Spoof Face Detection Via Semi-Supervised Adversarial Training

Face spoofing causes severe security threats in face recognition systems. The previous anti-spoofing mainly focused on supervised techniques, typically with either binary or auxiliary supervision. Most of them have to 'see' both spoofing face data and live face data during training to realize the task of face anti-spoofing. In this paper, we propose a semi-supervised adversarial learning framework for spoof face detection, which largely relaxes the supervision condition. To capture the underlying structure of live face data in latent representation space, we propose to train the live face data only, with a convolutional Encoder-Decoder network acting as a Generator, and a second convolutional network serving as a Discriminator. The generator and discriminator are trained by competing with each other while collaborating to understand the live faces. Since the spoof face detection is video-based (i.e., temporal information), we intuitively take the optical flow maps converted from consecutive video frames as input. Our approach is free of the spoof faces, thus being robust and general to different types of face spoofing (even unknown spoofing). Experiments on cross-dataset tests show that our semi-supervised method achieves better or comparable results to state-of-the-art supervised techniques. We also conduct ablation studies for the proposed method.