Could you do something with
Hash (pubkey + phone /email)
Generate new pubkey+phone private key.
Sharing that private key would allow friends on nostr to see your pubkey+phone private key.
Then if receiver of pubkey+phone private key can take normal pubkey+receiver contacts to see if there is a match. If that key matches any in contacts you could link?
The solution will have to piggy back off pubkeys.
How are you going to lookup people based on their number with that approach? 🐶🐾🤔
If user receives pubkey+phone private key. They can take pubkey from user + address book to generate private keys and if there is a private key match they know they are friends. It would require call it pubkeyphone private key for user A to share.
If user B can take pubkey + any address in contacts, hash it and generate the same pubkeyphone private key and match it to user A they know they are friends.
(Phone number share)
User A wants to share phone number.
Private key of User A is generated using Npub+ phone number.
User A shares that private key.
User B wants to see if they are friends with anyone.
User B takes friend list Npub + phone number list and hashes it (might be lots of random guessing but possible)
If user B generates the same key as user A shared they know they are friends.
