Great papers linked from that. At the time, it seemed the sensor APIs didn't provide a key with sufficient entropy to be considered a cryptographic verification

Great papers linked from that. At the time, it seemed the sensor APIs didn't provide a key with sufficient entropy to be considered a cryptographic verification for the tokens we were using. We didn't take it further because the entropy of the biometric sample was going to be diminished by using it to generate a static key, even though the papers linked show you can compose a key with error correcting codes, and intuitively, you could use some kind of probabilistic filter to verify a set of bits in the sample via shamir secret sharing to provide a threshold for a key. It still relies on separate security domains between the biometric sample collection and the cryptographic verifier, and we'd be deep in to the engineering over the differences, but these papers are really useful for getting into the details. One of the early ones was a good intro to it: http://people.csail.mit.edu/madhu/papers/2002/ari-journ.pdf http://people.csail.mit.edu/madhu/papers/2002/ari-journ.pdf