Detecting GPS Spoofing via a Multi-Receiver Hybrid Communication Network for Power Grid Timing Verification Tara Yasmin Mina, Sriramya Bhamidipati and Grace Xingxin Gao University of Illinois at Urbana-Champaign BIOGRAPHIES Tara Yasmin Mina is a graduate student in the Electrical and Computer Engineering Department at the University of Illinois at Urbana-Champaign. She received her B.S. with honors in Electrical Engineering from Iowa State University in 2017. Sriramya Bhamidipati is a doctoral student in the Aerospace Engineering Department at the University of Illinois at Urbana- Champaign. She received her M.S. degree in Aerospace Engineering from University of Illinois at Urbana-Champaign in 2017. She received her B.Tech. with honors in Aerospace Engineering and minor in Systems and Controls Engineering from Indian Institute of Technology Bombay, India in 2015. Grace Xingxin Gao received her B.S. degree in Mechanical Engineering and her M.S. degree in Electrical Engineering from Tsinghua University, Beijing, China in 2001 and 2003. She received her PhD degree in Electrical Engineering from Stanford University in 2008, after which she was a research associate at Stanford University until 2012. Since then, she has been with University of Illinois at Urbana-Champaign, where she is an Assistant Professor in the Aerospace Engineering Department. ABSTRACT For the future Smart Grid, devices called Phasor Measurement Units (PMUs) are being widely deployed to continuously mon- itor the state of the power grid in real-time. The voltage and current phasor measurements are synchronized across the net- work using GPS. However, because civilian GPS signals are unencrypted, these receivers are susceptible to being spoofed. In this work, we propose a wide-area spoofing detection algorithm for PMUs using a hybrid communication architecture which overlays NAPSInet, a proposed communication structure for the future Smart Grid. We create conditioned signal snip- pets which contain the military P(Y) signal, whose precise code sequence is unavailable to civilian users and thus cannot be generated by an attacker. Thus, the encrypted signal establishes a type of signature in the background of all authentic GPS signals, the presence of which can be verified by correlating between conditioned signals from other distant receivers. We fur- ther consider the potential for a coordinated spoofing attack against regional collections of cross-check receivers and generate representative snippets for each regional network to verify against other distant sites. Additionally, we use real-world data recorded during a government-sponsored, live-sky spoofing event and demonstrate our algorithm can successfully evaluate the authenticity of a widely dispersed network of receivers. 1 I NTRODUCTION In Title XIII of the Energy Independence and Security Act of 2007 (EISA), the U.S. government endorsed a new, major effort to modernize the North American electric power grid with the creation of the “Smart Grid” [1]. The EISA officially defined the Smart Grid and described its key elements, including the implementation of a wide-area network of measurement devices to monitor the power grid state. Currently, this feature is largely comprised of a network of nearly 2000 Phasor Measurement Units (PMUs), devices that measure voltage and current phasors at critical substations [2], tagging each with a precise time- stamp using GPS. A map of the widely dispersed PMU network is shown in Fig. 1. Figure 1: Network of PMUs monitoring critical substations [2]