Asian Journal of Physics Vol 31, No 7 (2022) A1-A12

An asymmetric optical cryptosystem based on Radon transform for phase image encryption

Ravi Kumar, Sakshi and Kehar Singh
Department of Physics, SRM University-AP, Andhra Pradesh-522 502, India.
Ben-Gurion University of the Negev, P. O. Box 653, Beer-Sheva 8410501, Israel
Optics and Photonics Center, Indian Institute of Technology Delhi, New Delhi-110 016, India
Dedicated to Prof Maria J Yzuel

In this paper, we propose a fully-phase image encryption and decryption technique in the Radon transform (RT) domain, having multiuser capabilities. The RT of a two-dimensional (2D) digital image gives projections at arbitrarily given angles, providing additional layer of security in the system. Multiple private keys for decryption are obtained using polar decomposition (PD) in the encryption process, enabling the multiuser capability. For encryption, the input amplitude image is first converted to a phase image and modulated using a structured phase mask (SPM) having preset topological charge. Then the modulated complex image is Fresnel propagated to a certain distance at which the real and imaginary parts of the complex wavefront are separated making the scheme asymmetric. The imaginary part is stored as the private key and real part is further subjected to PD and RT to obtain a set of private keys and the final encrypted image. The proposed technique has large key space and is highly sensitive to the encryption parameters. The robustness of the proposed image encryption method is tested against various common attacks such as noise-, occlusion-, and brute force attacks. Numerical simulation results confirm the validity and effectiveness of the proposed cryptosystem. © Anita Publications. All rights reserved.
Keywords: Phase image, Optical image encryption, Radon transform, Polar decomposition, Structured phase mask.

Peer Review Information
Method: Single- anonymous; Screened for Plagiarism? Yes
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