Section: 6.8.1.4 R99+ ME
Content: Release 99+ ME that has UTRAN radio capability shall support the USIM-ME interface as specified in TS 31.102[ Characteristics of the Universal Subscriber Identity Module (USIM) application ]  [20]. Rel4- ME that has no UTRAN radio capabilities may support the USIM-ME interface as specified in TS 31.102[ Characteristics of the Universal Subscriber Identity Module (USIM) application ]  [20]. Rel5+ ME that has no UTRAN radio capabilities shall support the USIM-ME interface as specified in TS 31.102[ Characteristics of the Universal Subscriber Identity Module (USIM) application ]  [20]. A ME capable of UMTS AKA with a USIM active and attached to a UTRAN shall only participate in UMTS AKA and shall not participate in GSM AKA. A ME capable of UMTS AKA with a USIM active and attached to a GSM BSS shall participate in UMTS AKA and may participate in GSM AKA. Participation in GSM AKA is required to allow registration in a R98- VLR/SGSN. However, the use of GSM AKA in the MS shall be disabled on a particular visited network if instructed to do so by the USIM application. The mechanism is based on an EF ‘Disabled Authentications’ in the USIM application containing the unauthorized authentication methods per visited network. If the EF ‘Disabled Authentications’ is present and active, then the authentication methods marked as disabled shall not be used by the MS in the corresponding visited network. The disabled authentication method may be defined on a global, per country or per network basis. The relevant file in the USIM application is managed by the home operator based on information supplied to the home operator by the visited network. NOTE 1: It is possible for an attacker to spoof a PLMN id and therefore force the UE to use GSM AKA. This could be mitigated by the UE displaying the country name to the user. Displaying the country name is typically not done by today’s UEs and would have to be added as a new UE function. It should be further noted that the network name displayed to the user could be spoofed by an attacker as the displayed network name may not be based on MCC, MNC received via cell broadcast, but on additional signalling. NOTE 2: A similar mechanism to enforce the use of particular encryption algorithm(s) in a given network is described in clause 4.9 in TS 43.020[ Security related network functions ] . Editor's note: It is FFS whether disabling GSM AKA on a per network basis successfully achieves the intention of mitigating attacks by false basestations. A ME that not capable of UMTS AKA with a USIM active can only participate in GSM AKA. The execution of UMTS AKA results in the establishment of a UMTS security context; the UMTS cipher/integrity keys CK and IK and the key set identifier KSI are passed to the ME. If the USIM supports conversion function c3 and/or GSM AKA, the ME shall also receive a 64-bit GSM cipher key Kc derived at the USIM. If the ME supports 128-bit ciphering algorithms A5 and/or GEA for GSM, the ME shall also support the key derivation function for Kc128 as specified in annex B.5.The execution of GSM AKA results in the establishment of a GSM security context; the 64-bit GSM cipher key Kc and the cipher key sequence number CKSN are stored in the ME.