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Low-Tech Encryption

Date: 2013-08-18
Tags: cryptography cards books low-tech

I was thinking of a low-tech cryptography method that could be done by hand, but also very difficult for a computer to crack. I came across the Solitaire algorithm that uses a deck of cards (thanks to the helpful people at “##crypto”:irc://irc.freenode.com/##crypto). What I was thinking of builds upon Solitaire, with a pre-shared deck in a specific order, as a KEX channel and a shared book as a message key (which is used to shuffle another deck in order to use Solitaire on a message).

The book would act as a sort-of OTP. Over the KEX channel a page and line would be transmitted. This line would begin a passphase that can be fed into the passphrase keying mechanism described by Schneier (this will key another deck, not the KEX deck, although it could be possible to rekey the KEX deck if both parties agree).

So, by sharing a pre-shuffled deck and a book, we can transmit a secure message that should be very difficult to break with a computer.