Enhanced Boolean-based multi secret image sharing scheme

• We show the threshold security problem in Chen and Wu's (n, n)-MSIS scheme.
• We propose a strong threshold (n, n)-MSIS scheme to solve this security problem.
• We propose a modified (n, n)-MSIS scheme to enhance randomness of shared images.

Recently, Chen and Wu propose a (n, n) multi secret image sharing (MSIS) scheme that shares n secret images into n shared images. These n shared images can be together used for reconstructing n secret images by Boolean operations. However, there is an inaccuracy in Chen and Wu's (n, n)-MSIS scheme that one can recover some secret images (partial secret information) from (n−1) or fewer shared images. This compromises the threshold security in (n, n)-MSIS scheme. In this paper, we overcome this inaccuracy and propose a strong threshold (n, n)-MSIS scheme without leaking partial secret information from (n−1) or fewer shared images. Moreover, by an inherent property of image that a permutated image with a chaotic reallocation of pixels without effect on their intensity levels, we propose a modified strong (n, n)-MSIS scheme to further enhance the randomness of shared images.