A cheat preventing method with efficient pixel expansion for Naor-Shamir´s visual cryptography

This paper proposes a cheat-prevention method of visual cryptography (VC) for binary images. A VC technique encrypts a secret image into images referred to as shares so that stacking sufficient shares recovers the secret image, where shares are kept by different parties. The proposed method prevents malicious parties from deceiving an honest party, i.e., from cheating the honest party. To fight cheating, no further pixel expansion is introduced to the proposed method, so this method improves the contrast of recovered secret image and cheat-prevention functionality.