© 2020, IJSRCSE All Rights Reserved 97 International Journal of Scientific Research in ___________________________ Research Paper. Computer Science and Engineering Vol.8, Issue.4, pp.97-104, August (2020) E-ISSN: 2320-7639 Medical Image Encryption Scheme Based On Hybrid Chaotic Permutation J.B. Akan 1* , E.A. Adedokun 2 , G. Onuh 3 , A. Umar 4 , R. I Nwosu 5 , Y. Ibrahim 6 1,2,3,4,5,6 Dept. of Computer Engineering, Ahmadu Bello University, Zaria, Nigeria * Corresponding Author: akanbello@gmail.com, Tel: +2348162151101 Available online at: www.isroset.org Received: 27/May/2020, Accepted: 06/Jun/2020, Online: 31/Aug/2020 Abstract— Securing patient’s information in form digital image from unauthorized modification is a crucial concern in modern day information system. With respect to this, a variant of chaos-based image encryption algorithm is proposed for securing medical images, catering for the challenges observed in the chaos-based image encryption algorithm. In the proposed improved algorithm a hybrid permutation approach based on bit-level and block scrambling is used for shuffling pixel after which, chaotic random data with pixel format and inserted on the plain-image surrounding. The plain image is divide into 8 variable sub blocks, then a 3D logistic map is used for generation of scrambling sequence. A combination of bit-level and block level pixel scrambling process was performed using the generated scrambling sequence, before image pixel diffusion process is performed. Simulation results showed an improve performance with respect to information entropy distribution of image in the adjacent direction which greatly reduces pixel correlation and strong redundancy, NPCR and UACI respectively. Thus, the proposed algorithm shows high robustness, sensitivity and resistance to chosen plaintext, known plaintext and chosen cipher text attack. Keywords— Medical Image Encryption, Chaotic Cryptography, Differential Attacks, Pseudorandom Key-stream, Pixel Scrambling I. INTRODUCTION The advent of multimedia technology has witness tremendous advancement in recent time most especially in the area of information sharing such as images. These development has introduced a significant risk to information in the aspect of information security. Hence with the increasing use of telemedicine services in the health care industries, the quality of health service delivered to patients in remote location has been beneficial. However, this system most often demand for real time communication of medical images from different health service point. Thus, owning to illegal interception and eavesdropping, there exist a severe problem either, on storage or during transmission when images are acquired. Therefore, the general preservation of medical images from malicious and unauthorized usage is quite important [1-4]. İn Accordance with numerous literatures, using encryption is the most direct and simple approach for protecting and preserving images generally including medical images from unauthorized usage however, given the different views in literatures traditional cryptographic algorithm such as DES, AES, RSA appear not suitable for image encryption as a result of image properties such as high redundancy, pixel correlation in adjacent directions, high online health service demand and real time processing of medical diagnosis[1, 5-10]. Although there exist a large number of techniques adopted for image encryption range from DNA encoding, Fourier transform, Sudoku grid, compressed sensing, and based chaos theory [11, 12]. Image encryption technique based on chaotic system has shown prospect over the years and proven to exhibit similar cryptographic characteristic to the traditional cryptographic system, due to their desirable and pretty cryptographic properties of randomness, unpredictability, topological mixing, ergodicity and high sensitivity to initial condition and control parameters [13-16]. These non-linear chaotic properties based on complex chaotic maps usually exhibit chaotic behaviors with simple and a deterministic structure, which often provide fast and secure protection for information contain in an image against attacks [14, 17] in addition, the basic architecture used for by most chaos- based image encryption technique in literature was proposed by Fridrich is presented in[18]. Hence the focus of this paper is on chaos-based image encryption. An improved variant of chaos-based image encryption algorithm for securing medical images based on a hybrid pixel permutation and block diffusion is proposed catering for patient’s medical image privacy. The rest of this paper is structure as follows; section I contain the introduction which give background information about chaotic system, in Section II related works are discussed, meanwhile in Section III, our proposed encryption method is explain with the structure of the algorithm also presented, whereas in Section 4 the