Key optimization for automata network based cryptosystems∗

The concept of Glu2kov product was introduced by V. M. Glu2kov in 1961. It was intensively studied by several scientists since the middle of 60's. Contrary of the large number of excellent publications, application of Glu2kov-type products of automata in cryptography did not arise until recent past, when in [1] and [2] the authors introduced novel block ciphers based on the composition of abstract nite automata without outputs. In both cryptosystem, the size of the key automaton exceeds the standard key size of block ciphers. In this presentation we are going to introduce the concept of latin cubes, and we are going to show a new method for generating key automaton having a latin cube form. Using this new key generating algorithm, the cryptosystems are able to build up the whole key automaton from a short keyword.