Region Incrementing Visual Cryptography

This letter presents a novel visual cryptography scheme, called region incrementing visual cryptography (RIVC), for sharing visual secrets with multiple secrecy levels in a single image. In the proposed n-level RIVC scheme, the content of an image S is designated to multiple regions associated with n secret levels, and encoded to n+1 shares with the following features: (a) each share cannot obtain any of the secrets in S, (b) any t (2lestlesn+1) shares can be used to reveal t-1 levels of secrets, (c) the number and locations of not-yet-revealed secrets are unknown to users, (d) all secrets in S can be disclosed when all of the n+1 shares are available, and (e) the secrets are recognized by visually inspecting correctly stacked shares without computation. The basis matrices for constructing the proposed n-level RIVC with small values of n=2, 3, 4 are introduced, and the results from two experiments are presented.