Secure Key Management Device for Root-Key Isolation

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Solution Overview

Problem

Existing wide area networks, such as LoRaWAN, lack secure methods for initializing and managing root keys and session keys, leading to potential cyber vulnerabilities.

Innovation Solution

Introduce a secure key management device (SKMD) with a secure storage component, interface, and processing unit to generate and manage master, root, and session keys on-the-fly, ensuring these critical data elements remain within a centralized, secure environment, preventing exposure to intermediate network components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If root keys and session keys are stored in intermediate network components (e.g., join server), then key distribution and authentication become simpler, but network security deteriorates due to potential key exposure and compromise

Engineering Contradiction:
Improvekey distributionVSAvoidnetwork security
Core Design Contradiction:
Ease of operationVSReliability

Solution Approach 1:

The patent extracts the root key storage function from intermediate network components and places it in a dedicated secure key management device. The join server no longer stores root keys but instead receives session keys on-demand from the secure device, eliminating the security vulnerability while maintaining authentication functionality.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces a secure key management device as an intermediary between the key provisioning authority and the network. This mediator generates session keys on-demand using stored root keys and distributes them to the join server, preventing direct exposure of root keys while enabling key distribution.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Reliability

If master keys are stored in centralized secure storage, then key compromise risk is reduced, but key management complexity increases

Engineering Contradiction:
Improvekey compromise riskVSAvoidkey management complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The secure key management device performs self-service by automatically generating session keys on-demand using the stored master key and device-specific identifiers. The system autonomously manages key lifecycle without requiring manual intervention, reducing operational complexity despite the centralized security architecture.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The master key is pre-loaded into the secure storage device during manufacturing or initialization, before deployment. This preliminary action ensures the key is securely in place before the system operates, simplifying ongoing key management while maintaining high security.

Inventive Principle:
Principle #10Preliminary action

3Reliability

If session keys are generated on-the-fly from master key, then security is enhanced by avoiding key storage in network components, but processing time increases

Engineering Contradiction:
ImprovesecurityVSAvoidsession key generation time
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

Root keys are pre-generated from the master key during device initialization or key provisioning, and stored in the secure key management device. When session keys are needed, the system uses these pre-computed root keys along with session-specific parameters to rapidly generate session keys, reducing the processing time compared to generating everything from the master key each time.

Inventive Principle:
Principle #10Preliminary action

Data Source

PatentEP4057588B1Secure key management device, authentication system, wide area network and method for generating session keys
Publication Date: 2025.10.08 HITACHI ENERGY LTD
  • EP4057588B1 patent drawingFigure 1
  • EP4057588B1 patent drawingFigure 2
  • EP4057588B1 patent drawingFigure 3~4

AI summary

The present disclosure relates to a secure key management device (SKMD) for a wide area network comprising an end-device (ED), a network server (NS), an application server (AS), and a join server (JS). The secure key management device (SKMD) comprises a secure storage component (SSC) for storage of secret key information, a secure interface (I/F) for securely exchanging data with the join server (JS); and at least one processing component. The at least one processing component is configured to generate and store at least one master key (Ka) in the secure storage component (SSC); generate, based on the at least one master key (Ka) and a unique identifier (S/N) of the end-device (ED), at least one root key (RKey), and provide the at least one generated root key (RKey) to the end-device (ED); receive, from the join server (JS) via the secure interface (I/F), a first request comprising the unique identifier (S/N) of the end-device (ED) and session information (SID); generate, based on the at least one master key (Ka) stored in the secure storage component (SSC), and the unique identifier (S/N) of the end-device (ED) and the session information (SID) comprised in the first request, at least one session key (SKey); and provide the at least one session key (SKey) via the secure interface (I/F) to the join server (JS).