Novel Stream Cipher Using 2-D Hybrid CA and Variable Ordered Recursive CA Substitutions

This paper presents a new stream cipher for data security, which is based on the replacement of data values using variable ordered recursive cellular automata (CA) substitutions. To achieve this aim, 2-D hybrid CA was built firstly, then 1^st-ordered and 2^nd-ordered generalized CA transforms were developed to build variable ordered recursive CA substitutions. The proposed stream cipher satisfies the properties of confusion and diffusion because of the proposed CA substitutions are flexible. Moreover, the characteristics of the proposed stream cipher are loss-less, symmetric private key, very large number of security keys (number of possible security keys is more than 10²⁷⁴), and key-dependent pixel value replacement. Simulation results obtained using some color images clearly demonstrate the strong performance of the proposed stream cipher.

1. Introduction

With the ever-increasing growth of multimedia applications, data security is an important issue in communication and storage of data, and encryption is one the ways to ensure security. Data security has applications in inter-net communication, multimedia systems, medical imaging, telemedicine, and military communication. There already exist several methods of data security. They include SCAN-based methods [1], chaos-based methods [2], tree structure-based methods [3], and other miscellaneous methods [4]. However, each of them has its strength and weakness in terms of security level, speed, and resulting stream size metrics. The proposed data security is based on replacement of the data values. The data values are replaced using the variable ordered recursive CA substitution with a sequence of CA data that is generated from 2-D hybrid CA with special evolution rules. The proposed data security is loss-less and key-dependent data value replacement. Additionally, it is a symmetric private key security, meaning that the same key is needed for encryption and decryption; both sender and receiver must know the key.