## 4 Secure 5G Network Architecture for Mutual Authentication  
The overall structure of the framework proposed in this study is shown in Figure 1, and Table 2 shows the abbreviations used in the framework. To mitigate the impact of authentication traffic generated by secondary authentication on the home network of 5G, we designed two novel network functions: Secondary Authentication Function (SAF) and Authentication Data Management Function (ADMF). The role of SAF is to process primary operations of secondary authentication. The SAF receives requests for secondary authentication from the user, processes the request, and interacts with ADMF. The final goal of ADMF is to enhance the auditability of the communication environment. ADMF manages the identity and authentication information for users and DN-AAA(Data Network Authentication, Authorization and Accounting) servers and holds the authentication authority of DN-AAA. ADMF periodically sends a list of Data Networks it owns to SAFs in the surrounding serving network to announce its status. Also, ADMF periodically sends a list of authorized users it stores to the DN-AAA server for efficient management of connected users on the data network. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Research** & **Availability** & **Flexibility** & **Auditability** & **Independence** \\ \hline \multirow{3}{*}{[PERSON] et al. [26]} & Efficient connection & & & \\  & establishment mechanism & - & - & - \\  & on 5G core network & & & \\ \hline \multirow{3}{*}{[PERSON] et al. [15]} & Kerberos for & Cloud mesh architecture & & \\  & communication security & for network & - & - \\  & on mobile devices & service chaining & & \\ \hline \multirow{3}{*}{[PERSON] et al. [13]} & Energy-efficient & & & \\  & computational offload & - & - & - \\  & mechanisms for MEC & & & \\ \hline \multirow{3}{*}{[PERSON] et al. [27]} & \multirow{3}{*}{-} & Distributed device & Key Management and & \\  & & management mechanism & User Authentication for & - \\  & & for resource-limited & Fog Computing & \\ \hline \multirow{3}{*}{[PERSON] et al. [28]} & Efficient mechanism for & Security architecture & & \\  & distribution of & based on edge computing & - & - \\  & security module & for flexibility of key & & \\  & & management & & \\ \hline \multirow{3}{*}{[PERSON] et al. [24]} & Low-cost local & Distributed architecture & Context-awareness on & \\  & authentication & for local authentication & user equipment and & - \\  & & & virtualized & \\  & & network functions & & \\ \hline \multirow{3}{*}{[PERSON] et al. [23]} & Solutions for DoS and & & Security architecture for & \\  & Jamming attacks & - & mobile edge & - \\  & & & cashing system & \\ \hline \multirow{3}{*}{[PERSON] et al. [12]} & SDN and NFV for & & & \\  & MEC-based vehicle & - & - & - \\ \hline \multirow{3}{*}{proposed framework} & Traffic optimization with & Hierarchical architecture & Data management node & Authorization on the \\  & authentication relaying & for authentication & on the middle layer of & trusted node as a \\ \cline{1-1}  & & management & architecture & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of considerations between the previous works and the proposed framework. For the efficient operation of SAF and ADMF, the proposed framework consists of a hierarchical computing network architecture. SAF and ADMF, which are vital entities for efficient mutual authentication, are configured in the form of network functions and can be installed and operated in various types of equipment such as servers and general-purpose routers. In this way, the SAF can be freely located in a wide range of areas, from the network where the terminal nodes are located to the fog layer that controls the terminal node, and the SAF that handles secondary authentication requests from neighboring networks. ADMF is located in the fog layer to store and manage the information related to secondary authentication, collected and operated from SAFs.