Threshold DSS signatures without a trusted party

Abstract

A t-out-of-l threshold signature scheme allows l members of a group to own shares of a private key such that any t of them can create a signature, while fewer than t cannot. Most of these schemes require a single trusted party to create the secret key and calculate the l shares. Harn [10] and Li, Hwang, and Lee [13] have devised threshold schemes based on the difficulty of solving the discrete logarithm problem which do not require such a trusted party. This paper extends that property to 2-out-of-l threshold signatures based on the Digital Signature Standard and describes two possible generalizations to a t-out-of-l scheme.