网络与信息安全学报 ›› 2022, Vol. 8 ›› Issue (2): 48-63.doi: 10.11959/j.issn.2096-109x.2022016

• 专栏:网络攻击与防御技术 • 上一篇    下一篇

基于softmax激活变换的对抗防御方法

陈晋音1,2, 吴长安2, 郑海斌2   

  1. 1 浙江工业大学网络空间安全研究院,浙江 杭州 310023
    2 浙江工业大学信息工程学院,浙江 杭州310023
  • 修回日期:2021-11-23 出版日期:2022-04-15 发布日期:2022-04-01
  • 作者简介:陈晋音(1982− ),女,浙江象山人,浙江工业大学教授,主要研究方向为人工智能安全、图数据挖掘和进化计算
    吴长安(1996− ),男,浙江长兴人,浙江工业大学硕士生,主要研究方向为深度学习、计算机视觉和图像的对抗攻击和防御
    郑海斌(1995− ),男,浙江台州人,浙江工业大学博士生,主要研究方向为深度学习、人工智能安全和图像识别
  • 基金资助:
    国家自然科学基金(62072406);信息系统安全技术重点实验室基金(61421110502)

Novel defense based on softmax activation transformation

Jinyin CHEN1,2, Changan WU2, Haibin ZHENG2   

  1. 1 Institute of Cyberspace Security, Zhejiang University of Technology, Hangzhou 310023, China
    2 College of Information Engineering, Zhejiang University of Technology, Hangzhou 310023, China
  • Revised:2021-11-23 Online:2022-04-15 Published:2022-04-01
  • Supported by:
    The National Natural Science Foundation of China(62072406);National Key Laboratory of Science and Technology on Information System Security(61421110502)

摘要:

深度学习广泛应用于图像处理、自然语言处理、网络挖掘等各个领域并取得良好效果,但其容易受到对抗攻击、存在安全漏洞的问题引起广泛关注。目前已有一些有效的防御方法,包括对抗训练、数据变化、模型增强等方法。但是,依然存在一些问题,如提前已知攻击方法与对抗样本才能实现有效防御、面向黑盒攻击的防御能力差、以牺牲部分正常样本的处理性能为代价、防御性能无法验证等。因此,提出可验证的、对抗样本不依赖的防御方法是关键。提出了 softmax 激活变换防御(SAT,softmax activation transformation),这是一种针对黑盒攻击的轻量级的快速防御。SAT不参与模型的训练,在推理阶段对目标模型的输出概率进行隐私保护加固并重新激活,通过softmax激活变换与深度模型防御的连接定义,证明通过softmax函数的变换后能实现概率信息的隐私保护从而防御黑盒攻击。SAT的实现不依赖对抗攻击方法与对抗样本,不仅避免了制作大量对抗样本的负担,也实现了攻击的事前防御。通过理论证明 SAT 的激活具有单调性,从而保证其防御过程中正常样本的识别准确率。在激活过程中,提出可变的softmax激活函数变换系数保护策略,在给定范围内随机选择隐私保护变换系数实现动态防御。最重要的一点,SAT 是一种可验证的防御,能够基于概率信息隐私保护和softmax激活变换推导其防御的有效性和可靠性。为了评估SAT的有效性,在MNIST、CIFAR10和ImageNet数据集上进行了针对9种黑盒攻击的防御实验,令所有攻击方法的平均攻击成功率从 87.06%降低为 5.94%,与多种先进黑盒攻击防御方法比较,验证了所提方法可以达到最优防御性能。

关键词: 深度学习, 对抗防御, 可验证, 攻击无关

Abstract:

Deep learning is widely used in various fields such as image processing, natural language processing, network mining and so on.However, it is vulnerable to malicious adversarial attacks and many defensive methods have been proposed accordingly.Most defense methods are attack-dependent and require defenders to generate massive adversarial examples in advance.The defense cost is high and it is difficult to resist black-box attacks.Some of these defenses even affect the recognition of normal examples.In addition, the current defense methods are mostly empirical, without certifiable theoretical support.Softmax activation transformation (SAT) was proposed in this paper, which was a light-weight and fast defense scheme against black-box attacks.SAT reactivates the output probability of the target model in the testing phase, and then it guarantees privacy of the probability information.As an attack-free defense, SAT not only avoids the burden of generating massive adversarial examples, but also realizes the advance defense of attacks.The activation of SAT is monotonic, so it will not affect the recognition of normal examples.During the activation process, a variable privacy protection transformation coefficient was designed to achieve dynamic defense.Above all, SAT is a certifiable defense that can derive the effectiveness and reliability of its defense based on softmax activation transformation.To evaluate the effectiveness of SAT, defense experiments against 9 attacks on MNIST, CIFAR10 and ImageNet datasets were conducted, and the average attack success rate was reduced from 87.06% to 5.94%.

Key words: deep learning, adversarial defense, certifiable, attack-free

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