Novel chaos based cryptosystem using four-dimensional hyper chaotic map with efficient permutation and substitution techniques

In this paper, a competent hyper chaos-based image encryption technique is proposed. The cryptosystem uses a four-dimensional hyper chaotic map for implementing the secret key information. In terms of Lyapunov expo-nents, NIST test results and bifurcation diagrams, 4-D hyperchaotic system exhibits better dynamical behavior than lower dimensional chaotic systems. Also, 4-D map has superior hyperchaotic performance in views of ergodicity, complexity, and randomness behavior and is capable to generate an unpredictable keystream, which is highly suitable for encryption. Therefore, a novel image encryption algorithm using four-dimensional hyper chaotic system is proposed here. A novel method with sequence of mathematical operations is used for the secret key generation. Both the confusion and diffusion phases are implemented on the basis of this secrete random values with innovative designs. In permutation phase, keystream-based pixel level and bit level scrambling are performed to shuffle the image pixels effectively. Novel methods are implemented to accomplish pixel level scrambling with row and column shift operations. The bit level scrambling is also instigated with a novel cyclic rotation technique. Thus, the pixel level and bit level scrambling ensure higher security in the permutation process. In substitution phase, the keystream is XORed with scrambled images in an effective manner to obtain the final encrypted image. Various evaluation measures are used to access the safety and security of the proposed system. The evaluation result of the projected method with numerous other techniques shows the sovereignty and higher security of the planned technique. The keystreams are generated from the hyperchaotic Lorenz system using a novel approach, and its generation is completely independent of the original image. The algorithm has wider application prospects, including encryption of images in medical field and cloud environment.