> Hold up, how are they generating a private key from a public key?
They are not. They are generating a private/public key pair where the first 46 bits of the public key happen to match the victim's BLE address.
The find-my network then accepts beacons (encrypted with the attacker's private key) from this address, and stores it in iCloud to be retrieved by the attacker via the 46-bit prefix.
They patched the finders, presumably by fixing this:
> The lost device advertisements are supposed to be "Random Static", but the researchers found that Apple "Find My" listeners ("finders") will accept advertisements for any address type.
Expensive computed public key first 46 bits == Victim's BLE address
The Apple FindMy system doesn't (or didn't) validate that the public key being broadcast had ever been manufactured or registered. So anyone with an iCloud account could query the Apple FindMy hashtable for the last observed encrypted payload, which contains the observed location generated by the nearby phone.
If you have root on the victim's device, you don't need the expensive computation step. You just take a public/private keypair of your choice and reprogram the victim's Bluetooth hardware to broadcast that instead.
ok so it seems like 2 attack patterns, one where you can replace the bluetooth on the target device, and another where you can find a matching public key prefix and set up an beacon for it using your own private key ? or am I still not getting that
It was always possible to configure a victim device to be a Bluetooth beacon if you had root on the victim device. You just clone an AirTag to the victim by changing the victim's Bluetooth address (using root access) and start broadcasting FindMy beacons.
What is novel in this attack is that you can use non-root access. You observe the victim's fixed Bluetooth address, and then craft a FindMy beacon that happens to match. Since the FindMy beacon is basically just a public key that the receiver uses to encrypt location data, crafting the beacon is just finding a public/private key pair that matches the victim's Bluetooth address. Since broadcasting a beacon requires less rights (less than root), this is much more broadly exploitable (excluding the expensive precomputation step).
No, they find the victim's MAC and generate a payload to broadcast from the victim's device, which will make the device appear to Apple devices as a genuine Airtag. Apple devices then upload location reports to Apple, and the attacker downloads them. No real Airtags are involved.
They are not. They are generating a private/public key pair where the first 46 bits of the public key happen to match the victim's BLE address.
The find-my network then accepts beacons (encrypted with the attacker's private key) from this address, and stores it in iCloud to be retrieved by the attacker via the 46-bit prefix.