Efficient Protection of Response Messages in DTLS-Based Secure Multicast Communication

DTLS is a standardized security protocol designed to provide end-to-end secure communication among two peers, and particularly considered for the emerging Internet of Things. In order to protect group communication, the IETF is currently working on a method to secure multicast messages through the same DTLS security services. However, such an approach relies on traditional DTLS sessions to protect unicast responses to multicast messages. This increases the amount of security material stored by group members and can have a relevant impact on network performance. In this paper we propose an extension to the IETF approach which allows to efficiently protect group responses by reusing the same group key material. Our proposal does not require to establish additional DTLS sessions, thus preserving high communication performance within the group and limiting storage overhead on group members. Furthermore, we discuss a suitable key management policy to provision and renew group key material.