I’m leaning toward this for the hashed phone number that you could optionally share on your profile so that damus could automatically find all your friends. It would really hard to build a rainbow table for this with a high argon2 security parameter. 

What do you think nostr:npub1gcxzte5zlkncx26j68ez60fzkvtkm9e0vrwdcvsjakxf9mu9qewqlfnj5z, nostr:npub1n0sturny6w9zn2wwexju3m6asu7zh7jnv2jt2kx6tlmfhs7thq0qnflahe, any other mobile nostr devs ? Should we get a NIP going ? nostr:note1q8kxrrtlat9ezh6evwnqce4mhcqnt6xm5k5vn5xqwmmpeuqa0xusuzl6nc