Security Weakness in Ren et al.’s Group Key Agreement Scheme Built on Secure Two-Party Protocols

摘要

A group key agreement protocol is designed to allow a group of parties communicating over an insecure, public network to agree on a common secret key. Recently, in WISA’04, Ren et al. proposed an efficient group key agreement scheme for dynamic groups, which can be built on any of secure two-party key establishment protocols. In the present work we study the main EGAKA-KE protocol of the scheme and point out a critical security flaw in the protocol. We show that the security flaw leads to a vulnerability to an active attack mounted by two colluding adversaries.