Scalable and reliable group key management schemes for secure multicast

Abstract

Multicast security is one of the important problems to solve for the successful deployment of group communication applications. Many of the popular multicast applications such as private conferencing, video streaming, satellite TV distribution, or on-line games require that only authorized subscribers who acquired the group key should be allowed for the multicast service. Thus, the secure multicast problem can be reduced to the cryptographic key generation and distribution problem. It can be seen that multicast security is motivated by enforcement of group access control, confidentiality and authentication of data transmission, and protection of the network infrastructure. Group key update upon a group membership change is one of the most important measures for the backward or forward secrecy of the group communication. In this thesis, we study the literature of the secure group key management protocols and propose group key management schemes having different target environments: a centralized group key management scheme for reliable broadcast, and decentralized group key management schemes for multi-sender secure multicast in dynamic networks. The proposed schemes consider unreliable or untrusted network environment such as unreliable communication channel for delivering rekeying messages or network dynamic where the topology changes frequently by untrusted intermediate relaying nodes. First, we propose a centralized group key management scheme for a reliable group communication in a public broadcasting. It features a mechanism that allows legitimate receivers to recover the current group key even if they lose key update messages for long-term sessions using short hint messages and member computation. Thus, even a stateless user who cannot update its state from session to session can take part in a group communication even if the channel for delivering rekeying messages might be unreliable. This scheme targets a conditional access system in a medi...