SIMAGE: Secure and Link-Quality Cognizant Image Distribution for wireless sensor networks

Wireless sensor networks (WSNs) are used in a range of critical domains (e.g., health care, military, critical infrastructure) where it is necessary that the nodes be reprogrammed with a new or modified code image without removing them from the deployment area. Various protocols have been developed for the dissemination of code images between sensors in multi-hop WSNs, where these sensor nodes may have varying levels of link quality. However, the code dissemination process in these protocols is hindered by the nodes with poor link quality. This results in an increased number of retransmissions and code dissemination time. Also, in several of the techniques, the code dissemination process is not secure and can be eavesdropped or disrupted by a malicious wireless sensor node in the transmission range. In this paper, we propose a simple approach, Secure and Link-Quality Cognizant Image Distribution (SIMAGE), to enhance the existing code dissemination protocol using the available resources in the sensors. Specifically, our approach adapts to the varying link conditions via dynamic packet sizing to reduce the number of retransmissions and overall code dissemination time. Our approach also provides confidentiality and integrity to the code dissemination process by utilizing energy-efficient encryption and authentication mechanisms with RC4 and the CBC-MAC. We have evaluated SIMAGE in a network of real sensors and the results show that adjusting the packet size as a function of link quality reduces the retransmitted data by 93% and the image transmission time by 35% when compared to the existing code dissemination protocols. The trade-offs between reliability, security overhead, and overall transmission time for SIMAGE are also discussed.