We investigate the security of wireless sensor
networks under the pairwise key distribution scheme of
Chan et al. [2]. We present conditions on how to scale the
model parameters so that the network is i) unassailable,
and ii) unsplittable, both with high probability, as the
number of sensor nodes becomes large. We show that the
required number of secure keys to be stored in the memory
of each sensors is order of magnitude smaller than what
is required for the Eschenauer-Gligor scheme [5].
