A Hierarchical Threshold Scheme with Unique Partial Keys

. We will present an extension of Shamir's threshold scheme [14]. Shamir's scheme demonstrates how to divide a master key D into n pieces so that it is easily reconstructed from any k pieces, where even complete knowledge of k \Gamma 1 pieces reveals nothing about D. Shamir calls it a (k,n) threshold scheme. We propose a method that enables the creation of hierarchical information threshold schemes with s security levels, so that k l partial keys (shares) are required for computation of a master key D l for level l. The higher the security level, the more partial keys required. We call our scheme a (k l ; s; n) multithreshold scheme, l = 1; \Delta \Delta \Delta ; s. Keywords: cryptography, threshold schemes 1 Introduction We will consider the following scenario: A group of ten experts is responsible for operating a protected system. In order to carry out some minor changes in the system, at least three of them must be present. If they want to change more sensitive elements, more gro..