I am wondering if a biometric device can be used to generate some entropy or key material that would be stable across each authentication.
The contrary would be for biometric devices to act like an oracle, with a simple YES/NO answer to any authentication request.
What I am thinking about would be to gather the results of a biometric authentication and always come up with the same "number", which would be unique for any given biometric input.
For example, Alice biometric ouput would always be 64489c85dc2fe0787b85cd87214b3810, without having that number stored in advance somewhere, like I would generate a key from a password to decrypt something, without having store the password or key anywhere in advance.
I'm not interested (yet) in any standards or API for this, or in implementation details like the fact that all fingers from a same person would have a different (but stable) output. My question relates to the biometric authentication process inside the device.