# Quantum Key Distribution for 5G Networks: A Review, State of Art and Future Directions
## 2 Security Challenges in 5G Network
### Policies  
New technologies, stakeholders, regulations, verticals, businesses, and end-users will be included in the extremely large 5G networks. The 5G are considered the best platform for the new generation of networks such as industries, smart cities, vehicles, and IoT. The applications, devices, users, and machines will produce a large quantity of data. This enormous data will be collected, analyzed, processed, combined, and stored for various purposes such as cross-border data flows. Furthermore, the data belong to the applications, organizations, societies, citizens, individual consumers, etc. In the classical network, the risk of user privacy mostly originates from the plaintext communication of the application data in the network. There is a high risk that user privacy is exposed to data leaks. Consequently, one of the challenges in 5G network is to secure end-user privacy. Solving privacy issues for all the stakeholders is a complex task since there are multiple interests at risk. However, some privacy issues are highlighted from the cloud computing perspective because of the relevance of cloud computing concepts to various 5G network technologies, for instance, NFV, SDN [17]. * End-to-End data privacy issues: Stakeholders such as service providers, mobile operators, businesses, and new technologies utilizing new business models are currently supported by 5G networks. Most of the stakeholders use cloud computing technology to store and access users' data. These personal data will then be managed and shared among various stakeholders for multiple purposes, leading to privacy breaches. Consequently, methodology for end-to-end data confidentiality must be considered to secure user privacy [14; 15]. * Personal data ownership and shared environment issues: The 5G network can assist application controls such as smart grid and healthcare running on virtual networks and providing shared network infrastructure. However, these network infrastructures are vulnerable to unauthorized data access [16]. Thus, effective functions of share network infrastructure without affecting users' privacy are needed. Furthermore, the party responsible for the data losses in shared network infrastructure is still a major concern for the users. Therefore, different stakeholders such as service providers, network operators and other third parties must be assigned licensing and ownership of personal information. * Various trust objectives issues: For classical 5G network, communication service providers and mobile operators might joint ventures and migrate some segment of their network into the cloud. For such cases, these stakeholders may decide the trust objectives based on their regulations and policies [17]. Consequently, these stakeholders may not take all the aspects of user data privacy into consideration. * Cross-border data flow issues: As a result of global digitalization, personal data is considered an essential commodity of the modern market. The information is expected to flow freely across the borders. Therefore, it is crucial to require consent from the government and individuals for any data transfers, including the methodology for storing and processing across the border [17; 18]. * Issues of the third party in the 5G network: 5G and IoT offer a new opportunity to the application developers to develop immersive applications that employ various communication protocols. Since the application developers can access the 5G network, the developers can sell or disclose the private data to a third party. In [58], the author explained that by using the mobile application, \"the health insurance portability and accountability act (HIPPA) allow a share out of individual's health data\". Furthermore, the cloud network policies for information sharing can consequently invoke the issues of data privacy.