And how to we know they don't collect other data but don't advertise it?
If they have a special deal with government, the court wouldn't even know about those, or might be instructed not to ask them and not disclose anything.
If they have a special deal with government, the court wouldn't even know about those, or might be instructed not to ask them and not disclose anything.
E.g. could we build it ourselves in, say, Xcode, and compare a hash of the resulting app binary with the installed one?
Not sure about Signal.
The point is not just that everyone can make their own, but that anyone who is competent enough can prove that their client code is exactly what is used to produce the version that gets distributed.
This means that with Telegram it shouldn't be possible to hide a backdoor in the client in a way that is impossible to spot.
If it matters to you, you should build it from source.
If it's just out of curiosity... yeah reproducible builds are a thing, but generally that's not super straightforward in practice, I would say.
Now realistically, most people can do that, so they have to trust that somebody who can actually did it. Security experts have been and are looking into messengers like Signal: they have an interest to do so as security researchers, because that would look good on their CV.
Of course there is trust somewhere, you cannot do without trust. But Signal is amongst the best you can find.
See my other question. Audit how? Sure, you can examine the source.
But how can one tell the app blob in their phone is the same as the one produced if you build the code?
https://github.com/signalapp/Signal-Android/blob/main/reprod...
(I haven't tested this myself.)
Edit: You can also build the client yourself and use your own version. No need to use the Google Play store version.
The problem being that apps as installed from the App Store come (to my knowledge, could be wrong) encrypted. So you can't just compare an unencrypted local build with the encrypted installed app (and you can't decrypt the app or encrypt your build the same way, because you don't have the key, e.g. Apple has it - and iirc, there's no access to it, because it's held in the secure enclave in iOS case).