Paper Review : Reliable Group Rekeying: A Performance Analysis

Reviewer : Seh Leng Lim

This paper discusses the scalability issues of reliable group rekeying, and provide a performance analysis of a group key management system (called keygem) based upon the use of key trees.

The main contribution of the paper is its detailed performance analysis of the batch rekeying algorithms versus individual rekeying ones, the three key assignment algorithms of Breadth First Assignment (BFA), Depth First Assignment (DFA), and Recursive BFA(RFA), and receiver protocol with sparseness property in terms of conventional reliable multi-cast.

The key main ideas expounded are :

(a) To alleviate the out-of-sync problems, periodic batch rekeying delays the usage of a new group key until the next rekey interval, and rekey transport can guarantee with a high probability that the rekey message has been delivered before the next interval

(b) The idea of a key tree for group key management

© The idea of using FEC proactive for rekey transport

I think that the paper has a significant contribution (rating of 4) to the study of group key management . The authors have proposed an interesting concept to achieve reliable and efficient rekeying for a group key management system. They have also performed detailed simulations to support their claims that batch rekeying offers significant performance gains over individual rekeying, that reliable rekey multicast can be analysed in terms of conventional reliable multicast, and that group rekeying interval serves as a design parameter that allows tradeoffs between rekeying overheads, group access delay and the degree of forward access vulnerability. As acknowledged by the authors, there is still work to be done to consider dynamic partitioning of group users, and more detailed trace based experimental evaluations.

Network and system application builders may have a better appreciation from this paper of the difficulties involved in implementing group key management.