## 2 Concerns Related to User Identity and Privacy in 5G Core Networks
### Newly Adopted Technologies  
The authors of [20] provide a breakdown of the identity and privacy risks in 5G networks introduced by newly adopted technologies. A unique perspective presented in this article focuses on the subscribers' viewpoint, although this is subjective. They  
Figure 3: High-level overview of the creation and mapping of the 5G-GUTI in a 5G SA network.  
Figure 2: The 5G VNFs that are associated with, or directly utilize, a subscriber’s SUPI or SUCI.  
state that there is a gap in users' attention to privacy implications, while there are tools and techniques to assist organizations in performing privacy impact assessments. The authors argue that, even though service providers perform these assessments to fulfill legal, regulatory, and policy requirements, the user may not be aware of the potential privacy risks that come along with using 5G systems. The privacy risks due to new technologies identified by the authors within 5G networks are listed in Table 3, with an emphasis on privacy issues within CNs.  
\begin{table}
\begin{tabular}{c c c} \hline \hline \multicolumn{3}{c}{**Identifiers in 5G Communications**} \\ \hline
**Identifier** & **Applicable Standards** & **Description** \\ \hline \multirow{6}{*}{Subscription Permanent Identifier (SUPI)} & \multirow{6}{*}{TS 33.501 [21], TS 23.003 [22], TS 22.261 [23], TS 23.316 [24]} & A globally unique SUPI is allocated to each subscriber and provisioned in the UDM (Unified Data Management)/UDR (Unified Data Repository). The SUPI may contain an IMSI (International Mobile Subscriber Identity), a network-specific identifier, or other identifiers for specific use cases. It is concealed for privacy and supports roaming and interoperability with (Long-Term Evolution) networks. \\ \hline \multirow{6}{*}{Subscription Concealed Identifier (SUCI)} & \multirow{6}{*}{TS 33.501, TS 23.316} & The SUCI is a privacy-preserving identifier containing the concealed SUPI. It is used for secure identification in the 5G system. The usage of SUCI for non-3 GPP network access is also specified within TS 23.316. \\ \hline \multirow{6}{*}{Permanent Equipment Identifier (PEI)} & \multirow{6}{*}{TS 23.003, TS 23.316} & The PEI identifies the UE in the 5G system. In 3 GPP access modes, the PEI must be either the IMEI (International Mobile Equipment Identity) or IMEISV (International Mobile Equipment Identity Software Version). For non-3 GPP access scenarios, the UE sends the IEEE Extended Unique Identifier EUI-64 [25]. \\ \hline \multirow{6}{*}{5G-GUTI} & \multirow{6}{*}{TS 33.501, TS 23.003, TS 38.304 [26], TS 36.304 [27], TS 38.331 [28], TS 36.331 [29]} & The 5G-GUTI is a temporary identifier assigned by the AMF to the UE. It is structured as [\(<\)GUAMI\(>\) \(<\)5G-TMSI\(>\)] (Globally Unique AMF ID) and supports both 3 GPP and non-3 GPP access. The AMF ensures the uniqueness of the 5G-TMSI within the GUAMI. \\ \hline \multirow{6}{*}{AMF Name} & \multirow{6}{*}{TS 23.003} & The AMF is identified by a globally unique Fully Qualified Domain Name (FQDN). Each AMF can be associated with one or more GUAMI(s). \\ \hline \multirow{6}{*}{Data Network Name (DNN)} & \multirow{6}{*}{TS 23.003, TS 23.502 [30]} & The DNN is equivalent to an APN (Access Point Name) and is used to select SMF (Session Management Function), UPF (User Plane Function), and N6 (5G Internet Connectivity Interface) interfaces for a PDU Session. \\ \hline \multirow{2}{*}{Internal-Group Identifier} & \multirow{2}{*}{TS 23.502} & The Internal-Group Identifier associates a UE with groups in the subscription data. It is used for applying group-specific policies in the SMF and AMF. \\ \hline \multirow{6}{*}{Generic Public Subscription Identifier (GPSI)} & \multirow{6}{*}{TS 23.003} & The GPSI is a public identifier (Phone Number or External Identifier) used to address a 3 GPP subscription outside the 3 GPP system. It is stored in the subscription data and associated with the SUPI. \\ \cline{1-1} \cline{