| Research Abstract |
Recently, the use of a decentralized application has become general by the development of the computer networks. The totally-ordered group communication service is effective and it is necessary and indispensable to design a decentralized application. For the privacy protection in the totally-ordered group communication service, we have proposed the method of renewing the group key of the totally-ordered multicast protocol which considers synchronization by all members. The multicast group is composed of two or more domains with two or more members and one key delivery server (KDS) in the method, and KDS takes the responsibility of delivering the group key to the member in the domain that oneself manages. If some assumptions are filled, this method can be applied to any totally-ordered multicast protocol. However, the loss of the packet which can happen because of an actual communication is not considered in this method. The group key request of the member increases if the packet is lost when the group key is delivered. And, the group key request becomes a bottleneck, and the performance of the entire system is downed. Then, to deliver the group key efficiently by adding the function of FEC(Forward Error Correction) to the key delivery in this research, and adding a tedious parity packet beforehand under the environment with the packet loss, the group key delivery method based on the push has been improved. However, the loss, rate on an actual network changes. If a lot of parity packets are given in the environment with a low loss rate, the bandwidth is consumed. Moreover, if the parity packet is few in the environment with a high loss rate, most members are not original packet restorable. It proposed the method of dynamically changing the parity packet to correspond to the change in such a loss rate, and the effectiveness was evaluated.
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