# A Trustworthy Communication Hub for Cyber-Physical Systems
## 7 Conclusions  
As the results of this research, we provide a trustworthy communication hub for cyber-physical systems and contribute towards solving the challenges related to trustworthy communications between physical resources owned by different stakeholders. The CPS hub realizes the communication spaces concept, and enables the combined trust and communications process when dynamic resources owned by different stakeholders are exchanging information. The solutions contribute towards solving the introduced grand challenge related to trustworthy communications of cyber-physical systems, especially in the energy flexibility and emergency mobile cases.  
The evaluation shows that the provided CPS hub enables information exchanges between distributed energy resources of different stakeholders, so that they can join the aggregation process for more flexible and efficient resource usage in the energy markets. However, the evaluation was limited in the sense that only simulated energy resources were used in a specific test scenario. In the emergency mobile case, the CPS hub enables interaction between heterogeneous physical devices of multiple stakeholders to exchange information, so that, for example, authorities can see the situation in the emergency area and, simultaneously, the policies of the owners can be taken into concern. However, the evaluation was limited in the sense that only very simple security policies of the owners were involved in the test scenario.  
Despite these limitations, the evaluation cases showed that consideration of the ownership issues in the communication for information exchanges between heterogeneous physical resources (devices) is possible and feasible. The evaluations of the CPS hub demonstrated potential methods for including the policies of the owners for the creation of trustable interactions between CPS resources. However, for example, scalability, real-time and streams-based operation, application of physical DERs, aggregation, virtual power plants, and interaction with in day ahead/intraday energy markets are seen to be issues for future research. In addition, consideration of the security, privacy, trust, and safety challenges with a larger set of service providers, OEMs, and owners, as well as more constrained physical CPS resources, ad hoc wireless communications, and information semantic levels in dynamic contexts, is an open area for future research. However, it is envisioned based on evaluations that the constructed CPS hub contributes a set of very essential technical enablers for future smart CPS systems and creates a strong basis for such future research towards a future smart society.  
**Author Contributions:** [PERSON] wrote and authored all the chapters of this article. [PERSON] contributed to the realization and evaluation of the CPS hub, and some pictures and part of texts in Sections 5 and 6.  
**Funding:** This article is based on the research actions executed within ITEA 2 call 8 project 13011 M2 MGrids, Smart M2 MGrids - M2M Internet for dynamic M2M information business ecosystem. The M2 MGrids project was made possible by ITEA framework and was funded by public authorities in Belgium, Finland, Netherlands, Portugal, Turkey, and Israel.  
**Acknowledgments:** Acknowledgments are offerred for all ITEA M2 MGrids project partners for their active contributions and discussions during the project. Especially, acknowledgements are offered to [PERSON], [PERSON], and [PERSON] from Bittium; [PERSON], [PERSON], and [PERSON] from Polar; [PERSON] from Tracker; [PERSON] and [PERSON] from Valopaa; [PERSON] and [PERSON] from Empower IM; and [PERSON] from Business Finland.  
**Conflicts of Interest:** The authors declare no conflict of interest.