Some attacks upon authenticated group key agreement protocols

Abstract

During the last few years, a number of authenticated group key agreement protocols have been proposed in the literature. We observed that the efforts in this domain were mostly dedicated to the improvement of their performance in term of bandwidth or computational requirements, but that there were very few systematic studies on their security properties. In this paper, we tried to develop a systematic way to analyse protocol suites extending the Diffie-Hellman key-exchange scheme to a group setting and presented in the context of the Cliques project. This led us to propose a very simple machinery that allowed us to manually pinpoint several unpublished attacks against the main security properties claimed in the definition of these protocols (implicit key agreement, perfect forward secrecy, resistance to known-key attacks).