As far as that goes: the more he thinks about it, the more he believes he has some good stuff to go on—thanks to Enoch, who (in retrospect) has been feeding him some useful clues when not spamming him through the bars with theogonical analysis. Enoch mentioned that when the NSA started attacking what later turned out to be the fake Arethusa intercepts, they were going on the assumption that they were somehow related to another cryptosystem dubbed Azure. And sure enough, Randy learns from the Cryptonomicon that Azure was an oddball system used by both the Nipponese and the Germans that employed a mathematical algorithm to generate a different one-time pad every day. This is awfully vague, but it helps Randy rule out a lot. He knows for example that Arethusa isn’t a rotor system like Enigma. And he knows that if he can find two messages that were sent on the same day, they will probably use the same one-time pad.