LTE GAA architecture, how LTE uses TLS

The architecture of GAA is given in TR133919

Among them,GBA includes HTTP Digest, pre-shared Key TLS, IKE with pre-shared secret and a priori any mechanism based on username and P Assword , SSC assumes that the
Entity that needs to is authenticated (one or both partners in the communication) possesses a (public, private) key pair A nd a corresponding digital certificate. The latter validates the key pair and binds the key pair to its legitimate owner. Well-known protocols whose authentication is based on (public, private) key pairs include PGP and HTTP over TLS,
RFC 2818 [5] (the later is commonly called by its protocol identifier, "HTTPS").

GBA presents an application implementation mechanism based on 3GPP aka that provides a shared secret to client and application server, which can be used to authenticate the client and application communication between servers; GAA also proposes a new network element (NE) called bootstrapping Server Function (BSF), and the authentication between UE and HSS is done through BSF. From the resulting (CK, IK), a session key was derived in BSF and UE. An application server (called Network application Function (NAF) with TS 33.220 [2]) can fetch this session key from the BSF Together with subscriber profile information. In this is the application server (NAF) and the UE share a secret key that can subsequently is used for application secur ity, in particular-authenticate UE and NAF at the start of the application session (possibly also for integrity and/or Confidentiality protection Although that might is strictly in the scope of GAA). The communication between the UE and the BSF as well as, between NAF and BSF and between BSF and HSS are application I Ndependent and is described in TS 33.220

If only SIM cards or SIMs on UICC are available, and 2g_gba is allowed, the BSF and UE mutually authenticates using the 2G AKA and TLS protocol.

SSC provides a mechanism for the dynamic issuance of digital certificates for mobile subscriber; If A mobile subscriber wants to has and made use of a (public, private) key pair, T He key pair and a certificate should either be preloaded or the subscriber must has the means to either generate or Obtai n a key pair and dynamically obtain a corresponding digital certificate.

In order to request a certificate, the user is required to send an appropriate certificate request to the PKI portal of Home operator, which can be seen as an example of a mobile application. And the process requires mutual authentication between the two entities. If a certificate is already available for both parties, it can be authenticated with an existing certificate, otherwise the GBA is required to obtain a shared secret for authentication and finally obtain a new certificate. As with many mobile applications it requires authentication of the communicating entities, in this case the UE and the PKI Portal (the latter plays the role of the application server). As for any other application there is 2 options for this authentication:pre-shared secret based or based on asymmetric C Ryptography and certificates. The latter is a option when a new certificate was requested from the PKI portal while another still valid certificate is already loaded in the UE. The former method requires a shared secret between the PKI portal and the UE. If the shared secret is not pre-configured, GBA can being used to obtain such a shared secret.

HTTPS is commonly used to protect application sesstion security between UE and application server. It is envisaged this HTTPS (or HTTP/TLS) may be used in a number of services to secure the application session between the UE and the Application server (Ua interface in TS 33.220, see TS 33.222 [4]). TS 33.222 [4] describes the details of the possible authentication options when HTTPS are used between a UE and an applicat Ion server. Any existing or future application based on HTTPS or pre-shared Key TLS can refer to TS 33.222 [4] for details on Authenti Cation and the set up of a secure HTTP session. There are four types of applications in this case:

HTTPS with authentication Proxy:ue can connect multiple as at the same time, saving AV, saving the number of TLS sessions that UE needs to open and maintain

HTTPS without authentication Proxy

Pre-shared key Tls:http client and server are certified with GBA, the session Key obtained through BSF is NAF extracted as a shared secret, the shared Secret can be used as the master secret in a TLS session to generate session keys in the TLS protocol.

To summarize, in the application layer of LTE, 3GPP gives a common authentication architecture GAA, which can realize mutual authentication mechanism of user and server independent of application server and authentication proxy, of course, Independent as can develop a specific authentication method. In general, GAA can reduce the complexity of application development, and the mechanism can be built into Usim card storage.

LTE GAA architecture, how LTE uses TLS