Bruce Schneier dug out this little gem: Forbidden Spheres. A nuclear weapons lab, so the (apparently unconfirmed) story goes, classified all spherical objects as confidential, rather than just those related to nuclear weapons design. In the security-as-classification paradigm this makes a lot of sense. The desired security policy is to keep everything related to weapons design confidential. This includes objects that might give away information, which one will naturally find in an R&D lab. To enforce this policy, however, requires either comprehensive tracking of all objects, or complicated considerations to decide whether an object is classified as confidential under the policy or not. But a subset of the objects under consideration has a common, easy-to-detect property: they are spherical. The classification required as a prerequisite for policy enforcement becomes much simpler if one considers only this feature. The classification also becomes less perfect, there are classification errors. However, if it’s all about nuclear spheres, than the simplified classifier errs systematically towards the safe side, erroneously classifying innocuous spherical objects as confidential. As long as it doesn’t disturb the intended operations of the lab, this may well be acceptable. This approach would break down if an adversary, or an accident, could easily change relevant shapes without defeating purpose.