I don't. I think we can decompile WhatsApp and look if something suspicious has been implemented (e. g. some backdoor that hides the key change message), but I'

I don't. I think we can decompile WhatsApp and look if something suspicious has been implemented (e. g. some backdoor that hides the key change message), but I'm not sure if somebody does this on a regular basis. That's a bit simpler with the open source Signal, although we still need to verify they haven't slipped a backdoor to their official build. And this backdoor might not be needed though, as UX for key change is (was?) atrocious in both Signal and WhatsApp: https://keybase.io/blog/chat-apps-softer-than-tofu https://keybase.io/blog/chat-apps-softer-than-tofu (2019)