  Wireless sensor networks place sensors into an area to collect data and send
them back to a base station. Data fusion, which fuses the collected data before
they are sent to the base station, is usually implemented over the network.
Since the sensor is typically placed in locations accessible to malicious
attackers, information assurance of the data fusion process is very important.
A witness-based approach has been proposed to validate the fusion data. In this
approach, the base station receives the fusion data and "votes" on the data
from a randomly chosen sensor node. The vote comes from other sensor nodes,
called "witnesses," to verify the correctness of the fusion data. Because the
base station obtains the vote through the chosen node, the chosen node could
forge the vote if it is compromised. Thus, the witness node must encrypt the
vote to prevent this forgery. Compared with the vote, the encryption requires
more bits, increasing transmission burden from the chosen node to the base
station. The chosen node consumes more power. This work improves the
witness-based approach using direct voting mechanism such that the proposed
scheme has better performance in terms of assurance, overhead, and delay. The
witness node transmits the vote directly to the base station. Forgery is not a
problem in this scheme. Moreover, fewer bits are necessary to represent the
vote, significantly reducing the power consumption. Performance analysis and
simulation results indicate that the proposed approach can achieve a 40 times
better overhead than the witness-based approach.
