Verifiable Visual Cryptography

The paper presents a verifiable visual cryptography (VC) scheme for checking the validness to the shares engaged in a VC decoding instance. The idea is to stamp a continuous pattern on the shares belonging to the same secret image, and a part of the pattern can be revealed through aligning and stacking half of two shares together. The visual coherent among the revealed patterns of all pair of shares provides evidence to the genuine of the shares engaged in the decoding process. Compare to the reported cheating prevention VC schemes, the proposed scheme maintains the original pixel expansion in VC scheme without cheating prevention ability, and the share verification process is done without resorting to any additional verification image. Besides, the proposed verification mechanism can easily be attached to any VC schemes in the literature to endow legitimate user with the ability to prevent cheating from malicious participants.