Subscription-Period-Aware Key Management for Secure Vehicular Multicast Communications

As many applications based on wireless communications are being embedded on a vehicular platform, multicast communications have begun to be essential for efficient information delivery. Since multicast communications are vulnerable to unauthorized access, group key management (GKM) is expected to play an essential role as access control. However, we note that the legacy GKM schemes are not cost effective and adequate for use in vehicular environments. This is because the dynamic mobility of a large number of vehicles causes a high frequency of group rekeying, which is used to share a new group key (GK) among the authorized group members for every membership change. To overcome the high frequency of group rekeying, we propose a new GKM scheme, which is called subscription-period-aware key management (SPKM), for cost-effective and secure vehicular multicast group rekeying. As a design problem, we analyze its key management cost, including the communication, computation, and storage costs, for multicast group rekeying, and find an optimal condition to minimize the key management cost. Through simulations under different conditions, we show that the proposed SPKM scheme can greatly reduce the communication, computation, and storage complexity in multicast group rekeying from O(log N) to O(1), where N is the number of vehicles in a single group rekeying process. In addition, we show that the key management cost of the proposed SPKM scheme is lower than those of the well-known GKM schemes for secure vehicular multicast communications.