Digital Signature Management via Milestone Hash Chain Segmentation

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Solution Overview

Problem

Existing digital signature management systems face challenges in verifying the authenticity of signature target data when some items of signature target data have been deleted, as this can break the hash chain, making it impossible to verify the authenticity of previous data whose signature has expired.

Innovation Solution

A digital signature management method and system that generates milestone data at predetermined intervals, which includes hash values of previous milestone data and signature record data, allowing for authenticity verification even after deletion of expired signature target data by tracing the hash chain through the milestone data.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If signature target data and signature record data are deleted after expiration to save storage space, then storage space is reduced, but the ability to verify authenticity of previous data is lost

Engineering Contradiction:
Improvestorage spaceVSAvoidauthenticity verification capability
Core Design Contradiction:
Quantity of substanceVSReliability

Solution Approach 1:

The patent segments the continuous hash chain into discrete milestone points. Instead of maintaining the entire hash chain in storage, only milestone hash values are preserved. This segmentation allows deletion of intermediate data while maintaining verification capability through the remaining milestone points, thus resolving the contradiction between storage space reduction and authenticity verification capability.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent performs preliminary action by pre-calculating and storing milestone hash values before data deletion occurs. These milestone hash values serve as predetermined verification points that enable future authenticity checks without requiring the original data to be retained, thus allowing storage space reduction while preserving verification capability.

Inventive Principle:
Principle #10Preliminary action

2Reliability

If all signature target data and signature record data are retained to maintain authenticity verification capability, then authenticity verification is always possible, but storage space increases significantly

Engineering Contradiction:
Improveauthenticity verification capabilityVSAvoidstorage space
Core Design Contradiction:
ReliabilityVSQuantity of substance

Solution Approach 1:

The patent extracts only the essential milestone hash values from the complete hash chain and stores them separately. This extraction allows the system to discard the bulk of intermediate signature data while retaining the critical verification information needed for authenticity checks, thus significantly reducing storage space while maintaining verification capability.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The patent creates a simplified copy of the hash chain information in the form of milestone hash values. Instead of storing the entire complex hash chain structure, only the essential milestone points are copied and retained, enabling verification with minimal storage requirements while preserving the core authenticity verification function.

Inventive Principle:
Principle #26Copying

Data Source

PatentEP3901801B1Digital signature management method and digital signature management system
Publication Date: 2022.09.14 HITACHI LTD
  • EP3901801B1 patent drawingFigure 1
  • EP3901801B1 patent drawingFigure 2
  • EP3901801B1 patent drawingFigure 3

AI summary

A digital signature management method includes generating items of signature record data for items of signature target data inputted in chronological order; and generating an item of milestone data as a new item of signature target data every time the number of items of signature target data inputted reaches a predetermined value. Each item of signature record data includes a hash value of a corresponding item of signature target data, a hash value of an item of signature target data inputted immediately previously, and a signature for the hash value of the corresponding item of signature target data and the hash value of the item of signature target data inputted immediately previously. Each item of milestone data includes a hash value of at least one item of milestone data generated earlier, and hash values of items of signature record data corresponding to all items of signature target data inputted after generation of an immediately previous item of milestone data.