  We propose a secure data aggregation (SDA) framework for mobile sensor
networks whose topology changes dynamically with time. The SDA framework
(designed to be resilient to both insider and outsider attacks) comprises of a
pair-wise key establishment mechanism run along the edges of a data gathering
tree and a distributed trust evaluation model that is tightly integrated with
the data aggregation process itself. If an aggregator node already shares a
secret key with its child node, the two nodes locally coordinate to refresh and
establish a new pair-wise secret key; otherwise, the aggregator node requests
the sink to send a seed-secret key message that is used as the basis to
establish a new pair-wise secret key. The trust evaluation model uses the
two-sided Grubbs test to identify outlier data in the periodic beacons
collected from the child nodes (neighbor) nodes. Once the estimated trust score
for a neighbor node falls below a threshold, the sensor node locally classifies
its neighbor node as a Compromised or Faulty (CF) node, and discards the data
or aggregated data received from the CF node. This way, the erroneous data
generated by the CF nodes could be filtered at various levels of the data
gathering tree and are prevented from reaching the root node (sink node).
Finally, we assess the effectiveness of our trust evaluation model through a
comprehensive simulation study.
