Remote UE Key Management for Secure 5G Relay Discovery
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Solution Overview
Problem
In 5G systems, there is no defined solution for commercial services to enable a remote UE to discover and communicate with a UE-to-network relay over a PC5 interface, as the remote UE does not know beforehand which UE-to-Network Relay it can find in its vicinity, and there is no established method for retrieving common security keys for discovery and communication.
Innovation Solution
The remote UE and UE-to-network relay discover each other by obtaining the address of key management servers (AFs) in their home PLMN, retrieve discovery keys through AF-1 and AF-2, and use shared algorithms to generate communication keys for PC5 communication, enabling secure discovery and communication over the PC5 interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the remote UE contacts all PKMFs of potential relays to fetch PRUK while still in coverage, then the remote UE can obtain necessary security keys for relay communication, but the complexity of key management increases and time is lost due to contacting multiple PKMFs
Solution Approach 1:
The patent introduces a ProSe Application Function (ProSe AF) as an intermediary between the remote UE and the ProSe Key Management Function (PKMF). The ProSe AF receives key management requests from the remote UE, determines the appropriate relay UE and its associated PKMF, and forwards the request to the correct PKMF. This intermediary approach simplifies the remote UE's key management process by eliminating the need to contact multiple PKMFs directly, while still ensuring reliable security key establishment for the desired relay communication.
2Adaptability or versatility
If the remote UE contacts multiple PKMFs to ensure it can use potential relays, then the adaptability for relay selection is improved, but the time required for key establishment increases
Solution Approach 1:
The patent implements preliminary action by having the ProSe AF determine the appropriate relay UE and its associated PKMF before the remote UE initiates key establishment. The ProSe AF uses stored mapping information (relay UE ID to PKMF identifier) to pre-determine the correct key management path. This preliminary determination eliminates the need for the remote UE to try multiple PKMFs, significantly reducing key establishment time while maintaining adaptability for relay selection through the ProSe AF's intelligent routing.
3Adaptability or versatility
If the remote UE stores multiple PRUKs for different PKMFs, then the versatility for relay communication is improved, but the device complexity and memory requirements increase
Solution Approach 1:
The ProSe AF acts as an intermediary that manages the mapping between relay UEs and their associated PKMFs. Instead of requiring the remote UE to store and manage multiple PRUKs for different PKMFs, the ProSe AF maintains the mapping information centrally and directs the remote UE to the specific PKMF corresponding to the desired relay UE. This approach maintains versatile relay communication capability while significantly reducing device complexity and memory requirements at the remote UE.
Data Source
AI summary
A remote communication device can receive a discovery key; receive a communication key and a key identifier, ID, for the communication key; and discover a relay communication device. Discovering the relay communication device can include receiving an encrypted discovery message from the relay communication device and decrypting the encrypted discovery message using the discovery key. The remote communication device can further transmit a direct communication request to the relay communication device responsive to receiving and decrypting the encrypted discovery message from the relay communication device. The direct communication request can include the key ID for the communication key. The remote communication device can further receive an encrypted direct communication response from the relay communication device. Receiving the encrypted direct communication response can include decrypting the encrypted direct communication response.