> Naively I would think that if you have a secure 1:1 communication protocol, then you can send N*(1:1) secure messages to a group of N people IIUC this is wha

> Naively I would think that if you have a secure 1:1 communication protocol, then you can send N*(1:1) secure messages to a group of N people IIUC this is what iMessage does (at least when Messages in iCloud or whatever it's called is disabled), except s/people/devices: say you have three devices and someone sends you one message, the message is encrypted once per recipient device, and three encrypted messages get sent. Whether it's 1 person with 3 devices, 3 people each with 1 device, or 2 persons with one having 2 devices and the other a single one becomes largely immaterial.