  The two most important criteria for vectorial Boolean functions used as
S-boxes in block ciphers are differential uniformity and nonlinearity. Previous
work in this field has focused only on nonlinearity and a different criterion,
autocorrelation. In this paper, we describe the results of experiments in using
simulated annealing, memetic algorithms, and ant colony optimisation to create
vectorial Boolean functions with low differential uniformity.
  Keywords: Metaheuristics, simulated annealing, memetic algorithms, ant colony
optimization, cryptography, Boolean functions, vectorial Boolean functions.
