Similar to conventional wireless networks, WSNs are based on multi hop routing to ensure connectivity and data forwarding which makes the routing service a challenging task due to the nature of sensors usually limited in memory, battery and computing capacities as well as the nature of the environment which is hostile and unpredictable making the routing protocols developed for conventional wireless network useless for WSNs without modifications and adaptations for the new context of WSNs. Thus in this paper we present an optimized version of AODV protocol for WSNs which takes into consideration the traffic pattern of WSNs and sensors’ constraints. In the proposed protocol we affect the task of route discovery to the base station which periodically informs sensors about its location instead of letting this task to sensors which consumes the network resources due to the broadcasting nature of the route discovery. We have also proposed a key distribution scheme destined to establish a symmetric encrypting key between each sensor and the base station, the proposed key management scheme uses the underlying routing requests to execute handshakes and key update which have greatly saved the network resources and ensured a good threshold of security.

The emergence of wireless networking as well as the development in embedded systems and technologies have given birth to application specific networks called wireless sensor networks WSNs, their flexibility, facility of use and deployment as well as their low cost give them an increasing field of applications. Usually sensors are limited in capacities deployed in a hostile and unpredictable environment, making the security of these networks a challenging task. In this paper we are going to present a key management scheme in which the base station play the role of the secure third party responsible of distributing key and managing security in the network, two versions of this scheme are presented the first one for flat networks and the second one for hierarchical networks in which the cluster head play the key role in all key agreement with the base station.