CD copy protection/unlocking, on the other hand, has all the necessary data, code, and keys on the client machine all at once (at least at some point during the transaction), and has a fixed (non-unique) encryption for every session. This makes all sorts of hacks possible, from reverse-engineering to brute-force decryption.

I'm no privacy expert here, but I won't rule out a method :) -- for example, you assume all the necessary data, code and keys are on the client machine all at once. What if some of the necessary data, code and keys are on the client machine? What if NONE of the necessary code and keys are there? These are rhetorical because I don't know the answer, and I don't doubt a system can be put together that either cost wise, it would be too expensive to bother picking the locks or cost wise, people can just very cheaply buy personalized keys outright.

Did you see that movie Gone in 60 seconds? How come people just don't built a manufacturing plant (or get in the know with someboyd at one) and obtain master keys to cars and steal them at will? Surely some people can and do, but yet people continue to buy and sell cars right? I think a lot of the 2000 and 2001 generation cars have interesting features in them like chips and extra notches and odd shapes, none of which are beyond the technology to duplicate but it's such a pain in the $*&( to do it that people don't bother.

Calvin