It is well-known that GPS is vulnerable to signal spoofing attacks. Although several spoofing detection techniques exist, they are incapable of mitigation and recovery from stealthy attackers. In this work, we present SemperFi, a single antenna GPS receiver capable of tracking legitimate GPS satellite signals and estimating the true location even during a spoofing attack. The main challenge in building SemperFi is, unlike most wireless systems where \emph{the data} contained in the wireless signals is important, GPS relies on the time of arrival (ToA) of satellite signals. SemperFi is capable of distinguishing spoofing signals and recovering legitimate GPS signals that are even completely overshadowed by a strong adversary. We exploit the short-term stability of inertial sensors to identify the spoofing signal and extend the successive interference cancellation algorithm to preserve the legitimate signal's ToA. We implement SemperFi in GNSS-SDR, an open-source software-defined GNSS receiver, and evaluate its performance using UAV simulators, real drones, a variety of real-world GPS datasets, and various embedded platforms. Our evaluation results indicate that in many scenarios, SemperFi can identify adversarial peaks by executing flight patterns that are less than 50 m long and recover the true location within 10 seconds (Jetson Xavier). We show that our receiver is secure against stealthy attackers who exploit inertial sensor errors and execute seamless takeover attacks. We design SemperFi as a pluggable module capable of generating a spoofer-free GPS signal for processing on any commercial-off-the-shelf GPS receiver available today. Finally, we release our implementation to the community for usage and further research.

中文翻译：

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SemperFi：一种消除无人机的Spoofer GPS接收器

众所周知，GPS容易遭受信号欺骗攻击。尽管存在几种欺骗检测技术，但它们无法缓解隐匿攻击者的攻击并从中恢复。在这项工作中，我们介绍了SemperFi，这是一种单天线GPS接收器，即使在欺骗攻击期间也能跟踪合法的GPS卫星信号并估计真实位置。构建SemperFi的主要挑战在于，与大多数无线系统中无线信号中包含的\ emph {数据}非常重要的情况不同，GPS依赖于卫星信号的到达时间（ToA）。SemperFi能够区分欺骗信号并恢复合法的GPS信号，这些信号甚至被强大的对手完全掩盖了。我们利用惯性传感器的短期稳定性来识别欺骗信号，并扩展连续干扰消除算法以保留合法信号的ToA。我们在开源软件定义的GNSS接收器GNSS-SDR中实现SemperFi，并使用无人机模拟器，真实无人机，各种实际GPS数据集和各种嵌入式平台来评估其性能。我们的评估结果表明，在许多情况下，SemperFi都可以通过执行小于50 m长的飞行模式来识别对抗峰，并在10秒内恢复真实位置（Jetson Xavier）。我们证明了我们的接收器对利用惯性传感器错误并执行无缝接管攻击的隐身攻击者是安全的。我们将SemperFi设计为可插拔模块，能够生成无干扰的GPS信号，以便在当今任何可用的现成GPS接收器上进行处理。最后，我们将实施方案发布给社区，以供使用和进一步研究。