  In many hybrid wireless sensor networks' applications, sensor nodes are
deployed in hostile environments where trusted and un-trusted nodes co-exist.
In anchor-based hybrid networks, it becomes important to allow trusted nodes to
gain full access to the location information transmitted in beacon frames
while, at the same time, prevent un-trusted nodes from using this information.
The main challenge is that un-trusted nodes can measure the physical signal
transmitted from anchor nodes, even if these nodes encrypt their transmission.
Using the measured signal strength, un-trusted nodes can still tri-laterate the
location of anchor nodes. In this paper, we propose HyberLoc, an algorithm that
provides anchor physical layer location privacy in anchor-based hybrid sensor
networks. The idea is for anchor nodes to dynamically change their transmission
power following a certain probability distribution, degrading the localization
accuracy at un-trusted nodes while maintaining high localization accuracy at
trusted nodes. Given an average power constraint, our analysis shows that the
discretized exponential distribution is the distribution that maximizes
location uncertainty at the untrusted nodes. Detailed evaluation through
analysis, simulation, and implementation shows that HyberLoc gives trusted
nodes up to 3.5 times better localization accuracy as compared to untrusted
nodes.
