Source code for torchattacks.attacks.mifgsm

import torch
import torch.nn as nn

from ..attack import Attack


[docs] class MIFGSM(Attack): r""" MI-FGSM in the paper 'Boosting Adversarial Attacks with Momentum' [https://arxiv.org/abs/1710.06081] Distance Measure : Linf Arguments: model (nn.Module): model to attack. eps (float): maximum perturbation. (Default: 8/255) alpha (float): step size. (Default: 2/255) decay (float): momentum factor. (Default: 1.0) steps (int): number of iterations. (Default: 10) Shape: - images: :math:`(N, C, H, W)` where `N = number of batches`, `C = number of channels`, `H = height` and `W = width`. It must have a range [0, 1]. - labels: :math:`(N)` where each value :math:`y_i` is :math:`0 \leq y_i \leq` `number of labels`. - output: :math:`(N, C, H, W)`. Examples:: >>> attack = torchattacks.MIFGSM(model, eps=8/255, steps=10, decay=1.0) >>> adv_images = attack(images, labels) """ def __init__(self, model, eps=8 / 255, alpha=2 / 255, steps=10, decay=1.0): super().__init__("MIFGSM", model) self.eps = eps self.steps = steps self.decay = decay self.alpha = alpha self.supported_mode = ["default", "targeted"]
[docs] def forward(self, images, labels): r""" Overridden. """ images = images.clone().detach().to(self.device) labels = labels.clone().detach().to(self.device) if self.targeted: target_labels = self.get_target_label(images, labels) momentum = torch.zeros_like(images).detach().to(self.device) loss = nn.CrossEntropyLoss() adv_images = images.clone().detach() for _ in range(self.steps): adv_images.requires_grad = True outputs = self.get_logits(adv_images) # Calculate loss if self.targeted: cost = -loss(outputs, target_labels) else: cost = loss(outputs, labels) # Update adversarial images grad = torch.autograd.grad( cost, adv_images, retain_graph=False, create_graph=False )[0] grad = grad / torch.mean(torch.abs(grad), dim=(1, 2, 3), keepdim=True) grad = grad + momentum * self.decay momentum = grad adv_images = adv_images.detach() + self.alpha * grad.sign() delta = torch.clamp(adv_images - images, min=-self.eps, max=self.eps) adv_images = torch.clamp(images + delta, min=0, max=1).detach() return adv_images