Abstract
This paper proposes a new method to strengthen the nonlinear kinetic complexity and ergodicity of Lorenz system. Through the analysis of auto-correlation, frequency distribution, approximate entropy and information entropy, the improved Lorenz system has better dynamical properties than Lorenz system. According to NIST-800-22 test results, the chaotic sequences generated from proposed system have passed all random tests, which denotes that the improved Lorenz system is applicable to chaotic encryption. Once the plaintext image is color, the size of scramble image is three times as big as plaintext image, so that a lot more pixel information participant in permutation and diffusion to get better encryption results. Simulation results show that the image encryption scheme provides good security and high capacity to resist common attacks.
Highlights
Since Lorenz proposed the first two scrolls system in 1963 [1], chaotic systems have attracted attention of scientific community due to their vast applications in many areas such as physics, biology, complex networks, economics and so on [2]–[6]
Non-predictability, ergodicity, random-like behavior, and high sensitivity to initial conditions are the main characteristics of chaotic systems, which can be used in encryption and secure communication [7]–[20]
Amir has proposed a robust image encryption scheme for low profile applications based on chaotic Lorenz system [22]
Summary
Since Lorenz proposed the first two scrolls system in 1963 [1], chaotic systems have attracted attention of scientific community due to their vast applications in many areas such as physics, biology, complex networks, economics and so on [2]–[6]. Diffusion and permutation are two significant steps in chaotic image encryption. In many proposed chaotic image encryption algorithms, Lorenz system as pseudo random number generator (PRNG) to generate chaotic sequences. Amir has proposed a robust image encryption scheme for low profile applications based on chaotic Lorenz system [22]. Younas and Khan combined inverse left almost semi group with Lorenz system in image encryption scheme to obtain better confusion and diffusion effect through a modern substitution-permutation network [23]. Girdhar and Kumar hybridized Lorenz system and Rossler system to generate the random sequence, and applied the rules of DNA cryptosystem to encrypt image [25]. Hyper-chaotic systems possess more complex dynamical characteristics and higher randomness than low-dimensional chaotic systems, so that hyper-Lorenz system is more applicable to image encryption [27]–[29]. Z2(t τ) sin (t) where x (t), y (t) and z (t) are output sequences
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