title = "Cellular automata, boolean functions and combinatorial
designs",
title_fr = "Automates cellulaires, fonctions booleennes et dessins
combinatoires",
school = "Laboratoire d'Informatique, Signaux et Systemes de
Sophia Antipolis (I3S), COMUE Universite Cote d'Azur
and Universita degli studi di Milano - Bicocca",
abstract = "The goal of this thesis is the investigation of
Cellular Automata (CA) from the perspective of Boolean
functions and combinatorial designs. Beside its
theoretical interest, this research finds its
motivation in cryptography, since Boolean functions and
combinatorial designs are used to construct Pseudo
random Number Generators (PRNG) and Secret Sharing
Schemes (SSS). The results presented in the thesis are
developed along three research lines, organized as
follows. The first line considers the use of heuristic
optimization algorithms to search for Boolean functions
with good cryptographic properties, to be used as local
rules in CA-based PRNG. The main motivation is to
improve Wolfram's generator based on rule 30, which has
been shown to be vulnerable against two cryptanalytic
attacks. The second line deals with vectorial Boolean
functions induced by CA global rules. The first
contribution considers the period of preimages of
spatially periodic configurations in surjective CA, and
analyze the cryptographic properties of CA global
rules. The third line focuses on the combinatorial
designs generated by CA, specifically considering
Orthogonal Latin Squares (OLS), which are equivalent to
SSS. In particular, an algebraic characterization of
OLS generated by linear CA is given, and heuristic
algorithms are used to build OLS based on nonlinear
CA.",
notes = "French National Number(NNT) 2018AZUR4011
Supervisors: Alberto Leporati and Enrico Formenti",