Abstract: Visual secret sharing (VSS) was proposed by Naor and Shamir in 1995. Visual secret sharing schemes encode a secret image into two or more share images, and single share image can’t obtain any information about the secret image. When superimposes the shares, it can restore the secret by human vision. Due to the traditional VSS have some problems like pixel expansion and the cost of sophisticated. And this method only can encode one secret image. The schemes of encrypting more secret images by random grids into two shares were proposed by Chen et al. in 2008. But when those restored secret images have much distortion, those schemes are almost limited in decoding. In the other words, if there is too much distortion, we can’t encrypt too much information. So, if we can adjust distortion to very small, we can encrypt more secret images. In this paper, four new algorithms which based on Chang et al.’s scheme be held in 2010 are proposed. First algorithm can adjust distortion to very small. Second algorithm distributes the distortion into two restored secret images. Third algorithm achieves no distortion for special secret images. Fourth algorithm encrypts three secret images, which not only retain the advantage of VSS but also improve on the problems of decoding.
Abstract: This paper proposes a visual cryptography by random
grids scheme with identifiable shares. The method encodes an image
O in two shares that exhibits the following features: (1) each generated
share has the same scale as O, (2) any share singly has noise-like
appearance that reveals no secret information on O, (3) the secrets can
be revealed by superimposing the two shares, (4) folding a share up
can disclose some identification patterns, and (5) both of the secret
information and the designated identification patterns are recognized
by naked eye without any computation. The property to show up
identification patterns on folded shares establishes a simple and
friendly interface for users to manage the numerous shares created by
VC schemes.