Secret key cryptography with cellular automata

The paper presents new results concerning application of cellular automata (CA) to secret key cryptography extending results presented in Tomassini and Perrenoud (2000), and Tomassini and Sipper (2000). One dimensional, nonuniform CA is considered as a generator of pseudorandom number sequences (PNS) used in cryptography with the secret key. The quality of PNS highly depends on a set of applied CA rules. To find such rules nonuniform CA with two types of rules is considered. The search of rules is performed with use of an evolutionary technique called cellular programming. As the result of the collective behavior of the discovered set of CA rules very high quality PNS are generated. The quality of PNS outperforms the quality of known one dimensional CA-based PNS generators used in secret key cryptography. The extended set of CA rules which was found makes the cryptography system much more resistant on breaking a cryptography key.