||The considerable development of new technologies of communication leads nowadays to an increasing need for security of the exchanges of information. In this context, cryptography plays a major role as a huge amount of information exchange is carried out through public networks. Since the early 1960s, cryptography has no longer been restricted to military or governmental concerns, what has spurred an unprecedented development of it. The proposal concerns a special class of ciphers, namely the self-synchronizing stream ciphers. Self-synchronizing stream ciphers offer serious advantages, the main one being the ability to automatically achieve synchronization between the two parts of a communication setup. As a result, there is no need for self-synchronizing stream ciphers to call for resynchronization protocols or synchronization flags. It is of first importance when one must face, for example, drastic constraints concerning the throughput. Actually, the self-synchronizing stream ciphers can admit models in the form of dynamical systems. Hence, the property of self-synchronization can be characterized in terms of control theoretical concepts.
The aim of the PhD thesis is threefold.
- finding out algebraic conditions under which a dynamical system can act from a structural point of view as a self-synchronizing stream cipher.
- provide systematic and constructive approaches to design master-slave setups having the self-synchronizing property in connection with cryptographic purposes
- implementing, testing and validating algorithms in a realistic platform provided by Cassidian Cybersecurity
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J. PARRIAUX, P. GUILLOT and G. MILLERIOUX, 2011, Towards a Spectral Approach for the Design of Self-Synchronizing Stream-Ciphers, Cryptography and communications: discrete structures, Boolean functions and sequences, Springer, Vol.3, N.4, pp. 258-274
P. VO TAN, G. MILLERIOUX and J. DAAFOUZ, 2010, Left invertibility, flatness and identifiability of switched linear dynamical systems: a framework for cryptographic applications, International Journal of Control, Vol. 83, N. 1, pp. 145-153
G. MILLERIOUX and P. GUILLOT, 2010, Self-synchronizing stream ciphers and dynamical systems: state of the art and open issues, International Journal of Bifurcation and Chaos, Vol. 20, N.9, pp. 2979-2991