Analyzing and Creating Playing Card Cryptosystems

Before computers, military tacticians and government agents had to rely on pencil-and-paper methods to encrypt information. For agents that want to use low-tech options in order to minimize their digital footprint, non-computerized ciphers are an essential component of their toolbox. Still, the presence of computers limits the pool of effective hand ciphers. If a cipher is not unpredictable enough, then a computer will easily be able to break it. There are 52! ≈ 2^225.58 ways to mix a deck of cards. If each deck order is a key, this means that there are 52! ≈ 2^225.58 different ways to encrypt a given message. To create some perspective, most computer ciphers feature either 2^128 or 2^256 different ways of encrypting the same message. Hence, a cipher created from a deck of cards has the potential to emulate the security of many computer ciphers. Dr. Landquist and I spent the summer of 2019 examining existing playing card ciphers. This led to the main focus of this paper: the creation of a unique, secure playing card cipher. Because of the inspiration provided by the cipher VIC, I am calling our original cipher VICCard. VICCard has gone through multiple versions, each better than the last. Its security is rooted in its combination of numerous cryptographic principles, including a substitution checkerboard, columnar transpositions, lagged Fibonacci generators, and junk letters. As evidenced by certain randomness tests, VICCard has the potential to extensively randomize an English plaintext