  The widespread usage of machine learning (ML) in a myriad of domains has
raised questions about its trustworthiness in security-critical environments.
Part of the quest for trustworthy ML is robustness evaluation of ML models to
test-time adversarial examples. Inline with the trustworthy ML goal, a useful
input to potentially aid robustness evaluation is feature-based explanations of
model predictions. In this paper, we present a novel approach called EG-Booster
that leverages techniques from explainable ML to guide adversarial example
crafting for improved robustness evaluation of ML models before deploying them
in security-critical settings. The key insight in EG-Booster is the use of
feature-based explanations of model predictions to guide adversarial example
crafting by adding consequential perturbations likely to result in model
evasion and avoiding non-consequential ones unlikely to contribute to evasion.
EG-Booster is agnostic to model architecture, threat model, and supports
diverse distance metrics used previously in the literature. We evaluate
EG-Booster using image classification benchmark datasets, MNIST and CIFAR10.
Our findings suggest that EG-Booster significantly improves evasion rate of
state-of-the-art attacks while performing less number of perturbations. Through
extensive experiments that covers four white-box and three black-box attacks,
we demonstrate the effectiveness of EG-Booster against two undefended neural
networks trained on MNIST and CIFAR10, and another adversarially-trained ResNet
model trained on CIFAR10. Furthermore, we introduce a stability assessment
metric and evaluate the reliability of our explanation-based approach by
observing the similarity between the model's classification outputs across
multiple runs of EG-Booster.
