Hibrit kriptolama için benekli maskeleme

The increasing amount of data with the increasing use of the Internet has led to an increase in the studies on the protection of these data in the scientific world. This thesis has been written to develop a new optical image encoding system by addressing the problems of both commonly used optical encryption systems and multiple image encryption methods. Hybrid method has been developed combining diffractive imaging and image hiding algorithms by considering the weak points of double random phase encoding (DRPE), phase truncated Fourier transform (PTFT) and diffractive imaging based optical image encryption systems. The carrier and the parameters used in the hiding step provide additional key space in the hybrid method while simultaneously encrypting more than one image. The problems of PTFT, DRPE and diffractive imaging systems can be solved by the hybrid method developed in nonlinear structure. The problems faced by the multiple image encryption methods are briefly discussed and a hybrid multiple image encryption method based on compressive sensing and diffractive imaging is developed. Space multiplexing enables images to be combined on a single plane and authorized for different users. By recombining the phase and amplitude of the images, the size of the matrix carrying the images is further reduced. The method with a non-linear structure can solve the problems of multiple-image encryption methods. In this thesis, in the coding stage of the images with diffractive imaging used for both hybrid methods, two different masks are used, one is a private key and the other one is a public key that changes at each encryption and consists of different values for each receiver. The fact that both masks must be on the receiving side in order to decrypt the password and the total number of probabilities to be tried to obtain these masks correctly for the first method is 256^2*512*512 and for the second method is 256^2*256*256 for a 256*256 matrix sized image, which provides strong key space to hybrid methods. Two different hybrid methods developed in this study provide different solutions to optical image encryption and multiple image encryption methods. This study could be further developed for practical application and could be an example for future studies.