## 2 Concerns Related to User Identity and Privacy in 5G Core Networks
### Linkability  
The use of data, in particular in connection with cloud services and internet activities, has grown dramatically in recent years. With this increase in data consumption and production comes an inherent increase in concerns regarding identity protections on the internet. The NIST (National Institute of Science and Technology) defines linkable data as \"information about or related to an individual for which there is a possibility of logical association with other information about the individual\" [33]. Such attacks, where data can be linked back to the person of origin if not handled properly, can be seen in healthcare scenarios [34]. Data linkability concerns cover many different domains and are also highly \begin{table}
\begin{tabular}{c c c} \hline \multicolumn{3}{c}{**Identifiers in 5G Communications**} \\ \hline
**Identifier** & **Applicable Standards** & **Description** \\ \hline AMF UE NGAP & & The AMF UE NGAP ID is used to identify the UE on the N2 reference point. It is unique per AMF set and may be updated without changing the AMF. \\ \hline UE Radio Capability ID & TS 23.003 & The UE Radio Capability ID uniquely identifies a set of UE radio capabilities. It can be assigned by the UE manufacturer or the serving PLMN. The PLMN-assigned ID includes a Version ID to ensure its validity. \\ \hline \end{tabular}
\end{table} 
Table 2: _Cont._ \begin{table}
\begin{tabular}{c c} \hline \multicolumn{3}{c}{**New Adopted Technologies in 5G and Potential Threats They Pose to User Identity Protections [20]**} \\ \hline
**Technology** & **Summarized Description** \\ \hline Cross-Border Data Flows & As nations’ data networks are interconnected, data must be transmitted and shared \\  & securely while also maintaining user privacy. Different countries around the world \\  & may have different standards for protecting user privacy. \\ \hline Virtualization and & The use of Software-Defined Networking (SDN) and VNFs allow for virtual \\  & connections between cloud services, compared to previous generations where all \\  & interfaces and network connections were closely coupled physically. If these cloud \\  & services or resources are shared, there is a possibility for unauthorized user \\  & data access. \\ \hline SDN is a vital enabler of 5G networks, enhancing flexibility and performance by \\  & separating the control, data, and application layers through standard interfaces. The \\  & control layer, managed by the SDN controller, oversees data flow, while the \\  & application layer supports functions like load balancing and quality assurance. \\  & Despite its advantages, SDN introduces privacy risks, such as attacks on the \\  & controller or application layer that can lead to unauthorized access and manipulation \\  & of data flows [31]. To mitigate these risks, robust authentication, together with \\  & authorization mechanisms and privacy impact assessments, is essential in \\  & SDN-based 5G deployments. \\ \hline \end{tabular}
\begin{tabular}{c c} \hline \multicolumn{3}{c}{It is vital that a user of a network can afford a high degree of trust towards the \\  & operators. The complexity of a 5G environment increases the opportunity for \\  & intentional or unintentional user privacy compromises. Similarly, it is possible for \\  & insiders to misuse critical network elements, resulting in a lack of integrity of the \\  & user’s privacy [32]. As this was a threat in previous generations of cellular networks, \\  & the threat model has only grown and become more complex due to the deployment \\  & of the extensible technologies listed earlier. The increased dependence on cloud \\  & services and Software-Defined Networking has provided more areas for misuse. The \\  & additions to 5G infrastructure thus require strict access and monitoring procedures. \\ \hline \end{tabular}
\end{table} 
Table 3: Description of new technologies adopted in 5G CNs that could affect user identity protections. relevant in 5G networks.