[mandelbrotwurst]

My understanding is that the Signal protocol is exactly that and is even used (or at least claimed to me used) by WhatsApp under the hood, although obviously we shouldn't take them at their word re: the details of their implementation / that they aren't capturing / collecting / sending user input before and/or after the "ends" of the "E2E", so to speak.

The issue isn't as much the lack of an open and secure messaging protocol as it is an inability to build a social network on an open client that is as large as the ones that private corporations have been able to build with their closed source solutions.

Their adding of additional features into their messaging apps that add both usability and complexity makes this an even more difficult barrier to overcome.