# A Trustworthy Communication Hub for Cyber-Physical Systems
## 1 Introduction  
Today, industries and consumer markets are increasingly using services exposed from various physical devices, such as, for example, sensors and actuators, via heterogeneous networks. The aim of such systems is to enable the physical world to collaborate with the cyber-world to boost the real-time economies of companies. Such cyber-physical systems usually consist of physical resources (devices), subsystems, and service clouds owned, provided, and/or hosted by different stakeholders. The essential grand challenge arises from the need for trustworthy interactions between the referred resources and different stakeholders. This research focuses on solving this grand challenge related to trustworthy communications in such cyber-physical systems (CPS), especially in the energy and mobility domains. There are multiple cyber-physical entities in the energy domain, such as, for example, solar power plants; wind mills; electric vehicles; buildings; energy sensitive household appliances; and other kindsof distributed energy resources (DERs) consuming, producing, or storing energy, which have caused challenges for distribution network operators in balancing power levels in the energy grid. The peak consumption hours are becoming ever more expensive for the energy sector, energy intensive industry, and consumers. The industry is looking for more flexible and smarter operational models for the energy grid. Therefore, an essential industrial objective has been to cut down the peak loads of a day to lower the cost of energy and its distribution. Such flexibility capabilities require trustworthy communications for information exchange between the cyber-physical entities from multiple energy sensitive domains and energy domain systems and stakeholders. There is huge number of appliances in the mobility sector, such as smart watches, smart phones, sensors, tracking devices, vehicles, and multiple stakeholders, which are often not able to interact with each other. This is because, usually in CPS business sectors, a service provider (SP) hosts specialized physical resources (e.g., products of the SP) and the related exposed data/information in their own service cloud as a kind of vertical silo. However, the owners of the referred physical resources may not be the SPs themselves, but instead their customers, which may be individuals (private persons or their groups), companies, organizations, or a combination. Today, such owner stakeholders require ever more trustworthy, smart, and interoperable operation from their SPs, which is in line with their own collaboration agreements and privacy regulations (GDPR, General Data Protection Regulation (EU) 2016/679). For example, if some unexpected emergency type of event, such as, for example, a traffic accident, happens, it is challenging to know the situation, even if the information could be available. There are people, vehicles, and other referred devices that have the capabilities to collect data/information from the event. However, the devices cannot interact with each other, and thus it is very challenging to know the situation even if the information could be available. These situations require trustworthy communications for information exchange for smart operation with the appliances from multiple sectors, hosted by multiple SPs, and SP service systems/clouds. Both energy flexibility and traffic accident cases indicate the needs for smart, trustable, secure, and interoperable communications for information exchanges between physical resources owned by different stakeholders, that is, the focused grand challenge of this research. This inherently includes such aspects as privacy, confidentiality, end-to-end security, secure data management, and access control. In particular, which other CPS entities and users are allowed to communicate and exchange data with this specific CPS entity. Such communication access rights depend on the privacy and security policies of the owner and the service provider (SP) of the referred entity.