(2,n) secret sharing scheme for gray and color images based on Boolean operation

Traditional secret sharing (SS) schemes can reconstruct the secret precisely, but have high computation complexity. Visual secret sharing (VSS) schemes use human visual system to reconstruct the secret without cryptographic computation, but have pixel expansion and loss of contrast. Wang et al. proposed a (2,n)-SS scheme for binary images based on Boolean operation, which has low computation complexity, no pixel expansion and the contrast is 1/2. In this paper, we first construct an r runs (2,n)-SS scheme to improve the contrast of Wang at al.'s binary (2,n)-SS scheme. Then we present two approaches to construct r runs (2,n)-SS schemes for grayscale image and color image. The two approaches are both based on Boolean operation, while one approach uses halftone technology and the other uses bit level processing. These proposed schemes have low computation complexity and almost ideal contrast.