Paper 2008/337

Modified Huang-Wang's Convertible Nominative Signature Scheme

Wei Zhao and Dingfeng Ye

Abstract

At ACISP 2004, Huang and Wang first introduced the concept of convertible nominative signatures and also proposed a concrete scheme. However, it was pointed out by many works that Huang-Wang's scheme is in fact not a nominative signature. In this paper, we first present a security model for convertible nominative signatures. The properties of Unforgeability, Invisibility, Non-impersonation and Non-repudiation in the setting of convertible nominative signatures are defined formally. Then we modify Huang-Wang's scheme into a secure one. Formal proofs are provided to show that the modified Huang-Wang's scheme satisfies all the security properties under some conventional assumptions in the random oracle model.