Hardening Deep Neural Networks via Adversarial Model Cascades

Deep neural networks (DNNs) have been shown to be vulnerable to adversarial examples - malicious inputs which are crafted by the adversary to induce the trained model to produce erroneous outputs. This vulnerability has inspired a lot of research on how to secure neural networks against these kinds of attacks. Although existing techniques increase the robustness of the models against white-box attacks, they are ineffective against black-box attacks. To address the challenge of black-box adversarial attacks, we propose Adversarial Model Cascades (AMC); a framework that performs better than existing state-of-the-art defenses, in both black-box and white-box settings and is easy to integrate into existing set-ups. Our approach trains a cascade of models by injecting images crafted from an already defended proxy model, to improve the robustness of the target models against adversarial attacks. AMC provides an increase in robustness of 8.175% & 7.115% for white-box attacks and 30.218% & 4.717% for black-box, in comparison to defensive distillation and adversarial hardening. To the best of our knowledge, ours is the first work that aims to provide a defense mechanism that can improve robustness against multiple adversarial attacks simultaneously.