They vary by enough, and have unique identifiers. And there are four of them per car, which makes it easier to build a profile for each car. This car has these four identifiers, this other car has these four, etc. Couple that with info from license plate cameras and you can track a car without seeing it’s plate.
That’s alarming, but how much can these really vary? I’d be surprised if a lot of vehicles weren’t the same.
CADmonkey@lemmy.world 9 hours ago
iglou@programming.dev 21 hours ago
Well, from my knowledge, the person you replied to is inacurrate. All tires will transmit at the same frequency. But every X seconds, when each tire transmits its data, it transmits an ID unique to its transmitter with it.
dual_sport_dork@lemmy.world 20 hours ago
Every X seconds is pretty generous. My Subaru only seems to poll the sensors every few minutes, and only when the wheel speed is above 35 MPH or so, at least via what I’ve observed with my diagnostic tool. The sensors are battery powered and I suspect the low refresh rate is a deliberate gambit to conserve battery life.
You are correct on the ID point, though. They can contain up to 16 hexidecimal digits as far as I’ve seen, and while there doesn’t seem to be any mechanism for truly enforcing uniqueness the chances of an ID collision are so low that you may as well consider it impossible. Some aftermarket sensors can be wirelessly reprogrammed with an arbitrary ID, though, which may be of marginal utility for the truly paranoid. (My diagnostic tool can do this, too. The intended use case is cloning the ID from an OEM sensor for a car whose TPMS relearn procedure is more trouble than it’s worth.)
Regardless of your vehicle’s polling frequency, most sensors can be woken up any time by a specific radio pulse, which my diagnostic tool can also do, and the range is surprisingly long. Just my car’s own BMS where the receiver is (above the rear left wheel well) can pick up the sensors in my snow tire rims even when said rims are sitting in their storage rack inside my garage, about three car lengths away.
iglou@programming.dev 16 hours ago
If my memory serves well, it is configurable. I say X seconds because it can be 5, 10, 30, but of course also 60, 120… This is my programmer brain talking :)
oyenyaaow@lemmy.zip 20 hours ago
can’t believe i’m quoting a transformers fanfic but here we are…
but if there’s also cameras everywhere then every time a negative match comes out then it just triggers the cameras to pick out those cars. best bet would be collectively agreeing to use one set of specific id for everyone, not a randomized id and thus unique id’s