that's a different issue, but for this you'll have to have visibility into the code that your counterparty runs, and that's impractical
you can use tor or vpn, and provide as little information as possible to the process that runs on your machine, but you can never validate what information your counterparty keeps and how it uses it
no, its possible to backdoor apps in a lot of ways, not only faulted crypto implementations
like?
client side scanning.
Whatsapp is closed source, and could implement a switch that can be remotely enabled by them that makes your client to start scanning your messages + upload plain text messages to their server in case it reveal some particular words.
Just a possible example of a backdoor well obfuscated in binary release that doesnt deal with crypto. This backdoor with open source and reproducible builds would be pretty impossible, but with closed source complex apps it is realistic and possible at least...
of course, but i only relate to the functionality of fedi for LN payments and of fountain. can’t think of any information too sensitive they cannot figure out by the server
