CODEWITHSUNDEEP
bluetooth-lowenergyprivacymac-address
david
david

Reputation: 188

Get BLE MAC from random private resolvable address

I'd like to connect an Android device (client) to an External BLE device (server). I've a couple of questions concerning the private random resolvable address mechanism.

In the end I'd like a BLE connection, which uses private random resolvable addresses to ensure privacy and still be able to obtain the original BLE MAC of the Client on my Server for internal purpose.

I'd very much appreciate if someone could answer my questions.

Best david

Upvotes: 4

Views: 3665

Answers (1)

Emil
Emil

Reputation: 18452

When bonding, zero, one or both devices can send Resolving keys if negotiated so. For each device that sends Resolving key (IRK), the Identity Address is also always sent. This contains the original Bluetooth Device address and can be either public or static random. It's this address that only bonded devices know.

The idea of the privacy feature is to never use the original Bluetooth device address in Link Layer packets but instead a randomly generated one that is changed every x minutes (usually 15). This way, if it advertises regularly, someone can't track it since it disappears after 15 min. However if you have the corresponding IRK then you can determine if the IRK matches or not. If it matches you also know the original Bluetooth Device address since your bond data contains both the IRK and original address. But if you throw away that address then you can't recover the original address, even if you have the IRK.

If only one of two devices uses random resolvable address, then the one with resolvable address can't be tracked by a non-bonded device and the one that does not use a random resolvable address can be tracked.

Upvotes: 4

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