[UncleMeat]

> You send a msg that only personA can decrypt

How are you going to do this without getting this person's public key? And how are you going to get their public key without asking signal?

[SailingSperm]

Yes, signal would manage that. This is still more privacy preserving than a phone number because the the public key isn't attached to your identity in the way a phone number is. You'd still need to getAllContactsPubKey()->encr(PersonAKey)->SendToAllContacts

So signal knows you requested all your contact pubkeys, that you sent a duplicate broadcast to all contacts, obscuring who it was intended for... that could be 0-n of m persons.