Patent ID: 11917055
Assignee: TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)
Field: Digital communication (Electrical engineering)
Classification: CPC H | IPC H

Claim 2:
3. A method comprising:
establishing, in a User Equipment (UE), a security key for protecting Radio Resource Control/User Plane traffic exchanged with a serving radio base station, wherein establishing the security key comprises:
Sending a Non access Stratum (NAS) message containing a NAS service request to a mobility management entity (MME), the NAS message indicating a NAS uplink sequence number;
Deriving the security key from at least said indicated NAS uplink sequence number and from a stored access security management entity-key shared with said mobility management entity, using a key derivation function taking the NAS uplink sequence number and the stored access security management entity-key as inputs.