I imagine for example, the protocol could be opensource and documented, and then the app-maker could be a different company than the server-owner.
The server-owner need not be trustworthy as long as the protocol is sufficiently reviewed.
The app-maker still needs to be trusted, but you can at least constrain the app to only communicating with the one allowed server and having no other network access.
Perhaps the server owner could also make a webpage showing all the people you have communicated with... That way a malicious client couldn't send your data astray.
I imagine for example, the protocol could be opensource and documented, and then the app-maker could be a different company than the server-owner.
The server-owner need not be trustworthy as long as the protocol is sufficiently reviewed.
The app-maker still needs to be trusted, but you can at least constrain the app to only communicating with the one allowed server and having no other network access.
Perhaps the server owner could also make a webpage showing all the people you have communicated with... That way a malicious client couldn't send your data astray.