## 8 Conclusions and Future Work  
ITS are complex, time-critical systems in which the physical safety of road users and the efficiency of transport services directly depend on the provision of cybersecurity. Although developments for ITS standards exist, the imposition of a comprehensive standard as well as the creation of a security strategy is not yet a fact. The interoperability between the various standards within the ITS and the interaction with the surrounding world (Smart Cities, IoT) needs to be well considered and tested.  
Some of the described technologies such as blockchain, lightweight cryptographic methods, network segmentation and sensor fusion will certainly find a place in the appearance of ITS, although more experimental results are needed, as well as tests on how they will fit into the overall system.  
Another part of the discussed technologies is in the initial stage of research regarding their application in ITS. AI and Machine Learning are mentioned in many sources as an important technology that will determine the vision of ITS. The advantages of utilizing such approaches are greatly publicized, while the security implications of their integration with ITS remain not studied  
\begin{table}
\begin{tabular}{c c c c} \hline
**Architecture Layer** & **Security Issue** & **Cyberattack** & **Security Approach** \\ \hline \multirow{4}{*}{Perception layer} & Configuration and & & \\  & initialization of the & & \\  & devices during & Denial-of-Service; & Security by contract; \\  & manufacturer; & Spoofing; & Sensor fusion; \\  & Internal vehicular & & \\  & network design; & & \\ \hline \multirow{4}{*}{Network layer} & Anonymous & Sybil Attacks; & Blockchain; \\  & authentication in & Denial-of-Service; & Reputation based \\  & VANET; & Eavesdropping; & Mane-in-the-Middle; \\  & & VANET; & Eavesdropping; & Bloom filter combined \\  & & Routing attacks; & \\ \hline \multirow{4}{*}{Support layer} & \multirow{4}{*}{Fog defense;} & \multirow{4}{*}{Attack against Fog;} & Authentication; \\  & & & Encryption; \\ \cline{1-1}  & & & Key management; \\ \cline{1-1}  & & & Regular auditing; \\ \hline \multirow{4}{*}{Application layer} & Complicated data model; & Data poisoning; & Blockchain; \\  & AI defense. & Environmental & AI; \\ \cline{1-1}  & & Perturbations; & Machine learning; \\ \cline{1-1}  & & Policy manipulation. & Ontology; \\ \cline{1-1}  & & Game theory. \\ \hline \end{tabular}
\end{table}
Table 2: ITS architecture and cybersecurity issues and approaches.  
enough. On the other hand, experimental results from the application of these technologies in ITS security systems are needed. Another technologies that is expected to be developed under ITS domain are Game theory and Security-by-Contract. They are successfully applied in IoT cybersecurity solutions and is likely to find a place in ITS cybersecurity.  
**Author Contributions:** Conceptualization, N.K. and T.M.; investigation, T.M.; resources, T.M.; writing--original draft preparation, T.M.; writing--review and editing, N.K.; visualization, T.M.; supervision, N.K.; funding acquisition, N.K. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was partially supported by the European Regional Development Fund within the OP \"Science and Education for Smart Growth 2014-2020\", Project CoC \"Smart Mechatronic, Eco- And Energy Saving Systems And Technologies\", No BG05M2 OP001-1.002-0023 233.  
**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses or interpretation of data; in the writing of the manuscript or in the decision to publish the results.