  To accomplish secure group communication, it is essential to share a unique
cryptographic key among group members. The underlying challenges to group key
agreement are scalability, efficiency, and security. In a dynamic group
environment, the rekeying process is more frequent; therefore, it is more
crucial to design an efficient group key agreement protocol. Moreover, with the
emergence of various group-based services, it is becoming common for several
multicast groups to coexist in the same network. These multicast groups may
have several shared users; a join or leave request by a single user can trigger
regeneration of multiple group keys. Under the given circumstances the rekeying
process becomes a challenging task. In this work, we propose a novel
methodology for group key agreement which exploits the state vectors of group
members. The state vector is a set of randomly generated nonce instances which
determine the logical link between group members and which empowers the group
member to generate multiple cryptographic keys independently. Using local
knowledge of a secret nonce, each member can generate and share a large number
of secure keys, indicating that SGRS inherently provides a considerable amount
of secure subgroup multicast communication using subgroup multicasting keys
derived from local state vectors. The resulting protocol is secure and
efficient in terms of both communication and computation.
