Abstract
Image encryption is often used to protect private images during transmission on a public channel. A high dimensional chaotic map has a greater secret key space, better ergodicity and dynamic property than a low-dimensional chaotic system. A seven-dimensional (7D) hyperchaotic map is used to produce chaotic sequences. Given secret keys and SHA-512 function are employed to generate initial values for iteration. Many stochastic signals are injected into one of the variables during iteration to transfer trajectory and increase dynamic behavior of a chaotic system. Three matrices are constructed with generated chaotic sequences. Permutation is performed on the basis of a control matrix. It keeps the pixel far from its neighboring pixels. Cycle shift is executed during bit-level permutation. Characteristic values of scrambling image are calculated and temporary values are achieved successfully. Two dynamic values are also applied during the diffusion process. Experimental results display the effects of the proposed algorithm. Security analysis reveals that the proposed method has some special advantages.
Highlights
With the help of modern information and communication technologies, it becomes much easier and faster to exchange multimedia information on the Internet
Shannon [8] proposed a confusion-diffusion framework for secure communication in 1949, and Fridrich [9] was the first to apply it for image encryption
To alter chaotic orbits and improve dynamic performances, some noise signals are injected into one of the iterating variables, and this could availably increase the key space of the cryptosystem
Summary
With the help of modern information and communication technologies, it becomes much easier and faster to exchange multimedia information on the Internet. In contrast from low-dimensional chaotic maps, hyperchaotic maps have more positive Lyapunov exponents (LEs) and more sophisticated structure They have larger secret key space, better ergodicity and dynamic property [18]. Xu et al [33] presented an encryption method based on dynamic index and block scrambling technologies. A dynamic index was applied to diffuse the scrambled image. In this manuscript, chaotic sequences are generated by a 7D hyperchaotic map. To alter chaotic orbits and improve dynamic performances, some noise signals are injected into one of the iterating variables, and this could availably increase the key space of the cryptosystem.
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