Handover Target Base Station Key Generation
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Solution Overview
Problem
Conventional mobile communication systems require complex procedures for generating and updating keys during handovers, involving multiple parameters and functions across different radio base stations, which complicates the process and restricts flexibility in C-RNTI allocation.
Innovation Solution
A simplified mobile communication method where the first key used in a handover target radio base station is generated without an intermediate key, using a master key and sequence numbers from the NAS protocol, allowing for streamlined key generation and update processes across different handover types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If intermediate keys and multiple parameters are used for key generation during handover, then security is improved, but device complexity and procedure complexity increase
Solution Approach 1:
The patent extracts and eliminates the intermediate key from the key generation process. Instead of using an intermediate key generated by the source base station, the target base station directly generates the necessary keys using its own identifier (target PCI) and the master key, thereby simplifying the procedure while maintaining security.
Solution Approach 2:
The patent makes the target base station self-sufficient in key generation by enabling it to directly generate keys using universal inputs (master key and target PCI) without requiring source base station-specific intermediate keys. This multi-functional capability allows the target base station to perform both key reception and key generation functions.
2Reliability
If keys are updated according to PCI and C-RNTI of handover target, then forward security is improved, but ease of operation deteriorates due to restrictive allocation
Solution Approach 1:
The patent segments the key generation process into two independent components: the target PCI (which ensures forward security) and the C-RNTI (which provides flexibility). By separating these functions, the system can update keys based on target PCI without being constrained by C-RNTI allocation requirements, allowing flexible C-RNTI assignment while maintaining security.
3Reliability
If multiple KDF functions are used by source and target base stations, then key security is improved, but manufacturing precision and ease of manufacture worsen due to complexity
Solution Approach 1:
The patent merges the key generation functions into a single unified process at the target base station. Instead of having separate KDF functions at the source base station (for intermediate key generation) and target base station (for final key generation), the system uses a single key generation process at the target using its PCI and the master key, simplifying implementation while maintaining cryptographic security.
Data Source
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AI summary
The present invention relates to a mobile communication method in which a mobile station performs a handover from a handover source radio base station to a handover target radio base station. The mobile communication method includes the steps of: (A) acquiring, at the handover target radio base station, from the handover source radio base station or a switching center, a key for calculating a first key for generating a certain key used in a communication between the handover target radio base station and the mobile station; and (B) acquiring, at the handover target radio base station, from the switching center, a second key for calculating a first key for generating a certain key used in a communication between a next handover target radio base station and the mobile station.