Cryptographic Key Stack Segmentation for Reduced Re-Pairing

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Solution Overview

Problem

Industrial field devices face challenges in managing multiple users for secure data connections due to limited storage capacity and the need for frequent re-pairing when cryptographic device keys are deleted, which affects data communication efficiency.

Innovation Solution

A method for managing cryptographic device keys by storing them in a key stack with an immortality status flag, where keys with a positive immortality status are protected from deletion, ensuring secure and efficient data connections without frequent re-pairing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If cryptographic device keys are stored in limited storage capacity of industrial field devices, then secure data connections can be established, but frequent re-pairing occurs when keys are deleted due to storage constraints

Engineering Contradiction:
Improvesecure data connectionVSAvoidre-pairing frequency
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The key stack is segmented into two distinct regions: a first region for storing cryptographic device keys associated with device identifiers, and a second region for storing cryptographic device keys associated with user identifiers. This segmentation allows independent management of device-level and user-level keys, enabling selective preservation of important keys while managing storage efficiently.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The system changes the parameter of key immortality by implementing an immortality status flag for each key in the key stack. Keys can be marked as immortal (protected from deletion) or mortal (subject to deletion when storage is full). This parameter change allows critical keys to be preserved indefinitely while allowing non-critical keys to be rotated, resolving the contradiction between limited storage and maintaining secure connections.

Inventive Principle:
Principle #35Parameter changes

2Adaptability or versatility

If multiple users are supported for data gathering and automation, then device functionality is enhanced, but managing multiple users becomes challenging with limited storage capacity

Engineering Contradiction:
Improvemulti-user supportVSAvoiduser management complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The key stack is segmented into two distinct regions: a first region for storing cryptographic device keys associated with device identifiers, and a second region for storing cryptographic device keys associated with user identifiers. This segmentation allows independent management of device-level and user-level keys, enabling selective preservation of important keys while managing storage efficiently.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The key stack controller is designed to universally manage both device identifier-based keys and user identifier-based keys through a unified interface. The controller can automatically determine which region to access based on the connection context, providing multi-functional key management that supports both device-level and user-level access control without requiring separate management systems.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Data Source

PatentEP3879748B1Immortal cryptographic device keys
Publication Date: 2025.12.31 ABB (SCHWEIZ) AG
  • EP3879748B1 patent drawingFigure 1
  • EP3879748B1 patent drawingFigure 2

AI summary

A method (100) for managing cryptographic device keys is provided. The method (100) includes storing a plurality of cryptographic device keys (220) in a key stack of the industrial field device. The method (100) further includes determining a respective immortality status (230) for each of the cryptographic device keys (220) and selecting one of the cryptographic device keys for being deleted, whereby those of the cryptographic device keys having a positive immortality status (230) are systematically blocked from being deleted.