I'm not sure how much you know about GPS, but position in GPS is intrinsically linked to time. You know a satellite's orbit from its orbital elements, so, a given moment in time, you know where it is. The satellite emits signals with its internal time. You receive the signal sometime later. The difference between those times gives you the distance to the satellite at that frame[0]. When you have three or more measurements, you can triangulate your position in 3D.
In terms of spoofing, one method is to emit signals from ground based transmitters that match the signal from the actual satellite, but with offset times, and at higher power levels than the actual satellite[1]. This gives the receiver a false location.[2] If you have a source of time-truth, you can reject these signals.
In terms of jamming, you'll note that it allows rapid resynchronization after jamming. During jamming, you don't know where you are. After jamming, without a highly precise clock, you need to solve for the actual time by integrating signals from >=4 satellites. With a highly precise clock, this step is removed.
[0] There are confounding factors, like refraction in the ionosphere, but a rough approximation is that the signal is travelling at c
[1] Higher power is trivial because the signals from the satellites are very weak
This is not quite how GPS works. Because of relativity, there is a difference between local time and remote time for all GPS satellites relative to the drone.
Jamming nowadays does not work by simply throwing off random numbers. This is trivially defeated by gyroscope. It works by feeding time data that initially is exactly the same as the satellite, and slowly changes that as if it was in some other plausible direction, ultimately giving total control.
Against primitive forms of jamming, sure this might work. Against modern spoofing attacks, no there is no fix. Overall, what worked works and what doesn't work won't.
Relativity doesn't really factor into this issue; the core of the issue is false timing signals.
Any introduction of a false timing signal whose time offset from the true signal is greater than the local clock's uncertainty can be flagged as false. Higher-accuracy local clocks reduce the amount of error that can be introduced without detection.
CSACs don't solve the issue, but they do allow for detection of more spoofing signals, and they reduce the amount of error that any successful spoofing signal can introduce.
No, relativity absolutely does factor. The timing signal from the GPS satellites is warped by relativity as you move relative to them.
Without a source of location truth, you have no way of knowing if the change in the time signal is because of your movement relative to the GPS satellites, or because of spoofing.
As I said, the false GPS signal will start with a time offset of zero. They will then progressively offset the time signal of each satellite as if, for example, the GPS receiver was deviating slightly right, after which the drone will turn left.
Relativity matters in GNSS in general, but it doesn't really matter for the issue of spoof detection; relativistic effects would be solved for by both the attacker and receiver. There's no uncertainty in them.
Relativistic effects dictate that it is impossible to distinguish changes in relative time and changes in relative position.
Because of relativity you cannot use local time to estimate remote time, and hence you cannot use local time to make the difference between time spoofing and location changes.
Comments
I'm not sure how much you know about GPS, but position in GPS is intrinsically linked to time. You know a satellite's orbit from its orbital elements, so, a given moment in time, you know where it is. The satellite emits signals with its internal time. You receive the signal sometime later. The difference between those times gives you the distance to the satellite at that frame[0]. When you have three or more measurements, you can triangulate your position in 3D.
In terms of spoofing, one method is to emit signals from ground based transmitters that match the signal from the actual satellite, but with offset times, and at higher power levels than the actual satellite[1]. This gives the receiver a false location.[2] If you have a source of time-truth, you can reject these signals.
In terms of jamming, you'll note that it allows rapid resynchronization after jamming. During jamming, you don't know where you are. After jamming, without a highly precise clock, you need to solve for the actual time by integrating signals from >=4 satellites. With a highly precise clock, this step is removed.
[0] There are confounding factors, like refraction in the ionosphere, but a rough approximation is that the signal is travelling at c
[1] Higher power is trivial because the signals from the satellites are very weak
[2] This is a classic example: https://en.wikipedia.org/wiki/Iran%E2%80%93U.S._RQ-170_incid...
TL;DR: useful for existing ground/air based threats.
This is not quite how GPS works. Because of relativity, there is a difference between local time and remote time for all GPS satellites relative to the drone.
Jamming nowadays does not work by simply throwing off random numbers. This is trivially defeated by gyroscope. It works by feeding time data that initially is exactly the same as the satellite, and slowly changes that as if it was in some other plausible direction, ultimately giving total control.
Against primitive forms of jamming, sure this might work. Against modern spoofing attacks, no there is no fix. Overall, what worked works and what doesn't work won't.
Relativity doesn't really factor into this issue; the core of the issue is false timing signals.
Any introduction of a false timing signal whose time offset from the true signal is greater than the local clock's uncertainty can be flagged as false. Higher-accuracy local clocks reduce the amount of error that can be introduced without detection.
CSACs don't solve the issue, but they do allow for detection of more spoofing signals, and they reduce the amount of error that any successful spoofing signal can introduce.
No, relativity absolutely does factor. The timing signal from the GPS satellites is warped by relativity as you move relative to them.
Without a source of location truth, you have no way of knowing if the change in the time signal is because of your movement relative to the GPS satellites, or because of spoofing.
As I said, the false GPS signal will start with a time offset of zero. They will then progressively offset the time signal of each satellite as if, for example, the GPS receiver was deviating slightly right, after which the drone will turn left.
Relativity matters in GNSS in general, but it doesn't really matter for the issue of spoof detection; relativistic effects would be solved for by both the attacker and receiver. There's no uncertainty in them.
Relativistic effects dictate that it is impossible to distinguish changes in relative time and changes in relative position.
Because of relativity you cannot use local time to estimate remote time, and hence you cannot use local time to make the difference between time spoofing and location changes.
You've lost me.
No. If you have both a source of time-truth and a source of location-truth you can reject these signals.
But if you had a source of location-truth you wouldn't need GPS.