The scariest part of this recent news is that TM Signal seem(ed) to be interoperable. People using TM Signal could interact with actual Signal users. How are you to know whether or not your groups have people using bastardized versions of Signal? Are things like Session interoperable with Signal?
Even then, nothing stops the client from lying to the server.
That’s the point of digitally signing the app, to ensure its authenticity and integrity. TM and others wouldn’t be able to resign the modified app with the Signal Foundation signature.
EDIT: Yeah after thinking more about it it’s not a trivial problem, as you need to assume that the endpoint is inherently untrusted.
It’s actually possible in a way:
https://en.m.wikipedia.org/wiki/SafetyNet
But you necessarily need to limit the devices and operating systems that are allowed. No custom ROMs, no root access, etc.
It’s bullshit and breaks open computing as a concept.
Not to mention that a device that would pass Play Integrity is precisely the device I wouldn’t ever consider doing anything private on. Which would defeat the whole point of Signal. It’s already bad enough that it’s so desktop-unfriendly while much fewer phones than computers that can run non-privacy-invasive OSes than computers…
Isn’t that just delegating trust to a third party, e.g. here Google? It’s not as if Google was somehow immune to 0 days.
Fuck Safetynet and Play Integrity.