Earlier quoted context omitted.
They could literally have a hidden function in WhatsApp that scoops up all your chat history and sends it to Facebook if the government ask them to. It’s closed source. No one has a clue what it’s doing. To be clear I’m not suggesting this is absolutely happening. I’m merely pointing out it’s entirely possible from a technological perspective given it’s closed source software owned by Facebook. That’s not a recipe fo…
To be clear about the threat vector, there's also nothing stopping signal from doing the same if they wanted to. Its impossible to tell if the version of signal you download from the app store is unmodified from the code you can find on github. I trust signal more than I trust facebook, but if you use signal, even though its opensource you still have to trust them not to put anything funky in the binary they upload t…
On iOS it's a lot more difficult to get the required certificates from Apple but you can run your own build in Xcode and deploy it to your personal device if you are a registered Apple developer.
While reproducible builds are obviously the gold standard, for apps you install from the Play Store or the App Store, developers sign the apps that get distributed with their own private keys. As Google and Apple don’t have access to these it should be verifiable that the apps are not tampered with.
There is an exception here with the Play Store, where there is an opt-in option for Google to sign the app on your behalf [1], but I think we can safely assume Signal are manually signing with their own private keys.
In any case it's easy to just grab an APK from an Android device and check signatures for yourself.
For iOS though, no surprises here it’s locked down. Although from what I gather reading Apple’s security documentation, it confirms that apps must be signed by developers with their private keys. [2] But unlike Android there’s sadly no way I can tell for the user to independently verify this without jailbreaking.
But ultimately, short of building each version yourself, all this is moot if you distrust the developers.
[1] https://developer.android.com/studio/publish/app-signing [2] https://manuals.info.apple.com/MANUALS/1000/MA1902/en_US/app...