Client-Server Biometric Collation via Challenge-Response Concealment

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Solution Overview

Problem

In client-server systems, there is a risk of biometric information leakage when templates are stored on clients, and existing solutions do not adequately protect secret information such as passwords or secret keys, especially when concealed information is stored on the client side.

Innovation Solution

A challenge-response method is employed where the client generates a random number and conceals registered information using a secret key, computing a response to a challenge from the server that includes a concealed index indicating closeness between registered and authentication information, while the server uses a public key and the random number to verify the response, preventing leakage of biometric or secret information.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If biometric templates are stored on the client side for fast authentication, then authentication speed is improved, but the risk of biometric information leakage increases

Engineering Contradiction:

Improveauthentication speedVSAvoidbiometric information leakage risk

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The authentication system is segmented into client-side components (authentication information, random number generator, response generator) and server-side components (challenge generator, verification unit). The client stores only authentication information and generates random numbers locally, while the server manages challenges and verification. This segmentation allows fast local processing while distributing security responsibilities to prevent information leakage.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The client pre-generates and stores random numbers and authentication information before authentication is needed. During authentication, the client quickly generates a response by combining the pre-stored authentication information with a newly generated random number and the server's challenge, without needing to retrieve or process large biometric templates during the actual authentication event.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If concealed information is stored on the client to protect secret keys and passwords, then security against client compromise is improved, but the complexity of secure processing increases

Engineering Contradiction:

Improvesecurity against client compromiseVSAvoidsecure processing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The server acts as an intermediary that receives the client's response, generates the challenge, and performs verification. The client never directly handles or transmits concealed information such as secret keys or passwords. Instead, the client generates a response based on authentication information and random numbers, and the server verifies this response against the challenge. This intermediary approach protects concealed information while maintaining manageable processing complexity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system replaces direct handling of concealed information with cryptographic operations. Instead of mechanically storing and processing secret keys and passwords on the client, the system uses mathematical operations (generating random numbers, creating responses based on challenges, verifying cryptographic proofs) to achieve the same security goals with reduced risk and manageable complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Object-affected harmful factors

If encrypted biometric information is stored in the client, then protection against unauthorized access is improved, but the vulnerability to decryption attacks increases

Engineering Contradiction:

Improveunauthorized access protectionVSAvoiddecryption attack vulnerability

Core Design Contradiction:

Object-affected harmful factorsVSObject-generated harmful factors

Solution Approach 1:

The system extracts and removes encrypted biometric information from the client environment entirely. Instead of storing decryption keys or encrypted templates on the client that could be targeted by decryption attacks, the client only stores authentication information and random numbers. The actual biometric verification is performed by the server through challenge-response authentication, eliminating the decryption attack vector on the client side.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS12200147B2Collation system, client, and server

Publication Date: 2025.01.14 NEC CORP

AI summary

The client includes a random number generation unit which generates a random number, a concealed information storage unit which stores concealed information generated by concealing registered information and the generated random number using a secret key, and a response computation unit which, on the basis of a challenge transmitted from the server, the collation information input for collation with the registered information, and the concealed information, computes a response corresponding to the challenge and including a concealed index, generated by concealing an index indicating closeness between the registered information and the collation information. The server includes a challenge generation unit which generates the challenge using a public key corresponding to the secret key, and a determination unit which uses the public key and the random number transmitted from the client to determine whether or not the response transmitted from the client corresponds to the challenge.