Wireless Device NAS Message Count Derivation for Handover
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Solution Overview
Problem
Current methods for configuring security keys during handover between wireless networks are not robust enough, leading to potential security vulnerabilities and disruptions in seamless network access.
Innovation Solution
A method is introduced where a wireless device derives a message count by combining local and remote network message counts, specifically using the least significant bits (LSBs) received from the remote network node with the remaining bits from the local count, and modifies them based on a threshold maximum lower difference to ensure accurate security key generation for seamless handover.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current methods for configuring security keys during handover are used, then the process is simple, but the security robustness is insufficient
Solution Approach 1:
The 32-bit message count is segmented into two parts: the upper 24 bits are derived from the local counter, and the lower 8 bits are received from the remote network. This segmentation allows the device to maintain most of the counting functionality locally while only needing to synchronize the lower bits, reducing the complexity of full message count synchronization while improving security robustness.
Solution Approach 2:
The device performs preliminary derivation of the upper bits of the message count using its local counter before receiving the lower bits from the remote network. This preliminary action allows the device to be prepared with the majority of the message count value, reducing the synchronization burden and enabling faster, more secure key configuration during handover.
2Measurement precision
If message count synchronization is performed without handling wrap cases, then the process is simpler, but message count alignment accuracy deteriorates
Solution Approach 1:
The device applies a preliminary adjustment to the local counter to prevent wrap-around issues. By checking if the lower 8 bits of the local counter exceed the received lower 8 bits from the remote network, and subtracting 256 (2^8) when necessary, the device proactively corrects potential misalignment before it affects security key generation, ensuring accurate message count alignment without complex continuous synchronization.
3Measurement precision
If full message count is transmitted during handover, then alignment accuracy is maintained, but network overhead increases
Solution Approach 1:
The invention extracts only the necessary lower 8 bits of the message count for transmission during handover, while the upper 24 bits are derived locally by the device using its existing counter. This extraction approach maintains message count alignment accuracy while significantly reducing network overhead, as only 8 bits need to be transmitted rather than the full 32-bit message count.
Data Source
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AI summary
Techniques for deriving message counts based at least in part on a locally stored message count and at least a portion of a message count received from a remote network node are disclosed. The message counts can relate to downlink (DL) non-access stratum (NAS) counts. In one aspect, a device can receive a number of least significant bits of the DL NAS count in a handover message. The device can derive a DL NAS count by utilizing a remaining portion of most significant bits of a locally stored DL NAS count, and can determine whether to increment or decrement the most significant bits based at least in part on a parameter to handle cases where the least significant bits of the locally stored DL NAS count have wrapped due to overflow and/or underflow.