An unalterable bipmetric marker used in locking systems already on the field and people sign up in mass to give the information away in exchange for some crypto token. Why not just ask people for their password lists and be done with it? They say sign up for it and the original scan is deleted, that doesn’t matter though when the hash representation of it is tied to a person. Just wait until this kind of thing becomes standard practice in the maternity wards of hospitals…