A New Medical Image Encryption Algorithm Using Multiple 1-D Chaotic Maps

This paper presents a new chaos-based medical image encryption algorithm using iterative permutation and substitution operation. To address the drawbacks encountered when using the invertible area-preserving chaotic maps, we introduce a pixel swapping-based image scrambling method with permutation keystream sequence generated from the logistic map. In the substitution stage, each keystream element is generated from a 1-D chaotic map selected from a group of three 1-D chaotic maps according to the value of the pixel previous to the one it applies to, making the keystream sequence dependent on plain-image. As a result, the robustness of the proposed algorithm against chosen-plaintext attack is ensured and the diffusion intensity is increased. The results of NPCR and UACI tests indicate that the proposed algorithm takes only two cipher rounds to achieve a desired diffusion effect. Moreover, each of the three 1-D chaotic maps is constructed by combining of two existing 1-D chaotic maps (seed maps). Compared with its corresponding seed maps, the compound map has larger chaotic ranges and more complex chaotic properties while remaining simplicity, making it a good candidate for constructing image ciphers with a sufficiently large key space and high computational efficiency. Our theoretical analysis and experimental results indicate that the proposed algorithm has a high level of security.

I. Introduction

Starting out over forty years ago with demonstrations of hospitals extending care to patients in remote areas, the use of telemedicine has spread rapidly and is now becoming integrated into the ongoing operations of hospitals, specialty departments, home health agencies, private physician offices as well as consumer's homes and workplaces. The increasing use of telemedicine has realized significant health care benefits, ranging from increased compliance in taking medications, to improved healthcare delivery in rural and underserved areas, to improved delivery of healthcare services outside hospitals and clinics, and better utilization of healthcare professionals. Meanwhile, how to effectively protect the privacy and confidentiality of patients' data transmitted over open networks has become an important issue [1]–[4].