On the price of security in large-scale wireless ad hoc networks

Security always comes with a price in terms of performance degradation, which should be carefully quantified. This is especially the case for wireless ad hoc networks (WANETs), which offer communications over a shared wireless channel without any preexisting infrastructure. Forming end-to-end secure paths in such WANETs is more challenging than in conventional networks due to the lack of central authorities, and its impact on network performance is largely untouched in the literature. In this paper, based on a general random network model, the asymptotic behaviors of secure throughput and delay with the common transmission range r_n and the probability p_f of neighboring nodes having a primary security association are quantified when the network size n is sufficiently large. The costs and benefits of secure-link-augmentation operations on the secure throughput and delay are also analyzed. In general, security has a cost: Since we require all the communications operate on secure links, there is a degradation in the network performance when p_f<1. However, one important exception is that when p_f is Ω(1/log n), the secure throughput remains at the Gupta and Kumar bound of Θ(1/√n log n) packets/time slot, wherein no security requirements are enforced on WANETs. This implies that even when the p_f goes to zero as the network size becomes arbitrarily large, it is still possible to build throughput-order-optimal secure WANETs, which is of practical interest since p_f is very small in many practical large-scale WANETs.