  Wireless sensor networks (WSNs) are vulnerable to eavesdropping as the sensor
nodes (SNs) communicate over an open radio channel. Intelligent reflecting
surface (IRS) technology can be leveraged for physical layer security in WSNs.
In this paper, we propose a joint transmit and reflective beamformer (JTRB)
design for secure parameter estimation at the fusion center (FC) in the
presence of an eavesdropper (ED) in a WSN. We develop a semidefinite relaxation
(SDR)-based iterative algorithm, which alternately yields the transmit
beamformer at each SN and the corresponding reflection phases at the IRS, to
achieve the minimum mean-squared error (MSE) parameter estimate at the FC,
subject to transmit power and ED signal-to-noise ratio constraints. Our
simulation results demonstrate robust MSE and security performance of the
proposed IRS-based JTRB technique.
