Low Redundancy Secret Image Sharing Scheme

As a category of secret sharing,Secret Image Sharing(SIS)allows secure sharing of secret images among a group of participants.Traditional SIS schemes introduce a threshold structure,which is simple in structure but are relatively inflexible.In order to extend the functionality of the schemes.Visual Cryptography Scheme(VCS),Weighted Secret Image Sharing(WSIS)and Essential Secret Image Sharing(ESIS)have been proposed,but these schemes have various shortcomings.For example,VCSs are only applicable to binary images and have limited scalability,especially VCSs have pixel expansion problems.WSIS and ESIS only support simple access policies and lack flexibility.Therefore,in order to meet the requirements of different scenarios,in this thesis,we propose three different SIS schemes.The main contributions are as follows:(1)Existing VCSs only support binary images and have limited flexibility.To address this problem,based on scalable basis matrix and Gaussian noise,we propose a Progressive Visual Cryptography Scheme(PVCS),which supports non-binary images.This scheme solves the pixel expansion problem,and therefore it is an ideal VCS.When the secret image changes,the matrix expansion algorithm can directly expand the basis matrix and Gaussian matrix,which greatly improves the flexibility of the scheme.In addition,we propose a method to derive noise volume according to Structure Similarly(SSIM).Sufficient experimental results show that our scheme has good visual effects.(2)SIS schemes implement a simple access policy.To solve this problem,we firstly extend the Linear Secret Sharing Scheme(LSSS)and propose a Secret Matrix Sharing Scheme(SMSS).Secondly,based on SMSS,we propose an SIS scheme named LM-SIS,which supports complex access policies.Compared with other SIS schemes,LM-SIS has advantages in flexibility,our scheme can provide approximately lossless or lossless recovery images,and our scheme gets a small shadow image size ratio,therefore,LM-SIS has the advantage of low redundancy.The experimental results demonstrate the superiority of the scheme.(3)The shadow images generated by the LM-SIS scheme are meaningless noise-like images,which may cause suspicion of attackers during storage and transmission.To solve this problem,we use the information hiding technique to embed shadow images into the specified cover images to achieve an Extended Secret Image Sharing scheme.Experiments demonstrate that the final shadow images generated by our scheme is visually indistinguishable from the cover images,and this scheme only has slight pixel expansion.So,our scheme has excellent performance.