Secure group communication protocols have been designed to meet needs such as confidential authenticated communication among coalition members or secure management of group membership and access control. New languages and models are necessary to appropriately capture the concepts of such protocols and make them amenable to formal analysis.

For this purpose, we developed MuCAPSL (Multicast Common Authentication Protocol Specification Language) and its intermediate language MuCIL (MuCAPSL Intermediate Language). In this paper we introduce the MuCAPSL features and motivate our design decisions by illustrating the practical use of MuCAPL with the help of a simplified version of the secure group communication protocol used in SecureSpread. We also briefly introduce the MuCIL language that serves as semantics for MuCAPSL and also as the interface language for analysis tools.