Paper 2005/423

ID-based signature and Key-insulated threshold signature

Jin Li and Fangguo Zhang

Abstract

Identity-based (simply ID-based) cryptosystem was proposed in order to simplify key management procedures of certificate-based public key infrastructures. In 2003 Sakai and Kasahara proposed a new ID-based encryption scheme (SK-IBE). In our paper, it is intended to build a new ID-based signature (IBS) scheme which shares the same system parameters with SK-IBE. SK-IBE and our signature scheme yield a new complete ID-based public key cryptosystem. The proposed signature scheme is provably secure against existential forgery for adaptive chosen message and identity attack in the random oracle model based on a reasonably well-explored hardness assumption. Another contribution of this paper is that we first propose the notion of key-insulated threshold signature and present a generic method for constructing key-insulated threshold signature scheme.