[mikeash]

People have been coming up with and breaking codes for thousands of years. The Caesar Cipher is not named such just because of some fascination with ancient Rome, for example.

One-time pads have been around for more than a century. Book ciphers can be quite secure and are centuries old. Criminals have been substituting phrases (e.g. "I gave the flowers to Wanda" -> "I murdered Bob the Snitch") since they've been aware they might be eavesdropped upon.

It has pretty much always been the case that you can encrypt your correspondence if you wish and then the state can attempt to read it anyway if they wish, and in states which require this sort of thing, if they can get a warrant.

Encrypting your correspondence has gotten easier. Nobody would have bothered to use a good cipher for "Don't forget to get eggs at the store" (meaning, actually get eggs, not some substitute phrase for "murder Bob the Snitch") twenty years ago, but now we do it all the time.

But that doesn't change a whole lot. Criminals who gave a shit about not being spied upon have always had ways to ensure it couldn't happen.