5G Terminal Connection Reestablishment Key Derivation
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Solution Overview
Problem
In 5G communication systems, RRC connection reestablishment fails when a core network key is updated during handover, as the access network key of the terminal differs from that of the selected base station, leading to inconsistencies in key management.
Innovation Solution
A method where the terminal reverts to a source configuration, obtains a new access network key based on an indication message from the selected radio access network device, ensuring key consistency between the terminal, the core network device, and the selected radio access network device, facilitating successful connection reestablishment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the terminal reverts back to a source configuration before performing connection reestablishment, then the connection reestablishment procedure can be initiated, but the access network key of the terminal differs from that of the selected base station, causing connection reestablishment to fail
Solution Approach 1:
The patent changes the key derivation parameters by introducing indication information that specifies whether to use the source core network key or the first core network key for deriving the access network key. This allows the terminal to adapt its key derivation process based on the handover outcome, ensuring key consistency with the selected base station while maintaining the ability to revert to source configuration when needed.
Solution Approach 2:
The patent performs preliminary key derivation preparation by having the terminal derive both a second access network key (based on source core network key) and a third access network key (based on first core network key) before the handover completes. This preliminary action ensures that the terminal has the necessary keys ready to match whichever base station is selected, preventing key inconsistency issues during connection reestablishment.
2Reliability
If the core network device updates the core network key during handover, then security is enhanced, but the terminal and selected base station have different access network keys, leading to reestablishment failure
Solution Approach 1:
The patent implements a feedback mechanism where the core network device sends indication information to the terminal regarding which core network key to use for access network key derivation. This feedback loop ensures that the terminal's key derivation process is synchronized with the core network device's key state, maintaining both security through key updates and operational ease through consistent key synchronization.
Solution Approach 2:
The indication information acts as an intermediary that bridges the core network device and the terminal, conveying the appropriate key derivation instructions. This intermediary mechanism ensures that even when the core network key is updated, the terminal can derive the correct access network key to match the selected base station, resolving the synchronization issue without compromising security.
3Adaptability or versatility
If the terminal derives a new access network key based on an updated core network key, then communication with the target base station is enabled, but connection reestablishment fails when the handover fails due to key inconsistency
Solution Approach 1:
The patent makes the key derivation process dynamic by allowing the terminal to switch between deriving the access network key from the source core network key or the first core network key based on handover success. This dynamic adaptation enables the terminal to maintain communication capability with the target base station when handover succeeds while ensuring connection reestablishment reliability when handover fails, as the indication information guides the appropriate key selection.
Data Source
AI summary
The present disclosure relates to connection reestablishment methods and apparatus. In one example method, when a handover fails, a terminal reverts back to a source configuration, and obtains a selected cell. The terminal sends a connection reestablishment request to a selected radio access network device. The terminal receives a first message from the selected radio access network device, where the first message includes indication information used to indicate to derive an access network key based on a core network key. The terminal obtains a first core network key based on the indication information, and derives a first access network key based on the first core network key. The terminal communicates with the selected radio access network device by using the first access network key.