EXTENDED VISUAL CRYPTOGRAPHY SCHEME FOR COLOR IMAGES WITH NO PIXEL EXPANSION

A k-out-of-n Extended Visual Cryptography Scheme (EVCS) is a secret sharing scheme which hides a secret image into n shares, which are also some images. The secret image can be recovered if at least k of the shares are superimposed, while nothing can be obtained if less than k shares are known. Previous EVCS schemes are either for black-and-white images or having pixel expansion. In this paper, we propose the first k-out-of-n EVCS for color images with no pixel expansion. The scheme also improves the contrast of the n shares and the reconstructed secret image (i.e. the superimposed image of any k or more shares) by allowing users to specify the level of each primary color (i.e. Red, Green and Blue) in the image shares as well as the reconstructed secret image.