## 3 Development History of Navigation Signal Authentication Technology
### Concept  
The concept of satellite navigation signal authentication was first proposed in the report, \"Vulnerability Assessment of Transportation Infrastructure Based on GPS\", issued by the Center for Transportation Systems in the United States in 2001, which comprehensively  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Spoofing** & **NMA** & **SCA** \\ \hline \multirow{4}{*}{Generated spoofing} & Primary generated spoofing (low-cost software & \multirow{2}{*}{High} & \multirow{2}{*}{High} \\  & radio or commercial signal simulator) & & \\ \cline{2-3}  & Intermediate generated spoofing (receive GNSS & \multirow{2}{*}{High} & \multirow{2}{*}{High} \\  & signal first and then generate spoofing signal) & & \\ \cline{2-3}  & SCER & Low & \\ \cline{2-3}  & Advanced generated spoofing (multiple & \multirow{2}{*}{High/Medium} & \multirow{2}{*}{High} \\  & intermediate generative spoofing) & & \\ \hline \multirow{4}{*}{Maeaconing} & Simple meaconing (same delay for each & \multirow{2}{*}{Low} & \multirow{2}{*}{Low} \\  & satellite channel) & & \\ \cline{1-1} \cline{3-3}  & Multichannel meaconing (the delay of each & \multirow{2}{*}{Low} & \multirow{2}{*}{Low} \\  & satellite channel is inconsistent) & & \\ \hline \hline \end{tabular}
\end{table}
Table 4: Signal authentication anti-spoofing effect [17].  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Anti-Spoofing Method** & **Description** & **Effect** \\ \hline Navigation signal encryption [32] & Encrypted signals serve authorized users, making it difficult & \\  & for attackers to predict signals & High \\ \hline Navigation signal authentication [17] & It is difficult for spoofed attackers to predict the & \\  & authentication message/spreading code & High \\ \hline DOA detection based on multi-array antennas [7; 8] & The spoofing signal is generally emitted from a single & \\  & transmitting antenna, and its satellites come from the same & \\  & direction, while the real satellites of the signal come from & \\  & different directions & \\ \hline Multiple correlation peaks [33; 34] & The superposition of the spoofed signal and the real signal & \\  & will bring multiple correlation peaks, and it will also cause & \\  & distortion of the correlation peaks & \\ \hline Signal power [35; 36] & The spoofing signal has more power, and the signal power & \\  & changes during the spoofing implementation & \\ \hline Doppler consistency [37; 38] & It is difficult for spoofing signals to keep the carrier Doppler & \\  & shift consistent with the pseudocode Doppler shift & \\ \hline Auxiliary information of external & Spoofing signals cannot deceive sensors such as inertial & \\   sensors [4; 5] & navigation, chip-scale atomic clocks, and lidar & \\ \hline \hline \end{tabular}
\end{table}
Table 3: Comparison of common anti-spoofing algorithms.  
studied the anti-jamming and anti-spoofing methods of the Global Positioning System (GPS) and proposed several strategies to mitigate GPS spoofing. Although the report believes that \"the best anti-spoofing technology will be based on the multiantenna array measurement method\", it proposes an anti-spoofing method for encrypted authentication signals for the first time [42].