I have been spending many hours thinking about an nostr based app called Proof.

A unique nsec is created in app. Only able add another Proof npub with a safeword to a nickname via nfc tapping in real life.

You ask for Proof if you get a phone call etc.

Only the Proof app would be able to generate the safe word of the nickname and send it as an encrypted dm.

nostr:nprofile1qqsqddupn4l3cl65wggcyehd009g0pwuatsfudh28f90vewx68vrylqpvemhxue69uhkv6tvw3jhytnwdaehgu3wwa5kuef0dec82c33wymx6cmj8p6xcu3nds6xwatnxdekvmnhxcmnwvnnxaaxzefkdpckucmdwu6hw63jxajk5atyx4mkx7rxxacnqmncxajr20mzwfhkzerrv9ehg0t5wf6k2qgwwaehxw309ahx7uewd3hkctcpremhxue69uhkummnw3ez6ur4vgh8wetvd3hhyer9wghxuet59uyj8h7j credential system in safebox has this potential use as well