[easytiger]

> I don't think there is any precedent for impenetrable private communication legally or culturally.

Two people can communicate fairly trivially in person with a reasonable level of certainty that their conversation remains privy to only them and the most a 3rd actor might glean is that the conversation took place; not it's contents.

What you might be confusing is that historically there are inherent weaknesses in using a physical or radio or electronic medium to transfer information from one mind to another and that those have always been exploitable. That exploitation usually comes by "force", for some definition of force depending of the value systems held by the parties involved.