Apple’s Bluetooth Mesh

How  AirTag Work

Photo by Onur Binay on Unsplash

AirTag is Apple’s tracking device, but it’s more than a simple bluetooth device that tracks your keys under a sofa. No GPS, no WiFi, no SIM card — yet it works to track our work.

I have a few of these devices lying around (I can find them though!) so I’m interested how they work, and as an iOS developer why I should care (other than attaching an AirTag to my dog). So as ever I thought I’d write a blog post about this technology.

Ready?

What’s in the Tag?

An AirTag is a small computer in your pocket.

It contains:

• A tiny CPU
• A Bluetooth Low Energy (BLE) chip
• A U1 Ultra Wideband chip
• A small amount of memory
• A coin cell battery

The U1 chip is used for precise local finding, but you’ll notice no network stack. You’ll notice there’s no GPS so the device doesn’t have access to knowing where it is.

So how does it possibly find your stuff?

Key Pairs and Rotating Public Keys 🔑

When you pair an AirTag to your Apple ID, it generates a public-private key pair. The private key stays on your iphone…