An EXTENDED VISUAL CRYPTOGRAPHY SCHEME WITHOUT PIXEL EXPANSION USING DITHERING

Abstract: Visual Cryptography is secret sharing scheme which uses images distributed as shares such that when they are superimposed, the hidden secret image is revealed. In extended visual cryptography (EVC), the shares are constructed to contain meaningful cover images. Here, we propose a technique called dithering to block replacement methods of EVC, in order to improve the quality of recovered secret image. The size of share image and recovered image is same as that of original secret image. The resulting scheme also maintains perfect security by applying random number generation to the secret image. Keywords: Extended Visual Cryptography, halftone images, Dithering, Pixel expansion