An Optimization Model for Visual Cryptography Schemes with Unexpanded Shares

[[abstract]]The method of visual cryptography is to encrypt a secret image into N shares so that any qualified set of participants can recover the hidden secret by their eyes; whereas any forbidden set of participants cannot obtain any secret information. In the study of visual cryptography, pixel expansion and contrast are two important issues. Most visual cryptographic methods are based on the technique of pixel expansion, and the result is that the size of each share is larger than that of the secret image. Pixel expansion not only results in distortion of the shares, but also consumes more storage space. In this paper, we proposed a new method to cope with the problems of pixel expansion. We used the concept of probability and considered the security issue on the forbidden set and the contrast issue on the qualified set to construct an optimization model for general access structures. Finally, we analyzed the contrast and blackness of black pixels of our experimental result, and we found that our method is better than Ateniese et al.’s.[[incitationindex]]SCI[[incitationindex]]EI[[booktype]]紙