Visual multi secret sharing by cylindrical random grid

Visual secret sharing (VSS) is the process of encoding a secret image into several share images in which the original secret image can be reconstructed and recognized by stacking all of the share images together. VSS has two categories: visual cryptography (VC) and Random Grid (RG). The VC is affected by various drawbacks such as: enlarging the size of original image, need for a codebook and the limitation to encode only one secret image at a time. RG solves the first two drawbacks of VC. To solve the third drawback and provide a solution to optimize recent algorithms, we propose a novel RG-based VSS scheme which encodes several secret images at a time. Instead of using only (2, 2) visual secret sharing, (2, n) and (n, n) is employed. This scheme has the ability to encode one or multiple secret images into multiple shares in place of two shares. In our proposed scheme, instead of Circular Random Grid, a new algorithm named Cylindrical Random Grid is used. It encrypts multiple secret images into two or more shares. To decrypt the first secret image, shares are stacked together. For decrypting of other secret images, one of the stacked shares is rotated in a fixed size over other shares based on the number of secret images which are encrypted. This algorithm is simple to implement and less time consuming.