Democratic group signatures with linkability from gap Diffie-Hellman group

Democratic group signatures (DGSs) attract many researchers due to their appealing properties, i.e., anonymity, traceability and no group manager. Security results of existing work are based on decisional Diffie-Hellman (DDH) assumption. In this paper, we present a democratic group signature scheme based on any gap Diffie-Hellman (GDH) group where DDH problem is easily but computational Diffe-Hellman (CDH) problem is hard to be solved. Besides the properties of ordinary DGSs, our scheme also provides the property of linkability, i.e., any public verifier can tell whether two group signatures are generated using the same private key. Security properties of our scheme employ a new and independently interesting decisional product Diffie-Hellman (DPDH) assumption which is weaker than DDH one. Copyright.