  We address the fundamental performance issues of template protection (TP) for
iris verification. We base our work on the popular Bloom-Filter templates
protection & address the key challenges like sub-optimal performance and low
unlinkability. Specifically, we focus on cases where Bloom-filter templates
results in non-ideal performance due to presence of large degradations within
iris images. Iris recognition is challenged with number of occluding factors
such as presence of eye-lashes within captured image, occlusion due to eyelids,
low quality iris images due to motion blur. All of such degrading factors
result in obtaining non-reliable iris codes & thereby provide non-ideal
biometric performance. These factors directly impact the protected templates
derived from iris images when classical Bloom-filters are employed. To this
end, we propose and extend our earlier ideas of Morton-filters for obtaining
better and reliable templates for iris. Morton filter based TP for iris codes
is based on leveraging the intra and inter-class distribution by exploiting
low-rank iris codes to derive the stable bits across iris images for a
particular subject and also analyzing the discriminable bits across various
subjects. Such low-rank non-noisy iris codes enables realizing the template
protection in a superior way which not only can be used in constrained setting,
but also in relaxed iris imaging. We further extend the work to analyze the
applicability to VIS iris images by employing a large scale public iris image
database - UBIRIS(v1 & v2), captured in a unconstrained setting. Through a set
of experiments, we demonstrate the applicability of proposed approach and vet
the strengths and weakness. Yet another contribution of this work stems in
assessing the security of the proposed approach where factors of Unlinkability
is studied to indicate the antagonistic nature to relaxed iris imaging
scenarios.
