A fast chaos-based image encryption scheme with a dynamic state variables selection mechanism

• A dynamic state variables selection mechanism is proposed to dynamically assign chaotic variables for pixel encryption.
• Pixel-swapping based confusion strategy is developed to produce certain diffusion effect in the permutation stage.
• Diffusion is implemented in snake-like mode to accelerate the diffusion effect.
• Experimental results and security analyzes prove the superior security and high efficiency of the proposed scheme.

In recent years, a variety of chaos-based image cryptosystems have been investigated to meet the increasing demand for real-time secure image transmission. Most of them are based on permutation–diffusion architecture, in which permutation and diffusion are two independent procedures with fixed control parameters. This property results in two flaws. (1) At least two chaotic state variables are required for encrypting one plain pixel, in permutation and diffusion stages respectively. Chaotic state variables produced with high computation complexity are not sufficiently used. (2) The key stream solely depends on the secret key, and hence the cryptosystem is vulnerable against known/chosen-plaintext attacks. In this paper, a fast chaos-based image encryption scheme with a dynamic state variables selection mechanism is proposed to enhance the security and promote the efficiency of chaos-based image cryptosystems. Experimental simulations and extensive cryptanalysis have been carried out and the results prove the superior security and high efficiency of the scheme.