IMS-AKA (IMS Authentication and Key Agreement)

Also known as: IMS Authentication and Key Agreement, TS 33.203 AKA

IMS-AKA is the authentication and key agreement protocol used to register a subscriber with the IMS core over the Gm interface. It reuses the 3GPP AKA challenge-response run between the ISIM and the HSS, carried inside SIP REGISTER exchanges with the P-CSCF, and derives keys that protect the SIP signalling with IPsec ESP in transport mode. IMS-AKA is specified in 3GPP TS 33.203 and is mandatory for VoLTE and VoNR access to the IMS.

Categories: Radio Access NetworkCore NetworkSignaling

IMS-AKA in context

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

The mobile core carries subscriber sessions, mobility and policy. 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.

To place IMS-AKA in the wider telecom-security picture, review IPsec, GTP-U, N3, IAP, User Plane Security and NGAP: each entry cross-references back to this page so you can walk the topic in either direction.

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