Distributed server networks for secure multicast

Multicast is an efficient technique for delivering data to a large group of users. For some applications, offering multicast security is an important issue. In such a system, a new member should not be able to decrypt the multicast data sent before its joining and a former member should not be able to decrypt the multicast data sent after its leaving. Traditional approaches generally focus on reducing the re-key messages for a single server. However, these approaches still lead to large exchange overhead when the group is large. We consider a distributed server network in which the user pool is split into multiple groups and served by multiple servers. Given the user traffic, there is a trade-off between the amount of re-key messaging and the total data bandwidth needed. We present a simple model for the system and study how the total bandwidth (including the re-key messaging and data traffic) can be minimized by optimizing the number of servers in the network. As the underlying user traffic is dynamic, a server should be able to split and merge user groups to minimize its total bandwidth. We propose a scheme for such a purpose. We show that a distributed server network is able to reduce substantively the total bandwidth required in the system as compared to the traditional scheme