FIBNet: Privacy-Enhancing Approach for Face Biometrics Based on the Information Bottleneck Principle

Deep Neural Networks (DNNs) have been extensively employed for automatic face recognition, enabling the extraction of compact and discriminative representations from facial images. However, these representations typically encode a multitude of information ranging from individual identities to sensitive soft-biometric attributes such as gender, race, or age. This raises concerns regarding the privacy disclosure of soft-biometric as these attributes should be protected. To address this issue, we propose a novel Face Information Bottleneck Network (FIBNet), which is a representation-level privacy-enhancing framework based on the Information Bottleneck (IB) principle. The proposed FIBNet differs significantly from previous representation-level privacy-enhancing techniques in three key aspects. First, it generates a privacy-enhanced face representation, providing novel insights through an information-theoretic privacy framework. Second, we formulate the privacy protection of soft-biometric attributes as an IB optimization problem by striking a tradeoff between preserving a controlled amount of identity information within face representations and suppressing soft-biometric attribute information. Last, the proposed approach protects soft-biometric privacy from adversaries interested in specific sensitive attributes that are unknown to the biometric system designers or users. Detailed experimental results obtained on widely recognized facial recognition datasets demonstrate that the proposed FIBNet significantly outperforms the state-of-the-art methods in terms of both biometric performance for face verification and its soft-biometric attribute suppression efficiency. These notable results verify FIBNet as a novel and effective approach for ensuring representation-level soft-biometric privacy.