In Neal Stephenson’s book, Cryptonomicon
, the character Enoch Root describes a low-tech, but arguably secure encryption algorithm which he calls both Solitaire (to describe its nature) and Pontifex (to obscure the fact that it’s done with two decks of cards.) The algorithm, invented by Bruce Schneier, author of Applied Cryptography, is an output-feedback mode stream cipher that uses a deck of cards for the cyphertext and can use a second deck of cards for the key. Schneier describes the algorithm in detail on his website. (more…)