“…However, most of existing face recognition systems are easily to be spoofed through presentation attacks (PAs) ranging from printing a face on paper (print attack) to replaying a face on a digital device (replay attack) or bringing a 3D-mask (3D-mask attack). Therefore, not only the research community but also the industry has recognized face anti-spoofing [18,19,4,33,39,11,23,55,1,29,12,49,45,54,21] as a critical role in securing the face recognition system. In the past few years, both traditional methods [14,42,9] and CNN-based methods [35,38,20,24,46] have shown effectiveness in discriminating between the living and spoofing face.…”