document: Distributed servers approach for large-scale secure multicast In order to offer backward and forward secrecy for multicast applications -LRB- i.e. , a new member can not decrypt the multicast data sent before its joining and a former member can not decrypt the data sent after its leaving -RRB- , the data encryption key has to be changed whenever a user joins or leaves the system . Such a change has to be made known to all the current users . The bandwidth used for such re-key messaging can be high when the user pool is large . We propose a distributed servers approach to minimize the overall system bandwidth -LRB- and complexity -RRB- by splitting the user pool into multiple groups each served by a -LRB- logical -RRB- server . After presenting an analytic model for the system based on a hierarchical key tree , we show that there is an optimal number of servers to achieve minimum system bandwidth . As the underlying user traffic fluctuates , we propose a simple dynamic scheme with low overhead where a physical server adaptively splits and merges its traffic into multiple groups each served by a logical server so as to minimize its total bandwidth . Our results show that a distributed servers approach is able to substantially reduce the total bandwidth required as compared with the traditional single-server approach , especially for those applications with a large user pool , short holding time , and relatively low bandwidth of a data stream , as in the Internet stock quote applications
doc_bio_tags: B I O O O O O O O O O O O B I O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O B I O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O B I I I
extractive_keyphrases: distributed servers forward secrecy multicast applications data encryption key system bandwidth hierarchical key tree user traffic short holding time internet stock quote applications
abstractive_keyphrases: large-scale secure multicast backward secrecy re-key messaging system complexity traffic merging dynamic split-and-merge scheme key management