page_title: IMS security
section_title: AKA (Authentication and Key Agreement)
hierarchical_section_title: IMS security / Security / AKA (Authentication and Key Agreement)
caption_attribution_description: Español: Arquitectura seguridad ims
context_page_description: IMS is a set of specifications to offer multimedia services through IP protocol. This makes it possible to incorporate all kinds of services, such as voice, multimedia and data, on an accessible platform through any Internet connection.
context_section_description: The security in IMS is based on a secret key of long duration shared between the ISIM and the AUC (Authentication Center) of the local network.
  ISIM: it is an application that runs on a smart card UICC (Universal Integrated Circuit Card) that contains the identification parameters and authentication of the IMS user.
  AUC: Associate in this case to the HSS. Contains information required to perform the authentication and encryption services. Stores the authentication and encryption algorithms and generates the necessary keys for each service.
  The AKA used to establish both the encryption keys (3DES or AES-CBC) and the integrity keys (HMAC-MD5 or HMAC-SHA-1).
  ISIM ↔ HSS: Required for the mutual authentication. Both the HSS and the ISIM have stored a secret key and private identification (IMPI) associated with that key.
  UA ↔ P-CSCF: Ensures a secure link between the UE and network.
  I/S-CSCF ↔ HSS: Establishes a security association for information transfer between the I/S-CSCF and the HSS.
  P-CSCF ↔ I/S-CSCF: This security association applies only when the P-CSCF is not in the Home Network.
  I-CSCF ↔ S-CSCF: Provides security between SIP nodes within a network.
caption: Security architecture
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