RAB: A lightweight block cipher algorithm with variable key length

With the increasing security issues of data transmitted from wireless sensor network terminals, the traditional cryptographic algorithms cannot meet the different security requirements of different types of data in wireless sensor networks (WSN). In this paper, we propose a new lightweight block cipher algorithm RAB that supports variable key length based on Feistel and Substitution-Permutation Network (SPN) structure. To address the inherent slow diffusion in the Feistel structure, the RAB algorithm uses a diffusion layer consisting of MDS matrix. This enhancement ensures that even a 3-round implementation of the RAB algorithm exhibits the ideal avalanche effect, enhancing its security. To handle keys of different lengths and provide different security strengths, the RAB algorithm applies a key schedule function that can receive different lengths of keys. This paper performs differential and linear cryptanalysis of the RAB algorithm using Mixed Integer Linear Programming (MILP) techniques. The results confirm that the RAB algorithm can meet the security demands of resource-constrained devices. Furthermore, the results of the efficiency analyses of the software and hardware performance of the RAB algorithm show that the RAB algorithm has a high software performance efficiency and the hardware performance meets the requirements of lightweight block ciphers. The algorithm is applied to encrypt the data on the sensor nodes, which can correctly encrypt and decrypt the sensor data, and runs smoothly. It indicates that the proposed algorithm is suitable for securing data in resource constrained nodes.