A Lossless physical-layer encryption scheme in medical Picture Archiving and Communication Systems using highly-robust chaotic signals

This paper reviews some major techniques related to the security issues in Picture Archiving and Communications System (PACS) of medical images. Three conventional techniques including watermarking, digital signature and encryptions are studied. The encryption scheme using highly-robust chaotic signals is also proposed as a new lossless physical-layer that improves security in medical images in PACS. The dynamical system utilizing signum function is employed to generate chaotic signals with smooth bifurcation, i.e. no appearance of periodic windows. Nonlinear dynamics of the chaotic maps were initially investigated in terms of Cobweb map, chaotic attractor, Lyapunov exponent spectrum, bifurcation diagram, and 2-dimensional parameter spaces. Encryption qualitative performances are evaluated through pixel density histograms, 2-dimensional power spectral density, key space analysis, key sensitivity, vertical, horizontal, and diagonal correlation plots. Encryption quantitative performances are evaluated through correlation coefficients, NPCR and UACI. Demonstrations of wrong-key decrypted image are also included.