Controlling communication goes back much further. The oldest example I can think of right now is https://en.m.wikipedia.org/wiki/Cabinet_noir https://en.m.wikip

Controlling communication goes back much further. The oldest example I can think of right now is https://en.m.wikipedia.org/wiki/Cabinet_noir https://en.m.wikipedia.org/wiki/Cabinet_noir but I'd be surprised if it didn't go as far back as writing itself.