Bruce Schneier's Pontifex cipher that turns a deck of cards into a keystream.
The Solitaire Cipher, also known as Pontifex, was designed by Bruce Schneier for the novel Cryptonomicon.
It uses an ordered deck of 54 cards (52 cards plus two jokers) to generate a letter-by-letter keystream.
Provide an optional passphrase to key the deck before the keystream is produced; with no passphrase the deck
starts in its natural 1 to 54 order. See more information on
Wikipedia.