4 ms·

But you don't permanently see them, because the ID rolls over quite often to prevent tracking the beacon. Conceivably the beacons co-operate in preventing trac

But you don't permanently see them, because the ID rolls over quite often to prevent tracking the beacon. Conceivably the beacons co-operate in preventing tracking by conversing with iPhones nearby to store a random code supplied by the phone for a period of time, and allowing any iDevice to ask for the list. If your iDevice sees the same random code it transmitted to a stranger beacon appear in multiple time periods it knows it is colocated. I would guess that the colocation feature would allow you to track devices actively (tailing someone). Spies will have to be alert the potential for both exposure and tracking. Hopefully Apple commissions Spy Vs Spy ad campaigns!

function_seven 6y ago
My guess was simpler. If the phone sees a random tag for 30 minutes, then coincidentally that tag disappears but a new one shows up--for 30 minutes--and this keeps happening, then it's probably the same tag that's following you around. Especially if it's always about X meters away, or whatever. Random tags passing by wouldn't maintain the same distance or RSSI, and they wouldn't be spaced perfectly apart in time either. Of course I'm making assumptions here about the key rotation frequency, or even if it's a regular intervals. I guess if you're spending a lot of time in crowds, the rotating beacon that's with you would be hard to pick out of the myriad other beacons coming within range all the time. ("Was that a key rotation, or another person?")
- angry_octet 6y ago
  I can see how that might work, but signal reception is always noisy. I doubt RSSI would be a reliable measure. You could partially wrap the AirTag in a scrunch of alfoil and it would mean every movement of the phone would massively change the reception, it would look like a variable distance. Also, I wonder if it is a fixed time with no overlap? Because you could certainly track someone, eg through a shopping centre, by seeing when a beacon turns off and then listening to new beacons. Correlation would be trivial. And if the e.g. 30m clock is accurate then you could reidentify hours later by just listening to the rollover time, so they would have to vary the rollover at least. I wonder about false alarms, because you can easily sit on commuter train for an hour and have someone next to you, even more so for long distance travel.

function_seven 6y ago

My guess was simpler. If the phone sees a random tag for 30 minutes, then coincidentally that tag disappears but a new one shows up--for 30 minutes--and this keeps happening, then it's probably the same tag that's following you around. Especially if it's always about X meters away, or whatever. Random tags passing by wouldn't maintain the same distance or RSSI, and they wouldn't be spaced perfectly apart in time either. Of course I'm making assumptions here about the key rotation frequency, or even if it's a regular intervals. I guess if you're spending a lot of time in crowds, the rotating beacon that's with you would be hard to pick out of the myriad other beacons coming within range all the time. ("Was that a key rotation, or another person?")

angry_octet 6y ago
I can see how that might work, but signal reception is always noisy. I doubt RSSI would be a reliable measure. You could partially wrap the AirTag in a scrunch of alfoil and it would mean every movement of the phone would massively change the reception, it would look like a variable distance. Also, I wonder if it is a fixed time with no overlap? Because you could certainly track someone, eg through a shopping centre, by seeing when a beacon turns off and then listening to new beacons. Correlation would be trivial. And if the e.g. 30m clock is accurate then you could reidentify hours later by just listening to the rollover time, so they would have to vary the rollover at least. I wonder about false alarms, because you can easily sit on commuter train for an hour and have someone next to you, even more so for long distance travel.