An Implementation of Probabilistic Relaxation in the Cryptanalysis of Simple Substitution Ciphers

Relaxation algorithms have been used successfully in the automated cryptanalysis of simple substitution ciphers [5,6,7]. This paper describes a Pascal implementation of relaxation using an adjustment formula by Shannon [8]. The formula is used to generate trigram statistics suitable for the solution of simple substitution ciphers without word divisions. Problems encountered when applying relaxation to homophonic ciphers are identified.