A stateful multicast key distribution protocol based on identity-based encryption

Group key is used to encrypt group data in group communication. Multicast key distribution scheme updates and distributes group keys safely when a member joins or leaves the group. However it has problems when arbitrary group members want to build a dynamic conference, because traditional distribution scheme uses group controller to manage the work. In fact, a n-member group will have 2 n - n - 1 possible conferences. Moreover, members may need to join and/or leave the group dynamically. If a group controller deals with all the members' requests, it will be the performance bottleneck. In this paper, we propose a new stateful multicast key distribution protocol based on identity-based encryption. This protocol can distribute the group keys safely and allows the group members to build dynamic conferences by themselves. It greatly reduces the group controller's workload. In addition, compared with traditional rekeying messages contain identifier and group key's version, our protocol can reduce the size of rekeying messages by customizing the public key. We provide three algorithms (INIT, JOIN, LEAVE) for rekeying when a group membership changes and a revocation algorithm for building dynamic conferences without the group controller. We also give the security proof of our protocol in a symbolic security model and the implementation of the protocol.