Fingerprint recognition needs to steps:
- Fingerprint registration
- Fingerprint authentication
During fingerprint registration, the fingerprint image(s) are converted into what is called Fingerprints Minutiae Data (FMD). FMD is saved into the database, not the fingerprint image itself.
During fingerprint authentication, fingerprint image is converted into FMD. Aftewards, the registered FMD and the recently obtained FMD are compared. If they match, it is considered that user has been successfully authenticated.
If FMD is exposed, a fingerprint image can be obtained. This image will not probably match the original fingerprints, but it may be used to impersonate the owner.