Contrast-improved visual secret sharing based on random grid for general access structure

Random grid (RG)-based visual secret sharing (VSS) owns the advantages of no pixel expansion and codebook design. VSS for general access structure (GAS) possesses wider applications than VSS for (k,n) threshold. Previous RG-based VSS studies for GAS had the drawbacks of “all-or-nothing” or low visual quality. In this paper, we will develop a progressive VSS (PVSS) algorithm for GAS with improved visual quality based on RG. We employ different regions of the secret image and their generated corresponding random bits to improve the visual quality of the revealed secret image as well as to gain GAS with progressive feature, where the random bits are divided into three parts. In addition, our scheme has neither pixel expansion nor codebook design due to RG. We show the effectiveness of our proposed scheme in terms of experiments and analyses.