Batch Verification Of Short Group Signatures And Research On Hierarchical Group Signature Scheme

Group signature is a sort of special digital signatures that allows any group member to sign messages anonymously on behalf of the group. In case of dispute later on, the manager can open signatures to revoke anonymity. It realizes the unity of authentication and anonymity, and has broad prospect in the field of information security. Consider the special structure and application requirements of group signature, so how to shorten the length and verification time of signature, how to realize the revocation of group members and how to alleviate the burden of key management have been key and difficult problems in the research of group signature.A number of recent research initiatives aim to enhance safety and efficiency of transporta- tion system. Secure vehicular communication networks lie at the core of these efforts and have particular requirements on the applicable cryptographic primitives. First, cryptographic overhead remain short. Thus, different messages from different sources may need to be verified quickly. Third, privacy-friendly. The first work in this dissertation is that we give a batch verifier for an efficient group signature scheme proposed by Furukawa and Imai, with a verification time where the dominant operation requires only 2 pairings, while individually verifyingηsignatures would cost 2ηpairings. Whereas the short signature length of FI group signature scheme and inherent anonymity of group signatures, so we realize all above three requirements. In addition, we propose an efficient revocation mechanism for the FI group signature scheme.In the identity-based group signatures, it is undesirable for a large network because the Private Key Generator (PKG), which means group manager here, becomes a bottle. Not only is private key generation computationally expensive, but also the PKG must verify proofs of identity and must establish secure channels to transmit private keys. Therefore, the second work in this dissertation is that we introduce a hierarchy of authorities into group signatures for the first time. Hierarchical identity-based group signatures (HIDGS) allow the group manager to distribute the workload by delegating private key generation and identity authentication to lower-level PKGs. Moreover, we propose two HIDGS schemes which are provably secure without random oracles.