Optical encryption by double-random phase encoding in the fractional Fourier domain

TLDR

In a quadratic phase system, any two planes are related by a fractional Fourier transform, providing a continuum of planes for encoding. The study proposes an optical architecture that encodes a primary image into stationary white noise using two independent random phase codes. Encoding is performed in the fractional Fourier domain of a quadratic phase system, where six system parameters together with the random phase codes constitute the encryption key. The method demonstrates higher security than previous approaches, as confirmed by experimental results.

Abstract

We propose an optical architecture that encodes a primary image to stationary white noise by using two statistically independent random phase codes. The encoding is done in the fractional Fourier domain. The optical distribution in any two planes of a quadratic phase system (QPS) are related by fractional Fourier transform of the appropriately scaled distribution in the two input planes. Thus a QPS offers a continuum of planes in which encoding can be done. The six parameters that characterize the QPS in addition to the random phase codes form the key to the encrypted image. The proposed method has an enhanced security value compared with earlier methods. Experimental results in support of the proposed idea are presented.