  Wireless sensor networks are collections of large number of sensor nodes. The
sensor nodes are featured with limited energy, computation and transmission
power. Each node in the network coordinates with every other node in forwarding
their packets to reach the destination. Since these nodes operate in a
physically insecure environment; they are vulnerable to different types of
attacks such as selective forwarding and sinkhole. These attacks can inject
malicious packets by compromising the node. Geographical routing protocols of
wireless sensor networks have been developed without considering the security
aspects against these attacks. In this paper, a secure routing protocol named
secured greedy perimeter stateless routing protocol (S-GPSR) is proposed for
mobile sensor networks by incorporating trust based mechanism in the existing
greedy perimeter stateless routing protocol (GPSR). Simulation results prove
that S-GPSR outperforms the GPSR by reducing the overhead and improving the
delivery ratio of the networks.
