Unified Key Derivation for LTE Re-establishment
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Solution Overview
Problem
The conventional mobile communication system's key re-establishment procedure is complex, requiring multiple parameters and different key derivation functions for radio base stations and involving cumbersome updates based on Physical Cell ID, which can lead to key mismatches and re-establishment failures.
Innovation Solution
A simplified method for generating the first key used by a radio base station managing a re-establishment target cell, where the key is calculated using a master key and sequence numbers without an intermediate key, allowing for intra-eNB and inter-eNB re-establishment procedures without the need for intermediate key generation, and enabling flexible C-RNTI allocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the conventional re-establishment procedure uses multiple parameters and different key derivation functions for generating the first key, then the security of key generation is improved, but the device complexity and procedure complexity increase significantly
Solution Approach 1:
The patent merges multiple key derivation functions into a single unified key derivation function. Instead of using different KDFs with different parameters at source eNB and target eNB, the invention employs one standardized KDF that both entities use, taking inputs such as previous KeNB, target PCI, and C-RNTI to generate the new KeNB. This consolidation reduces procedural complexity while maintaining security through consistent key derivation across the network.
Solution Approach 2:
The unified key derivation function serves multiple purposes: it generates KeNB for intra-eNB re-establishment, inter-eNB re-establishment, and handover scenarios. The same KDF is universally applied across different radio base stations and re-establishment contexts, eliminating the need for multiple specialized KDFs and reducing overall system complexity while preserving security requirements.
2Reliability
If the key update procedure depends on Physical Cell ID for re-establishment target cell, then the key generation is more secure, but the ease of operation decreases due to key mismatches and re-establishment failures
Solution Approach 1:
The patent implements a feedback mechanism where the target eNB derives the expected KeNB using the unified KDF with the provided C-RNTI and target PCI, then compares this derived key with the actual key used by the UE. This feedback loop ensures key consistency: if keys match, re-establishment succeeds; if not, the system can identify and correct the mismatch. This resolves the key mismatch problem while maintaining PCI-dependent security.
Solution Approach 2:
The invention changes the parameters input to the key derivation function to ensure consistency. Instead of relying solely on PCI which may vary, the system uses a combination of parameters including the previously shared KeNB, target PCI, and C-RNTI. By adjusting these input parameters and ensuring they are consistently provided and processed, the system maintains security while avoiding key mismatches that cause re-establishment failures.
3Adaptability or versatility
If the conventional procedure requires both source eNB and target eNB to have different KDFs with different parameters, then the key generation adapts to specific scenarios, but the ease of manufacture and deployment decreases
Solution Approach 1:
The patent segments the key generation process into distinct input parameters (previous KeNB, target PCI, C-RNTI) that are processed by a unified KDF. This segmentation allows the system to adapt to different scenarios (intra-eNB, inter-eNB, handover) by providing different parameter combinations to the same KDF, rather than requiring different KDFs for each scenario. This reduces deployment complexity while maintaining adaptability.
Data Source
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AI summary
A mobile communication method according to the present invention communicates between a mobile station(UE) and a radio base station (eNB) by using a certain key. The method includes the step of: (A) acquiring, at a radio base station managing a re-establishment target cell for the mobile station (UE), a first key (KeNB [n+1]) for generating a certain key from a switching center (MME) in a procedure for re-establishment of the mobile station (UE), the certain key to be used for communication between the mobile station (UE) and a next re-establishment target cell for the mobile station (UE).