Any analogy has its limitations, but I think it is helpful for talking about things like "back doors" (and how that is no different from not having doors at all

Any analogy has its limitations, but I think it is helpful for talking about things like "back doors" (and how that is no different from not having doors at all) or how a proposal is basically only "unintended" consequences and no gain. Feel free to suggest a better analogy. The main difference where this analogy breaks down is that it is much easier to build practically unbreakable encryption (assuming P != NP), versus practically unbreakable doors or safes.