Encrypted Text Matching Using Hamming Distance Verification

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Solution Overview

Problem

Existing biometric authentication methods fail to adequately protect encrypted text during matching processes, leading to potential leaks of plaintext information, which can result in security breaches and impersonation risks, especially when the matching process is repeated or handled by malicious administrators.

Innovation Solution

An encrypted text matching system that generates auxiliary data for verifying the matching between encrypted texts using a Hamming distance between plaintexts, with one-way conversion of intermediate data to determine if the distance is within a predetermined value, ensuring secure and concealed authentication without revealing original plaintext information.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If biometric authentication is performed by storing template information in a database for repeated verification, then authentication convenience is improved, but the risk of plaintext information leakage increases when templates are leaked or administrators are malicious

Engineering Contradiction:
Improveauthentication convenienceVSAvoidplaintext information leakage risk
Core Design Contradiction:
Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The authentication system is divided into two independent components: encrypted template storage in the database and auxiliary data storage. The template information is segmented into encrypted form and auxiliary verification data, allowing authentication to proceed without exposing the original plaintext template. This segmentation enables repeated authentication while maintaining security against template leakage.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

Auxiliary data acts as an intermediary element that enables verification of encrypted templates without revealing the plaintext information. The auxiliary data includes hash values and other verification materials that mediate between the encrypted template storage and the authentication process, allowing verification while preventing direct access to sensitive plaintext data.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Reliability

If encryption keys are changed with each matching process to enhance security, then resistance to attacks is improved, but the complexity of the matching process increases

Engineering Contradiction:
Improvesecurity and resistance to attacksVSAvoidmatching process complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

Encryption keys and auxiliary data are prepared in advance during the template enrollment phase. The system pre-computes hash values and auxiliary verification data that will be used in future authentication processes. This preliminary action eliminates the need for complex real-time key generation during matching, reducing computational complexity while maintaining security.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The system changes cryptographic parameters (encryption keys, hash values) between template enrollment and authentication phases. Different parameters are used for template creation versus verification, allowing the system to adapt security parameters to specific operational contexts while maintaining efficient processing through pre-computation.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentEP2991265B1Encrypted text matching system, method and program
Publication Date: 2020.05.27 NEC CORP
  • EP2991265B1 patent drawingFigure 1
  • EP2991265B1 patent drawingFigure 2(A)~2(B)
  • EP2991265B1 patent drawingFigure 3

AI summary

The present invention makes it possible, in encrypted text matching, to avoid leakage of the information in an original plain text and to ensure security. In the present invention, a system is provided with: a means for respectively generating first and second auxiliary data for verifying that a first encrypted text, which is input data that is encrypted and recorded in a storage device, and a second encrypted text, which is input data to be matched that has been encrypted, match using the Hamming distance of the plain texts; and a means for unidirectionally converting at least one portion of the first auxiliary data, unidirectionally converting intermediate data generated on the basis of the second auxiliary data and the difference between the first encrypted text and the second encrypted text, and using the unidrectionally converted first auxiliary data and the results of the unidirectional conversion of the intermediate data to determine whether or not the Hamming distance of the plain texts corresponding to the difference between the first encrypted text and the second encrypted text is at or below a predetermined designated value.