Performance analysis of a civilian GPS position authentication system

A position authentication method utilizing the white-noise-like GPS spreading codes as tamper proof watermarks is described. In this method a segment of the GPS signal collected by a trusted user (the authenticator) is used as a template. Another user whose position and time report needs to be verified (the supplicant) sends a sample of its signal. The supplicant's sample is compared with the authenticator's template. The absence of a correlation peak between the two signals indicates that the supplicant is using a non-authentic GPS signal. A correlation peak having a delay that is inconsistent with relative range between supplicant and authenticator indicates a falsification of the position or time report. Analysis, simulation and experimental results documenting the system's performance are presented. These results show that this approach can detect a deceptive position report with a resolution of 15 meters (1-sigma) or better.