FARMUR: Fair Adversarial Retraining to Mitigate Unfairness in Robustness

Deep Neural Networks (DNNs) have been deployed in safetycritical real-world applications, including automated decision-making systems. There are often concerns about two aspects of these systems: the fairness of the predictions and their robustness against adversarial attacks. In recent years, extensive studies have been devoted to addressing these issues independently through adversarial training and unfairness mitigation techniques. To consider fairness and robustness simultaneously, the robustness bias concept is introduced, which means an attacker can more easily target a particular sub-partition in the dataset. However, there is no unified and mathematical definition for measuring fairness in the robustness of DNNs independent of the type of adversarial attacks. In this paper, we first provide a unified, precise, and mathematical theory and measurement for fairness in robustness independent of adversarial attacks for a DNN model. Finally, we proposed a fair adversarial retraining method (FARMUR) to mitigate unfairness in robustness that retrains the DNN models based on vulnerable and robust sub-partitions. In particular, FARMUR leverages different objective functions for vulnerable and robust sub-partitions to retrain the DNN. Experimental results demonstrate the effectiveness of FARMUR in mitigating the unfairness in robustness during adversarial training without significantly degrading robustness. FARMUR improves fairness in robustness by 19.18% with only 2.22% reduction in robustness in comparison with adversarial training on the UTKFace dataset, which is partitioned based on race attributes.