Re: Perfect vs Trade-offs
"In fact, all security is like this. There is no absolute unbreakability, but we can invest in a level of difficulty which is appropriate to the value of the asset and the capability and intent of adversaries. If you're using an encryption scheme with larger key sizes, for example, you are not guaranteeing that your messages will never be broken, but you are ensuring that they'll remain secret for, say, 50 years. (Notwithstanding quantum possibilities, which are driving some paranoid agencies to deploy high-tech one-time pads again.)"
But the problem with your idea is that cryptographic warfare can easily get VERY asymmetric. Like you said, what if the US actually has a working quantum computer hidden under its data center in Utah? Then most every encryption out there is already broken wider than open, and practically all the post-quantum algorithms out there have weaknesses that can be exploited to break them. Even the one-time pad is not immune. You simply have to take your quarry by surprise and they won't have a chance to destroy the pad before it's used up, Even if they do, you've disrupted their communication channel, meaning they have to get another, opening up avenues for interception and doubling.
In the end, cryptographic warfare is a lot like a siege. You can only hold out for so long. Problem is, many of your adversaries are either patient enough to wait you out or resourceful enough to overwhelm you.