-SA-impaired GPS more accurate (beyond design limitations): differential based on the timing of the chips, differential based on the carrier's phase shift, etc. All you need is a fixed station.
  • This an FCC regualation for Cell phone companies - to be able to locate 911 callers within 10-20 Meters. The mandatory system has nothing to do with placing GPS systems in phone because ALL phones - old AND new - must be trackable. They are doing this using sycronized receivers on the Cellular stations and using time differentials to pinpoint the position of the cell phone.

    This is a good example of a "Trusted" 3rd party system. And I mean trusted in teh sense "I trust the information" and not in the sense "I trust the phone company"

    Also TDMA / GSM systems use "advance timing" signaling to tell the cell phone broadcasts a packet a little ahead of its time slot so that when the signal reaches the antena from a far off distance, the packet will arrive within its window - thus on digital systems the switch knows how far you are based on timing errors!!
  • Maybe I should clear up what I mean by "advance timing" !!!

    The current digital Cellular standards - in the US this is VoiceStream, AT&T - including GSM and D-AMPS (Not Sure about CDMA) use some thing called Time Division Multiplexed Access (TDMA). For North America every cellular "channel" ( channel is 30 Mhz of bandwidth) is split into 3 time slots (This is why all cellular companies are moving to digital 3 times as many phone calls in one older analogue - AMPS - channel )

    Now if I am 20 km from a cell site it will take 60 micro seconds for my signal to arrive at the antenae. The switch will detect this. If my signal arrives to much out of sync I will squash the signal arriving from someone else using the next time slot. So the switch - through signaling embeded in the downstream link (phone is full-duplex) - will tell my phone to send the digitized voice packet 60 micro seconds ahead of time so that the time to travel to the antanea is taken into account and my packet hits its time slot to perfection. A time slot is in the order of 10's of milliseconds wide - I don't remember.

    From this - the switch can know roughly how far you are from the antenae. This info is currently not collected unless you are debugging the air interface - and collecting this information IS CPU intensive on a switch degrading its performance. That is "advanced timming" ... should have called it "timing advance inforamtion" or something !!

    Currently what they are doing for phone tracking is placing a second receiver on the base station antenae. The switch also know what other antanae are in the vicity of the cell phone (for handoff purposes). On a 911 call the switch will signal these additional receivers on the surrounding base stations to listen and time stamp your voice packet. This information is passed back to a computer that can calculate your location.

    In Any given cellular switch ( handles about 60000 simultaneous phone calls !!! ) there is only a handfull of 911 calls - a switch could not track EVERY phone call in a system, it would make the network cost too much!!! And remember AT&T makes no money tracking you ... they make money on phone calls. As long as they make more money on phone calls than on collecting and selling this information (Point to point phone calls makes more money than advertising by a long shot - and collecting that info on millions of calls a day would cost a shitload) they will not concentrate on it - they are tracking you because they must - not because they can or want (well they may want to but for cheaper, much cheaper)

  • One could use a device reading fingerprints connected to your computer/cellphone/... This would prove that it is you.

    Mark
  • It would be possible to set something up with the collusion of your ISP, if you have CLID anyway. Short of getting a certified tamper proof networkable GPS chip surgically implanted into your body, well you can't. Which is a good thing indeed. It's very hard to set up a system that you couldn't relay round somehow. Oh, actually... if you want to prove your physical location to someone, have them come and meet you.
  • So what you really want is the GPS receiver to internally sign the data coming out with a private key that the receiver manufacturer holds?
    This would prove that the GPS data was provided by the card and was not tampered with after it came out. From there, it's up to the person to sign the GPS data to verify that he/she believes the GPS data represents their position.
    It would be quite simple for a GPS receiver to have a built in manufacturer key and sign data it produces.
  • Heh. That just gives proof that your eye or finger is with the GPS wherever it is located. A crafty kidnapper could cut off a finger and take it somewhere else with a GPS.

    or something like that.
  • Oh, and the alternative is?
    --------
    Life is a race condition: your success or failure depends on whether you get the work done on time.
  • Nope, EEPROM isn't secure enough. You need DRAM, and you need to shuffle the key around to avoid electron migration.

    Then just have it so if it's tampered with, the power is cut.
    --------
    Life is a race condition: your success or failure depends on whether you get the work done on time.

  • IPv4 addresses can also be traced to you, albeit with *slightly* more difficulty.

    NAT and dynamic IP addresses are the two most troublesome systems on the internet. They're the reason we have all these klugy client-server protocols (instant messengers and the DynDNS come to mind) that would be better replaced by true peer-to-peer protocols (like SMTP, DNS, internet phone, etc).

    If you're worried about anonymity, have a look at the Freenet [sourceforge.net] project, rather than hindering the much-needed adoption of IPv6.

    Some benefits of IPv6 off the top of my head:

    • Users get a block of addresses, rather than a single address to split/NAT/etc (Remember: dynIP != security)
    • Autoconfiguration (plug your new 'net appliance into you home network, and away you go)
    • Zillions of addresses (good for organization and allowing your appliances to be connected)
    • Better routing

    --------
    Life is a race condition: your success or failure depends on whether you get the work done on time.
  • There's nothing really different about the military-grade signal, except the sequence is significantly longer (repeats every 3 days, IIRC), and there are 2 frequencies (for compensation of atmospheric interference).

    AFAIK, it's not signed or anything.
    --------
    Life is a race condition: your success or failure depends on whether you get the work done on time.
  • A combo GPS/cell-phone device. The device is manufactured in such a way that attempting to
    hack it physically will destroy the device. Then you call a phone number, or some agency calls your cell phone, and you give a voiceprint and some PIN-like key to prove that it is, in fact, you on the other end.

    This should be sufficient if you want to prevent others from impersonating you. For situations where one might *want* their buddy to impersonate them (e.g. provide an alibi), the agency that is relying on this device as proof of position, could equip the device with a fingerprint scan or a retina scan. That way, *you* are confident that nobody will impersonate you against your will, and *they* are confident that nobody is impersonating you against *their* will.
  • The problem inherent to the use of any positive - identification technique, be it
    • smart cards,
    • Unique person IP's
    • geographically asigned IP's,
    • or eyeball / fingerprint / DNA recognition,
    is that someone, on the other end knows who you are

    Any company that we depend upon to design or implement this technique, will become (at least to some perspectives) a big-brother entity.

    Who can be trusted to take on such a role? If it is an open - source solution, how would we keep the code from forking like the Windows Manager(s) of an OS that we all know and love? What happens when a company is trusted to implement this system by 51% of the "known good and decent computers of the world" and then mandates the use of an obscure field (MS-Kerberos)?

    And why can we expect that this would be accepted by the computing public, given our reaction to cookies, the PIII Proc. ID, and any number of other percieved infringements on our privacy? I know Slashdot is not representative of the Computing Public as a Whole, but our sample reactions may not be too far off-base.

    Where does the right to privacy give way to the right to be properly identified and trusted? and Vice Versa?

  • Any one-sided transmission can assert anything you like about your location. The receiver can use the transmission and other available information to *disprove* an assertion made within the transmission (you aren't at 45N90W because that's where I'm standing) but can't *verify* the assertion without some sort of reliable test.

    It could be something like a tightbeam transmission to the asserted location (which must then be encoded and sent back to us), but what you've actually done there is verify that the person making the assertion has a receiver at the tested location.

    An Orwellian "1984"-esque surveillance system would allow for visual verification of asserted location (and depending on the available data, verification that you aren't anywhere else either (you don't have a doppel at the claimed location)), but would come at a serious cost of privacy, hopefully made obvious by my choice of a definition.

    In short, I'm not interested in paying for the installation of an infrastructure that allows you or anyone else to verify my current location...

    Regards, Ross

  • All this proves is that Bob's internet uplink is in France.
  • A Private h2g2-like database could do this.
    For instance, (after establishing identity conventionally) I claim that I am at my college's computer lab, at XX terminal. It tells me to read the serial number from under the keyboard. if I get it right, I'm in.
    Of course you would need a large number of facts for any verifiable location, and they'd have to be things you wouldn't think to memorize beforehand, and preferably things that won't change too often, unless you can keep the DB up to date with the changes, in which case fast changes are good.
  • As far as I can see, this discussion is trying to figure out how to prove where a user is. This could be done via GPS or some other position specification technology. On a different tack, one could use source defined routes if they were available. That way, when a user is first logged into a system, the server can figure out how to get to their subnet. Once this has been found once, all subsequent transmissions could be sent to the same location. This way, someone connecting from the wrong network will not be able to use the server. I'm guessing that internet backbone routers don't like being told what to do, so this is wouldn't be a viable option.
  • And even worse, Amazon could now target prices based on the economy of your neighborhood.

    They already have your ZIP. Wouldn't that work just as well?
    --
  • As strong as digital signatures?

    Art thou on crack? If so what brand crack of art on thou?

    A fax counts as digitally secure and binding. Yuck. A 5 year old could forge one easy. Clicks count as a binding agreement.

    Digital signatures may be strong "legally" in that you can get sued even if you don't even own a computer, but that only makes me more worried.

    The other thing was:

    Someone earlier mention an interesting chain of authentication to prove that they were who they said they were.

    How about having the user enter the key into the system to decrypt that days instructions on how to finish authenticating.

  • I think Casio makes a watch.
  • Hehehe. Pr0n sites wouldn't be dumb enough to restrict lots of potential income, just because the bible belt might not like pr0n as a category...
    -----
  • How about Digitally signing your SecureGPS encoded urine sample, before it is teleported to the local Fuzz.
  • Well, there are several ways that you can prove to have been at a certain location at a certain point in time:

    • positive evidence: You shoot yourself in the head. The police finds you and estimates the time of death.
    • negative evidence: You blow yourself up. Your body is nowwhere to be found. This proves that you must have been there at the time of the explosion.
    • circumstancial evidence: You make the woman next to you pregnant. The prove will be there nine months later. This method is rather fuzzy. Sometimes the uncertainty principle kicks in and you're not the father.
    • solipsistic evidence: you are the center of the universe, therefoer your location never changes. There is nothing to prove. To whom, anyway?
    • democratic evidence: people vote where you are right now. This works in some states. Others will not reach a decision and keep on recounting the votes. Not recommended.
  • You don't have to have it embedded in your skin - you simply have to provide a piece of information only you would know, such as your PGP/GPG private key...

  • As I am reading this thread, I just returned from a job interview at a company that manufactures GPS receiver chips and learned that a new FCC regulation will require all new mobile phones released on the market starting in January 2001 to have onboard GPS.

    The interviewer would not go into details as to which purpose the FCC hopes to achieve (find wounded hunters lost in the middle of nowhere in an emergency situation, or make localization of mobile-savvy criminals easier) but it sure looks like Big Brother is watching us.

  • Re:GPS (Score:2)

    by Elvii ( 428 )
    Correct me if i'm wrong but current handhelp GPS technology does not allow you to determine your exact position due to military restrictions. This is accomplished by not giving the real algorithm that the GPS satelites run off of but a inexact version thereof.

    No problem. It's not a different algorithm, but not giving an exact timing. It was called SA (Selective Availibity) and it basiclly made the time recieved from the sats a bit random. Seeing as the sats/reciever depend on timing to get position, IIRC, you had up to 100m epe (estimated position error) on a civilian gps unit. Two ways to bypass this: Get a differintal GPS, basicly two recievers in one unit, and average your location, so to speak. Or get the encrypted miliary band, via military reciever, which broadcasts the corrections to cancel out SA.

    BTW, SA has been off for the better part of this year, so my handheld garmin gets accuracy near that of a military handheld unit. Thou differential units found in aircraft are still more accurate. :)

    bash: ispell: command not found
  • Such a situation needs to be safe not only against spoofs, but also permit the owner to prove that he didn't do a spoof himself.

    Let's say that I'm accused of an armed robbery which occured while I'm on a hunting trip (this really happened to a friend of mine). To have a system intended to prove my location which were usable as a defense, it would have to be proof against my own spoofing.

    As a result, it would be more effective to have a system with two-way communication (thus utterly unlike GPS) which permits a user to request that their position and some arbitrary data (eg. biometrics, signed by the user's key, recovered from the user to demonstrate that they're with their equipment) be returned with the digital signature of the verifying service. Such a token would demonstrate the position of my equipment (via the reading) and my presence (via the biometrics... yeah, I know this is shaky... I hate biometrics too). A timestamp should also go inside the service-verified info.

    Though I haven't had 'nuff sleep lately to really think something like this through seriously, that should work. Main issues is that it requires two-way communication, and a replacement of the current GPS system (perhaps w/ towers doing triangulation if it only needs to be used inside a fairly small area; otherwise larger/heavier/more expensive equipment is needed).
  • I am seeing a lot of misconception here about what my thought experiment implies.

    I am most definatley NOT talking about a proof of location that is broadcast without user control. I'm talking about a voluntary "location signature" type technology. (For example I do not have to use digital signatures at all times and I can produce an "anonymous" one as needed to hide my own identity.)

    I've also had the suggestion from someone else in the office that a third party signature of time stamps would be handy. For example, instead of having certified postal mail sent back to myself to prove my patent is pre-dated, perhaps there could be a way to get a third party time stamp included in my digital signature.

    Just more fun thoughts. :)
    ---
    Don Rude - AKA - RudeDude

  • ...for Jon Katz's ICBM coordinates.
    --
  • I know of a bank that once looked at a GPS based security system. The problem was that different countries have different laws on data protection, so it was important that the laptops of it's employees couldn't do certain things (or release certain informatiom) in countries with restrictive (or 'good' as I think of it) data protection laws. Such as the UK.

    So, the laptops were fitted with PCMCIA GPS cards, and these were integrated with some of the apps on the laptops. The employee couldn't access some things if they were in the wrong country.

    I'm not sure if the project was ever widely released or seen as practical. Obviously it relies on not being able to hack the GPS card, and not getting administrator/root access to the machine.

    GPS, fun as it is, is limited. The GPS system is passive and cannot determine the location of GPS devices - unlike, say, the mobile GSM system that CAN determine where mobile phone devices are. Rather, the GPS receiver devices can determine the location of the GPS satellites, and then compute their own location from that data. That makes it rather less useful for proving the location of a GPS receiver.

    Also, in my experience of GPS, which is quite good, it is utterly useless at determining altitude. But maybe I've been unlucky with handsets :-)
  • Okay, each location that has to be able to authenticate you can combine a GPS with biometric security & an atomic-clock-syncronized timestamp. You put whatever bodypart needs to be authenticated (or multiple ones), the thing recognizes you. Then it checks the GPS location & combines that with the verified time. Voila. The information can then be transmitted security to wherever it needs to be via encrypted means.
  • A simple solution might be the following. The GPS satellites each send out their own version of the time, and the GPS receiver compares this to its time to determine its position relative to the satellites. What you could do is have each satellite periodically (once a minute?) send their time with a digital signature. You can then use the GPS company's public key to demonstrate that you have data from a GPS unit that was at a given location at a given time. Of course as the previous poster pointed out, you still have to prove that you were also at the same location as the GPS unit.
  • Currently they can't do it for fear of being sued in areas where gambling is illegal.

    why should they be afraid? There has been numerous cases where people in countries that don't have any anti-cracking laws couldn't be touched by US laws for crimes they committed in the US...why should it be different the other way around?

    Gambling is legal in North America..the only catch I can see is making sure that the gambler is 18 (or 21 or what ever).
  • ..I believe IP allocation is to a certain extent on a regional basis, so it shoulkd be possible to prove that at least you are on the right continent.

    Similarly ISPs are allocated a pool of IP addresses, so when you connect it is highly probable you can be located down to country or even local level, unless you indulge in a little spoofing.

  • The author mentioned timestamps, but timestamps have all of the same problems GPS data have.

    When you create a signature with a timestamp, where does the time come from? If you're using only software, the timestamp is probably coming from the operating system, which thinks the time is whatever you tell it it is. It's not especially hard to generate an incorrect timestamp.

    So in both cases we have to rely on trusted hardware, which is always a tricky thing. Even if I have a hardware device which includes a clock as well as the ability to store keys and generate timestamps, I still have to trust that all of the code involved is bug-free and the clock is correct. And it's easy to make sure the clock is correct only if you assume a few different parties can be trusted.

    So sure, you can make a GPS receiver that signs and timestamps its data. But you have to trust everything inside the box, you have to trust the people who created the firmware, and you have to trust that the box can't be modified. Even the most secure hardware devices are subject to attacks. And this doesn't even address the question of where the GPS signal itself might bve coming from...

  • GPS won't cut it though, there is no trust, you could pick a location at random, encrypt it and say you were there.. Now I can think of two ways to do this.
    • You could start building trusted GPS recievers than authenticate their results. When you read a location you are also given a signature from the machine.

      I believe this is the proper way to do it in a military setting where you can serialize each device, hand create and install encrpytion and authentication keys. It's not entirely useful in the general sense because after you sell a million trusted GPS devices people could start doing fraudulent things like buying two, leaving one in a particular place, having their friend read the numbers off of it to you over the phone and then let you report that you're in a place where you're not. Plus you still have to hand create each GPS reciever to keep it trusted..

    • The other idea I can think of that might be possible without making too many serious changes to the system would be to send encrypted and timestamped streams of GPS data from the satellites with random tokens added. Then when a person wants to claim that are at a given location they could sign/authenticate the data given by the GPS to show that they are who they say and that data could include the raw transmition from the satellite which was used to triangulate their location. Then if you know the what stream were transmitted or have access to a trusted third party who does (the DoD?) then you can verify that they are where they say and that the tokens they used to claim that location match the ones you broadcasted. Of course this only works if GPS is a closed system because I could still intercept the same satellite transmition streams from some other location and if I knew how to massage the data correctly I could string the streams together to make it look like I was in a different place. It may be mathematically possible to come up with a scheme this way that works.

      I'm thinking that it would be partially realtime though. Like this. Billy claims he is at 40NX105W and send you a stream of bits sent to him by a set of satellites. Susie examines his signature and believes that he is Billy then she examines the data and it looks like he really is where he says. To be positive Susie talks to the set of satellites Billy is in contact with and causes them to send random tokens in a random order and since she knows the order and his location she can tell what order he should recieve them in. Then Billy has some small number of milliseconds to report the series of bits he sees in the correct order to verify his location, if he has too much time he could be in a different location, recieve all the streams, reassemble them as they should be and then transmit them back so we're talking about very very small timing tolerences. Maybe you need anonymous satellites to do this.. Right now GPS knows which satellites it is talking to and can tell the difference between them.

  • How are you to know in advance that you're going to be framed for a crime, in order to use the services? Or are you gonna dole out $32 a day (say every 15 mins, 8 hours a day) on the chance that someone might in the future?
  • So if you sent the actual data you recieve from the satillites to you whoever you want to prove to, then all that is required is that the stream from the sattilite is signed and you know the public key of the GPS satillite.

    However, this does not prevent some one who is at one location sending the stream he recieves to an intermediary at a different location who will then authenticate with the first (fake) location.

    There could also be a sort of small scale distributed location finding algorithim. If you have a large group of people with transmitter/receiver pairs within some distance (dependant on transmit/recieve power), you could have everyone triangulate on each other. The more people you have in your system, the more compromised units you'd have to have before you'd get spoofed results. Of course you could never be sure that the location data hasn't been spoofed, but given enough people, you could have some high confidence probability in the result. If you have a high enough density of people, you could spred the network of transmitter/recivers across the entire planet.

    Now what do you folks think, should I get a patent on this? :-P
  • Here I am, in front of the Eiffel tower, holding a newspaper that says "Bush Wins!"...
  • I invite you to the Geographical Anonymizer Project, where people are streaming their timestamped NMEA data. Pick and choose from data over the past four weeks...and if you want to participate, note that you can delay the delivery of your data by up to two hours, so others know where you were two hours ago but not now; the software in your unit will only report data from areas you designate, so you can have it turn off before you get near home.
  • Of course, this is almost what Stoll did in "The Cuckoo's Egg". He measured network delays of the intruder and found the distance to the intruder. Unfortunately, he decided it was impossibly far and something was wrong with his measurement. It turned out that the actual location, Germany, was that distance away.
  • Uh... no. You're confusing two technologies. The "rice grain sized" device is a transponder which is often used on pets and racing animals. The reader is a book-sized device which can detect the device's serial number from a few inches away.

    A GPS antenna is significantly larger.

  • Singapore has had this for a while. very tech stuff. UK govt is sponsoring research into a GPS type system that would allow them to monitors cars positions and speeds.
  • As Fiber To The Curb becomes more readily available, and our bandwidth is a "given" just like the phone and electrical lines, we'll be able to roughly pinpoint locations easier.
    The edge device you connect to to access the 'Net will be registered with the Feds (this is only a matter of time). Knowing how long it takes light to travel to the closest fiber-to-copper demarc point by your house, it will be easy for the edge device and/or your PC to spit out some numbers showing what will essentially be a ping time delay. Knowing that Registered Router X serves the geographic area of Y, and you are 2.003ms away from Router X, then you must be 1.22 miles from the router. The fiber run you are on goes down Big Brother Ave, so you're 1.22 miles from the end of Big Brother Ave.
    It's not a pin-pointer, but it proves that you're not on the other side of the world impersonating yourself...

  • Re:GPS (Score:2)

    by BrK ( 39585 )
    Correct me if i'm wrong but current handhelp GPS technology does not allow you to determine your exact position due to military restrictions.

    You're wrong :) The inaccuracy factor in the GPS system was recently disables. ALL GPS units (within their own design limitations) are now equally accurate.
  • First, your digital signature doesn't prove anything about who you are. Rather, the people you communicate with trust that it identifies you, and trust is antithetical to proof.

    As a for-instance, I've been doing a lot of transatlantic communications lately with a fellow named Roger [last name deleted]. At least, he says his name is Roger... but since I've never met him, I haven't been able to verify his identity by examining his passport, his driver's license, etc. So I just have a voice to identify, and that voice is self-identified as Roger, which is no identification at all.

    Roger and I exchanged OpenPGP keys. His OpenPGP key identifies him as "Roger John Laurence [last name deleted]". But I still didn't know if this was really him or not, so we talked voice. After verifying that it was the same voice I'd talked to earlier, and he doing the same (a process no more complex than "Hey, Roger?" "Yeah, mate?"), we exchanged SHA-1 hashes of our OpenPGP keys and verified we'd received each other's keys successfully.

    We still haven't verified anything.

    For all I know, Roger has given a copy of his OpenPGP key and passphrase to another person, and all of my email is coming from this third person who's not Roger. And for all Roger knows, I've done the exact same thing.

    Signatures can only verify identity in the case of two parties who trust each other. Trust is antithetical to proof; therefore, it's hard to say "digital signatures prove identities". They don't. They make it easier to trust, but that's not the same as proof.

    Insofar as this GPS verification scheme--good luck. The likelihood of a system being subverted increases with the square of the number of people involved. How does the trusted third party ensure that both parties are reporting their location honestly? If I'm really in Cedar Rapids, Iowa (42N 42W--Cedar Rapids is the closest city I could find to the Magical Location of Life, the Universe and Everything), I can have a conspirator in Quito, Ecuador (0N, approx 55W). When the third party tells me, "Okay, verify your location according to this protocol," I can have my conspirator in Quito perform the protocol and send the result back to me; then I send the result on to Trent, the trusted arbitrator.

    How is Trent to know that I've done a man-in-the-middle attack against his system? Well, it's possible that this system can be patched up to solve the man-in-the-middle problem. But those patches will themselves have attacks against them, and the entire situation quickly devolves from there.

    Crypto works well with communicants who (a) want to talk to each other and (b) trust each other to apply a protocol properly. Once you take away either assumption, most crypto falls flat on its face.
  • Further, even if you could somehow tie your position and identity together, a GPS Constellation simulator [jcair.com] only costs about $250,000 USD. If it was really important to generate a fake, that's really not too high a price.

    I work in the GPS business and would be interested in pursuing this a little further. If anyone has any bright ideas, let's throw a prototype together.
  • All this proves is that Bob's internet uplink is in France.

    Nope. The satellite can be sure of Bob's location if he signs a reply to its message and sends it "instantly". Then only somebody with his key could be in France.

    BUT... he could leave a copy of his key in France. And at this point you're right, and that is the killer for my original suggestion. Protocols which relly on secret information are broken if one of the parties doesn't want to keep it secret! We can't trust Bob not to duplicate his identity, unless his "location key" is embedded in a closed box, which is designed to self destruct if anyone breaks the seal :)

    Now of course, the perfect self destructing locked box is non-existent. However, you can do pretty well with pre-written EEPROMs inside a microcontroller. Beaking one of those open and reading it would be a pain and a half; add a few anti-tamper measures, and it gets really evil. If you were completely paranoid, you could add an "expiry date" so that you needed a new chip each month.

    Maybe I shouldn't be saying any of this, because I can think of many more evil applications of this technology than good ones.

  • If I'm really in Cedar Rapids, Iowa (42N 42W--Cedar Rapids is the closest city I could find to the Magical Location of Life, the Universe and Everything)Sorry buddy, Cedar Rapids, IA is not at 42N 42W. That location [mapquest.com] is in the middle of the North Atlantic. I will however verify my location (Cedar Rapids, IA) from the output of my Magellan 310 Handheld GPS receiver:

    -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 41 58 34N 91 57 12W -----BEGIN PGP SIGNATURE----- Version: PGPfreeware 6.5.8 for non-commercial use iQA/AwUBOgxdnbfXGCgiKZQGEQL5PgCg3hQJ0M6tred1KlkV86 IJqcQzXLIAoKhy 2PP5lm6s9Mm/iBeqv07cEYYv =LCrB -----END PGP SIGNATURE-----

    If you'd like to verify that signature, my public key is posted on my user page here on /. and also on the common key servers. I can't however provide any was for you to actually verify that I correctly keyed in the location displayed on my GPS receiver, nor do you have any way of verifying that the position it reported was accurate.
    _____________

  • -----BEGIN PGP SIGNED MESSAGE-----
    Hash: SHA1

    41 58 34N 91 57 12W

    -----BEGIN PGP SIGNATURE-----
    Version: PGPfreeware 6.5.8 for non-commercial use <http://www.pgp.com>

    iQA/AwUBOgxeoLfXGCgiKZQGEQKVHwCeKFq+fp9CmTNOQp0o UGwrjQ21x6gAmwUB
    lw5HmpKwc2AJDqzDxJtacLji
    =q06U
    -----END PGP SIGNATURE-----
    Trying that again. Gotta remember, Preview is the one on the right.

    _____________
  • I don't like the idea of this. Just think about it...as an earlier poster commented, it becomes possible for say France to block certain Englishmen, or Afghanistan to block Russians. The wonderful thing about the net is anonymity, and once we decide to give our exact location every time we get on a web site, that is totally lost.

    I'd rather keep it so that no one really knows where I'm from online, unless I tell them (and don't lie).
  • GPS isn't really enough. You need to have something which you couldn't have had if you were anywhere else. Satellites could give you this, but only if they beamed different, cryptographically secure,messages in different directions. [...]Of course, Bob could just have a tranceiver in France

    That problem can be (theoretically) solved with a very exact clock and an (almost) direct link. The satellite sends an encrypted signal containing the exact time. Bob then immediately forwards the signal. If the time difference equals (distance(Satellite,France) + distance(France,Alice))/C, (with C the speed of light), Bob cannot be using a transceiver.

    Of course, in real life, switching speed and other inevitable technical delays will forbid pinpoint accuracy, but it might be good enough for guaranteeing location within a couple of miles.

  • Similarly ISPs are allocated a pool of IP addresses, so when you connect it is highly probable you can be located down to country or even local level

    Unless you happen to be on AOL?
  • I think you misunderstood the technology used in the article you reference here. The technological problem posed by this question is completely different.

    First of all, to clarify: no, Quova can NOT _pinpoint_ users in real time. They have catalogued IP addresses and correlated them with locations. If your IP is not static, or has changed since their cataloguing (sp?), their data is meaningless. Same for dial-up users, who will all appear to be in the same place (wherever the server is) even though they may be spread far and wide. Think AOL. A simple example: say I have an account with my ISP. I could be dialing in to the same number from home; or from a friend's house; or from across town; or from another state, for that matter, if I'm willing to pay long-distance charges; all of these would give an IP address that appears to be in the same location.

    The main thrust of this problem is not just knowing where someone is generally, but using exact location for authentication/identification. You would need a way of verifying that the person/device is precisely where they claim to be. Knowing that a particular IP implies that they are in a certain city or even on a certain street means little in this context. Authentication requires much more precise, verifiable information than could be provided by Quova.

  • Imagine a system that can accept appointment requests for you and based on rules you specify, either accept, reject, or notify you of this appointment request. This sounds great, right: agent based appointment scheduling. Might save everyone a lot of time, etc.

    Okay, pretend you want to build this system. If your agent wants to schedule you (or you do it yourself) for an appointment at 2:30 and you are currently engaged until about 2:15 it may only be a good idea to schedule this if the travel time is less than 15 minutes.

    Now you could specify a "map" of your normal stomping grounds and the distances between some of them, and let the computer do the math, but this is limiting and requires "thought". If all the little networked devices involved in all this scheduling know thier co-ords (either stored, accessed from a database, or by GPS) the whole problem becomes easier. You enter some upper/lower bounds for travel times (over some set ranges) and the whole system becomes more more general.

    Finally, one of the best reasons to have security and encryption is so people can prove they are who they say they are... If you build geographics into the authentication this may be useful but wouldn't it be easy to spoof the location? The input has to come from somewhere...

    --8<--

  • GPS (Score:2)

    by AoT ( 107216 )
    Correct me if i'm wrong but current handhelp GPS technology does not allow you to determine your exact position due to military restrictions. This is accomplished by not giving the real algorithm that the GPS satelites run off of but a inexact version thereof. If this is true then whoever controls the GPS sattelites(US govt. i think) could alter the signals to allow a direct data stream from a GPS unit to be identified as either a true or false stream using the real algorithm through some sort of authentication server. of course it would be really scary if any govt had control of this, but hey it might work

  • I am no GPS guru, but I think I know enough to do some handwaving -

    My understanding is that the GPS satellites transmit timing information, and the receivers use this information (from multiple satellites) to perform a triangulation computation, and to determine a location.

    What you could do is have the satellites transmit a signature along with the timing information, and this could prove that the timing information could only have come from a GPS satellite.

    This means that your receiver knows that it is receiving real GPS information - however, everyone else in your immediate vicinity also receives the same information. The receiver actually carries out the computation to determine a location, so therefore, you would need to have the receiver sign the computation - this proves that the output was computed by a legitimate process.

    Then, you could sign the result with your private key - this would prove that you signed some location information.

    To verify all of this, the client (who you are proving to) would verify that you signed the location information - then it could verify that the location was created by a trusted process, but verifying the signature. It could also verify the timing signals from the satellite, to verify that they were legitmate, and that your signed location information was generated within a recent period of time (to prevent a replay of older information).

    How does that sound ? Other technologies - differential GPS may blur this, and perhaps a GPS guru could comment on the above.

  • Your detail is fine, but to protect against malicious users, the GPS data needs to be signed by the "GPS server" [1] to prevent the user from simply changing the GPS location data to another value. In this instance and MD5 isn't sufficient: the user could simply substitute the MD5 for another known value.

    Oh, the GPS data will also need to be timestamped - this prevents replay attacks.

    [1]Either the data from the satelite could be signed in some way I guess, or the GPS decoder could be a "trusted host".

  • Here's the idea. I believe it's provable given a few assumptions; like Einstein was right, f'rinstance.

    A network of satellites constantly transmit time-coded challenges.

    The land based receiver grabs at least three of these challenges at the same time, combines them, signs them with the user's private key and sends them back up to the sky. By using the time difference and the speed of light, the receiving satellite can verify that the private key is within a certain distance from the receiving satellite. Verifying that the private key is the same place as the user is a bit more difficult, but we have to start somewhere.

    The actual precision with which this method could pinpoint the user would depend upon the speed of computation.

    If specialized hardware could perform the capture, signing and transmission in 10 microseconds, then the position of the signer could be pinpointed to within 3e8 * 1e-5 / 2 = 1.5 kilometers. (Speed of light in m/s times the number of seconds equals the time it would take to transmit the signal to somewere else and back)

    Assumptions:
    * User alone maintains control of their private key. (This is a biggie. A user could give the signing device to an accomplice and send them off somewhere. )
    * Tamper proof, time-synchronized satellites (this is fairly safe now, but for how long?).
    * No information travels faster than the speed of light in a vacuum. (I believe work has been done with connected quantum spins that already threatens this assumption.)
  • The only way I can think of doing this is in undefeatably secure way would be to put up another GPS satellite system [or perhaps merely reprogram the current ones, if they can handle sensitive reception as well], in which the protocal would be:

    A: Your device sends a authentication session request to the satellite network.
    B: Several satellites in range [after coordinating with each other to ensure precise timing] send out a "packet" addressed specifically to your device.
    C: Your device, upon recieving each packet, immediately sends out a response.
    D: The satellites compare the time they recieved the response, and know where you are.

    Basically, it's like being pinged from several locations at once. It's a reversal of the semantics of GPS itself. Current GPS works because each satellite is sending out time stamps continously, and your reciever compares the difference in local arrival time from the stamps sent at the same time. [This is because the speed of light is finite, and the satellites are at different distances from you].

    You just need to reverse the process, sending back a ping, and have the satellites coordinate the difference in arrival time of the signal.

    Come to think of it, a special device wouldn't really be necessary. Any transmission that can be intercepted by the sattelites could be sampled, and arrival time differences used to locate the source precisely. Hmmm.

    I'd be willing to bet good money the government already has just such a capability.


    ---
    man sig
  • Doesn't Heisenberg have something to say about being able to tell where something is, exactly when? If you come up with a way to beat him, let me know ;)

  • I was trying to be humorous. Hence the ;) at the end of my post. But, thanks for the physics lesson.

  • The biggest beneficiary of geo-signature technology: Jon Katz...

    ...because the rest of us might finally understand where he's coming from :)

  • the question - which I read as "How can I prevent someone masquarading as me from a remote location at a given time?"

    I'm not sure how read the question, but I started to think about the question "how can I prove after the event that I wasn't at the scene of a crime?"

    Now at very first thinking various issues come up:

    Data must be controlled by me - I don't want my location tracked by any third parties; I just want to be able to reveal/prove where I was at a certain time, at my instigation.

    Maybe some kind of trusted third party injecting random but recorded bitstreams into the ether as radio waves at every gridpoint, and changing every minute or so.

    There would need to be process and crytographic controls on this infrastructure.. might not be possible.

    You would record the bitstreams on a pocket recorder or mobile phone device, and then you can say "look, the random code at this time and place was xxx".

    Then there is the question of cheating... I just ask my friend who was there what the number was. So I guess I have to record the numbers on a "tamper proof" (see Secrets& Lies [slashdot.org] for why I put quotes around that) device like a Smart card, that only the "authorities" (whoever they are) can extract the information from.

    There would need be a password protected scheme so I have to give my authorisation for a date-range of location data to be extracted as well. So I would have to trust this device, a lot more than I trust say Canivore.

    Then what if know I'm going somewhere bad and I just give my card to a friend for a day or so. Not sure here.. maybe the device has to randomly demand some biometric data from me at random times.

    Pretty interesting stuff.. gonna have to re-read Schneier's books (again). I recommend the section in Applied Cryptography that deals with protocols, for stuff along these lines.

    I might put this up and work on it some more at my web site [lot105.com]. Or I might not.

  • Well, quite - I'm sure you could use GPS and signatures to prove that a machine was in a location at the same time, but I could be using any form of remote access tools to talk to that machine.
    The idea of using a trusted third party to validate people's locations, already mentioned here, would need an international standard to be agreed and would probably need to rely on fingerprints / retina scans et cetera to work, so probably not any time soon...
    I'm a bit worried that people who don't want to prove that they are in a particular region (don't want their fingerprints on file, for example) will be denied various services, such as the latest encryption software.
  • Suddenly all on-campus Micro$oft employees find that they are blocked from accessing Slashdot, and are presented with the mesage "Access denied until you produce something stable".

    "There's a party," she said,
    "We'll sing and we'll dance,
    It's come as you are."

  • This idea has been investigated before. Dorothy Denning calls it "the grounding of cyberspace" There is a chapter on this coauthored by her and Peter MacDoran in the book [aw.com] edited by Peter Denning.

    Title of the paper is Location-Based Authentication: Grounding Cyberspace for Better Security

    This idea is also explained in her book Information Warfare. The idea is using GPS signatures which are not forward-predictable. As other posters pointed out, that only proves the existence/access to GPS receiver located at some point and time not necessarily the presence of the *individual* there.

    WakeTurbulence

  • Base it on a SecurID-type model? (Score:3)

    by The Dodger ( 10689 ) on Friday November 10, 2000 @03:19AM (#633049) Homepage

    Hmmmmmmmmm... How about a gadget that combines a GPS receiver with a SecurID-style method of embedding your physical location, along with your digital signature, into a string of numbers.

    The idea is, you're doing whatever you're doing, wherever in the world, on whatever computer. Let's say you're logging into something - you just use the Gadget the same way as we use SecurID cards/fobs today - tap in the string of digits that appears on the screen. Actually, it would have to be longer than six digits. Perhaps using Hexadecimal would be better, although that would mean that the Gadget would need a better display... Well, most GPS receivers I've seen are capable of displaying text anyway.

    Anyway, if you do that, the equivalent of the ACE Server (the server that authenticates SecurID users) at the other end can authenticate you and determine where you are.

    Only problem is I can't figure out how to make this an open system, without opening it to abuse, in the same way that if we all knew what algorithm RSA use for SecurID, we'd be able to come up with the 6-digit code, simply by knowing a fob's serial number.

    Also, how to use it to digitally sign emails...

    Hmmmmm... Further thought required.


    D.

  • Re:But... (Score:3)

    by SEWilco ( 27983 ) on Friday November 10, 2000 @06:05AM (#633050) Journal
    Let's see.. the induction charger in my bed was working, so my battery is charged. When I step by the window, my phone chirped in my ear to tell me the GPS unit and the phone are working. I just need to polish the webcam lens in my forehead, and I'll be ready to step out in Public where I have nothing to hide. I sure am not going to be like that sap last week that couldn't prove that he wasn't at the bar robbery...

  • Impossible in the general case (Score:3)

    by DrZircon ( 28779 ) on Friday November 10, 2000 @02:48AM (#633051)
    A simple hardware solution is not enough - the hardware needs to be permanently fixed to the same location as the person (i.e. physically embedded and all that that implies) and needs to be non-spoofable. Embedded solutions present the rather daunting prospect of spoofers removing the apparatus.... (Think Leila in Futurama and her job chip)

    The only other way to achieve position guarantees would involve trusted 3rd parties (postion escrow anyone?) and we all know how much we trust those kinds of solutions! (Unless we are talking about people who are detained at the government's pleasure)

  • Doesn't this exist already? (Score:3)

    by edibleplastic ( 98111 ) on Friday November 10, 2000 @06:34AM (#633052)
    At least in theory? Unless I misread/misunderstood this article/question, Quova can pinpoint the geographic location of Internet users [slashdot.org] in real time. Would this be what is needed?

    Of course then you'd have to deal with spoofing...

  • Re:But... (Score:3)

    by DrWiggy ( 143807 ) on Friday November 10, 2000 @05:58AM (#633053)
    Errmm.... surely if his GPS data is encrypted with his private key then isn't that enough to "prove" that at least he believes that his GPS is with him?

    The problem here is dealing with the GPS data. You basically have to prove that the data has come a GPS receiver that has been unmodified. There is nothing stopping me fixing the stream of GPS data to the application signing it, to make it look as though I was anywhere in the world. Therefore there are several areas you have to lock down to make sure that this data is authenticable:

    1. The position determined by the GPS receiver is accurate, and can not be manipulated by somebody with a small transceiver nearby convincing the GPS receiver that you are located somewhere else. On a 3 or 4 satellite track, you may not be able to move youself very far, but in the US you could probably "cross" a state boundary, and in Europe you could probably mangle things around to move across country borders.

    2. Once you can be sure that the data being received by the GPS receiver is genuine, you have to get it into the PC untampered. What's more, it has to make it all the way to being signed without being vulnerable to tampering at any point. If the longitude and latitude is stored somewhere in memory location 'X' just before being signed, I could conceivably tamper with it.

    3. You then of course have to sign it, and then ensure that this mechanism is strong and that it can't be manipulated either at this stage or further along the transmission.

    The problem really is that signing the location is the wrong approach - you have both your private and public key, and you can sign *ANYTHING* you want to authenticate it as belonging to you, but in actual fact, you need the GPS receiver to store the private/public pair and not divulge it to anybody else. How then, do you stop people tampering with the receiver?

    Thinking about it, I think that may be the best approach - the GPS does the crypto internally, and you build measures to ensure that it can't be tampered with. Even then, you still have to make sure you're talking to a real GPS receiver etc. so challenge/response stuff may have to be added in. Nasty.

  • The future is here (Score:3)

    by CaptainZapp ( 182233 ) on Friday November 10, 2000 @03:16AM (#633054) Homepage
    Actually that works pretty well with GSM phones (and probably other standards too).

    The SIM is your encrypted device. To activate it you need a PIN, which could be considered your digital signature and presto:

    The location of Your SIM is trackable within a couple 100 yards or so.

    The problem of course is, that the location is attached to the device. Nobody prevents you from sticking it under a car and pretend that you went all the way from Malmoe to Lissabon.

    That's probably also the most tricky issue with your question:

    How can you make a position dependant signature device independant, or at least (if you use a device) make it non-functional if you're not physically there.

  • Pseudo-random data stream? (Score:3)

    by AlphaOne ( 209575 ) on Friday November 10, 2000 @02:49AM (#633055)
    Since GPS uses pseudo-random data streams, couldn't you prove your position at a particular time by somehow inserting the timestamp data from the four satellites you're talking to into the digital signature?

    Or would that be easily faked?

    I'm not a GPS expert, so I don't really know for certain.

    -C
    --

  • Re:Location Authenticator? (Score:3)

    by billybob2001 ( 234675 ) on Friday November 10, 2000 @03:25AM (#633056)
    How about having to provide a DNA sample?

    Extremely easy when surfing pr0n.

  • Re:But... (Score:4)

    by henley ( 29988 ) on Friday November 10, 2000 @03:19AM (#633057) Homepage

    Errmm.... surely if his GPS data is encrypted with his private key then isn't that enough to "prove" that at least he believes that his GPS is with him?

    The chain of trust is therefore:

    • Exchange public keys
    • Validate trust in public keys (as per normal)
    • Owner validates trust in GPS location
    • Owner encrypts / signs position information packet from GPS with private key
    • Receiver party validates postion against public key

    At the end of this exchange, the receiver trusts that the owner believes s/he's in the position exchanged between them.

    This doesn't cover the case that the authentic Owner is trying to spoof his location, but I don't believe that was the question - which I read as "How can I prevent someone masquarading as me from a remote location at a given time?"

  • But... (Score:4)

    by komet ( 36303 ) on Friday November 10, 2000 @02:46AM (#633058) Homepage
    even if you could prove that your GPS receiver was at position X at time T, how would you prove that YOU were also there? Unless it's implanted under your skin...

    Of course, it really depends what you want to do. In Switzerland, devices are being installed into trucks which register position and time in order to collect road taxes. The device is attached to the vehicle and tampering with the fixing will probably get you a heavy fine.

  • Re:Pseudo-random data stream? (Score:4)

    by HuskyDog ( 143220 ) on Friday November 10, 2000 @03:15AM (#633059) Homepage
    Some of my colleagues here at the British MOD have a GPS simulator which they use for various navigation research tasks. Basically you connect your GPS receiver antenna input to this box of tricks, then type a lat/lon, date and time into the simulator and voila!

    So, the bottom line is that anything that relies on GPS data can be faked. Obviously these simulators are expensive, but I presume that the GPS receiver manufacturers all have them, so there most be quite a few in the world.

  • Mobile computing? (Score:4)

    by Engmir ( 152832 ) on Friday November 10, 2000 @02:48AM (#633060)
    Come on, this cant' be a serious idea. With the increase in mobile computing, you can't expect anyone to have his/her computer in a fixed place... Besides you can use a proxy that's not in the same location as you are, so that won't prove your identity either...
  • The internet gambling industry has been looking for something like this for quite a while. If people can prove they're inside physical areas that are allowed to gamble, suddenly internet gambling is wide open for companies like Harrah's and Caesar's to take on. Currently they can't do it for fear of being sued in areas where gambling is illegal.

    The drawback: pr0n users in the bible belt would be suddenly unable to hit their favorite sites. Site operators would restrict content to areas where they could be certain of legalities.

    And even worse, Amazon could now target prices based on the economy of your neighborhood.

  • A solution of sorts (Score:5)

    by Peter Eckersley ( 66542 ) on Friday November 10, 2000 @03:24AM (#633062) Homepage
    GPS isn't really enough. You need to have something which you couldn't have had if you were anywhere else. Satellites could give you this, but only if they beamed different, cryptographically secure, messages in different directions.

    The simplest example would be an "authentication satellite", where Jane asks the satellite,

    "is Bob really in France?"

    ...Satellite sends encrypted message for Bob in the direction of France...

    If Bob knows the contents of the message, he's in France.

    Of course, Bob could just have a tranceiver in France.... so.... quantum encrypt it in a single photon :). Single photon quantum encyption is nearly good enough for Earth-satellite links, IIRC.

    None of this fixes the "problem" (is it really a bad thing?) mentioned elsewhere in this discussion, that physical devices and people are separable...

  • only on slashdot (Score:5)

    by nomadic ( 141991 ) <`nomadicworld' `at' `gmail.com'> on Friday November 10, 2000 @04:13AM (#633063) Homepage
    So we go from people complaining that new technology can be used to track them to complaining that new technology can't be used to track them.
    --

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