FWIW, "It won't be supported by GrapheneOS. (...) Bluetooth still has to be configured and enabled by the OS to make it work that way."

https://discuss.grapheneos.org/d/11520-android-find-my-devic...

The article linked there has a few more details about the implementation:

https://www.androidpolice.com/android-15-powered-off-finding...:

> To solve this problem, Google is working on a “Powered Off Finding” feature that allows a device to store precomputed Bluetooth beacons in the memory of the Bluetooth controller. This means that even when a device is powered off, it can continue broadcasting Bluetooth beacons to nearby devices.

> Unfortunately, Powered Off Finding isn’t the kind of feature that can just be enabled on any device. This is because the device needs to have hardware support for powering the Bluetooth controller when the rest of the components are shut down. Plus, device makers need to put in some extra engineering work to support this feature. For example, they need to support the Bluetooth Finder hardware abstraction layer (HAL) so that the Android OS can enable Powered Off Finding mode and send those precomputed Bluetooth beacons that I mentioned.

I don't know how that could work if the battery is dead, unless they're letting the Bluetooth controller draw on some reserve battery capacity after the phone has powered itself down.

There is mostly dead and then there is all dead. A battery which is unable to supply enough power to keep the entire phone operating can likely supply enough for just the Bluetooth chip. Of course, the resulting deep discharge may damage the battery chemistry.

I'm pretty sure phones shut down long before they reach 0%, keeping plenty of charge for the Bluetooth beacon. The battery protection circuit will for sure prevent deep discharging by cutting the power.

We've discovered the mythical "unlimited". Unlimited Bluetooth power :-)

Putting my tinfoil hat on, this explains why Google was okay adding a toggle to location access for apps on Android. They don't need your device to send them their location anymore, they'd only need you to be in range of an UWB or BLE device.

I'm all for assuming bad intent when it comes to Google and, but this doesn't really make sense.

Google owns the OS; if they want your location, they don't need to care about per-app location permissions.

> Google owns the OS

Unless you install something else.

At which point how does what GP said matter? If you install something else, it doesn't matter what toggles exist in stock android....

Did I misunderstood that the Bluetooth device could exchange some data on its own when the phone is off?

> Google owns the OS

Google is still beholden to consumer privacy laws. I’m sure if you turn off location data in your Google account they won’t track you. The guys in the Room 641A will.

"Google has agreed to pay nearly $392 million in a settlement with 40 states over allegations that the company tracked people through their devices after location tracking had been turned off, a coalition of state prosecutors announced on Monday."

> Google is still beholden to consumer privacy laws.

To ignore them or what ? None of the FAANG respect the privacy laws (GDPR for example). They just pay lobby money and insignificant fines from time to time and no government cares about it.

iOS-style runtime permissions (for things like location access) were introduced in Android 6.0, which was released back in 2015. That's quite the long play.

Does anyone know if the baseband chip communication with the tower is disabled in airplane mode?

I've measured with an external, unconnected RF monitor. The cell phone shows clear activity when not in airplane mode, and then zero activity when in airplane mode.

There's my anecdata...

I was told: "I suspect that in airplane mode it would only communicate at the specific request of the system (and perhaps in spread spectrum mode), so [before baseband is activated from outside] it would not be worth measuring." What do you think?

Isn't that... totally expected? After all, it's the system that told the modem/baseband to enter airplane mode in the first place. Of course it can also tell it to exit airplane mode.

You are right, bad translation. She was trying to explain that the problem is that, independently of you and against your will, the remote telecommunications system is able to activate the broadband chip of your mobile phone while it is in airplane mode, where you expect the baseband system to be deactivated.

I was considering a Pixel 8a when it's released, now I'm not so sure. Not really keen on a mobile botnet.

IMHO if you cary around anything that contains a cellular modem you're fair game anyways.

On my phone, the modem can be killed with a hardware kill switch.

Which one? I have a Pinephone and it is a great device. It's just not a good phone.

Librem 5.

The if here is some phones can be turned off and not transmit anything, at all.

Modems are usually directly connected to the battery rail, because (so the saying goes) they have high peak power consumption.

I once built a cell phone from scratch. They do have high peak power consumption, and I did connect it to the battery rail directly, along with some capacitors to handle the surges.

I have a Pinephone, which has hardware switches to turn off potential privacy destroying features.

But it's even more secure than that - them made it so it's such a poor phone that I never managed to get it into use as a daily driver phone for more than a day or two at a time! The most private device is one you never bother carrying!

If you need to worry about cellular tracking, you should either carry your phone in a faraday bag or carry a dumb phone whose battery can be taken out.

Does this have any implications for "Airplane mode". Or the requirement to turn off your cell phone during takeoff.

You already don't have to turn your phone's Bluetooth off during takeoff, so, no, it shouldn't.