Block Cipher S-box Modification Based on Fisher-Yates Shuffle and Ikeda Map

Abstract

Block cipher is an encryption algorithm that performs a substitution and permutation operations on a block of data using a secret key. Block cipher relies on substitution boxes to provide the element of data confusion; thus, S-box had a large impact on the cryptographic system. Implementing an efficient S-box becomes a new challenge to bring up an effective and secure encryption algorithm. The proposed S-box is generated using Fisher-Yates shuffle to enforce nonlinearity in a block cipher. The random number generator used in the shuffling technique is based on the Ikeda map. Serpent algorithm is the case of study to appraise the performance of the generated S-box. The S-boxes generation is under the full control of the secret key. The performance appraisal for the generated S-box against bijective property, strict avalanche criterion and nonlinearity shows a good performance; moreover, the security analysis of the modified Serpent confirms that the modification is secure to be used for protecting vital data.