Patent ID: 11963000
Assignee: TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)
Field: Digital communication (Electrical engineering)
Classification: CPC H | IPC H

Claim 0:
1. A host computer, comprising:
processing circuitry configured to provide user data; and
a communication interface configured to forward the user data to a cellular network for transmission to a user equipment (UE), wherein the cellular network comprises a key management arrangement configured to perform operations comprising:
deriving a first 4G-master key based on a 5G key, KAMF, available at an Access and Mobility management Function (AMF) constituting a core network node supporting mobility management of a source 5G wireless communication system, and on a 5G-freshness parameter;
forwarding the first 4G-master key to a target mobility managing entity (MME) of a target 4G wireless communication system for enabling deriving a second 4G-master key based on the first 4G-master key and a 4G-freshness parameter; and
forwarding the 5G-freshness parameter to the user equipment for enabling deriving the first 4G-master key based on the 5G key, KAMF, and the 5G-freshness parameter and deriving the second 4G-master key based on the first 4G-master key and the 4G-freshness parameter.