Comment on Wu et al.'s Server-aided Verification Signature Schemes.

Abstract

In ProvSec 2008, Wu et al. constructed two server-aided verification signature (SAV-Σ) schemes based on BLS signature. In this paper, we provide a new definition of the security of SAV-Σ against collusion and adaptive cho-sen message attacks. We founded that Wu et al.’s first scheme is secure, while their second scheme is insecure based on our definition.