(A) study on identity-based group key agreement schemes with anonymity

Abstract

ID-based group key agreement (GKA) has been increasingly researched with the advantage of simple public key management. However, identities of group members can be exposed in this protocol, so eavesdroppers can easily learn the information of the group members. Recently, Wan et al. [11] proposed a solution for this problem, an anonymous ID-based GKA protocol, which can keep group members` anonymity to outside eavesdroppers; nevertheless, the protocol has some security flaws. This paper shows that Wan et al.`s GKA is insecure against colluding attack and their joining/leaving protocols do not guarantee forward and backward secrecy. We also propose a new forward secure ID-based GKA with anonymity from enhancing Wan et al.`s joining/leaving protocols. In our scheme, i) impersonation by colluding attack cannot be done because ID-based signature is used, ii) joining or leaving members cannot obtain the previous or later session group key using the previous individual secrets, so group forward and backward secrecy are provided. Moreover, our protocols can operate efficiently compared with the previous ID-based GKA protocols.