A new efficient lightweight and secure image cipher scheme

The protection of multimedia content has become a key area of research, since very often a user's privacy and confidentiality can be at risk. Although a large number of image encryption algorithms have recently emerged, only a subset of these algorithms are suitable for real applications. These algorithms however use non-integer operations such as chaotic solutions that introduce a sizeable overhead in terms of latency and resources, in addition to floating-point hardware that is costly to implement. Designing an efficient, lightweight, and secure image encryption algorithm is still a hard challenge; yet, it is crucial to have in order to meet the demands of recent multimedia applications running on energy-limited devices. In this paper, an efficient image encryption scheme based on a dynamic structure is proposed. The structure of the proposed cipher consists of two different lightweight rounds (forward and backward chaining blocks) and a block permutation process. In addition, a key derivation function is proposed to produce a dynamic key based on a secret key and a nonce. This key, according to its configuration, can be changed for each validate time (session) or for each new input image. Then, based on this key, the cipher layers are produced, which are an integer or a binary diffusion matrix and a substitution table S-box, together with a permutation table P-box. The proposed dynamic cipher is designed to provide high robustness against contemporary powerful attacks, and permits reducing the required number of rounds for achieving the lightweight property. Experimental simulations demonstrate the efficiency and robustness levels of the proposed scheme.