[Cryptography] RNGs, Entropy, and Unguessability (really clock synchrony)

[Robert Wilson]

A few millennia ago I was working on "provable" security. (Orange book 
stuff.) Lots of people wanted to use inductive proofs: Start in a known 
good state, prove that all possible transitions maintain what you want, 
voila.

We had to consider distributed systems. It was obvious to me that there 
is no place in the universe (per relativity) where one could know a 
well-defined state. What could it even mean?

I had then been thinking of distributed as meaning something like 
network-connected machines. But as Kent correctly points out, even 
within what we call a CPU chip, at any instant (and what does even that 
mean?) any distinct points will have different notions of what's going 
on! What kinds of systems, if any, can have well defined states?

Bob Wilson