Threshold Visual Cryptographic Scheme With Meaningful Shares

In a conventional threshold k out of n visual cryptographic scheme (( k,n)-VCS, for short), one secret image P can be encoded into n seemingly random transparencies (called shares) such that the superimposed result of any group of k or more transparencies can reveal P to our eyes, while that of less than k ones cannot. To ease the management and identification, the shares may look meaningful, instead of seemingly random, pictures. Given secret image P shared by n participants and cover image C, we study ( k, n)-VCS with meaningful shares (denoted as ( k, n)-VCS-MS) in this letter where the n shares could be recognized as the meaningful cover C and their superimpositions follow the threshold requirements of ( k, n)-VCS. We present a formal definition to ( k, n)-VCS-MS and develop an efficient construction by way of integer linear programming. Experimental results demonstrate the effectiveness of our construction.