Shared-key signature and its application to anonymous authentication in ad hoc group

Abstract

We formalize the notion of shared-key signatures, which makes it possible to anonymously sign any message with verification by a shared common public key. Unlike group signatures, shared-key signatures require no group manager or other third party to help the group members to generate signing keys. Also unlike ring signatures, shared-key signatures have no special structure such as a ring and the signing and verification procedures are the same as those of the ordinary signatures. In addition, they can be easily transformed into interactive authentication protocols while the ring signatures cannot. A concrete construction of such signatures is proposed based on Weak Dependence Problem (WDP). Since WDP is NP-complete and many researchers believe that NPC problems are intractable even in the quantum computation model, our scheme may be used to sign the documents requiring a longer-term validity with anonymity. © Springer-Verlag 2004.