Visual Cryptography

Visual Cryptography Schemes (VCS) are a special kind of secret sharing schemes. The idea of visual cryptography is a fascinating invention by Moni Naor and Adi Shamir (1994). A VCS is a method to secretly share an image among a given group of participants. A VCS for a set of participants encodes a secret image into shadow images which constitute the shares given to the participants. The visual recovery consists of xeroxing the shares onto transparencies, and then stacking them. If ⊆ is qualified, then the participants in can visually recover the secret image by stacking their transparencies without any cryptography knowledge and without performing any cryptographic computation. If is forbidden, then its participants have no information on the secret image. In this talk we present an overview of visual cryptography. Also, we introduce several generalizations of this basic idea.