Editing Extensible Authentication Protocol (section)

===EAP Subscriber Identity Module (EAP-SIM)===
EAP  [[Subscriber Identity Module]] (EAP-SIM) is used for authentication and session key distribution using the subscriber identity module (SIM) from the Global System for Mobile Communications ([[GSM]]).

GSM cellular networks use a subscriber identity module card to carry out user authentication. EAP-SIM use a SIM authentication algorithm between the client and an [[AAA protocol|Authentication, Authorization and Accounting (AAA)]] server providing mutual authentication between the client and the network.

In EAP-SIM the communication between the SIM card and the Authentication Centre (AuC) replaces the need for a pre-established password between the client and the AAA server.

The A3/A8 algorithms are being run a few times, with different 128 bit challenges, so there will be more 64 bit Kc-s which will be combined/mixed to create stronger keys (Kc-s won't be used directly). The lack of mutual authentication in GSM has also been overcome.

EAP-SIM is described in {{IETF RFC|4186}}.