Wireless Sensor Networks, (WSN), are composed of battery-powered and resource-limited small devices called sensor nodes. WSNs are used for sensing and collecting data in the deployment area to be relayed to a Base Station (BS). In order to secure WSNs, first of all key distribution problems must be addressed. Key distribution problem is extensively studied for static WSNs, but has not been studied widely for mobile WSNs (MWSN). In this thesis, we proposed key distribution mechanisms for MWSNs. We propose a scheme in which both sensor nodes and the BS are mobile. In our scheme, the BS works as a key distribution center as well. It continuously moves in the environment and distributes pairwise keys to neighboring sensor nodes. In this way, the network gets securely connected. We conduct simulations to analyze the performance of our proposed scheme. The results show that our scheme achieves a local connectivity value of 0.73 for half-mobile network scenario and 0.54 for fully-mobile network scenario. These values can be further improved by using multiple BSs or increasing the speed of the BS. Moreover, our scheme provides perfect resiliency; an adversary cannot compromise any additional links using the captured nodes. We also incorporate two well-known key distribution mechanisms used for static networks into our scheme and provide a better connectivity in the early stages of the sensor network. The improvement in local connectivity, however, comes at the expense of reduced resiliency at the beginning. Nevertheless, the resiliency improves and connectivity converges to our original scheme's values in time
