Do smartphones record encounters with other smartphones?

Lukki

I have read that iPhones use Bluetooth Low Energy (BLE) to record contacts/encounters with other iPhones and use this information to create network maps of their owners' movements.
Android devices would do the same.
The recording/registration of contacts/encounters would now also work between Android and Apple devices.
My question: Is this true, and if so, is there a source for this information?
Am I protected from this with GrapheneOS?

Tandara

Lukki Yes, you are protected from that on GOS, especially if you have a timer for Bluetooth and wifi setup.

Duct9143

Tandara what do you mean by "especially"? So it does leak when you have bluetooth on?

fernlike

Duct9143

If you have Bluetooth and/or Bluetooth scanning on then yes, you are presumably visible to other devices. If both are off then you should not be visible since Graphene does not support the Find my device/Device hub network.

https://grapheneos.org/usage#wifi-privacy-scanning

Wi-Fi and Bluetooth scanning for improving location detection are disabled by default, unlike the stock OS. These can be toggled in Settings > Location > Location services > Wi-Fi and Bluetooth scanning. These features enable scanning even when Wi-Fi or Bluetooth is disabled, so these need to be kept disabled to fully disable the radios when Wi-Fi and Bluetooth are disabled.

fernlike

See also this Mastodon post by the project account on the topic: https://grapheneos.social/@GrapheneOS/113321788575432923