Abstract
Blockchains are confronted with challenges to store private files and grant access, especially for biometric-based schemes. We propose BSA, a biometric-based scheme for file storage and access authorization on blockchains. File storing, access request and response are performed on blockchains. Biometrics is the only secret information for storage and authorization, and can be repeatedly used with no privacy leakage. Such a scheme does not require a file owner to store any information locally, so it can be used on resource-constrained devices.