Traditionally, research in secure group key
agreement focuses on minimizing the computational
overhead for cryptographic operations, and
minimizing the communication overhead and the number
of protocol rounds is of secondary concern.
The dramatic increase in computation power that we
witnessed during the past years exposed network
delay in WANs as the primary culprit for a negative
performance impact on key agreement protocols.
The majority of previously proposed protocols
optimize the cryptographic overhead of the
protocol. However, high WAN delay negatively impacts
their efficiency.
The goal of this work is to construct a new protocol
that trades off computation with communication
efficiency. We resurrect a key agreement protocol
previously proposed by Steer et al. We extend it to
handle dynamic groups and network failures such as
network partitions and merges. The resulting
protocol suite is provably secure against passive
adversaries and provides key independence, i.e.\ a
passive adversary who knows any proper subset of
group keys cannot discover any other group key not
included in the subset. Furthermore, the protocol is
simple, fault-tolerant, and well-suited for
high-delay wide area network.