  Market research indicates that fingerprints are still the most popular
biometric modality for personal authentication. Even with the onset of new
modalities (e.g. vein matching), many applications within different domains
(e-ID, banking, border control...) and geographies rely on fingerprints
obtained from the distal phalanges (a.k.a. sections, digits) of the human hand
structure. Motivated by the problem of poor quality distal fingerprint images
affecting a non-trivial portion of the population (which decreases associated
authentication accuracy), we designed and tested a multifinger, multiphalanx
fusion scheme, that combines minutiae matching scores originating from
non-distal (ie. middle and proximal) phalanges based on (i) simple sum fusion,
(ii) NFIQ image-quality-based fusion, and (iii) phalanx-type-based fusion.
Utilizing a medium-size (50 individuals, 400 unique fingers, 1600 distinct
images) database collected in our laboratory with a commercial optical
fingerprint sensor, and a commercial minutiae extractor & matcher (without any
modification), allowed us to simulate a real-world fingerprint authentication
setting. Detailed analyses including ROC curves with statistical confidence
intervals show that the proposed system can be a viable alternative for cases
where (i) distal phalanx images are not usable (e.g. due to missing digits, or
low quality finger surface due to manual labor), and (ii) switching to a new
biometric modality (e.g. iris) is not possible due to economical or
infrastructure limits. Further, we show that when distal phalanx images are in
fact usable, combining them with images from other phalanges increases accuracy
as well.
