On restricted and elaborated code

I started reading this simply out of interest in the topic, but as I read on I realised that among other things it was an exploration of Bernstein's restricted and elaborated codes. I don't need to elaborate; but understanding is restricted to those who know the background (in two or even three senses).

This is of course not simply a pure illustration of the distinction; as in the real world (this may even be part of the real world!) it is embedded in and muddied by another discussion.