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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

#81

Post by imglorp »

stalfie wrote: post #70

Once again, Russia turns out to be the reason we can't have nice things. War truly is a waste for everyone involved. Now that Russia is also helping North Korea to launch satellites (one so far), expect everything to get worse in the future. I give it 2-10 years before one of the two threatens an imagined adversary with detonating a nuke in orbit, with the explicit intent of causing Kessler syndrome.

The article tiptoes around the who and the why but it's pretty clear.

The US has HARM (anti radiation missiles) but it would be very easy for Ukraine, or anyone, to create an inexpensive drone, which you would program with a frequency, a signal strength, and a general direction and send it to ride the radio signal straight to the jammer. Repeat daily as needed.

Anything on the ground transmitting high power on GPS freqs is up to no good for the global community.

Re: Satellite reveals immense scale of GPS signal tampering

#82

Post by eqvinox »

rkourdis wrote: post #72
eqvinox wrote: post #61

Earlier quoted context omitted.

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…

I did indeed mean instant replay, and yeah the better your clock in the receiver the narrower the window of delay that the spoofer has to work with. If you can get the time from a 5G network or NTP down to 10ms, that'd mean you can detect being spoofed at >=3km distance if the spoofer has 0 delay (which is doable with a plain analog rebroadcast).

Re: Satellite reveals immense scale of GPS signal tampering

#83

Post by BenjiWiebe »

minetest2048 wrote: post #8
vachina wrote: post #4

I honestly see this jamming as a win. GNSS is a global blanket opt-in American spyware.

My pedantic self says GNSS includes other non-US constellations such as GLONASS, Galileo and Beidou, and they flew those satellites because they don't fully trust US GPS

Ya I think they meant 'GPS'.

Re: Satellite reveals immense scale of GPS signal tampering

#84

Post by eqvinox »

DoctorOetker wrote: post #77
eqvinox wrote: post #61

Earlier quoted context omitted.

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.

You're overestimating how precise the clocks in normal electronic devices are. A typical PC clock is +/-100ppm. After 1 hour that's 0.36s, which is roughly 100km in distance. A good electronic clock is a tenth that. An OCXO is in the 1ppm range, but that's still a kilometre per hour.

There's a reason GPS satellites are used as reference clock for PPS, PTP and NTP. A naval vessel you could carry a Rubidium clock on, I guess. But on ground vehicles or mobile receivers... nope.

[ed.: OCXOs aren't that large, 1cm^3 box ballpark, too large* for a smartphone or laptop but not a problem on larger quadcopters, cars or military radio equipment. And 1ppm is long term drift, you can try compensating a bit beyond that, so - I guess it's a question of spending the money and energy** on OCXOs.

* thick specifically, can't easily be made thin AFAIK

** the first O there is Oven - roughly 0.5W continuous draw.]

Re: Satellite reveals immense scale of GPS signal tampering

#85

Post by londons_explore »

Enginerrrd wrote: post #67
londons_explore wrote: post #24

Earlier quoted context omitted.

Your satellite doesn't want to be sending out lots of different signals - due to a limited power budget. So you have to send out one (or maybe a couple) of signals protected by a key. Yes, you can distribute that key individually to clients using public key cryptography over the same link (and many services like pay TV do exactly that). But fundamentally any client who is able to decrypt the main stream can also shar…

Isn’t this the exact problem tree-based broadcast encryption schemes were designed to solve? You could surgically revoke the keys of a bad actor, and I’m not exactly sure, but I think the scope of their ability to affect the jamming resistance of other users is necessarily limited by the tree.

Indeed you can revoke anyone's keys any time with such a scheme. But a single leaked and unrevoked key is still enough to jam it for everyone.

Obviously you could have some "revoke each players keys in turn until the jamming stops" scheme, but it seems suboptimal.

Re: Satellite reveals immense scale of GPS signal tampering

#86

Post by Const-me »

eqvinox wrote: post #84
DoctorOetker wrote: post #77

Earlier quoted context omitted.

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

You're overestimating how precise the clocks in normal electronic devices are. A typical PC clock is +/-100ppm. After 1 hour that's 0.36s, which is roughly 100km in distance. A good electronic clock is a tenth that. An OCXO is in the 1ppm range, but that's still a kilometre per hour. There's a reason GPS satellites are used as reference clock for PPS, PTP and NTP. A naval vessel you could carry a Rubidium clock on, I…

> A typical PC clock is +/-100ppm. After 1 hour that's 0.36s

Are you confident in these numbers? They add up to 52 minutes of drift/year.

Good modern quartz watches specify 5 seconds/year drift, almost 3 orders of magnitude better.

Re: Satellite reveals immense scale of GPS signal tampering

#87

Post by eqvinox »

Const-me wrote: post #86
eqvinox wrote: post #84

Earlier quoted context omitted.

You're overestimating how precise the clocks in normal electronic devices are. A typical PC clock is +/-100ppm. After 1 hour that's 0.36s, which is roughly 100km in distance. A good electronic clock is a tenth that. An OCXO is in the 1ppm range, but that's still a kilometre per hour. There's a reason GPS satellites are used as reference clock for PPS, PTP and NTP. A naval vessel you could carry a Rubidium clock on, I…

> A typical PC clock is +/-100ppm. After 1 hour that's 0.36s Are you confident in these numbers? They add up to 52 minutes of drift/year. Good modern quartz watches specify 5 seconds/year drift, almost 3 orders of magnitude better.

Yes, albeit 100ppm is bad/cheap crystals. 50-30ppm is normal.

The difference with a quartz watch is that it's factory calibrated with the load capacitance on the crystal, and that it's a 32768Hz tuning fork. For a variety of reasons, generating higher frequency clocks off 32768Hz is... "annoying" (huge PLL ratio, very slow feedback loop step), and typical crystals in the 10-100MHz range are just less precise and thermally stable. (Not sure why, I'm not an oscillator manufacturer...)

(NB: you can of course correct for initial deviation in software. The actual problem is stability over temperature.)

Ed.: https://www.digikey.com/en/products/filter/crystals/171 (or, in the hopes the filter on the link works, https://www.digikey.com/en/products/filter/crystals/171?s=N4... ) - look at the options and prevalence for frequency stability & tolerance.

Ed.2: a wristwatch also benefits from being kept at constant-ish body temperature.

Re: Satellite reveals immense scale of GPS signal tampering

#88

Post by DoctorOetker »

Const-me wrote: post #86
eqvinox wrote: post #84

Earlier quoted context omitted.

You're overestimating how precise the clocks in normal electronic devices are. A typical PC clock is +/-100ppm. After 1 hour that's 0.36s, which is roughly 100km in distance. A good electronic clock is a tenth that. An OCXO is in the 1ppm range, but that's still a kilometre per hour. There's a reason GPS satellites are used as reference clock for PPS, PTP and NTP. A naval vessel you could carry a Rubidium clock on, I…

> A typical PC clock is +/-100ppm. After 1 hour that's 0.36s Are you confident in these numbers? They add up to 52 minutes of drift/year. Good modern quartz watches specify 5 seconds/year drift, almost 3 orders of magnitude better.

add on top of this that oven controlled crystal oscillators (or any more performant technologies if affordable) would be selected by militaries...

Re: Satellite reveals immense scale of GPS signal tampering

#89

Post by throw0101a »

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.)

> […] (just the time is slightly off/late, but that doesn't help much without a reference to check against.)

The 'time sync' does not need to be done in the same absolutely sense (time_t is the same everywhere), but only in the relative sense:

    Various approaches exist for time synchronization [15,16,17,18].
    TESLA only requires the receiver to know an upper bound on the delay
    of its local clock with respect to the sender's clock, so a simple
    algorithm is sufficient.
* https://datatracker.ietf.org/doc/html/rfc4082#section-3.3.1

Knowing the (rough) broadcast delay from sender to receiver is sufficient.

Re: Satellite reveals immense scale of GPS signal tampering

#90

Post by eqvinox »

DoctorOetker wrote: post #88
Const-me wrote: post #86

Earlier quoted context omitted.

> A typical PC clock is +/-100ppm. After 1 hour that's 0.36s Are you confident in these numbers? They add up to 52 minutes of drift/year. Good modern quartz watches specify 5 seconds/year drift, almost 3 orders of magnitude better.

add on top of this that oven controlled crystal oscillators (or any more performant technologies if affordable) would be selected by militaries...

I'm unaware of any technology between OCXOs and Rb standards. The latter have gotten smaller but not tiny and also need quite a bit of ongoing maintenance and calibration.
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