Reliable Group Rekeying: A Performance Analysis
- State the problem the paper is trying to solve.
The main problem the paper is trying to solve is the scalability issues of
reliable group rekey.
- State the main contribution of the paper: solving a new problem, proposing a
new algorithm, or presenting a new evaluation (analysis). If a new problem, why
was the problem important? Is the problem still important today? Will the
problem be important tomorrow? If a new algorithm or new
evaluation (analysis), what are the improvements over previous algorithms or
evaluations? How do they come up with the new algorithm or evaluation?
The main contribution of this paper is that it proposes a new scheme for group
rekey that is scalable, reliable, and alleviates out-of-sync problems. The
problem will become more and more important today and in the future as the
number of network application, such a pay-per-view distribution of digital
media, restricted teleconferences, and pay-per-use multi-party games, are
- Summarize the (at most) 3 key main ideas (each in 1 sentence.)
The three 3 key main ideas are:
The authors have developed a new scheme for reliable group rekeying that is
based on key trees and uses periodic batch rekeying to improve scalability,
alleviates out-of-sync problems among rekey messages, and acheives large
They observe that rekey transport has an eventual reliability and a soft
real-time requirement, and that the rekey workload has a sparseness property,
that is each each group user only needs to receive a small fraction of the
packets that carry a rekey message sent by the key server.
The authors then present a reliable rekey transport protocol based on proactive
FEC, show the tradeoffs between bandwidth requirements and rekey interval, and
then provide four system constraints that serve as guidelines for choosing an
appropriate rekey interval and determining the maximum nuber of users a key
server can support.
- Critique the main contribution
- Rate the significance of the paper on a scale of 5
(breakthrough), 4 (significant contribution), 3 (modest contribution), 2
(incremental contribution), 1 (no contribution or negative contribution).
Explain your rating in a sentence or two.
I give this paper a rating of 4 because it presents a great scheme for achieving
a scalable group rekey system that will be the groundwork for making network
applications both secure and financially workable.
- Rate how convincing the methodology is: how do the authors
justify the solution approach or evaluation? Do the authors use arguments,
analyses, experiments, simulations, or a combination of them? Do the claims
and conclusions follow from the arguments, analyses or experiments? Are the
assumptions realistic (at the time of the research)? Are the assumptions still
valid today? Are the experiments well designed? Are there different
experiments that would be more convincing? Are there other alternatives the
authors should have considered? (And, of course, is the paper free of
The authors' methodology was to present an analytical approach for why their
group rekeying system does not suffer from problems with scalability and
reliablity, and then they offer initial simulations done with an implementation
of their group rekeying system as a protocol.
- What is the most important limitation of the approach?
Though their simulation results were very close to their analytical results,
that is because the simulations were not done with very detailed traces. In
order for their system to be fully considered for full Internet use, it would be
best to run a more detailed trace based experimental evaluation to prove that
they system will indeed by robustly scalable and reliable even in the midst of
the very dynamic and intolerant behavior of the real Intenet. Even so, the
closeness of their analytical results with their less detailed simulation
results gives great hope that the same results will be obtained with tests done
for my detailed traces.
- What lessons should researchers and builders take away from this work. What
(if any) questions does this work leave open?
The lessons that researchers should take away from this work are that it is
now possible to build a scalable and reliable group rekeying system and the
secret currently lies in periodic batch rekeying, which is responsible for most
of the large performance and scalability gains. Future work spurred by this
paper include investigations of dynamic partitioning of group users, more
detailed trace based experimental evaluations, and investigations of FEC
encoding schemes that work better for a workload with the sparseness property.
an efficient, scalable, and implementable system for IP
traceback and it has been done despite the seeminly large memory requirements.
The potential memory requirent roadblock can be overcome using Bloom Filters
and this system can continue to be effective for tracing packets, even those
that undergo transformations.