Stronger Security Model of Group Key Agreement
In PKC 2009, Gorantla, Boyd and Gonz?alez Nieto presented a nice result on modeling security for Group Key Agreement (GKA) protocols. They proposed a novel security model (GBG model) that better supports the adversaries' queries than previous models for GKA protocols by considering KCI resilience. However, ephemeral key leakage attack resistance has been left outside the scope of the GBG model. In this paper, the authors demonstrate an ephemeral key leakage on an existing GKA protocol which has been shown secure in the GBG model. They then extend the GBG model by allowing the adversary greater attack powers of leaking ephemeral keys in GKA protocol session.