Multi-Modal Face Anti-Spoofing via Cross-Modal Feature Transitions

TL;DR

This paper introduces a Cross-modal Transition-guided Network (CTNet) for multi-modal face anti-spoofing, leveraging consistent and inconsistent feature transitions across modalities to improve detection robustness and handle missing data.

Contribution

The paper proposes a novel CTNet that models cross-modal feature transitions for live and spoof faces, enhancing generalization and out-of-distribution detection in multi-modal FAS.

Findings

Outperforms previous multi-modal FAS methods on most protocols.

Effectively detects OOD attacks using feature transition insights.

Addresses missing modality issues with auxiliary IR and depth features.

Abstract

Multi-modal face anti-spoofing (FAS) aims to detect genuine human presence by extracting discriminative liveness cues from multiple modalities, such as RGB, infrared (IR), and depth images, to enhance the robustness of biometric authentication systems. However, because data from different modalities are typically captured by various camera sensors and under diverse environmental conditions, multi-modal FAS often exhibits significantly greater distribution discrepancies across training and testing domains compared to single-modal FAS. Furthermore, during the inference stage, multi-modal FAS confronts even greater challenges when one or more modalities are unavailable or inaccessible. In this paper, we propose a novel Cross-modal Transition-guided Network (CTNet) to tackle the challenges in the multi-modal FAS task. Our motivation stems from that, within a single modality, the visual differences between live faces are typically much smaller than those of spoof faces. Additionally, feature transitions across modalities are more consistent for the live class compared to those between live and spoof classes. Upon this insight, we first propose learning consistent cross-modal feature transitions among live samples to construct a generalized feature space. Next, we introduce learning the inconsistent cross-modal feature transitions between live and spoof samples to effectively detect out-of-distribution (OOD) attacks during inference. To further address the issue of missing modalities, we propose learning complementary infrared (IR) and depth features from the RGB modality as auxiliary modalities. Extensive experiments demonstrate that the proposed CTNet outperforms previous two-class multi-modal FAS methods across most protocols.