Security enhancement of color image cryptosystem by optical interference principle and spiral phase encoding

Abstract

A color information cryptosystem based on optical interference principle and spiral phase encoding is proposed. A spiral phase mask (SPM) is used instead of a conventional random phase mask because it contains multiple storing keys in a single phase mask. The color image is decomposed into RGB channels. The decomposed three RGB channels can avoid the interference of crosstalks efficiently. Each channel is encoded into an SPM and analytically generates two spiral phase-only masks (SPOMs). The two SPOMs are then phase-truncated to get two encrypted images and amplitude-truncated to produce two asymmetric phase keys. The two SPOMs and the two asymmetric phase keys can be allocated to four different authorized users. The order, the wavelength, the focal length, and the radius are construction parameters of the SPM (or third SPOM) that can also be assigned to the four other different authorized users. The proposed technique can be used for a highly secure verification system, so an unauthorized user cannot retrieve the original image if only one key out of eight keys is missing. The proposed method does not require iterative encoding or postprocessing of SPOMs to overcome inherent silhouette problems, and its optical setup alleviates stringent alignment of SOPMs. The validity and feasibility of the proposed method are supported by numerical simulation results.

Chaotic image encryption using pseudo-random masks and pixel mapping

“…(6) is used to encrypt the hiding EIA. With x 0 as an initial value (also known as the seed), a non-periodic and nonconverging sequence fx i g can be iteratively generated The chaotic sequence S ¼ x i f g MN i ¼ 1 with given initial parameters (x 0 , ρ 0 ) is generated by map (6).…”

“…Because of the strong correlation in image data, conventional text encryption techniques are not appropriate for image encryption. In the past two decades, a large number of schemes have been proposed for image encryption utilizing all kinds of optical techniques [3][4][5][6], which combine the distinct advantages of processing two-dimensional (2D) image data with a parallel conduction mode. Among them, the most widely used transform methods are the fractional Fourier transform (FRT), extended FRT, gyrator transform, and Fresnel transform.…”

Modified computational integral imaging-based double image encryption using fractional Fourier transform

“…Optical techniques have the distinct strength of processing complex two-dimensional (2D) or threedimensional (3D) data in parallel and performing otherwise slow operations at great speeds. Many encryption algorithms have been reported based on different types of optical systems [1][2][3][4][5]. Among these, the most common are double random phase encoding in the Fourier domain, and more recently, in the fractional Fourier domain.…”

Optical interference-based image encryption using circular harmonic expansion and spherical illumination in gyrator transform domain

“…To alleviate the strict optical alignment, some DRPE systems based on configuration of joint transform correlator (JTC) [10,11] or joint fractional Fourier transform correlator (JFTC) [12,13] have been proposed. On the other hand, some modified schemes use structured instead of random phase mask to overcome the problem of axis alignment, and to enlarge the key space with some structure parameters [14,15]. These structured phase masks (SPM), generally, have a rotationally symmetric distribution and are made from a spiral phase plate [14] or a devil's vortex Fresnel lens (DVFL) [15].…”

“…On the other hand, some modified schemes use structured instead of random phase mask to overcome the problem of axis alignment, and to enlarge the key space with some structure parameters [14,15]. These structured phase masks (SPM), generally, have a rotationally symmetric distribution and are made from a spiral phase plate [14] or a devil's vortex Fresnel lens (DVFL) [15].…”