Again, with the client code you should be able to tell that the keys are generated there and not sent anywhere
then no one- including the intended recipient- can decode them without that physical device. kinda defeats the point of a messenger service. The codes have to be sent somehow. Either it’s sent along their servers, or the recipient’s device directly.
I really don’t care to get into it. Just know that if you’re using a generic, stock device… any message you send should be considered compromised. depending on the app, and the device in question, it may (but not necessarily) require physical access to the device. but, by it’s very nature, the messenger service meant to be decoded and read. it is fundamentally permissive in nature.
Is it secure enough for France’s needs? Probably. does it mean it’s the best? Probably not.