8. The method of claim 1 wherein: the method further comprises, prior to receiving the authentication request, engaging in an enrollment process for the user, the enrollment process including: displaying a plurality of test face images to the user; for each test face image of the plurality of test face images, receiving, from the user, a facial expression score for a particular emotion; and deriving a set of user-specific recognition properties based on the facial expression scores received in response to displaying the plurality of test face images to the user; and generating the set of one or more face images, each face image of the set of face images having the facial expression score for the particular emotion associated with that face image, the facial expression scores being specific to the user, includes referencing the derived set of user-specific recognition properties.
8. The method of claim 1 wherein: the method further comprises, prior to receiving the authentication request, engaging in an enrollment process for the user, the enrollment process including: displaying a plurality of test face images to the user; for each test face image of the plurality of test face images, receiving, from the user, a facial expression score for a particular emotion; and deriving a set of user-specific recognition properties based on the facial expression scores received in response to displaying the plurality of test face images to the user; and generating the set of one or more face images, each face image of the set of face images having the facial expression score for the particular emotion associated with that face image, the facial expression scores being specific to the user, includes referencing the derived set of user-specific recognition properties. 10. The method of claim 8 wherein the method further comprises modifying the set of user-specific recognition properties based on user feedback from continued use of the user-specific recognition properties for authentication purposes.