It would be better that before going to E-UTRAN just scroll through the 3G authentication procedure. E-UTRAN authentication also checks that the PLMN in which UE is roaming is authenticated or not. Here one key KASME is generated that takes visited PLMN Id, CK, IK as an input that are generated in the same way they are generated in 3G Authentication. Rest all is same as 3G authentication.
|4G Authentication Procedure|
KASME = HMAC-SHA-256(Key,S)where,
S = FC||P0||L0||P1||L1||P2||L2||P3||L3||... ||Pn||Ln
FC is single octet. Its value is defined by 3GPP.
All Px are inputs and Lx is the length of the inputs
Key = CK || IK
FC = 0x10,
P0 = SN id,
L0 = length of SN id (i.e.0x00 0x03),
P1 = SQN Å AK
L1 = length of SQN Å AK (i.e. 0x00 0x06)
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