As noted in the introduction, many modern collaborative and distributed applications require a reliable group communication platform. The latter, in turn, needs specialized security mechanisms to perform - among other things - group key management. This dependency (or need) is mutual since practical group key agreement protocols themselves rely on the underlying group communication semantics for protocol message transport and strong membership semantics. Implementing multi-party and multi-round cryptographic protocols without such support is foolhardy as, in the end, one winds up reinventing reliable group communication tools.
In this section we begin with a brief discussion of reliable group communication. Next, we summarize the relationship between group membership events and group key management protocols and conclude with the summary of desired cryptographic properties.