An Adversarial Perspective on Accuracy, Robustness, Fairness, and Privacy: Multilateral-Tradeoffs in Trustworthy ML

Model accuracy is the traditional metric employed in machine learning (ML) applications. However, privacy, fairness, and robustness guarantees are crucial as ML algorithms increasingly pervade our lives and play central roles in socially important systems. These four desiderata constitute the pillars of Trustworthy ML (TML) and may mutually inhibit or reinforce each other. It is necessary to understand and clearly delineate the trade-offs among these desiderata in the presence of adversarial attacks. However, threat models for the desiderata are different and the defenses introduced for each leads to further trade-offs in a multilateral adversarial setting (i.e., a setting attacking several pillars simultaneously). The first half of the paper reviews the state of the art in TML research, articulates known multilateral trade-offs, and identifies open problems and challenges in the presence of an adversary that may take advantage of such multilateral trade-offs. The fundamental shortcomings of statistical association-based TML are discussed, to motivate the use of causal methods to achieve TML. The second half of the paper, in turn, advocates the use of causal modeling in TML. Evidence is collected from across the literature that causal ML is well-suited to provide a unified approach to TML. Causal discovery and causal representation learning are introduced as essential stages of causal modeling, and a new threat model for causal ML is introduced to quantify the vulnerabilities introduced through the use of causal methods. The paper concludes with pointers to possible next steps in the development of a causal TML pipeline.