Correct, the AirTag's key will dynamically rotate after every 10 minutes and certain hours. Unless you created a tag using this project and the key doesn't rotate, or you know the pattern of rotation.

If I made some AirTag clone, with esp32 or similar, with a fixed public key and the relative private key, is there some limits about the maximum number of device managed by software OpenHayStack or Apple Find My Network? Is it possible to use them to track a fleet of vehicles? P.S. I think, the fixed public key should be different for every device, is it right?

Could you elaborate on how to clone an AirTag? It's unlikely you can get the private key of the AirTag, unless you can extract it from your iCloud Keychain.

If you wish to make a home-brew AirTag like OpenHayStack project, there isn't a noticeable limit at this moment. Yes, you might use these "tags" to monitor a fleet of vehicle in a not time-sensitive manner. It's not possible to use FindMy app tho. You will need tools to show the location on map, OwnTrack might be a great app for this.

You will need to generate your own private, public key, hashed adv pubkey pair. Each ESP32 shall has their own key, otherwise the location report will be mixed. To generate key, you can use the Mac app, or use the python script (https://github.com/Chapoly1305/FindMy/blob/main/generate_keys.py)

After you created the keys, (https://github.com/seemoo-lab/openhaystack/tree/main/Firmware/ESP32#deploy-the-firmware)

Remember, the Public Key is for advertisement, Hashed Public Key is for getting the report from Apple. Keep the private key as a secret, who has the private key will be able to download the location and see the location history.

Thank You so much.