Many modern collaborative and distributed applications require a reliable group communication platform. Current reliable group communication toolkits generally provide one (or both) of two strong group communication semantics: Extended Virtual Synchrony (EVS) [MAMSA94] and View Synchrony (VS) [FLS97]. Both semantics guarantee that: 1) group members see the same set of messages between two sequential group membership events, and, 2) the sender's requested message order (e.g., FIFO, Causal, or Total) is preserved. VS offers a stricter guarantee than EVS: Messages are delivered to all recipients in the same membership as viewed by the sender application when it originally sent the message. In the context of this paper we require the underlying group communication to provide VS. However, we stress that VS is needed for the sake of fault-tolerance and robustness; the security of our protocols is in no way affected by the lack of VS. More details on the interaction of key agreement protocols and reliable group communication are addressed in [AAH00].