Bootstrapping Server Function
A Bootstrapping Server Function is an intermediary element in Cellular networks which provides application-independent functions for mutual authentication of user equipment and servers unknown to each other and for 'bootstrapping' the exchange of secret session keys afterwards. This allows the use of additional services like Mobile TV and PKI, which need authentication and secured communication.
GBA/GAA Setup
The setup and function to deploy a generic security relation as described is called Generic Bootstrapping Architecture (GBA) or Generic Authentication Architecture. In short, it consists of the following elements.- user equipment, e. g. a mobile cellular telephone; needs access to a specific service
- application server, e. g. for mobile TV; provides the service
- BSF ; arranges security relation between UE and NAF
- mobile network operator's Home Subscriber Server ; hosts user profiles.
Workflow
The BSF is introduced by the application server, after an unknown UE device is trying to get service access: the NAF refers the UE to the BSF. UE and BSF mutually authenticate via 3GPP protocol AKA ; additionally, the BSF sends related queries to the Home Subscriber Server.Afterwards, UE and BSF agree on a session key to be used for encrypted data exchange with the application server. When the UE again connects to the NAF, the NAF is able to obtain the session key as well as user-specific data from the BSF and can start data exchange with the end device, using the related session keys for encryption.