Article

BlackBox Secret Sharing from Primitive Sets in Algebraic Number Fields

01/2005; DOI: 10.1007/11535218_21
Source: DBLP

ABSTRACT A black-box secret sharing scheme (BBSSS) for a given access structure works in exactly the same way over any finite Abelian group, as it only requires black-box access to group operations and to random group elements. In particular, there is no dependence on e.g. the structure of the group or its order. The expansion factor of a BBSSS is the length of a vector of shares (the number of group elements in it) divided by the number of players n. At CRYPTO 2002 Cramer and Fehr proposed a threshold BBSSS with an asymptotically minimal expansion factor Θ(log n). In this paper we propose a BBSSS that is based on a new paradigm, namely, primitive sets in algebraic number fields. This leads to a new BB- SSS with an expansion factor that is absolutely minimal up to an additive term of at most 2, which is an improvement by a constant additive factor. We provide good evidence that our scheme is considerably more ef- ficient in terms of the computational resources it requires. Indeed, the number of group operations to be performed is ˜ O(n2) instead of ˜ O(n3)

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