Awesome idea

Yes! Oh man I had an old urbit post that was eerily similar. Lost it in a breach unfortunately. But rather than public telephone I took the angle of "scifi computer terminal screen where it is personalized for whoever is currently using it" (by signing device, same idea)

It seems possible today. Just a matter of spreading the vision. I think I saw someone a long time ago use Nostr in this way with a signing device btw. Your address book would be associated with your keys, so the signing device would have it all. + the public terminal can include its own “yellow pages” for businesses and people in the area. This is the selling point of using Nostr for DMs btw. It’s not that it has the most advanced privacy. It’s the potential ease and ubiquity

How is what you're describing different than just signing into a web-based client? Would your "public terminal" also be a relay? Something else?

The sign-in would only be using a device. So way less friction. And maybe they’re built in such a way that they have no cache at all. Yeah I think they’d be a relay too. Because similar to phone booths, you’d need to be able for ppl to write back to you. So maybe using that one NIP it can signal “hey I’m contacting from this relay” (or “relay network” bc the terminals would probably all be gossiped in a city at least)