There's a whole appendix to the e-book edition of Neal Stephenson's “Cryptonomicon” dedicated to the subject of international telecommunications cables.
Ah, that's not in the Dead Tree version which I recently finished.
There is, however, a detailed discussion of the Solitaire Cipher by Bruce Schneier, the original author of the cypher.
Stephenson actually had Schneier invent this playing-card based cypher just for the book!
It's a cipher designed to be performed by hand, and required nothing more incriminating than an ordered deck of playing cards.
In the event the Secret Police come to the door, you simply shuffle the deck and the key is destroyed.
In the book, it is referred to as Pontifex.