Section: 6.8.5.1 UMTS security context
Content: A UMTS security context in GSM BSS is only established for UMTS subscribers with a ME that is capable of UMTS AKA under GSM BSS controlled by a R99+ VLR/SGSN. At the network side, two cases are distinguished: a) In case of a handover to a UTRAN controlled by the same MSC/VLR, the UMTS cipher/integrity keys CK and IK from the key set used before the intersystem handover are sent to the target RNC. b) In case of a handover to a UTRAN controlled by another MSC/VLR, the initial MSC/VLR sends the UMTS cipher/integrity keys CK and IK from the key set used before the intersystem handover to the new RNC via the new MSC/VLR that controls the target RNC. The initial MSC/VLR remains the anchor point for throughout the service. The anchor MSC/VLR also derives and sends to the non-anchor MSC/VLR the 64-bit GSM cipher key Kc, if any 64-bit ciphering algorithm is permitted, and/or the 128-bit ciphering key Kc128 if a 128-bit ciphering algorithm is also permitted. The non-anchor MSC/VLR stores all keys. This is done to allow subsequent handovers in a non-anchor R99+ MSC/VLR. At the user side, in either case, the ME applies the UMTS cipher/integrity keys CK and IK from the key set which was used before the intersystem handover.