dynamic visual cryptography (DVC) is a technique for the encryption and decryption of visual secret information. The confidential visual information in DVC is concealed embedding the secret image into the regular moir...
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dynamic visual cryptography (DVC) is a technique for the encryption and decryption of visual secret information. The confidential visual information in DVC is concealed embedding the secret image into the regular moire grating. The secret can be perceived from the cover image if only the cover image is oscillated according to a predefined law of motion and time-averaging techniques are used. The security of the encryption procedure and the quality of the decrypted image depend on the proper preselection of the pitches of a moire grating used in the encryption stage. This paper presents the main principles of the determination of near-optimal pair of the pitches of moire grating as well as graphical schemes and analytical equations in case of harmonic and chaotic oscillations.
We consider one applied global optimization problem where a set of feasible solutions is discrete and very large. The goal is to find optimal perfect gratings, which can guarantee high quality and security of the visu...
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We consider one applied global optimization problem where a set of feasible solutions is discrete and very large. The goal is to find optimal perfect gratings, which can guarantee high quality and security of the visualcryptography method. A priori estimation techniques, such as branch and bound type methods, cannot be applied to exclude an essential part of elements from the feasible set. Thus, a full search is required to solve this global optimization problem exactly, which is very computationally demanding. A library of C++ templates is developed that allows its user to implement parallel master-slave algorithms for his/her application without any knowledge of parallel programming API (application programming interface). Design of the templates allows users to build a parallel solver using MPI (message passing interface) API or distributed computing application using BOINC (Berkeley open infrastructure for network computing) API from the same C/C++ code with implementation of application-specific tasks. We build parallel and distributed computing solvers for the considered optimization problem and present results of computational experiments using a computer cluster and BOINC project for volunteer computing. Heuristic methods are also considered as an alternative to the full search algorithm. Due to complicated conditions defining feasible solutions (perfect gratings), genetic algorithms cannot be used to solve this problem efficiently. We propose two memetic heuristic algorithms, when a basic stochastic or simplified full search algorithm is combined with a local search algorithm. Parallel heuristic algorithms are also proposed and implemented. The efficiency and accuracy of heuristics are investigated and results of experiments are presented.
A technique of computational image encryption and optical decryption based on computer generated holography and time-averaged moire is investigated in this paper. dynamic visual cryptography (a visualcryptography sch...
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ISBN:
(数字)9781510613843
ISBN:
(纸本)9781510613843;9781510613836
A technique of computational image encryption and optical decryption based on computer generated holography and time-averaged moire is investigated in this paper. dynamic visual cryptography (a visualcryptography scheme based on time-averaging geometric moire), Gerchberg-Saxtonalgorithm and 3D microstructure manufacturing techniques are used to construct the optical scheme. The secret is embedded into a cover image by using a stochastic moire grating and can be visually decoded by a naked eye. The secret is revealed if the amplitude of harmonic oscillations in the Fourier plane corresponds to an accurately preselected value. The process of the production of 3D microstructure is described in details. Computer generated holography is used in the design step and electron beam lithography is exploited for physical 3D patterning. The phase data of a complex 3D microstructure is obtained by Gerchberg-Saxton algorithm and is used to produce a computer generated hologram. Physical implementation of microstructure is performed by using a single layer polymethyl methacrylate as a basis for 3D microstructure. Numerical simulations demonstrate efficient applicability of this technique.
Image hiding scheme based on time-averaged moire fringes on finite element grids is proposed in this paper. This visual communication scheme is based on the formation of time-averaged moire fringes in the digital dich...
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Image hiding scheme based on time-averaged moire fringes on finite element grids is proposed in this paper. This visual communication scheme is based on the formation of time-averaged moire fringes in the digital dichotomous cover image when it is oscillated according to a predefined Eigen-shape. Initial phase scrambling and phase normalization algorithms are used to encode the secret in the cover image. Theoretical relationships between the amplitude of the Eigen-shape, the order of the time-averaged moire fringe and the pitch of the deformable one-dimensional moire grating are derived. Computational experiments are used to illustrate the efficiency and applicability of this image hiding scheme in practical applications. (c) 2015 Elsevier Inc. All rights reserved.
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