A Bootstrapping Server Function (BSF) is an intermediary element in Cellular networks which provides application-independent functions for mutual

authentication Authentication (from ''authentikos'', "real, genuine", from αὐθέντης ''authentes'', "author") is the act of proving an assertion, such as the identity of a computer system user. In contrast with identification, the act of indicatin ...

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 Mobile television is television watched on a small handheld or mobile device. It includes service delivered via mobile phone networks, received free-to-air via terrestrial television stations, or via satellite broadcast. Regular broadcast stand ...

and

PKI PKI may refer to: * Partai Komunis Indonesia, the Communist Party of Indonesia * Peter Kiewit Institute The Peter Kiewit Institute is a facility in Omaha, Nebraska, United States which houses academic programs from the University of Nebraska� ...

, 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 (GAA). In short, it consists of the following elements. * user equipment (UE), e. g. a mobile cellular telephone; needs access to a specific service * application server (NAF: Network Application Function), e. g. for mobile TV; provides the service * BSF (Bootstrapping Server Function); arranges security relation between UE and NAF * mobile network operator's Home Subscriber Server (HSS); hosts user profiles. In this case, the term '

bootstrapping In general, bootstrapping usually refers to a self-starting process that is supposed to continue or grow without external input. Etymology Tall boots may have a tab, loop or handle at the top known as a bootstrap, allowing one to use fingers ...

' is related to building a security relation with a previously unknown device first and to allow installing security elements (keys) in the device and the BSF afterwards.

Workflow

The BSF is introduced by the application server (NAF), 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 (Authentication and Key Agreement); additionally, the BSF sends related queries to the Home Subscriber Server (HSS). Afterwards, UE and BSF agree on a session key to be used for encrypted data exchange with the application server (NAF). 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 (UE), using the related session keys for encryption.

Standards

BSF is standardised in recent versions of 3GPP Standards: GAA (Generic Authentication Architecture) and GBA ( Generic Bootstrapping Architecture), and 3GPP TS 33.919, 33.220 24.109, 29.109

GBA/GAA Setup

Workflow

Standards

External links