Further improvements on secret image sharing scheme

Secret image sharing technique has been widely researched in the past decade. This technique allows us to create the share images from a secret image in such a way that an individual share does not reveal any information about the secret image, however when a specified number of shares are brought together, they can be used to reconstruct the secret image. In this paper, we first point out the weaknesses of the existing secret image sharing methods proposed by Thien and Lin [8] and Alharthi and Atrey [1], and then propose a new method that overcomes these weaknesses. Thien and Lin [8] use a permutation step which leads to disclosure of the secret image if the permutation key is revealed. Alharthi and Atrey [1] suggested an improvement over Thien and Lin's method by removing the permutation step. However, their method has a limitation that the first few shares are not usable because of its similarity with the secret image. We propose further improvement over these two methods by repeatedly changing the value of share number using a modulo prime function. To show the superiority of our method over others, we present the security analysis and experimental results.