“…Among past biometrics-oriented challenges, events focusing on fingerprints [31], [32], [33] and facial images [3], [22], [41], [44] have likely been the most visible. Recent years have seen challenges and competitions on other modalities and biometric sub-problems ranging from iris [4], speaker [20], [34], sclera [9], finger-vein [52], [55], or keystroke dynamics [36] recognition to spoof detection [5], [7], [49], liveness detection [19], [35], [53], segmentation [9], [10] and others.…”