This paper presents a comparison of the performance of three optimisation heuristics in automated attacks on a simple classical cipher. The three optimisation heuristics considered are simulated annealing, the genetic algorithm, and the tabu search. Although
similar attacks have been proposed previously, a comparison of multiple techniques has not been performed. Performance criteria such as efficiency and speed are investigated. The use of tabu search in the field of automated cryptanalysis is a largely unexplored area of research. A new attack on the simple substitution cipher utilizing tabu search is also presented in this paper.