Tarot Stuff

If you're new here, you may want to subscribe to my RSS feed. Thanks for visiting!

Every spook needs a way to encrypt messages without carrying anything incriminating on his person. What more innocent than a pack of cards?

Long-haired and bearded Bruce Schneier is a cryptographer and computer security expert. He invented the Solitaire system referred to as Pontifex in the novel Cryptonomicon.

The system uses a standard deck of playing cards to generate a key exactly the same length as the message to be encrypted, but the encryption process (like that for pencil and paper systems of equivalent strength) is slow and requires great care.

One other problem is that sender and receiver must possess decks with the cards in identical sequences. You could shuffle one deck, then give your spook one or two decks with the cards in the same sequence - but then they’d be useless after encrypting one message, and what if he drops the deck on the floor? You need an ever-changing source available to you both that he can use to decide the order of his deck before each message he encrypts, and he shouldn’t need to carry this with him.

If you’re  both operating in the same country, he can use a daily column in a newspaper, but what if your spook is hiding in a foreign country? One trick is to use a poem that the sender knows by heart - then use the date of encryption to decide which bit(s) of the poem to use to create the key.

There’s no reason why you shouldn’t use a Tarot pack instead of standard modern cards - but your spook had better make it clear that he has a good reason for carrying such a pack, which shouldn’t be too difficult.