Comment by os2warpman

I imagine the same way you share a key for a HomeKit-enabled smart lock.

The only scenarios where one is so injured and/or drunk as to not be able to complete the non-rigamarolish process of sharing a HomeKit home key either by doing it themselves or walking someone through the process are ones where the key holder is so incapacitated that they would be unable to share a physical key.

All of that is someone irrelevant because Express Mode is enabled by default, so if you are unconscious all a person has to do is pull your phone out of your pocket and use it to unlock and start your car the exact same way physical keys work in that situation. It even works if the phone's battery is dead.

https://support.apple.com/en-us/118271

Also, every implementation of CarKit Car Keys I have seen is the same as HomeKit home keys: there is a backup. Either a physical key, PIN, fob, or card.

> non-rigamarolish process of sharing a HomeKit home key

I have not used homekit, but from some searches it only seems to be a non-rigamarole process to add someone as a homekit user if the other person has an apple device? Also, is the Internet required to enroll someone?

> ones where the key holder is so incapacitated that they would be unable to share a physical key.

I don't need to be conscious or my phone have battery (or reception) to have someone take a key from my pocket.

> Also, every implementation of CarKit Car Keys I have seen is the same as HomeKit home keys: there is a backup. Either a physical key, PIN, fob, or card.

I was responding to gp who wanted none of this as it all defeats the security they desired. A 1-factor physical authentication token as a backup would be suitable for nearly all edge cases I can think of. As long as the person carries it, but then we are at worst where we are today, at best I could potentially authenticate or add someone from afar.

I'm not saying that smart locks aren't useful, just that they can't only be "smart", which I assume you would agree with since you brought up things currently having backup methods?