On the gradual deployment of random pairwise key distribution schemes

The pairwise key distribution scheme of Chan et al. is a randomized key predistribution scheme which enables cryptographic protection in wireless sensor networks (WSNs). This pairwise scheme has many advantages over other randomized key predistribution schemes but has been deemed non-scalable due to (i) the large number of keys required to ensure secure connectivity; and (ii) implementation difficulties when sensors are required to be deployed in multiple stages. Here, we address this issue by proposing an implementation of the pairwise scheme that supports the gradual deployment of sensor nodes in several consecutive phases. We show how the scheme parameter should be adjusted with the number n of sensors so that secure connectivity is maintained in the network throughout all the stages of the deployment. We also discuss briefly the relation between the scheme parameter and the amount of memory that each sensor needs to spare for storing their keys. By showing that O(log n) many keys per node suffice to achieve secure connectivity at every step of the deployment, we confirm the scalability of the pairwise scheme in the context of WSNs.