  Biometric systems are vulnerable to Presentation Attacks (PA) performed using
various Presentation Attack Instruments (PAIs). Even though there are numerous
Presentation Attack Detection (PAD) techniques based on both deep learning and
hand-crafted features, the generalization of PAD for unknown PAI is still a
challenging problem. In this work, we empirically prove that the initialization
of the PAD model is a crucial factor for the generalization, which is rarely
discussed in the community. Based on such observation, we proposed a
self-supervised learning-based method, denoted as DF-DM. Specifically, DF-DM is
based on a global-local view coupled with De-Folding and De-Mixing to derive
the task-specific representation for PAD. During De-Folding, the proposed
technique will learn region-specific features to represent samples in a local
pattern by explicitly minimizing generative loss. While De-Mixing drives
detectors to obtain the instance-specific features with global information for
more comprehensive representation by minimizing interpolation-based
consistency. Extensive experimental results show that the proposed method can
achieve significant improvements in terms of both face and fingerprint PAD in
more complicated and hybrid datasets when compared with state-of-the-art
methods. When training in CASIA-FASD and Idiap Replay-Attack, the proposed
method can achieve an 18.60% Equal Error Rate (EER) in OULU-NPU and MSU-MFSD,
exceeding baseline performance by 9.54%. The source code of the proposed
technique is available at https://github.com/kongzhecn/dfdm.
