Pitfalls in a server-aided authenticated group key establishment

In this paper, we present a cryptanalysis of a recently proposed server-aided group key agreement scheme by Sun et al. This proposal is designed for mobile environments, in which a group of users aim at establishing a common secret key with the help of a semi trusted server. At this, authentication is achieved using certificateless public key cryptography. We evidence that the scheme does not achieve forward secrecy, is vulnerable to a known session attack (that can, for instance, be mounted by a semi-honest server) and is not (as claimed by the authors) contributory. Further security hardships in more restricted models (i.e. in which stronger corruptions are allowed) are also discussed.

provable secure group key agreement; certificateless signatures; cryptanalysis; server-aided key exchange

Pitfalls in a server-aided authenticated group key establishment Articles