What kind of mathematical algorithm was used? The contents of Grandpa’s trunk provide clues. He remembers the photograph of Grandpa with Turing and von Hacklheber at Princeton, where all three of them were evidently fooling around with zeta functions. And in the trunk were several monographs on the same subject. And the Cryptonomicon states that zeta functions are even today being used in cryptography, as sequence generators—which is to say, machines for spitting out series of pseudo-random numbers, which is exactly what a one-time pad is. Everything points to that Azure and Arethusa are siblings and that both are just implementations of zeta functions.