Dissecting the Protocols Inside Apple AirTags

The talk follows up on a previous year's session about Apple's Continuity protocol and focuses on the FindMy packets AirTags send over Bluetooth Low Energy. The speaker shows how to split raw captures into fields: the access address, packet header, rotating advertising address, and the manufacturer data marked with Apple's identifier. She cautions that this identifier alone does not prove a device is genuine, since any Bluetooth emitter can spoof it.

The central section covers offline finding. An AirTag has no GPS, so it broadcasts a public key that nearby phones use to encrypt their own location reports before uploading them to Apple. The speaker explains the P-224 elliptic curve exchange, the ECIES construction built on SHA-256 and AES-128, and how the owner's device derives matching keys to download and decrypt reports. She also walks through the pairing state machine and the separated-mode broadcast, which packs key material into the advertising address and spare bytes to fit Bluetooth size limits.

The talk closes by stressing limits: forged locations from compromised finder devices, delayed uploads, and the fact that this is not live tracking. Practitioners leave with a method for parsing Continuity packets and a view of why the design is strong on paper yet open to misuse. The speaker also looks ahead to new IETF standards that may affect how long this protocol remains in use.