Biometrically-independent fuzzy signatures: signing with biometrics without embedding them

In cryptocurrency transactions, effective wallet key management by users is crucial for asset protection. Fuzzy Signature (FS) schemes enhance the binding between signers and their keys by using biometric information instead of traditional signing keys, offering secure and convenient key management. However, FS faces two significant privacy concerns. First, using biometric information as the signing key restricts users’ ability to manage multiple distinct keys for different applications. Second, the design that absorbs biometric fuzziness during verification results in publicly available verification keys that contain data dependent on biometric information. This paper introduces Biometrically-Independent Fuzzy Signature (BIFS), a variant addressing existing FS scheme problems. We propose a generic construction for BIFS and present a BIFS scheme compatible with BLS signatures supported by Ethereum 2.0. Experimental results confirm that the success rate of signature generation maintains the same authentication accuracy as the employed facial recognition system. Moreover, our results show that the proposed scheme is practical since the signature generation process requires approximately 2 ms.