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The communication via network of private data could be subject to alteration by malicious entities. In order to ensure confidentiality, authentication, integrity and non-repudiation it is important to implement robust cryptosystems to protect data. Hence, cryptography is a mechanism that ensures data security. Being the science of secret, it has the aim to protect message transmission. In literature, there exists namely asymmetric and symmetric cryptosystems. The asymmetric or public key cryptosystems use a public key for encryption and secrete key for decryption. The symmetric or secrete key cryptosystems use the same key to both encryption and decryption (Smart, 2016a). Hence, Symmetric cryptosystems are namely block ciphers and stream ciphers. A block cipher split the message into fixed length blocks including the secrete key. A stream cipher encrypts bit by bit in real-time.
In our work, we propose a block cipher to provide messages’ confidentiality. This latter is ensured once the information can be intelligible only by the authorized entities. Generally, to ensure confidentiality, encryption mechanisms are used. Thus, the researchers focus on designing systems maximally resistant to the various attacks. Accordingly, we propose a novel block cipher named BC-CaACO that uses in its process cellular automata (CA) and an S-box based on chaos and ant colony optimization (ACO) (Ahmad et al., 2015).
Cellular automata (CA) are dynamic systems that are used to design numerous cryptosystems due to their properties such as homogeneity, locality, parallelism, simplicity and unpredictability (Wolfram, 2002). Additionally, it facilitates the hardware and software implementations (Shin et al., 2012). A block cipher is considered to be secure if the used both S-Boxes and keys satisfy both the security criterions. ACO based optimized S-Box (Ahmad et al., 2015) is an efficient S-Box that provides a high nonlinearity and other S-Boxes’ properties.
Hence, the computational results prove that our proposed design resists against statistical attacks. Further, the obtained experimental results confirm that the designed cipher has both good confusion and diffusion comparing to the existent well-known iterative block ciphers.
The paper is structured as follows: Section 2 covers the basic notions about cellular automata, substitution boxes and ant colony optimization algorithm. Thereafter, some related works are cited. Section 3 shows the description of the proposed block cipher. Afterwards, the security analysis and experimental results are showed in section 4. Finally, in section 5, the conclusion and future works are presented.