Key Management in Cellular IoT Networks
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Solution Overview
Problem
The Cellular Internet of Things (CloT) networks face challenges in minimizing signalling overhead and maintaining security, particularly due to the risk of key leakage when storing and reusing security keys for suspended RRC connections, which can be exploited by attackers.
Innovation Solution
A method is introduced where a Mobility Management Entity (MME) in the cellular communications network receives messages related to connection suspension or resumption, determines if a key renewal condition is met, and forwards a new Next Hop (NH) and Next Hop Chaining Counter (NCC) pair to the base station, ensuring secure key derivation and minimizing signalling overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If the K eNB is stored in the eNB for prolonged periods to support RRC connection suspension and resumption, then signalling overhead is reduced, but security risk increases due to potential key leakage
Solution Approach 1:
The patent implements dynamic key management where the K eNB is automatically renewed based on time-based conditions or usage counters. The MME determines whether key renewal is needed by evaluating time elapsed since last renewal or the number of times the suspended context has been used, making the key lifecycle dynamic rather than static.
Solution Approach 2:
The system employs feedback mechanisms where the eNB reports usage information (such as number of suspensions/resumptions) to the MME, which then decides whether to trigger key renewal. This feedback loop allows the network to monitor key usage and renew keys appropriately based on actual conditions.
2Reliability
If key renewal is performed frequently to enhance security, then security risk is reduced, but signalling overhead increases
Solution Approach 1:
The patent changes the parameter of key renewal from a fixed periodic schedule to a conditional trigger based on usage counters or time thresholds. The MME evaluates whether renewal conditions are met before initiating key renewal, allowing optimization between security and signalling overhead based on actual usage patterns.
Solution Approach 2:
Instead of renewing keys at every suspension/resumption cycle, the system performs key renewal only when necessary conditions are met (time-based or counter-based thresholds). This partial action approach maintains security while avoiding excessive signalling overhead from unnecessary key renewals.
Data Source
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AI summary
A basestation in a cellular communications network is operable to send a message to a Mobility Management Entity, relating to a suspension or resumption of a connection of a UE, wherein the message contains key renewal information. The Mobility Management Entity receives the message, and determines whether a key renewal condition is met. If the key renewal condition is met, the MME forwards a new NH, NCC pair to the base station. If a message received from the MME includes a NH, NCC pair, the basestation derives keying information using the NH, NCC pair for future use in deriving keys.