Efficient Identity-Based Conference Key Distribution Protocols

In this paper we study security properties of conference key distribution protocols and give a hierarchy of four security classes. We show various problems with the Burmester-Desmedt conference key distribution protocol and show that the authenticated version of the protocol belongs to class 2. We give a modification of the protocol that makes it identity-based. Another modification provides us a class 4 protocol that is secure against insiders' attacks. This protocol is most efficient compared to known authenticated conference key distribution protocols. Finally we propose a particular key confirmation protocol that may be combined with almost all conference key distribution protocols to achieve the highest security.