A new hybrid digital chaotic system with applications in image encryption

Image encryption provides confidentiality to images by transforming them into unrecognizable forms that resemble white noise. Digital chaos is one of the areas used to design image ciphers due to its many desirable properties such as ergodicity, initial state sensitivity and unpredictability. This paper proposes a new image cipher based on the perturbation of a new hybrid chaotic system. The proposed hybrid system cascades and combines two chaotic maps as part of a new chaotification method. Chaotic performance evaluation indicates that the new hybridization method has better complexity, higher sensitivity, and a larger chaotic parameter range as compared to other recently proposed chaotification methods. The new chaotic system is then used in the design of a new image cipher. Both confusion and diffusion properties are attained based on perturbing the chaotic states and system parameters, which are then involved in pixel shuffling and substitution operations respectively. Security and performance analysis indicates that the proposed scheme is highly resistant to various cryptanalytic attacks, is statistically superior and more secure than previously proposed chaos-based image ciphers. (C) 2019 Elsevier B.V. All rights reserved.