A New Group Re-Keying Protocol with Smaller Computational and Key Storage Overhead

A. Nemaney Pour, K. Kumekawa, T. Kato, and S. Itoh (Japan)


Group Key, Group Key Management, Key Storage Overhead, Computational and Communication Overhead


This paper presents and analyzes a new approach for making and updating the keys in secure multicast. In this protocol, the group is divided into some subgroups logically, and a key is assigned to each subgroup. The subgroup keys are generated by a one way function using the members’ secret key and server’s key. The group key in our protocol does not depend on the other keys. The group key and subgroup key (where there is a membership change) are updated on each membership change. These keys are sent to existing members by multicast and to new member by unicast. At leave, a set of hint keys (generated by a one way function) is broadcast to the subgroup (where there is a membership change) instead of transmitting the subgroup key directly to members in that subgroup. Then, each valid member generates the subgroup key from the assigned hint key by using his secret key. The security of the subgroup keys is based on difficulty of the discrete logarithm problem. In comparison with the previously Logical Key Hierarchy (LKH) protocols, our approach not only reduces computational overhead at each membership change, but also diminishes key storage requirements largely for each member.

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