Image quality and security through nonlinear joint transform encryption

Abstract

Abstract-Joint-transform correlator (JTC) architecture presents some advantages, such as no requirement of interferometric recording of the phase distribution or complex conjugation of the key phase mask, in order to optically implement the well-known double random phase encryption (DRPE) method. In addition, a practical optical realization was proposed in a way that the whole information (primary image and two random phase masks) was easily introduced in the same input plane of the JTC system. However, poor image quality was obtained in the decryption stage. Cryptanalysis of JTC-based encryption systems demonstrated that they were vulnerable to certain intruder attacks, similarly to the original DRPE method. In this work, we review recent modifications of encryption algorithms based on JTC architecture that permit, on the one hand, to significantly increase the quality of the retrieved image after information decryption, and on the other hand, to achieve a high security level against a variety of system attacks. The modifications, which were firstly introduced in the Fourier-based JTC system, have been also adapted to be used in the Fresnel and Fractional Fourier domains as well as in the Gyrator domain. Nonlinear operations have been also introduced in multifactor encryption-authentication.

Image encryption using the Gyrator transform and random phase masks generated by using chaos

“…One of the main drawbacks of the image encryption systems based on the initial DRPE is that the security of the system is vulnerable to attacks, this weakness is due to the linear property of the DRPE scheme [1][2][3]. The DRPE has been further extended from the Fourier domain to the Fresnel domain [4][5][6], the fractional Fourier domain [7][8][9][10][11][12], the Gyrator domain (GD) [13][14][15][16] and other domains [17][18][19][20], with the purpose of adding more keys and increasing the security of the DRPE system.The Gyrator transform (GT) is a mathematical tool for analysis and processing of twodimensional signals [21]. The GT has been used in optics [22], signal processing [13] and image encryption [13][14][15][16].…”