# Formulating Cybersecurity Requirements for Autonomous Ships Using the SQUARE Methodology
## 4 Security Requirements for Autonomous Ships
### Derive Security Requirements
#### 4.2.9 Requirements Inspection  
The devised requirements were mapped onto the IACS requirements, as shown in Table 7. \begin{table}
\begin{tabular}{c c c} \hline
**Group** & **Code** & **Requirements** \\ \hline \multirow{3}{*}{Integrity} & R-02 & Sensor data transmission must be protected against tampering. \\  & R-05 & An encryption mechanism should be used \\  & R-01 & to protect communication data. \\ \hline \multirow{3}{*}{Reliability} & R-01 & The sensor’s function of verifying the \\  & R-04 & \begin{tabular}{l} identification data should be provided. \\ Security design must be devised to \\ eliminate defects in the neural network. \\ An encryption mechanism should be used \\ to protect communication data. \\ \end{tabular} \\ \hline \multirow{3}{*}{Stability} & R-04 & Security design must be devised to \\  & R-06 & \begin{tabular}{l} eliminate defects in the neural network. \\ Artificial intelligence must be trained using \\ reliable training data. \\ Protective measures should be \\ implemented to prevent malware. \\ \end{tabular} \\ \hline \multirow{3}{*}{Access control} & R-07 & Unauthorized network connections should \\  & R-08 & \
\begin{tabular}{l} be blocked. \\ Protective measures should be \\ implemented to prevent malware. \\ \end{tabular} \\ \hline \multirow{3}{*}{Availability} & R-03 &
\begin{tabular}{l} In the event of a denial-of-service attack, \\ the minimum functionality for the \\ operation of ships must be provided. \\ \end{tabular} \\ \hline \end{tabular}
\end{table} 
Table 5: Grouped security requirements. Each requirement of IACS UR E27 follows IEC 62443-3-3, which describes the security requirements for industrial control systems. IEC 62443-3-3 defines a security level (SL) from SL-0, which does not require cybersecurity, to SL-4, which requires a strong cybersecurity level, as shown in Table 8. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Level** & **Code** & **Requirement** \\ \hline \multirow{8}{*}{High} & R-02 & Sensor data transmission must be protected against tampering. \\  & & In the event of a denial-of-service attack, the minimum functionality for the operation of ships must be provided. \\  & & Security design must be performed to eliminate defects in the neural network. \\  & & An encryption mechanism should be used to protect communication data. \\  & & Protective measures should be implemented to prevent malware. \\ \hline \multirow{4}{*}{Medium} & R-01 & The sensor’s function of verifying the identification data should be provided. \\  & & Artificial intelligence must be trained using reliable training data. \\  & & Unauthorized network connections should be blocked. \\ \hline \multirow{2}{*}{Low} & R-02 & Sensor data transmission must be protected against tampering. \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Prioritize requirements. \begin{table}
\begin{tabular}{c c} \hline \hline
**Requirements** & **IACS UR E27 Control** \\ \hline \multirow{2}{*}{R-01} & Software process and device identification and authentication \\ \hline \multirow{2}{*}{R-02} & Communication integrity \\ \hline \multirow{2}{*}{R-03} & Denial-of-service protection \\ \hline \multirow{2}{*}{R-04} & Security functionality verification \\ \hline \multirow{2}{*}{R-05} & Communication integrity \\ \hline \multirow{2}{*}{R-06} & Input validation \\ \hline \multirow{2}{*}{R-07} & Network and security configuration settings \\ \hline \multirow{2}{*}{R-08} & Malicious code protection \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Requirements mapping with E27.