The AUSF stands for Authentication Server Function. It is a network function in the 5G core network that is responsible for the security procedure for SIM authentication using the 5G-AKA authentication method. The AUSF interacts with the AMF and the UDM to perform the authentication and authorization of the users and devices accessing the 5G network. The AUSF also stores and manages the authentication keys and vectors for the users and devices.
Some of the main functions and features of the AUSF are:
• It supports the 5G-AKA authentication method, which is based on the challenge-response mechanism and uses symmetric cryptography. The 5G-AKA authentication method provides mutual authentication, identity protection, and key agreement between the user and the network.
• It supports the SUPI concealment, which is a mechanism to protect the privacy of the user’s permanent identity (SUPI) by using a public key encryption scheme. The AUSF generates and distributes the public key to the AMF, and uses the private key to decrypt the concealed SUPI from the user.
• It supports the slice-specific authentication and authorization, which is a mechanism to provide different levels of access and security for different network slices. The AUSF verifies the user’s subscription and credentials for each network slice, and assigns the appropriate security context and key hierarchy.
The AUSF is a key component of the 5G core network that ensures the security and privacy of the 5G communication and services. It is part of the service-based architecture (SBA) of the 5G core network, and uses the Nausf interface to communicate with other network functions, such as the AMF, the UDM, and the UDR.