# Secure Aviation Control through a Streamlined ADS-B Perception System
## 3 Related Work
### Securing ADS-B
#### 3.2.1 Cryptography and Fingerprinting
[25] fingerprinted the aircraft equipped with ADS-B to authenticate a stream of messages. They performed fingerprinting based on the time difference of arrival (TDoA) information of the messages they received from aircraft as they were received on various sensors. Then, a main server evaluates any similarity between the gathered samples and local data to catch any distinction. Lastly, [PERSON] et al. [26] emphasized that messages sent by aircraft are not encrypted in any form; since the ADS-B messages are in basic form, it is relatively easy to forge or tamper with ADS-B messages. Their research established an anti-counterfeiting system that consists of four stations based on the time difference of arrival to locate the actual position of the ADS-B signal and compare it with any alteration found in the claimed position in the counterfeit ADS-B message. We summarize the current cryptography and fingerprinting solutions to secure ADS-B in Table 2. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Ref.** & \multicolumn{2}{c}{**Approach**} & \multicolumn{2}{c}{**Contributions**} & \multicolumn{2}{c}{**Limitations**} \\ \hline \multirow{3}{*}{[2]} & \multirow{3}{*}{—} & Public key cryptography & \multirow{3}{*}{—} & Proof that cryptography and & \multirow{3}{*}{—} & \multirow{3}{*}{Costly changes to the ADS-B} \\  & & and fingerprinting. & & fingerprinting could improve the & & \\  & & & security of ADS-B & & & protocol must be performed. \\  & & & communications. & & & \\ \hline \multirow{3}{*}{[21]} & \multirow{3}{*}{—} & Fingerprinting wireless & \multirow{3}{*}{—} & Detect injected messages using & \multirow{3}{*}{—} & They were only able to detect 50\% \\  & & radio signals. & & fingerprinting on radio signals. & & of the injected messages. \\ \hline \multirow{3}{*}{[22]} & \multirow{3}{*}{—} & Merged cryptography with & \multirow{3}{*}{—} & Kept the ADS-B message & \multirow{3}{*}{—} & Huge and needs further testing to \\  & & timestamp validation. & & unchanged even though the size & & ensure it does not corrupt any \\  & & & is huge. & & messages or affect the detection of \\ \hline \multirow{3}{*}{[23]} & \multirow{3}{*}{—} & Fingerprinting data coming & \multirow{3}{*}{—} & Detect attacks that use a single & \multirow{3}{*}{—} & \multirow{3}{*}{—} \\  & & from antennas. & & transmitter by fingerprinting & & \\ \cline{1-1}  & & & information in the relative & & & out using a single transmitter. \\ \hline \multirow{3}{*}{[24]} & \multirow{3}{*}{—} & Adding a HASH value to & \multirow{3}{*}{—} & Added HMAC to a sequence of & \multirow{3}{*}{—} & \multirow{3}{*}{Requires further testing to ensure HMAC is suitable for ADS-B messages.} \\  & & verify ADS-B messages. & & validate them. & & \\ \hline \multirow{3}{*}{[26]} & \multirow{3}{*}{—} & Fingerprinting based on the & \multirow{3}{*}{—} & It is time-consuming as the main \\  & & & TDoA of the messages. & & server needs to evaluate the \\ \cline{1-1}  & & Time difference of arrival & \multirow{3}{*}{—} & Detecting and distinction in & similarity each time, and it is \\ \cline{1-1}  & & & messages by evaluating any & unreliable since any lost packet \\ \cline{1-1}  & & & similarities with the & & will jeopardize the whole \\ \cline{1-1}  & & & gathered samples. & checking process. \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Summary of the current cryptography and fingerprinting solutions to secure ADS-B.