A new highly fractal 1D- chaotic map-based novel encryption on HVS-based watermarked Fundus images for 2-level security in teleophthalmology applications

Abstract

Abstract In recent years the combination of medical image watermarking and encryption is becoming popular due to a better trade-off between authenticity and security, since, each of these methods alone is insufficient to offer complete security. In the proposed work, the watermark is embedded into the Fundus image using the Singular Value Decomposition (SVD) of the La*b* space image of the Fundus image. The scaling factor is selected based on the HVS property of the human eye. The proposed embedding algorithm is semi-blind because the system requires the singular values (s) of the La*b* image at the receiver side in order to extract the watermark. To improve security, the authenticated image then undergoes 2-levels of confusion process followed by diffusion for encryption. For diffusion, the key is generated from the newly developed Modified Sine-Logistic Chaotic System (MSLCS), which is constructed by the combination of logistic map and sine map. The performance evaluation of the new chaotic system has been done in terms of the Bifurcation diagram, Lyapunov exponent, Phase portrait and Entropy. Also, Different tests such as Blood vessel segmentation and Retinal object identification were carried out on the original image, watermarked image, decrypted image and recovered image. The results show that the embedding of watermarks followed by encryption, on Fundus images does not affect the diagnosis and identification of retinal objects. Correct decryption, secured recovery of Fundus image and guaranteed extraction of the watermark at the receiver side make the proposed system secure for Fundus images in tele-ophthalmology applications.