Way back in 2002, I had proposed an Internet Draft "Biometric based Digital Signature scheme". It did not make it to the status of an RFC, but I hope someone somewhere can build on the concept.
Digital Signatures are fast emerging as a viable information security
solution, satiating the objectives of data integrity, entity
authentication, privacy, non-repudiation and certification.
The technique, as it stands today, faces the problem of the
maintenance of the secrecy of the private key. This document provides
a conceptual framework for the establishment of a biometric-based key
In this scheme, the private key is generated each
time a document or record requires to be signed. Such generation is
based upon a combination of biometric traits.