Decrypting classical cipher text using Markov chain Monte Carlo

In this paper, we present the use of Markov Chain Monte Carlo (MCMC) methods to attack the classical ciphers. We use frequency analysis as our basic tool. First we investigate the MCMC algorithm to break a simple substitution cipher. Then the algorithm is modified to break a simple transposition cipher. Our results on the transposition cipher are better than the existing methods such as simulated annealing, genetic algorithm and tabu search. We also extend the algorithms to break a simple substitution-transposition cipher up to key length 40.

• Type: Journal
• Year: 2012
• Where: SAC
• Authors: Jian Chen, Jeffrey S. Rosenthal
• Keywords: Applied Computing, Classical Ciphers, Markov Chain Monte Carlo, MCMC Methods, SAC 2012