Realizing physical layer authentication using constellation perturbation on a software-defined radio testbed

Abstract

Ensuring secure command and control in a tactical military environment is vital as the combat forces face many potentially sophisticated adversaries who seek out the vulnerabilities in the communications infrastructure. Although authentication schemes has been substantially explored, the ability of new techniques to coexist with existing system (i.e., legacy systems) is often overlooked. The objective of this work is to establish feasibility of a physical (PHY) layer authentication technique that can be implemented easily to coexist with legacy systems. In this paper, we discuss the implementation of a PHY layer authentication scheme that can seamlessly integrate within systems containing legacy receivers, which do not have the ability to decode PHY layer authentication tags. To this end, we design and evaluate a quadrature phase shift keying (QPSK) and π/4 Differential quadrature phase shift keying (DQPSK) based authentication schemes and demonstrate their operation with legacy as well as non-legacy receivers. The addressed authentication scheme follows constellation perturbation by a pre-determined angle which performs the tag embedding without incurring additional network bandwidth. The implementation and evaluation platform consists of a software defined radio (SDR) testbed by using the open source radio framework, GNU Radio, and Universal Software Radio Peripherals (USRP-N210s). For moderate to high signal-to-noise ratios, the QPSK tagging scheme achieves low (<10−4) bit error rates (BER) and tag error rates (TER); this is due to a novel phase locked loop (PLL) design. The use of forward error correction (FEC) on the tag is also considered, and an improved TER and power saving is demonstrated. Results from our wireless SDR experiments validate the mechanism and demonstrate the practicality of the approach.