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Comment by kube-system | Hacker News Reader

Car keys usually remained powered off until a button is pressed.

Not mine, or any others that have hands free unlocking. I presume that they are in a deep sleep but not unpowered and wake up when the car pings them.

Do they though? Lots of cars unlock when you get near to them with the key, which I imagine is technology effectively identical to an AirTag.

I believe they're in a constant low-power mode, I think (?) the car periodically transmits a beacon that "wakes up" the key (assuming it's nearby, of course) and initiates the challenge/response process.

Ah yes let me hit the power button to turn my key on rq, then I'll unlock the car

That is patently false. Keyless car fobs are constantly transmitting and it is possible to shut them down for long term storage with a key combination that almost nobody ever uses or even knows about.

If you're going to use language like "patently false" it helps to be correct. Keyless car fobs are not constantly transmitting. If they were, the battery would die quite quick. The key combinations to disable them help to prevent relay attacks, not because they just constantly transmit.

They don't transmit continuously. The little CR2032 cell in my Tesla key would be dead in a day or two but in fact it lasts about at least six months, probably more like a year. I presume that they listen for a ping from the car and only then transmit. Unless you press a button of course. I've had the car almost five years and I think I have only replaced the battery four times.

An AirTag transmits constantly yet it manages to last 6 months too. They do not wait for phones to ping them, they just beacon all the time.

Not saying this is what Tesla do. For privacy reasons it would be way better to not transit until it sees the car. But battery life isn't proof of this.

All the time? Or at intervals? At what interval and what is the expected distance at which they can be detected?

All the time, as in several times per second. I have a bluetooth sniffer and these beacons are very very chatty. I didn't test the AirTags myself but it can't be lower than once every 5 seconds or so. But really I think they are like the other battery-operated BLE beacons with several times per second. BLE really is really low energy, they got that part totally licked.

The expected distance is pretty high. Officially up to 10m (like a keyless entry) but they can reach much higher distances. Because I often leave my AirTag in the house and it gets detected very often despite me not even having an iPhone :)

Ah, yeah I was thinking keyless entry not hands-free entry.

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