Optimizing Latent Variables in Integrating Transfer and Query Based Attack Framework.

Black-box adversarial attacks can be categorized into transfer-based and query-based attacks. The former usually has poor transfer performance due to the mismatch between the architectures of models, while the query-based attacks require massive queries and high dimensional optimization variables. In order to solve the above problems, we propose a novel attack framework integrating the advantages of transfer- and query-based attacks, where the framework is divided into two phases: training the adversarial generator and executing the black-box attacks. In the first stage, a generator is trained by the adversarial loss function so that it can output adversarial perturbation, where the latent variables are designed as the input of the generator to reduce the dimension of the optimization variables. In the second stage, based on the trained generator, we further employ a particle swarm optimization algorithm to optimize the latent variables so that the generator can output the perturbation that can achieve a successful attack. Extensive experiments are performed on the ImageNet dataset, and the results demonstrate that the proposed framework can obtain better attack performance compared with a number of the state-of-the-art black-box adversarial attack methods. In addition, we show the flexibility of the proposed framework by extending the experiment for few-pixel attacks.