Inference of Share Stacking Based on Progressive Visual Cryptography

The objective of visual cryptography is to hide secret in multiple share images. Then, stacking share images together decrypts hidden secret by human visual system. As the share images are given with different priorities, those share images hide various degrees of secret, which is the objective of progressive visual cryptography. This paper presents a scheme to realize progressive visual cryptography. A 2x2 block is the basic element of share image, and we design block pairs for secret hiding as well as secret encryption. The degrees of hidden secret depend on the priorities of share images. The proposed scheme is capable of decrypting partial secret and inferring the stacked shares. The experiment results will demonstrate that our scheme further achieves applications based on progressive visual cryptography, including self-decryption watermark, and inference of shares stacking.