Conditional PSCell Security-Key Handling Without RRC Signaling
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Solution Overview
Problem
Existing wireless communication systems require reconfiguration of security keys for each primary-secondary-cell (PSCell) change in the connected state of a UE using level-3 signaling, which can lead to security risks or failures when reusing stale keys upon returning to previously connected PSCells.
Innovation Solution
Implementing a mechanism where the UE derives and updates security keys using a KSN-Counter and KSN-Offset, allowing for unique key generation upon reconnecting to the same PSCell without requiring immediate reconfiguration through RRC signaling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If security keys are reconfigured for each PSCell change using RRC signaling, then security integrity is maintained, but signaling overhead and reconfiguration frequency increase
Solution Approach 1:
The network pre-configures multiple security keys (KSN) corresponding to different PSCells before the UE actually connects to those cells. When the UE returns to a previously connected PSCell, it can use the pre-configured key without requiring reconfiguration signaling, thus maintaining security while reducing signaling overhead.
Solution Approach 2:
Instead of reconfiguring the same security key each time, the system creates multiple copies of security keys (KSN1, KSN2, etc.) corresponding to different PSCells. The UE stores these key copies and selects the appropriate one based on the current PSCell, eliminating the need for repeated RRC reconfiguration signaling.
2Reliability
If security keys are updated for each PSCell change, then security risks are mitigated, but device complexity and signaling requirements increase
Solution Approach 1:
The security key management is segmented by dividing the network into multiple PSCells, each with its own dedicated security key (KSN). The UE maintains a mapping between PSCells and their corresponding keys, allowing it to select the appropriate key based on the current cell without managing a single complex key update mechanism.
Solution Approach 2:
The network introduces an intermediary mechanism (KSN-Counter and key derivation function) that automatically generates and manages multiple security keys. This intermediary handles the complexity of key management, while the UE simply follows straightforward procedures of selecting and using the appropriate pre-configured key.
3Reliability
If RRC signaling is used for each PSCell reconfiguration, then security keys are properly updated, but communication overhead and latency increase
Solution Approach 1:
The network performs preliminary configuration of multiple security keys corresponding to different PSCells before the UE actually needs to connect to those cells. This advance preparation eliminates the need for time-consuming RRC reconfiguration signaling when the UE returns to previously connected cells, thus improving reconfiguration efficiency while maintaining key update accuracy.
Data Source
AI summary
A user equipment (UE) includes a transceiver and a processor, which is configured to connect the UE, via the transceiver, with a plurality of radio access network (RAN) nodes including at least a master node for the UE, and at least a first secondary node and a second secondary node for the UE. The processor is configured to receive, from the master node, secondary cell group (SCG) configuration information including a respective security configuration structure for each secondary node of the at least two secondary nodes. After satisfying a conditional primary secondary cell (PSCell) change condition associated with connecting to a first secondary node, the processor is configured to derive a secondary node security key (KSN) corresponding to the first secondary node using a first security configuration structure associated with the first secondary node, and update and communicate a second security configuration structure associated with a second secondary node.