alt Hacker News> This is both true, and also useless: pretty much any E2E system is falling under this definition.
This is not true. I can build Signal from source from GitHub, and use Signal-the-service with the client (which did not come from Signal, but GitHub/my compiler).
Many cryptosystems are like this. In any case, if you are getting something from the App Store, you can get it once and disable autoupdates, which prevents the service provider (presuming they are the same as the people who published the app) from backdooring you at some point in the future. Alternately, even with updates, unless Apple is colluding with them to serve only you* a specific backdoored app, you can at least be reasonably confident that it's not specifically backdooring only you* in an undetectable fashion.
> This is not true. I can build Signal from source from GitHub
Sure, but can you find an NSA-designed backdoor in the source code?
> you can get it once and disable autoupdates
Try doing that with Signal, and you'll be unable to connect to the main network in just a few days because you get out of sync. Also, what do you do if there's a high severity CVE on the program? You still don't update or you re-audit all the new code?
What you describe may be possible for an intelligence agency, but completely out of reach for an individual.
> unless Apple is colluding with them
Given the most likely adversary is the US intelligence with a warrant, it's absolutely not far fetched to assume that in your threat model.
> you can at least be reasonably confident that it's not specifically backdooring only you
That's not really reassuring…