Toward Energy-Efficient Trust System Through Watchdog Optimization for WSNs

Watchdog technique is a fundamental building block to many trust systems that are designed for securing wireless sensor networks (WSNs). Unfortunately, this kind of technique consumes much energy and hence largely limits the lifespan of WSN. Although the state-of-the-art studies have realized the importance of trust systems' efficiency in WSNs and proposed several preliminary solutions, they have overlooked to optimize the watchdog technique, which is perhaps among the top energy-consuming units. In this paper, we reveal the inefficient use of watchdog technique in existing trust systems, and thereby propose a suite of optimization methods to minimize the energy cost of watchdog usage, while keeping the system's security in a sufficient level. Our contributions consist of theoretical analyses and practical algorithms, which can efficiently and effectively schedule the watchdog tasks depending on the sensor nodes' locations and the target nodes' trustworthiness. We have evaluated our algorithms through experiments on top of a WSNET simulation platform and an in-door WSN testbed in our collaborative lab. The results have successfully confirmed that our watchdog optimization techniques can save at least 39.44% energy without sacrificing much security (<;0.06 in terms of trust accuracy and robustness), even in some cases enhance the protection against certain attacks.