Physical layer security for wireless sensor networks

In the past decades, physical layer security has been extensively studied to exploit fundamental capabilities of physical layer such as randomness in wireless channels, signal-to-noise ratio gap, intended jamming, etc., for secure wireless communications. The notion of secrecy rate plays a crucial role in quantifying the transmission rate for secure communications in the presence of an eavesdropper. Wireless sensor networks (WSNs) often require secure communications as the transmissions from sensors to a fusion center are vulnerable to eavesdropping. Although the application of cryptography schemes has been considered in WSNs, most schemes would be too expensive for sensors in terms of computation and energy cost. Thus, it might be necessary to devise physical layer security schemes that exploit properties of wireless channels to avoid eavesdropping with much less computation and energy cost. In this paper, we discuss physical layer security techniques for the WSNs that perform distributed detection. Since the notion of secrecy rate may not be useful in WSNs, we employ the notion of the maximum equivocation in distributed detection to see whether or not perfect secrecy is achievable.