Weighted visual secret sharing for general access structures based on random grids

The traditional visual secret sharing (VSS) schemes share a secret image into multiple shares, and all the shares have the same importance. However, it is occasionally necessary to differentiate participants based on their different levels of importance in certain applications. In previous works, some weighted VSS schemes were implemented only for the (k,n) threshold access structure and were not applicable to other access structures. In this paper, a weighted VSS scheme is proposed for general access structures (GAS) based on random grids (RG). For the different qualified sets of shares, the amount of information we get about the secret image is different because the total weight of the shares participating in the recovery process is different. Moreover, both OR and XOR operations can be applied to recover the secret image, which can extend the applications of our scheme. For the same minimal qualified set, we can obtain better visual quality by stacking (XOR-ing) more shares. In addition, we can obtain the lossless secret image by performing the XOR operation on all shares. More importantly, our scheme is suitable for GAS; however, it has certain limitations in the weight assignment of participants for the non-threshold access structures. Finally, experiments and comparisons demonstrate the effectiveness of our scheme.