Fast Adversarial Robustness Certification of Nearest Prototype Classifiers for Arbitrary Seminorms

Methods for adversarial robustness certification aim to provide an upper bound on the test error of a classifier under adversarial manipulation of its input. Current certification methods are computationally expensive and limited to attacks that optimize the manipulation with respect to a norm. We overcome these limitations by investigating the robustness properties of Nearest Prototype Classifiers (NPCs) like learning vector quantization and large margin nearest neighbor. For this purpose, we study the hypothesis margin. We prove that if NPCs use a dissimilarity measure induced by a seminorm, the hypothesis margin is a tight lower bound on the size of adversarial attacks and can be calculated in constant time—this provides the first adversarial robustness certificate calculable in reasonable time. Finally, we show that each NPC trained by a triplet loss maximizes the hypothesis margin and is therefore optimized for adversarial robustness. In the presented evaluation, we demonstrate that NPCs optimized for adversarial robustness are competitive with state-of-the-art methods and set a new benchmark in certification speed.

Requirements

The package requires Python 3.6 and we recommend to use a virtual environment or Docker image. To install the Python requirements use the following command:

pip install -r requirements.txt

Training

The train.py script is available for training NPCs similar to the ones presented in the paper. To run the training script with the exact same parameters as the models in the paper, the --replicate parameter is available. Otherwise, see the available descriptions for defined arguments to define a model of your choice.

The following set of commands will train the models from the paper (specify the desired output directory by adding the argument --save_dir followed by the output path):

python train.py --model glvq --p_norm inf --dataset mnist --replicate
python train.py --model glvq --p_norm 2 --dataset mnist --replicate
python train.py --model rslvq --dataset mnist --replicate
python train.py --model gtlvq --dataset mnist --replicate

python train.py --model glvq --p_norm inf --dataset cifar10 --replicate
python train.py --model glvq --p_norm 2 --dataset cifar10 --replicate
python train.py --model rslvq --dataset cifar10 --replicate
python train.py --model gtlvq --dataset cifar10 --replicate

python train.py --dataset breast_cancer --replicate
python train.py --dataset diabetes --replicate
python train.py --dataset cod_rna --replicate

Pre-trained Models

If you wish to evaluate the models presented in the paper directly, without retraining them, they can be found in the weight_files folder. The model corresponding weight file is automatically loaded if --weights argument is None (default) and the evaluation flag --eval is set. For example:

python train.py --model glvq --p_norm inf --dataset mnist --replicate --eval
python train.py --dataset diabetes --replicate --eval

Evaluation

To evaluate an NPC two scripts are available. One for evaluating the robustness of a model, and one for evaluating the discussed rejection strategy. The evaluation scripts are designed to be used on newly trained models. For replicating the results of the paper the --replicate parameters is available.

Robustness evaluation

The evaluation_robustness.py reports the CTE, URTE, and LRTE for a given model. The script has a number of parameters for which the default value is dependent on a number of other parameters.

To obtain the results presented in the main part of the paper run the following commands:

python evaluation_robustness.py --save_dir ./output --model glvq --model_norm inf --dataset mnist --replicate
python evaluation_robustness.py --save_dir ./output --model rslvq --dataset mnist --replicate
python evaluation_robustness.py --save_dir ./output --model glvq --model_norm 2 --dataset mnist --replicate
python evaluation_robustness.py --save_dir ./output --model gtlvq --dataset mnist --replicate

python evaluation_robustness.py --save_dir ./output --model glvq --model_norm inf --dataset cifar10 --replicate
python evaluation_robustness.py --save_dir ./output --model rslvq --dataset cifar10 --replicate
python evaluation_robustness.py --save_dir ./output --model glvq --model_norm 2 --dataset cifar10 --replicate
python evaluation_robustness.py --save_dir ./output --model gtlvq --dataset cifar10 --replicate

Note that the certificate (without the empirical robustness evaluation) can be computed by the command presented in the Section Pre-trained Models.

Rejection evaluation

The evaluation_rejection.py script determines the false reject rate of an NPC classifier based on the strategy discussed in the paper. With the --plot parameter set, it also produces a similar plot as presented in the paper.

To obtain the results and plots as presented in the paper, run the following command:

python evaluation_rejection.py --save_dir ./output --replicate

Plots

In Figure 1 of the paper, three plots are presented. To replicate the plots the following scripts are available. Where possible, the scripts are designed to be reused with newly trained models.

URTE for different losses (Left)

The script plot_losses.py recreates the left plot of Figure 1. To reconstruct the plot, the script has to run the MNIST test dataset through 4 different models. To reduce the time this takes, the --number_of_samples parameter can be used.

To obtain the plot as presented in the paper, run:

python plot_losses.py --save_dir ./output  --replicate

Training logs (Middle)

The script plot_training.py can be used to create an overview of the development of URTE, CTE, and loss during training. To do this, it requires the path to the csv files with training logs to be given using the --csv_file parameter.

To replicate the plot from the paper, run:

python plot_training.py --save_dir ./output --replicate

False rejection rate (Right)

The final plot in Figure 1 is created using the evaluation_rejection.py script. To reconstruct the plot presented in the paper run the same command as for the full evaluation:

python evaluation_rejection.py --save_dir ./output  --plot --replicate