Contributory group key exchange in the presence of malicious participants

In a group key exchange protocol, the resulting group key should be computed by all participants such that none of them can gain any advantage concerning the protocol’s output: misbehaving participants might have personal advantage in influencing the final value of the key. In fact, the absence of trust relationship is the main feature of group key exchange (when compared to group key transport) protocols. This paper enlarges existing notions of security by identifying limitations in some previously proposed security models. To illustrate these notions, two efficient and provably secure generic solutions – compilers – are presented.