RoK: a Robust Key Pre-distribution Protocol for Multi-Phase Wireless Sensor Networks

Wireless sensor networks are usually deployed to operate for a long period of time. Because nodes are batteryoperated, they eventually run out of power and new nodes need to be periodically deployed to assure network connectivity. This type of networks is referred to as Multi-phase WSN in the literature[1]. Current key pre-distribution schemes, such as[2] and[3], are not adapted to multi-stage WSN. With these schemes, the security of the WSN degrades with time, since the proportion of corrupted links gradually increases. In this paper, we propose a new pre-distribution scheme adapted to multi-phase WSN. In the proposed scheme, the pre-distributed keys have limited lifetimes and are refreshed periodically. As a result, a network that is temporarily attacked (i.e. the attacker is active only during a limited amount of time) automatically self-heals, i.e. recovers its initial state when the attack stops. In contrast, with existing schemes, an attacker that corrupts a certain amount of nodes compromises a given fraction of the total number of secure channels. This ratio remains constant until the end of the network, even if the attacker stops its action. Furthermore, with our scheme, a network that is constantly attacked (i.e. the attacker regularly corrupts nodes of the network, without stopping) is much less impacted than a network that uses existing key pre-distribution protocols. With these schemes, the number of compromised links constantly increases until all the links are compromised. With our proposal, the proportion of compromised links is limited and constant.