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Chapter 37 Visual Cryptography Based on Optical Image Projection

A visual cryptography scheme based on optical image projection is proposed in this paper. Initially the secret image is split into two shares. Then, such digital images are constructed in share’s planes that their projections in the projection screen would correspond to each of the appropriate shares. Geometrical parameters describing the location of shares’ planes and focus points of projectors are additional security parameters of the encoded image. Direct overlapping of the reconstructed shares does not leak any information on the encrypted image. The original image can be interpreted by a naked eye when appropriate projectors are placed at predefined locations of the geometrical setup.