Lehrstuhl Mathematik & InformatikBoolean Composition of Visual Secret Sharing Schemes
Abstract. In this paper, we analyze the disjunction and the conjunction of two access structures for visual secret sharing schemes. The latter operation, when applied to k-out-of-n schemes, leads to schemes with multiple thresholds. We precisely determine the maximum relative contrast for schemes of this type. As in the case of classical schemes with a single threshold, the analysis proceeds by revealing a central relation between the relative contrast in a visual secret sharing scheme and the error-term in a related problem of approximation-theoretic flavor.