AUSF (Authentication Server Function)

The Authentication Server Function is the 5G core network function that performs subscriber authentication on behalf of the AMF, executing the 5G-AKA or EAP-AKA' procedure with credentials supplied by the UDM. It generates session keys that bind the subscriber to the serving network, helping defeat false base station and interconnect attacks. AUSF compromise would allow forged authentication, so it must be deployed in the operator's most trusted security zone with strong API controls.

Categories: Radio Access NetworkCore NetworkRoaming and Interconnect

AUSF in context

The radio access network is the layer where mobile devices attach to the operator's infrastructure. Attacks in this layer include IMSI catching, rogue base stations, downgrade attacks and jamming, and defenses hinge on mutual authentication, integrity-protected signaling and Open RAN supply-chain hygiene.

The mobile core is where subscriber sessions, mobility and policy live. In 4G it is the EPC (MME, HSS, S/PGW); in 5G it is the Service-Based Architecture with AMF, SMF, UPF, AUSF, UDM and the NRF. Core exposure is the difference between a single-subscriber leak and a fleet-wide breach.

To place AUSF in the wider telecom-security picture, review SUCI, AKA, AMF, CSCF, HLR and IAP.

Related terms

Equipment

Authentication servers (AUSF, 3GPP AAA, HSM)

Articles in the P1 mobile network security guide

Related topic hubs

  • 5G Security 5G SBA, SEPP, SUCI, 5G-AKA, N32 and service-based interface security.
  • Roaming Security IPX/GRX interconnect risk, home-routed vs local-breakout, SEPP.
  • 5G NEF Security Network Exposure Function security in the 5G core.
  • Diameter Attacks S6a IDR/PUR/CLR abuse, subscriber tracking, LTE signaling attacks.

More from the TelcoSec Glossary

Browse the full TelcoSec Glossary, the Ultimate Guide to Mobile Network Security, or the P1 Arsenal of telecom-security tools.