Threshold Digital Signatures based on Discrete Logarithm

This paper presents a (k,n) threshold digital signature scheme with no trusted dealer. Our idea is to use the EIGamal signature scheme modified for group use. Among many digital signature schemes, our modification has a nice property for our purpose. We also show a (k.n) threshold fail stop signature scheme and two (k.n) threshold undeniable signature schemes. We use [10] as the original fail stop signature scheme, and use [3] and [2] as the original undeniable signature schemes. Since all these schemes are based on the discrete log problem, we can use the same technique.