# Copyright 2019 Huawei Technologies Co., Ltd
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
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# http://www.apache.org/licenses/LICENSE-2.0
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"""
Natural-evolutionary-strategy Attack.
"""
import time
import numpy as np
from scipy.special import softmax
from mindarmour.utils.logger import LogUtil
from mindarmour.utils._check_param import check_pair_numpy_param, check_model, \
check_numpy_param, check_int_positive, check_value_positive, check_param_type
from ..attack import Attack
from .black_model import BlackModel
LOGGER = LogUtil.get_instance()
TAG = 'NES'
def _bound(image, epislon):
lower = np.clip(image - epislon, 0, 1)
upper = np.clip(image + epislon, 0, 1)
return lower, upper
[docs]class NES(Attack):
"""
The class is an implementation of the Natural Evolutionary Strategies Attack
Method. NES uses natural evolutionary strategies to estimate gradients to
improve query efficiency. NES covers three settings: Query-Limited setting,
Partial-Information setting and Label-Only setting. In the query-limit
setting, the attack has a limited number of queries to the target model but
access to the probabilities of all classes. In the partial-info setting,
the attack only has access to the probabilities for top-k classes.
In the label-only setting, the attack only has access to a list of k inferred
labels ordered by their predicted probabilities. In the Partial-Information
setting and Label-Only setting, NES do target attack so user need to use
set_target_images method to set target images of target classes.
References: `Andrew Ilyas, Logan Engstrom, Anish Athalye, and Jessy Lin.
Black-box adversarial attacks with limited queries and information. In
ICML, July 2018 <https://arxiv.org/abs/1804.08598>`_
Args:
model (BlackModel): Target model to be attacked.
scene (str): Scene in 'Label_Only', 'Partial_Info' or 'Query_Limit'.
max_queries (int): Maximum query numbers to generate an adversarial example. Default: 10000.
top_k (int): For Partial-Info or Label-Only setting, indicating how much (Top-k) information is
available for the attacker. For Query-Limited setting, this input should be set as -1. Default: -1.
num_class (int): Number of classes in dataset. Default: 10.
batch_size (int): Batch size. Default: 128.
epsilon (float): Maximum perturbation allowed in attack. Default: 0.3.
samples_per_draw (int): Number of samples draw in antithetic sampling. Default: 128.
momentum (float): Momentum. Default: 0.9.
learning_rate (float): Learning rate. Default: 1e-3.
max_lr (float): Max Learning rate. Default: 5e-2.
min_lr (float): Min Learning rate. Default: 5e-4.
sigma (float): Step size of random noise. Default: 1e-3.
plateau_length (int): Length of plateau used in Annealing algorithm. Default: 20.
plateau_drop (float): Drop of plateau used in Annealing algorithm. Default: 2.0.
adv_thresh (float): Threshold of adversarial. Default: 0.25.
zero_iters (int): Number of points to use for the proxy score. Default: 10.
starting_eps (float): Starting epsilon used in Label-Only setting. Default: 1.0.
starting_delta_eps (float): Delta epsilon used in Label-Only setting. Default: 0.5.
label_only_sigma (float): Sigma used in Label-Only setting. Default: 1e-3.
conservative (int): Conservation used in epsilon decay, it will increase if no convergence. Default: 2.
sparse (bool): If True, input labels are sparse-encoded. If False,
input labels are one-hot-encoded. Default: True.
Examples:
>>> from mindspore import Tensor
>>> from mindarmour import BlackModel
>>> from mindarmour.adv_robustness.attacks import NES
>>> from tests.ut.python.utils.mock_net import Net
>>> class ModelToBeAttacked(BlackModel):
... def __init__(self, network):
... super(ModelToBeAttacked, self).__init__()
... self._network = network
... def predict(self, inputs):
... if len(inputs.shape) == 3:
... inputs = inputs[np.newaxis, :]
... result = self._network(Tensor(inputs.astype(np.float32)))
... return result.asnumpy()
>>> net = Net()
>>> model = ModelToBeAttacked(net)
>>> SCENE = 'Query_Limit'
>>> TOP_K = -1
>>> attack= NES(model, SCENE, top_k=TOP_K)
>>> num_class = 5
>>> x_test = np.asarray(np.random.random((1, 1, 32, 32)), np.float32)
>>> target_image = np.asarray(np.random.random((1, 1, 32, 32)), np.float32)
>>> orig_class = 0
>>> target_class = 2
>>> attack.set_target_images(target_image)
>>> tag, adv, queries = attack.generate(np.array(x_test), np.array([target_class]))
"""
def __init__(self, model, scene, max_queries=10000, top_k=-1, num_class=10, batch_size=128, epsilon=0.3,
samples_per_draw=128, momentum=0.9, learning_rate=1e-3, max_lr=5e-2, min_lr=5e-4, sigma=1e-3,
plateau_length=20, plateau_drop=2.0, adv_thresh=0.25, zero_iters=10, starting_eps=1.0,
starting_delta_eps=0.5, label_only_sigma=1e-3, conservative=2, sparse=True):
super(NES, self).__init__()
self._model = check_model('model', model, BlackModel)
self._scene = scene
self._max_queries = check_int_positive('max_queries', max_queries)
self._num_class = check_int_positive('num_class', num_class)
self._batch_size = check_int_positive('batch_size', batch_size)
self._samples_per_draw = check_int_positive('samples_per_draw', samples_per_draw)
self._goal_epsilon = check_value_positive('epsilon', epsilon)
self._momentum = check_value_positive('momentum', momentum)
self._learning_rate = check_value_positive('learning_rate', learning_rate)
self._max_lr = check_value_positive('max_lr', max_lr)
self._min_lr = check_value_positive('min_lr', min_lr)
self._sigma = check_value_positive('sigma', sigma)
self._plateau_length = check_int_positive('plateau_length', plateau_length)
self._plateau_drop = check_value_positive('plateau_drop', plateau_drop)
# partial information arguments
self._k = top_k
self._adv_thresh = check_value_positive('adv_thresh', adv_thresh)
# label only arguments
self._zero_iters = check_int_positive('zero_iters', zero_iters)
self._starting_eps = check_value_positive('starting_eps', starting_eps)
self._starting_delta_eps = check_value_positive('starting_delta_eps', starting_delta_eps)
self._label_only_sigma = check_value_positive('label_only_sigma', label_only_sigma)
self._conservative = check_int_positive('conservative', conservative)
self._sparse = check_param_type('sparse', sparse, bool)
self.target_imgs = None
self.target_img = None
self.target_class = None
[docs] def generate(self, inputs, labels):
"""
Generate adversarial examples based on input data and target labels.
Args:
inputs (numpy.ndarray): Benign input samples.
labels (numpy.ndarray): Target labels.
Returns:
- numpy.ndarray, bool values for each attack result.
- numpy.ndarray, generated adversarial examples.
- numpy.ndarray, query times for each sample.
Raises:
ValueError: If the top_k less than 0 in Label-Only or Partial-Info setting.
ValueError: If the target_imgs is None in Label-Only or Partial-Info setting.
ValueError: If scene is not in ['Label_Only', 'Partial_Info', 'Query_Limit']
"""
inputs, labels = check_pair_numpy_param('inputs', inputs, 'labels', labels)
if not self._sparse:
labels = np.argmax(labels, axis=1)
if self._scene == 'Label_Only' or self._scene == 'Partial_Info':
if self._k < 1:
msg = "In 'Label_Only' or 'Partial_Info' mode, 'top_k' must more than 0."
LOGGER.error(TAG, msg)
raise ValueError(msg)
if self.target_imgs is None:
msg = "In 'Label_Only' or 'Partial_Info' mode, 'target_imgs' must be set."
LOGGER.error(TAG, msg)
raise ValueError(msg)
elif self._scene == 'Query_Limit':
self._k = self._num_class
else:
msg = "scene must be string in 'Label_Only', 'Partial_Info' or 'Query_Limit' "
LOGGER.error(TAG, msg)
raise ValueError(msg)
is_advs = []
advs = []
queries = []
for sample, label, target_img in zip(inputs, labels, self.target_imgs):
is_adv, adv, query = self._generate_one(sample, label, target_img)
is_advs.append(is_adv)
advs.append(adv)
queries.append(query)
return is_advs, advs, queries
[docs] def set_target_images(self, target_images):
"""
Set target samples for target attack in the Partial-Info setting or Label-Only setting.
Args:
target_images (numpy.ndarray): Target samples for target attack.
"""
self.target_imgs = check_numpy_param('target_images', target_images)
def _generate_one(self, origin_image, target_label, target_image):
"""
Main algorithm for NES.
Args:
origin_image (numpy.ndarray): Benign input sample.
target_label (int): Target label.
Returns:
- bool.
- If True: successfully make an adversarial example.
- If False: unsuccessfully make an adversarial example.
- numpy.ndarray, an adversarial example.
- int, number of queries.
"""
self.target_class = target_label
origin_image = check_numpy_param('origin_image', origin_image)
self._epsilon = self._starting_eps
lower, upper = _bound(origin_image, self._epsilon)
goal_epsilon = self._goal_epsilon
delta_epsilon = self._starting_delta_eps
if self._scene == 'Label_Only' or self._scene == 'Partial_Info':
adv = target_image
else:
adv = origin_image.copy()
# for backtracking and momentum
num_queries = 0
gradient = 0
last_ls = []
max_iters = int(np.ceil(self._max_queries // self._samples_per_draw))
for i in range(max_iters):
start = time.time()
# early stop
eval_preds = self._model.predict(adv)
eval_preds = np.argmax(eval_preds, axis=1)
padv = np.equal(eval_preds, self.target_class)
if padv and self._epsilon <= goal_epsilon:
LOGGER.debug(TAG, 'early stopping at iteration %d', i)
return True, adv, num_queries
# antithetic sampling noise
size = (self._batch_size // 2,) + origin_image.shape
noise_pos = np.random.normal(size=size)
noise = np.concatenate((noise_pos, -noise_pos), axis=0)
eval_points = adv + self._sigma*noise
prev_g = gradient
loss, gradient = self._get_grad(origin_image, eval_points, noise)
gradient = self._momentum*prev_g + (1.0 - self._momentum)*gradient
# plateau learning rate annealing
last_ls.append(loss)
last_ls = self._plateau_annealing(last_ls)
# search for learning rate and epsilon decay
current_lr = self._max_lr
prop_delta_eps = 0.0
if loss < self._adv_thresh and self._epsilon > goal_epsilon:
prop_delta_eps = delta_epsilon
while current_lr >= self._min_lr:
# in partial information only or label only setting
if self._scene == 'Label_Only' or self._scene == 'Partial_Info':
proposed_epsilon = max(self._epsilon - prop_delta_eps, goal_epsilon)
lower, upper = _bound(origin_image, proposed_epsilon)
proposed_adv = adv - current_lr*np.sign(gradient)
proposed_adv = np.clip(proposed_adv, lower, upper)
num_queries += 1
if self._preds_in_top_k(self.target_class, proposed_adv):
# The predicted label of proposed adversarial examples is in
# the top k observations.
if prop_delta_eps > 0:
delta_epsilon = max(prop_delta_eps, 0.1)
last_ls = []
adv = proposed_adv
self._epsilon = self._epsilon - prop_delta_eps / self._conservative
self._epsilon = max(self._epsilon, goal_epsilon)
break
elif current_lr >= self._min_lr*2:
current_lr = current_lr / 2
LOGGER.debug(TAG, "backtracking learning rate to %.3f", current_lr)
else:
prop_delta_eps = prop_delta_eps / 2
if prop_delta_eps < 2e-3:
LOGGER.debug(TAG, "Did not converge.")
return False, adv, num_queries
current_lr = self._max_lr
LOGGER.debug(TAG, "backtracking epsilon to %.3f", self._epsilon - prop_delta_eps)
# update the number of queries
if self._scene == 'Label_Only':
num_queries += self._samples_per_draw*self._zero_iters
else:
num_queries += self._samples_per_draw
LOGGER.debug(TAG,
'Step %d: loss %.4f, lr %.2E, eps %.3f, time %.4f.',
i,
loss,
current_lr,
self._epsilon,
time.time() - start)
return False, adv, num_queries
def _plateau_annealing(self, last_loss):
last_loss = last_loss[-self._plateau_length:]
if last_loss[-1] > last_loss[0] and len(last_loss) == self._plateau_length:
if self._max_lr > self._min_lr:
LOGGER.debug(TAG, "Annealing max learning rate.")
self._max_lr = max(self._max_lr / self._plateau_drop, self._min_lr)
last_loss = []
return last_loss
def _softmax_cross_entropy_with_logit(self, logit):
logit = softmax(logit, axis=1)
onehot_label = np.zeros(self._num_class)
onehot_label[self.target_class] = 1
onehot_labels = np.tile(onehot_label, (len(logit), 1))
entropy = -onehot_labels*np.log(logit)
loss = np.mean(entropy, axis=1)
return loss
def _query_limit_loss(self, eval_points, noise):
"""
Loss in Query-Limit setting.
"""
LOGGER.debug(TAG, 'enter the function _query_limit_loss().')
loss = self._softmax_cross_entropy_with_logit(self._model.predict(eval_points))
return loss, noise
def _partial_info_loss(self, eval_points, noise):
"""
Loss in Partial-Info setting.
"""
LOGGER.debug(TAG, 'enter the function _partial_info_loss.')
logit = self._model.predict(eval_points)
loss = np.sort(softmax(logit, axis=1))[:, -self._k:]
inds = np.argsort(logit)[:, -self._k:]
good_loss = np.where(np.equal(inds, self.target_class), loss, np.zeros(np.shape(inds)))
good_loss = np.max(good_loss, axis=1)
losses = -np.log(good_loss)
return losses, noise
def _label_only_loss(self, origin_image, eval_points, noise):
"""
Loss in Label-Only setting.
"""
LOGGER.debug(TAG, 'enter the function _label_only_loss().')
tiled_points = np.tile(np.expand_dims(eval_points, 0), [self._zero_iters, *[1]*len(eval_points.shape)])
noised_eval_im = tiled_points + np.random.randn(self._zero_iters,
self._batch_size,
*origin_image.shape)*self._label_only_sigma
noised_eval_im = np.reshape(noised_eval_im, (self._zero_iters*self._batch_size, *origin_image.shape))
logits = self._model.predict(noised_eval_im)
inds = np.argsort(logits)[:, -self._k:]
real_inds = np.reshape(inds, (self._zero_iters, self._batch_size, -1))
rank_range = np.arange(1, self._k + 1, 1, dtype=np.float32)
tiled_rank_range = np.tile(np.reshape(rank_range, (1, 1, self._k)), [self._zero_iters, self._batch_size, 1])
batches_in = np.where(np.equal(real_inds, self.target_class),
tiled_rank_range,
np.zeros(np.shape(tiled_rank_range)))
loss = 1 - np.mean(batches_in)
return loss, noise
def _preds_in_top_k(self, target_class, prop_adv_):
# query limit setting
if self._k == self._num_class:
return True
# label only and partial information setting
eval_preds = self._model.predict(prop_adv_)
if not target_class in eval_preds.argsort()[:, -self._k:]:
return False
return True
def _get_grad(self, origin_image, eval_points, noise):
"""Calculate gradient."""
losses = []
grads = []
for _ in range(self._samples_per_draw // self._batch_size):
if self._scene == 'Label_Only':
loss, np_noise = self._label_only_loss(origin_image, eval_points, noise)
elif self._scene == 'Partial_Info':
loss, np_noise = self._partial_info_loss(eval_points, noise)
else:
loss, np_noise = self._query_limit_loss(eval_points, noise)
# only support three channel images
losses_tiled = np.tile(np.reshape(loss, (-1, 1, 1, 1)), (1,) + origin_image.shape)
grad = np.mean(losses_tiled*np_noise, axis=0) / self._sigma
grads.append(grad)
losses.append(np.mean(loss))
return np.array(losses).mean(), np.mean(np.array(grads), axis=0)