Visual Cryptography and Random Grids Schemes

Visual Cryptography (VC) and Random Grids (RG) are both visual secret sharing (VSS) techniques, which decode the secret by stacking some authorized shares. It is claimed that RG scheme benefits more than VC scheme in terms of removing the problems of pixel expansion, tailor-made codebook design, and aspect ratio change. However, we find that the encryption rules of RGS are actually the matrices sets of probabilistic VCS. The transformation from RGS to PVCS is proved and shown by means of giving theoretical analysis and conducting some specific schemes. The relationship between codebook and computational complexity are analyzed for PVCS and RGS. Furthermore, the contrast of PVCS is no less than the one of RGS under the same access structure, which is shown by experimental results.