Extended capabilities for visual cryptography
An extended visual cryptography scheme, for an access structure \((\Gamma_{Qual},\Gamma_{Forb})\) on a set of \(n\) participants, is a technique to encode \(n\) images in such a way that when we stack together the transparencies associated to participants in any set \(X \in \Gamma_{\text{Qual}}\) we get the secret message with no trace of the original images, but any \(X \in \Gamma_{\text{Forb}}\) has no information on the shared image. Moreover, after the original images are encoded they are still meaningful, that is, any user will recognize the image on his transparency.
scientific article; zbMATH DE number 1542262