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Satellite reveals immense scale of GPS signal tampering

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Re: Satellite reveals immense scale of GPS signal tampering

#71

Post by geerlingguy »

oneshtein wrote: post #69
mirashii wrote: post #66

Earlier quoted context omitted.

It would take those devices having synchronized atomic clocks, which they do not.

Atomic clocks are not precise enough, they need nuclear clocks, which are not developed yet: https://thoriumclock.eu/

GPS uses atomic clocks, not sure why we'd need something more precise for a timing reference on any other satellite system, unless you wanted to get like millimeter-level accuracy using nothing but satellites (and that would require a lot more than just a better clock on the sats).

Re: Satellite reveals immense scale of GPS signal tampering

#72

Post by rkourdis »

eqvinox wrote: post #61
throw0101a wrote: post #58

Earlier quoted context omitted.

>> An even bigger WTF is why GPS data isn't signed with some official key so spoofing is impossible. > Because an attacker can just replay legitimate broadcasts with slightly skewed time and origin and introduce huge errors into the fix. Galileo uses a signing system (Timed Efficient Stream Loss-Tolerant Authentication, TESLA) to protect the authenticity of its messages, including preventing replays: * https://gssc.e…

I don't think this helps against someone receiving the signals (all satellites) and rebroadcasting them. The effect of that would be that any receiver of those rebroadcasted signals will believe they are located where the receiver of the rebroadcast is located (just the time is slightly off/late, but that doesn't help much without a reference to check against.)

It's been a few years since I've worked with this stuff but I'm under the impression that you can do this sort of replay only for a short amount of time. If so, is there a point?

If the receiver expects a key to have been revealed at a particular timestep, it won't accept a replayed message with that key after that, so you can't record and replay indefinitely.

EDIT: Unless you indeed meant to instantly replay - would the receiver accept the highest strength signal, ie. yours?

Re: Satellite reveals immense scale of GPS signal tampering

#74

Post by geerlingguy »

tw1984 wrote: post #59

US is not even investing in GPS anymore. Their L5 signal has been in experimental operation for probably over a decade, still "experimental".

The US invested $8 billion into upgrades... and then killed off the program due to tons of problems with the upgrades[1]:

> However, the program was unable to deliver needed capabilities on an operationally relevant timeline at an acceptable level of risk to meet the GPS constellation modernization needs.

Hopefully the newer equipment and incremental improvements can bridge over to whatever's next.

[1] https://www.spaceforce.mil/News/Article-Display/Article/4465...

Re: Satellite reveals immense scale of GPS signal tampering

#75

Post by brookst »

mirashii wrote: post #66
christophilus wrote: post #54

Earlier quoted context omitted.

It seems like we have enough satellites in space that are giving off enough unique signals that we could put together a device that solves the GPS problem without needing GPS itself. I wonder what it would take.

It would take those devices having synchronized atomic clocks, which they do not.

Is it really not possible to converge a location from implicit signals like frequency shift from relative motion? My intuition, maybe wrong, is that with enough compute and a thorough enough ephemeris of what should be broadcasting what, you could derive location.

Re: Satellite reveals immense scale of GPS signal tampering

#76

Post by plasticchris »

geerlingguy wrote: post #71
oneshtein wrote: post #69

Earlier quoted context omitted.

Atomic clocks are not precise enough, they need nuclear clocks, which are not developed yet: https://thoriumclock.eu/

GPS uses atomic clocks, not sure why we'd need something more precise for a timing reference on any other satellite system, unless you wanted to get like millimeter-level accuracy using nothing but satellites (and that would require a lot more than just a better clock on the sats).

The clocks aren’t even the biggest source of error in the pseudo ranges.

Re: Satellite reveals immense scale of GPS signal tampering

#77

Post by DoctorOetker »

eqvinox wrote: post #61
throw0101a wrote: post #58

Earlier quoted context omitted.

>> An even bigger WTF is why GPS data isn't signed with some official key so spoofing is impossible. > Because an attacker can just replay legitimate broadcasts with slightly skewed time and origin and introduce huge errors into the fix. Galileo uses a signing system (Timed Efficient Stream Loss-Tolerant Authentication, TESLA) to protect the authenticity of its messages, including preventing replays: * https://gssc.e…

I don't think this helps against someone receiving the signals (all satellites) and rebroadcasting them. The effect of that would be that any receiver of those rebroadcasted signals will believe they are located where the receiver of the rebroadcast is located (just the time is slightly off/late, but that doesn't help much without a reference to check against.)

nobody would send a military vehicle (manned or drone) without initializing a proper clock, the replays would be stale.

Re: Satellite reveals immense scale of GPS signal tampering

#78

Post by maxerickson »

brookst wrote: post #75
mirashii wrote: post #66

Earlier quoted context omitted.

It would take those devices having synchronized atomic clocks, which they do not.

Is it really not possible to converge a location from implicit signals like frequency shift from relative motion? My intuition, maybe wrong, is that with enough compute and a thorough enough ephemeris of what should be broadcasting what, you could derive location.

Your argument needs to be why it is practical in a smallish device, not that it seems possible.

Like you first have to infer what satellite you are even measuring, before you can decide where it might be.

Re: Satellite reveals immense scale of GPS signal tampering

#79

Post by DoctorOetker »

with directional antennas or telescope mounts, it would seem one could do positioning with catalogs of radio pulsars or optical pulsars (with clear skies or above the clouds), by more old-fashioned navigation like once used at sea.

To find your place on the globe you need to know the current time, and the azimuth and elevation of a feature in the astronomical sky.

Since the pulsars have different periods, observing them should allow you to reconstruct the time, and the directions of these emissions then allow you to determing where on the globe you are for such a time.

Re: Satellite reveals immense scale of GPS signal tampering

#80

Post by brookst »

maxerickson wrote: post #78
brookst wrote: post #75

Earlier quoted context omitted.

Is it really not possible to converge a location from implicit signals like frequency shift from relative motion? My intuition, maybe wrong, is that with enough compute and a thorough enough ephemeris of what should be broadcasting what, you could derive location.

Your argument needs to be why it is practical in a smallish device, not that it seems possible. Like you first have to infer what satellite you are even measuring, before you can decide where it might be.

Disagree. If the objection is just cost/complexiry, that’s really just a statement of how long until it’s practical. GPS itself was computationally impossible in the 1950’s.

If the math works, and it’s just the domain of one-off ridiculously expensive devices today, it’s inevitably feasible in the long run.

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