An Improved Essential Secret Image Sharing Scheme with Smaller Shadow Size

This article describes how in conventional (k, n) secret image sharing (SIS), any k or more shadows can be collaborated together to reveal the secret image. Usually, all shadows have the same importance. Recently, an essential (t, s, k, n) secret image sharing (ESIS) with different importance of shadows were proposed where the n shadows are divided into s essential shadows and n − s non-essential shadows. In reconstruction, it needs at least k shadows which should include at least t essential shadows. In this article, the authors propose an improved (t, s, k, n)-ESIS scheme, where t<k. In their scheme, essential shadows and non-essential shadows have the equal sizes. No concatenation operation is needed in generating shadows. Besides, all shadow sizes are reduced to 1/k times of the secret image. Theoretical analyses and experimental results show that the proposed scheme is feasible with optimal sharing ratios among related works.