On simpler solutions:

"But still you did not know the algorithm."

"Yes, but I had some idea that it was related to the Azure/Pufferfish algorithm, which in turn is related to the zeta functions that we studied at Princeton. So I just sat down and said to myself if Rudy were going to build the ultimate cryptosystem on this basis, and if Azure/Pufferfish is a simplified version of that system, then what is Arethusa? That gave me a handful of possibilities."

"And out of that handful you were able to pick the right one."

"No," Waterhouse says, "it was too hard. So I went to the church where Enoch was working, and looked through his wastebasket. "

Neal Stephenson, Cryptonomicon