That's an interesting and scary idea, but keep in mind that a lot has happened since WWII. Back then industrial-mechanical cryptography was seen as this magic wand that made all communications completely inscrutable. Then the Polish and British and others went to such crazy lengths building brute-forcing machines, etc, to actually break these ciphers, and since then the idea of an infallible crypto system is out of style.

So I think the strategy is much different and much more durable now. The military designs ciphers to be resistant to theoretical future quantum computer architectures. They fund research every year to prove various properties of crypto systems. And I'll bet there are lots of fallbacks for any critical infrastructure.