[kvark]

If I understand correctly, that's the point. Nobody should be able to read or copy your data without permission.

[BlueTemplar]

Again, the issue is that once you did share (= sent to) the data once with anyone, you don't have any technical control over what might happen to it (see the pirate bay as an example).

Quantum anti-tampering isn't going to help here, where it's your interlocutor that is the one that can't be trusted.