(2,2)-Secret Sharing scheme with improved share randomness

Visual secret sharing (VSS) is a method to scatter a secret image into shares of random patterns that have to be stacked together to reconstruct the secret. Since each share is a random pattern of black and white pixels, it is not enough to rebuild the secret from just one share. Stacking two shares reconstructs the first secret whereas rotating the first share by 90deg counterclockwise and stacking reconstructs the second secret. A novel algorithm to create both shares from two secrets with improved randomness is proposed in this paper. Share creation algorithm selects extended patterns of random pixels to satisfy contrast requirements of both secrets reconstructed by normal and rotated stacking. Proposed method have desirable security properties because of the improved randomness of shares.