Authentication System Using Independent Secret String to Prevent Biometric Linkability
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Solution Overview
Problem
Existing user authentication systems face challenges in providing enhanced privacy and security, particularly when using biometric data, as they often leak information that can be exploited in linkability attacks and compromise security and privacy.
Innovation Solution
A computer-implemented authentication method that incorporates a fixed authentication data as a second authentication factor, generating a secret string independently from fuzzy data, deriving metadata and helper data, encrypting the helper data, and decrypting it during the authentication process to validate the secret string, ensuring uncoupling and protection of sensitive information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fuzzy extractors are used to generate cryptographic keys from biometrics, then key generation is enabled, but information leakage occurs that allows linkability attacks
Solution Approach 1:
A secret string acts as an intermediary between the biometric data and the cryptographic key. The secret string is generated independently using a random number generator and is never derived from or stored with the biometric template. This intermediary prevents direct linkage between biometric samples and cryptographic keys, eliminating linkability attacks while maintaining authentication reliability.
Solution Approach 2:
The invention extracts and separates the secret string generation from the biometric processing pipeline. Instead of deriving keys directly from biometrics through fuzzy extractors, the secret string is extracted as an independent random value that serves as the actual cryptographic key, while biometrics only provide authentication verification capability without exposing key material.
2Ease of operation
If helper data is made public for authentication, then authentication functionality is enabled, but security vulnerabilities arise
Solution Approach 1:
The secret string serves as a mediator that decouples the public helper data from sensitive key material. Helper data can be freely published for authentication convenience, but the actual cryptographic security relies on the independently generated secret string that never appears in public communications or stored templates, maintaining security reliability.
3Reliability
If biometric templates are stored for verification, then authentication verification is enabled, but privacy concerns arise
Solution Approach 1:
The invention extracts the cryptographic key function from the biometric template. The stored template contains only verification data, while the actual key (secret string) is extracted as a separate independent entity during enrollment and never stored. This separation enables verification reliability while protecting biometric privacy, as the template alone cannot reconstruct the key.
Data Source
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AI summary
The present invention relates to an authentication method comprising an enrolment stage comprising: o receiving fuzzy data from a noisy authentication factor, and fixed authentication data, o generating a secret string independently from said received fuzzy data and said received fixed authentication data, o deriving metadata from the fuzzy data and the secret string and helper data from the secret string and the metadata, o encrypting the helper data using the fixed authentication data as encryption key, o outputting the encrypted helper data as public data, and an authentication stage comprising o receiving the public data output during the enrolment stage, further fuzzy data and said fixed authentication data, o decrypting the received public data using the fixed authentication data as decryption key, o recovering the helper data and the metadata from the decrypted public data, o reproducing the secret string using the further fuzzy data and the recovered metadata, o validating the reproduced secret string using the recovered helper data, o releasing the reproduced secret string if the validating yields a positive outcome.