A reversible system based on hybrid toggle radius-4 cellular automata and its application as a block cipher

The one-dimensional cellular automata (CA) system detailed herein uses a hybrid mechanism to attain reversibility, and this approach is adapted to create a novel block cipher algorithm called HCA (Hybrid Cellular Automata). CA are widely used for modeling complex systems and display inherently parallel properties. Therefore, applications derived from CA have a tendency to fit very well in the current computational paradigm where multithreading potential is very desirable. The HCA system has recently received a patent by the Brazilian agency INPI. Analyses performed on the model are presented here, including a theoretical discussion on its reversibility. Finally, the cryptographic robustness of HCA is empirically evaluated through avalanche property compliance and the NIST randomness suite.