Group Key Management Based On Chinese Remainder Theorem

The security of group communication is critical for multicast applications. The group key management strategy, including generation, distribution and rekeying of group key, is the foundation stone of multicast security. In this paper, we propose a decentralized group key management scheme based on the Chinese Remainder Theorem. The multicast group is divided into multiple independent subgroups. Each subgroup is controlled by a subgroup key server, which is in charge of the generation, distribution and rekeying of subgroup key. All subgroup key servers constitute a single subgroup controlled by group key server. The pre-calculation of public number for rekeying of subgroup key can reduce the computation cost and time cost. Each group member is required to hold three secrets, thus this proposed scheme has low storage. In addition, it has better scalability because the addition of subgroup does not affect the management of group key.Individual rekey requires the group and subgroup key servers have high capability. The pre-calculation can not be done with high efficiency in every process of rekey. Therefore, we propose another style of rekey called batch rekey. Batch rekey can decrease the requirement of capability of group and subgroup key servers and maintain a high efficiency of pre-calculation. The drawback of batch rekey is that it can neither satisfy the forward secrecy not the backward secrecy. There is a trade-off between security and capability in the style of batch rekey.