Controlled Path Traversal for a Mobile Element in Wireless Sensor Networks

Mobile elements (MEs) have been used to improve the scalability and the performance of wireless sensor networks (WSNs). In most of these approaches, the ME traverses an area of interest with a pre- determined path set by the basestation (BS) and is trusted to follow the determined path. This assumption is not realistic since the ME carries essential information about the network making it appealing to various attackers. An ME can be captured and can be used to deceive the BS. As a result, further protocols are required to verify the path travelled by the ME. In this paper, we propose two protocols to control the path of a semi-trusted ME using cryptographic methods including Message Authentication Code (MAC), and hash chains. First protocol collects node encounter information with MACs and allows the BS to construct an approximate path using this information. Density of the nodes and the broadcast range play an important role in the quality of the constructed path. Second protocol enforces a strict path using hash chains. The ME helps the sensors verify a hash chain in a distributed manner and deviation from the path results in breaking the chain. We believe these protocols will serve as a first step to a model where the ME has to prove all of its actions to the BS.