A while ago I wondered if I could think of any way of encrypting a physical object. I thought of a couple ways of doing it, one of which requires no future technology but which is very time-consuming and only works for certain types of objects. I'll leave that alone for the time being. The other way I thought of requires nanotech, and it's a special case of a cool-sounding general technology. I want to know whether anyone else has used this idea, and how. (And how!)
The general idea is that you send a swarm of nano-bots at an object and compress it into a block of very, very dense nanobot matter. The block has the same mass as the original object, but it comes in a standard shape--maybe the size of a brick, with a protrusion on top for attaching a crane hook or similar lifting device. Now, if you want to encrypt the object, then as part of the compression you simply scramble the smart matter so that the nanobots won't know what goes where without your private key.
Problems: this would probably take a lot of energy. If you tried it on something living, it would probably die unless the compression was incredibly fast. If you could do this you could also use nanobots to make a copy of the object, encrypt the data generated by the nanobots, destroy the object, and recreate it from the encrypted data as many times as you wanted, which is more useful. (Rebuttal: this technology ensures continuity of matter, and avoids the embarrassing situation where you need to reconstruct something but don't have enough spare mass on hand, and the Johnsons are coming over! Also, storing a molecular copy of an object may require about the same amount of mass, in which case the two technologies would be pretty much the same.)
Has anyone thought of such a technology, or encountered it anywhere in fiction? I can think of a couple things I'm working on (very, very slowly) where I could use this.