Section: B.4 Derivation of Kc’ from Kc for HSPA to UTRAN/GERAN SRVCC handover
Content: This input string is used for GSM subscribers when there is a need to derive Kc’ from the 64-bit Kc during mapping the security contexts from HSPA to UTRAN/GERAN. The Key is the concatenation of Kc || Kc || Kc || Kc || (which are 64 bits each), and the output Kc’ is the 64 most significant bits of the KDF output. - FC = 0x31 - P0 = NONCE - L0 = length of NONCE (i.e. 0x00 0x10) The Kc’ used in GERAN directly. When the access is over UTRAN, CK’CS||IK’CS shall be further derived from Kc’ using the key conversion functions c4 and c5 defined in this specification.