Medical image encryption using novel sine-tangent chaotic map

Abstract

Medical images play a crucial role in the diagnostic, planning, and monitoring of various types of diseases and physical problems. These images contain confidential details about the patient's condition. This confidential data can be safeguarded by using techniques like image encryption that transforms a given image into an unidentifiable format. This research paper proposes a medical image cryptosystem that uses a one-dimensional (1-D) novel Sine-Tangent Chaotic (STC) map and a shared key. Firstly, a private shared key is generated using the XOR operations, on which permutation and substitution operations are carried out. Secondly, a chaotic sequence is generated using the novel STC map. Finally, the permuted-substituted private shared key, the chaotic sequence, and one of the plain image components (i.e. Red, blue or Green) are XORed to construct the cipher image. To test the randomness of the proposed novel 1-D STC, we have used bifurcation diagram, Lyapunov Exponent (LE) and Shannon entropy (SE) parameters. The results show that the proposed mathematical chaotic equation has a wider chaotic range, and is more complex than some of the existing chaotic maps. Also, the observations prove that the proposed medical image encryption method performs well in comparison to the existing state of the art approaches, by obtaining values 7.99977, 99.66023 and 33.80065 for parameters Entropy, Number of Changing Pixel Rates (NPCR) and Unified Averaged Changed Intensity (UACI), respectively.