Exhaustive Evaluation of Radius 2 Toggle Rules for a Variable-Length Cryptographic Cellular Automata-Based Model

摘要

A cellular automata (CA) model in cryptography is investigated. A previous work analyzed the usage of reverse algorithm for pre-image computation as an encryption method. The main conclusion was that the simple adoption of such method is not viable, since it does not have 100% of guarantee of pre-image existence. A new approach was proposed that uses extra bits when the pre-image computation is not possible. It is expected that in practice few failures happens and the cipher text size will be close to the plaintext. Encryption always succeeds and the final length of the ciphertext is not fixed. We better investigate the secret key specification by using a more representative set formed by all radius 2 right-toggle rules, totalizing 65536 rules. An exhaustive analysis of this rule space has shown that using adequate specification the method has a good protection against differential cryptanalysis and a small increase in ciphertext length.