A developer has demonstrated sending Bitcoin over Apple's Find My network, the tracking system behind AirTags, by relaying Cashu ecash tokens through nearby iPhones. The sending device requires no internet connection during the transfer.
How the System Works
The proof-of-concept runs on inexpensive ESP32 boards and packages tokens into Bluetooth signals that mimic lost-item beacons. Passing iPhones pick up these signals and relay them through Apple's Find My network as they would for a missing AirTag.
The recipient recovers the transmitted data through an Apple account and rebuilds the token piece by piece. A Python script then verifies the rebuilt token for errors. Each signal carries only two bits of data, requiring well over 1,000 broadcasts to transmit a typical token.
Security and Limitations
The developer warns of significant security constraints. Every broadcast token is public, and because Cashu tokens function as digital cash, anyone who recovers one can spend it. The transport layer carries no encryption, and the identifiers needed to locate tokens are publicly visible.
The documentation advises sending only giveaway amounts and notes that delivery is slow, unofficial, and carries no guarantee. The receiver accesses Apple's Find My network through an unofficial interface, meaning the tool could stop working if Apple modifies that interface.
The experiment remains a novelty rather than a practical payment system. Other developers are exploring alternative approaches to enable private Bitcoin transfers.
