IACR News item: 23 February 2014
Oriol Farràs, Torben Hansen, Tarik Kaced, Carles Padró
ePrint ReportIn order to study perfect and non-perfect secret sharing schemes with all generality, we describe the structure of the schemes through their access function, a real function that measures the amount of information that every subset of participants knows about the secret value. We present new tools for the construction of secret sharing schemes. In particular, we construct a secret sharing scheme for every access function.
We extend the connections between polymatroids and perfect secret sharing schemes to the non-perfect ones to find new results on the information ratio. We find a new lower bound on the information ratio that is better than the ones previously known. In particular, this bound is tight for uniform access functions. The access function of a secret sharing scheme is uniform if all participants play the same role in a scheme (e.g. ramp secret sharing schemes). Moreover, we construct a secret sharing scheme with optimal information ratio for every rational uniform access function.
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