提出用格遍历方法严格验证多层感知机的对抗鲁棒性,兼具安全与完备性。
Interval Certifications for Multilayered Perceptrons via Lattice Traversal

- 将输入区间建模为格结构,通过遍历实现精确验证
- 首次定义并求解完备性认证,可保证扰动超出区间必改预测
- 在ℓ∞球对称区间中实现对数级高效算法,适合实际部署
本文构建了一个严格的理论框架,解决人工智能安全中的基础问题——对抗鲁棒性。我们证明,对抗鲁棒性问题可归约为格遍历问题。每个格元素对应一个包含输入点 𝐱 的区间(轴对齐超矩形)。对于多层感知机分类器(MLP),若𝐱 ∈ I 且在 I 内自由扰动不改变预测,则该区间构成安全认证;若𝐱 ∈ I 且当𝐱移出 I 时预测必变,则为完备认证。现有研究多关注安全认证,而完备认证此前未被系统探讨。我们设计了格遍历算子,结合精炼-验证迭代策略,使用形式化 MLP 验证器,确保安全最大化与完备最小化。此外,我们分析优化问题:完备认证可在多项式次数的预言机调用下求得最小解,而安全认证则为强难解。在对称区间(即 ℓ∞-球)中,我们提供对数时间算法。最后,通过新系统 ParallelepipedoNN 进行实证评估。
原文摘要 · Abstract (English)
In this work we present a rigorous theoretical framework to a foundational problem of AI safety, namely adversarial robustness. In particular, we show that the adversarial robustness problem can be reduced to a lattice traversal problem. Each element of this lattice corresponds to an interval, i.e., an axis-aligned hyper-rectangle, containing an input point $\mathbf{x}$. Consider a multilayered perceptron classifier (MLP). An interval $I$ constitutes a sound certification if $\mathbf{x} \in I$ and $\mathbf{x}$ can be freely perturbed in $I$ without changing the MLP's prediction. Complementarily, an interval $I$ constitutes a complete certification if $\mathbf{x} \in I$ and when $\mathbf{x}$ moves outside of $I$ the MLP's prediction is guaranteed to change. While the sound certification problem corresponds to the well-studied adversarial robustness, complete certifications have not been examined in the literature. We develop lattice traversal operators, which we apply in a refine & verify iterative scheme. Using formal MLP verifiers, sound maximality and complete minimality are guaranteed. Moreover, we examine objective optimization problems. There we discover some interesting asymmetries. For complete certifications, the minimum solution is obtained in polynomial oracle calls. This does not hold for sound certifications, where we prove strong intractability results. Additionally, we examine optimization problems in symmetric intervals (i.e., $\ell_\infty$-spheres), where we provide logarithmic algorithms. Finally, we present an empirical evaluation, using the novel ParallelepipedoNN system.
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