OpenHaystack

Apple has successfully leveraged popularity of its phones to create a global device tracking system known as Find My network. The way it works is you buy an AirTag (an Apple accessory), which is a Bluetooth - based puck the size of a big button, and then you attach it to whatever you want to track.

There is an initial setup / pairing process after which the AirTag starts working on its own, generally by periodically broadcasting a Bluetooth signal. There is also a phone app called Find My, which receives the signal. Bluetooth is a short range radio, so if the app receives the signal it means the tracked device is nearby. There are also some additional tracking aids such as you can (from teh app) trigger the AirTag to beep or you can enable another radio in the AirTag (the Ultra Wide Band - UWB) which enables precise direction and distance estimation, so the phone will direct you to look under the couch or in a jacket pocket in the closet.

The real power of the system though starts shining when you really lose the device. It keeps sending the Bluetooth signals which ANOTHER iPhone nearby can receive and forward to Apple's cloud, securely adding geolocation info. Then in turn your Find My app can call the Apple cloud to see if there is information about the whereabouts of the lost item.

The Bluetooth signal broadcast by the Tag is really simple - a single so called advertising PDU with the Tag's public key. The simplicity of the Bluetooth part means it is really a software function which can be ported to any Bluetooth Lowe Energy (LE) device. Apple is doing that by including the AirTag functionality in the Bluetooth earbuds.

And this is what OpenHaystack does. OpenHaystack is the result of reverse-engineering and security analysis work of Apple's Find My network at the Secure Mobile Networking Lab of TU Darmstadt. It is experimental software, but demonstrates the principle.

It would be interesting if Apple decided to officially license the AirTag specification. This way other companies which make Bluetooth accessories could also include the FindMy feature in their products. Think Logitech mice or Bose headphones. Unfortunately the business model of licensing AirTags is too weak to support the effort and that will never happen. So for non-Apple tags to leverage the ubiquity of Apple's Find My network, we are left to our own devices, which requires software coding skills and being able to merge the AirTag code with whatever is running on the target device.