Image encryption using a novel hybrid chaotic map and dynamic permutation-diffusion

In last few years, chaotic maps are being used extensively by the researchers to build image cryptosystems. This paper proposes a novel Hybrid chaotic map, and discusses the implementation of an image encryption method that uses an existing Sine-Cosine (SC) chaotic map, and the proposed novel Hybrid chaotic map. The proposed image encryption method uses these two maps in pairs, but dynamically, in both permutation and diffusion phases, where if one map is used for permutation of one-pixel block based on dynamic selection, then the other map will be used for diffusion of the same pixel block. This encryption mechanism uses 128-bit shared key along with the 128-bit Initial vector. The initialization phase of this encryption scheme consists of the initialization of the intermediate key, seeds and the control parameters for the chaotic maps. After that, the two different chaotic initial sequences are created using the SC and Hybrid chaotic map, respectively, where sequence from one map will be used for permutation, and sequence from other map will be used for diffusion. The chaotic range of proposed Hybrid map lies between 5.5 to 15, and its chaotic properties have been validated using Lyapunov exponent, Bifurcation diagram, and Shannon Entropy. The results show that the Bifurcation diagram of the Hybrid map is uniform in entire range. Also, the Lyapunov Exponent of the Hybrid map is greater than 0, and the value of the Shannon entropy of the Hybrid map is close to 10. Also, the proposed image encryption scheme is capable of resisting different types of security attacks.