Section: J.1 SRVCC from NR to UTRAN J.1.1 General
Content: 5G Single Radio Voice Call Continuity (SRVCC) is specified in 3GPP TS 23.216[ Single Radio Voice Call Continuity (SRVCC); Stage 2 ]  [72], TS 23.501[ System architecture for the 5G System (5GS) ]  [2] and TS 23.502[ Procedures for the 5G System (5GS) ]  [8]. This clause specifies the security aspect to support SRVCC from 5G to UTRAN. SRVCC from UTRAN to 5G shall not be allowed. After a 5G to UTRAN SRVCC session has terminated, a UE shall run a successfully (re)authentication in 5GS before allowed to access 5G. During SRVCC from 5G to UTRAN CS, the MSC server should never know the KAMF nor should the KAMF be revealed to an entity other than an AMF. The AMF derives new key(s) to create a mapped SRVCC security context for the MSC server instead of sending KAMF to the MSC server.