GA.CJJ@Forsythe.Stanford.EDU (Clifford Johnson) (04/26/89)
From: "Clifford Johnson" <GA.CJJ@Forsythe.Stanford.EDU>
I'm curious as to the planned military application of the Global
Positioning System, vis a vis spoofing. Is this a real problem?
A radio clock designer wrote to comp.risks:
I bet the GPS satellite time signals contain error detection
codes, if not error correction, which ought to reduce false
time output to a minimum, but won't stop a bad person from
faking the time.
Does this mean that giving our nuclear missiles GPS-based
guidance systems makes them vulnerable? Self-destruct mechanisms
were avoided because of the possibility of Soviets spoofing the
signals - what could they accomplish if they could spoof the GPS
signal, and how feasible is it to do so?
And at the tactical level, to what extent would any kind of GPS-based
guidance give rise to vulnerability?
To: MILITARY@ATT.ATT.COMdoug@loihi.hig.hawaii.edu (Doug Myhre) (04/27/89)
From: doug@loihi.hig.hawaii.edu (Doug Myhre) "Clifford Johnson" <GA.CJJ@Forsythe.Stanford.EDU> writes: > Does this mean that giving our nuclear missiles GPS- > based guidance systems makes them vulnerable? Self- > destruct mechanisms were avoided because of the > possibility of Soviets spoofing the signals - what > could they accomplish if they could spoof the GPS > signal, and how feasible is it to do so? The GPS satellites have two different sets of data coming from them. The first is for civilian use. With the correct equipment and satellite availability you can get GPS navigational data for yourself along with the time and other quality data. This might give a position to within 3 meters. I do not believe that there is error detection/correction data sent for the time itself. Even if there was, I would think that this could be falsified. The second set is a encrypted set of signals that is for military use only. The position data available to the military is much more accurate than for civilians. Undoubtedly they don't want the Soviets, or any other unfriendly force having accurate enough data for military uses. Because the military's signals are encrypted, I would think that this would make it hard for anyone to mess with them. I don't have any idea how the data is encrypted. Military used for location probably accurate to within inches would have may uses. Just look at missile guidance. If your nuclear missile knows exactly where it is at all times (not only latitude and longitude, but also altitude), it can hit very accurately. Doug Myhre <doug@loihi.hig.hawaii.edu> Hawaii Institute of Geophysics Research Computing Facility 2525 Correa Road Honolulu, HI 96822
nelson_p@apollo.com (Peter Nelson) (04/29/89)
From: Peter Nelson <nelson_p@apollo.com> > Does this mean that giving our nuclear missiles GPS-based >guidance systems makes them vulnerable? Self-destruct mechanisms >were avoided because of the possibility of Soviets spoofing the >signals - what could they accomplish if they could spoof the GPS >signal, and how feasible is it to do so? > >And at the tactical level, to what extent would any kind of GPS-based >guidance give rise to vulnerability? Is this true?? The US strategic missiles depend on GPS satellites to provide guidance? The Soviets have a demonstrated ASAT capability! It would be the first thing they'd take out in an attack. I can't believe the Pentagon could be *that* stupid. Could they? Hmmmm. --Peter
military@cbnews.ATT.COM (William B. Thacker) (05/01/89)
From: sun!sunburn!mcdphx!anasaz!john In article <5936@cbnews.ATT.COM> you write: > > I bet the GPS satellite time signals contain error detection > codes, if not error correction, which ought to reduce false > time output to a minimum, but won't stop a bad person from > faking the time. > >Does this mean that giving our nuclear missiles GPS-based >guidance systems makes them vulnerable? Self-destruct mechanisms >were avoided because of the possibility of Soviets spoofing the >signals - what could they accomplish if they could spoof the GPS >signal, and how feasible is it to do so? I believe that military GPS signals use spread spectrum transmission. This means that, except for the simplest spread spectrum scheme, concealing the spreading sequence is sufficient to conceal the information, and also to prevent effective spoofing. In other words, the spread spectrum modulation itself can be used as a form of encryption. Of course,... if they key got out, that would be bad news. Even if this trick isn't used, modern crypto techniques make it possible to have a very secure ID and checksum on a message. Even if the opposition knows how to test for a valid ID, they may not be able to generate one. For example: use a truly random (quantum effect determined) sequence generator to generate a random number for each message; put the resulting number at the start or end of a publicly known "signature" - It could even be the text name of the satellite with a high reliability checksum following; Now add the current time following the random number; Encrypt the whole thing using a trap-door type block cipher system where only the decryption key is "publicly" known. (of course, you wouldn't really publish the key - this just means that if the decryption key security is breached, the messages still cannot be spoofed - only read). With a scheme like this, the position can be derived by the normal method after decrypting and authenticating the message, and the message cannot be spoofed. I suspect a stronger way to attack weapons systems using GPSS is to jam the satellite signal, or just destroy the satellite. Of course, the spread spectrum signal is harder to jam if the spread sequence isn't known to the jammer. and the resulting numbers are used as "salt" in a message that also contains the publicly known
khb@fatcity.Sun.COM (Keith Bierman Sun Tactical Engineering) (05/01/89)
From: khb@fatcity.Sun.COM (Keith Bierman Sun Tactical Engineering) In article <5984@cbnews.ATT.COM> doug@loihi.hig.hawaii.edu (Doug Myhre) writes: > ....>along with the time and other quality data. This might give a >position to within 3 meters. It all depends on how long you watch, how many "birds" you can see, your a priori, and the quality of your sattelite emphermis. NASA/JPL routinely uses the civilan signals to obtain millimeter accuracies. > The second set is a encrypted set of signals that is for military >use only. The position data available to the military is much more >accurate than for civilians. Undoubtedly they don't want the Soviets, >or any other unfriendly force having accurate enough data for military >uses. What you get is range data, from which one derives the position. Spoofing presents some tricky problems. I don't know how current receivers would handle it; it is very receiver dependent. Keith H. Bierman |*My thoughts are my own. Only my work belongs to Sun* It's Not My Fault | Marketing Technical Specialist I Voted for Bill & | Languages and Performance Tools. Opus (* strange as it may seem, I do more engineering now *)
khb@fatcity.Sun.COM (Keith Bierman Sun Tactical Engineering) (05/01/89)
From: khb@fatcity.Sun.COM (Keith Bierman Sun Tactical Engineering) In article <6067@cbnews.ATT.COM> nelson_p@apollo.com (Peter Nelson) writes: > >.... <deleted> > Is this true?? The US strategic missiles depend on GPS satellites > to provide guidance? The Soviets have a demonstrated ASAT > capability! It would be the first thing they'd take out > in an attack. I can't believe the Pentagon could be *that* > stupid. Could they? Hmmmm. > Depends on is too strong. Uses GPS when available, is a better description. GPS is also very helpful for the lanuch vehicle. ASAT assault was considered early in the design of GPS, and it was decided that the many advantages of GPS made it worthwhile despite the ASAT threat. Keith H. Bierman |*My thoughts are my own. Only my work belongs to Sun* It's Not My Fault | Marketing Technical Specialist I Voted for Bill & | Languages and Performance Tools. Opus (* strange as it may seem, I do more engineering now *)
budden@manta.nosc.mil (Rex A. Buddenberg) (05/01/89)
From: budden@manta.nosc.mil (Rex A. Buddenberg) GPS comes in two flavors for users. P and c/s codes (can't decode the abbreviations at the moment). P-code requires the user to have a crypto key to properly receive. In brief, the GPS satellites 'lie' about their position (last few bits of a word) and you can't correct the lie without this code. Because it is the last few bits, the rest of the word is OK and c/s users get service, but at a reduced accuracy level. The p-code also suffices quite nicely as an anti-spoof measure. If you are in the local area, you can circumvent any spoofing problems by using differential GPS. Including the intentional spoofing due to p-code. Requires a reference receiver on a surveyed location as well as the user receiver. The diff-GPS ref receiver can tell how much the satellites are 'lying' because he knows where he really is. This degree of dishonesty is then communicated by local means to the user who then corrects his GPS signals accordingly. Same differential principle works quite nicely to correct for Loran propagation errors. Rex Buddenberg (usual disclaimers -- I work in USCG headquarters and nav systems is part of my job.)
henry@zoo.toronto.edu (Henry Spencer) (05/02/89)
From: henry@zoo.toronto.edu (Henry Spencer) > Is this true?? The US strategic missiles depend on GPS satellites > to provide guidance?... Not yet, partly because Navstar isn't really operational yet. But the next generation of missile guidance systems will probably use it for occasional updating, at least. > The Soviets have a demonstrated ASAT capability! The existing Soviet Asat system is good only in low orbit, and the Navstars are somewhat higher up. I agree that it doesn't sound like a wonderful idea, though. Navstar is unfortunately one of these systems that gets enshrined as an official panacea for all (in this case, navigational) ills. Henry Spencer at U of Toronto Zoology uunet!attcan!utzoo!henry henry@zoo.toronto.edu
henry@zoo.toronto.edu (Henry Spencer) (05/02/89)
From: henry@zoo.toronto.edu (Henry Spencer) >[Accuracy] depends on how long you watch, how many "birds" you can see, >your a priori, and the quality of your sattelite emphermis. NASA/JPL >routinely uses the civilan signals to obtain millimeter accuracies. One reason for this is that the current birds are "pre-production" versions. The "production" ones, now starting to be launched, include some sort of capability whereby DoD can degrade the accuracy of the unencrypted signal whenever they feel like it. Potential users in fields like aviation do *not* like this, especially since there is no provision for warning of it. Henry Spencer at U of Toronto Zoology uunet!attcan!utzoo!henry henry@zoo.toronto.edu