NAS Key Update Across Dual Access Without Communication Disruption
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Solution Overview
Problem
In a 5G system where a terminal accesses an AMF node using both 3GPP and non-3GPP access technologies, updating a NAS key during re-authentication on one technology affects normal communication via the other technology.
Innovation Solution
A method where the core network device performs re-authentication on a first connection and updates keys for both connections when specific trigger conditions are met, ensuring normal communication on the second connection is not affected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the core network device updates the NAS key during re-authentication on one access technology, then security is improved, but normal communication on the other access technology is affected
Solution Approach 1:
The patent segments the key management by maintaining separate state machines for 3GPP and non-3GPP access technologies. Each access technology has its own CM state machine that tracks connection state independently, allowing re-authentication on one access without affecting the other. The core network device can update NAS keys for one access technology while the other continues normal communication using its current key.
Solution Approach 2:
The patent introduces a key update indicator as an intermediary mechanism. When re-authentication is performed on one access technology, the core network device sets a key update indicator. The terminal then checks this indicator before communicating on the other access technology and updates its key accordingly, ensuring both accesses use consistent keys without interrupting communication.
2Device complexity
If the terminal and AMF node share a set of NAS keys for both access technologies, then device complexity is reduced, but key update on one technology affects the other technology
Solution Approach 1:
The patent introduces dynamic key management where the terminal and core network device can switch between shared key mode and separate key mode. The key update indicator enables dynamic transitions: when set, it triggers key updates to ensure both accesses use consistent keys; when cleared, normal shared key operation resumes. This dynamic approach maintains security while managing complexity.
Solution Approach 2:
The patent changes the state parameter of the key management system by introducing a key update indicator that can be set or cleared. This parameter change triggers different behaviors: when set, it initiates key update procedures; when cleared, it allows normal communication. This parameter-based control enables flexible key management without requiring permanently separate key storage.
Data Source
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AI summary
Embodiments of this application provide a key update method, relate to the field of communications technologies, and can resolve a problem that an update of a NAS key in a process in which an AMF node performs re-authentication on a terminal by using one access technology affects normal communication that is performed between the terminal and the AMF node by using another access technology. In the method, a communications system includes a terminal and a core network device, the terminal accesses the core network device by using both a first access technology and a second access technology simultaneously, and the method includes: performing, by the core network device, re-authentication on the terminal through a first connection corresponding to the first access technology; and if a trigger condition is met, updating, by the core network device, a key for a second connection corresponding to the second access technology.