That is the test in the first two bullet points. If the AirTags don’t listen then you’d have to add a “I am responsible for that AirTag” broadcast message from

That is the test in the first two bullet points. If the AirTags don’t listen then you’d have to add a “I am responsible for that AirTag” broadcast message from the responsible device. But I kind of suspect they do listen, if only for a short period after a beacon message. They need to get their public keys from somewhere.