Abstract
The concept of region incrementing in visual cryptography was introduced to encrypt an image into multiple secrecy levels. But, it suffers from the pixel expansion increasing exponentially as the number of participants grows. In this paper, we propose a region incrementing visual secret sharing (RIVSS) scheme based on random grids. The proposed scheme is a general (k, n)-RIVSS scheme, in which any t (k ≤ t ≤ n) shares can be used to reconstruct the secret regions up to t − k + 1 levels. However, no information about the input image can be revealed by any k − 1 or fewer shares. With a nice property of region incrementing, the proposed scheme benefits by sharing an image without any pixel expansion and codebook requirement. We give formal proofs and experimental results to confirm both correctness and feasibility of our scheme.