GPS time authentication against spoofing via a network of receivers for power systems

Due to the unencrypted structure of civil GPS signals, the timing information supplied to the PMUs in the power grid is vulnerable to spoofing attacks. We propose our GPS time authentication algorithm using a network of widely dispersed static receivers and their known positions. Without requiring the knowledge of the exact P(Y) code sequences, we cross-check for the presence of these encrypted codes across the receivers to detect spoofing attacks. First, we perform pair-wise cross-correlation of the conditioned quadrature-phase, carrier wiped-off incoming signal across the receivers. Later, we utilize position-information aiding to estimate the expected time offset between the received P(Y) codes at different receivers. Thereafter, we authenticate each receiver by analyzing the weighted summation of the pair-wise cross-correlation peak offset and magnitude across the receivers and their common satellites. To validate our networked spoofing detection algorithm, we utilize four GPS receivers located in Idaho, Illinois, Colorado and Ohio. Under the presence of simulated spoofing attacks, namely signal-level spoofing and a record-and-replay attack, we demonstrate that our networked approach successfully detects these spoofing events with high probability.