What does HackerNews think of opendrop?
An open Apple AirDrop implementation written in Python
I'm the author of the blogpost. You are spot on, Passkeys are exportable so the private key ends up both on iCloud and the Enclave/authenticator.
My understanding is that there's chatter about cross-vendor synchronization of passkeys but nothing concrete yet.
Meanwhile Apple allows people to share Passkeys via AirDrop (Settings > Passwords - select the passkey you want and click the "Share" icon to send it over Airdrop) so it should be possible with some effort to obtain the private key with something like this: https://github.com/seemoo-lab/opendrop. Haven't done extensive testing yet though, so I can't confirm.
Would love to hear if anybody knows more about how the sharing via AirDrop is implemented/protected.
An open Apple AirDrop implementation written in Python
I get what they mean here, but it has been done. It does require a Wi-Fi card with support for monitor mode and frame injection. OWL did it with an Atheros AR9280.
Open drop also requires extracting keys from an Apple device if you want Apple interop.
See OWL:
https://github.com/seemoo-lab/owl
And Open drop:
Provided of course that you have a wifi card that supports active monitor mode.. and you are root on your machine.