I thought it was clear it ran through iCloud: https://support.apple.com/en-au/HT209460

It only works between devices signed in with the same Apple ID

The encryption keys are shared via the iCloud keychain, but I think the actual sharing happens over a protocol called Companion Link.

> on what basis is this claim plausible?

The article shows the author holds some grudges against Apple. Those grudges probably influence their judgement.

The comment in question was not written by the article author.

From Apple Platform Security Guide [0] :

> The individual messages are encrypted much like messages in iMessage are. After the devices are paired, each device generates a symmetric 256-bit AES key that gets stored in the device’s keychain. This key can encrypt and authenticate the BLE advertisements that communicate the device’s current activity to other iCloud-paired devices using AES256 in GCM mode, with replay protection measures.

[1]: https://support.apple.com/en-gb/guide/security/secf78dbe639/...

> From a comment in the article:

To be clear, it's a comment on the article, in the public comments section appended to the article. The comment was not made by the article author.

Agreed. My comment was worded poorly. Thank you for clarifying.