Enhancing Diffusion-based Unrestricted Adversarial Attacks via Adversary Preferences Alignment
Journal:
arXiv
Published Date:
Jun 2, 2025
Abstract
Preference alignment in diffusion models has primarily focused on benign
human preferences (e.g., aesthetic). In this paper, we propose a novel
perspective: framing unrestricted adversarial example generation as a problem
of aligning with adversary preferences. Unlike benign alignment, adversarial
alignment involves two inherently conflicting preferences: visual consistency
and attack effectiveness, which often lead to unstable optimization and reward
hacking (e.g., reducing visual quality to improve attack success). To address
this, we propose APA (Adversary Preferences Alignment), a two-stage framework
that decouples conflicting preferences and optimizes each with differentiable
rewards. In the first stage, APA fine-tunes LoRA to improve visual consistency
using rule-based similarity reward. In the second stage, APA updates either the
image latent or prompt embedding based on feedback from a substitute
classifier, guided by trajectory-level and step-wise rewards. To enhance
black-box transferability, we further incorporate a diffusion augmentation
strategy. Experiments demonstrate that APA achieves significantly better attack
transferability while maintaining high visual consistency, inspiring further
research to approach adversarial attacks from an alignment perspective. Code
will be available at https://github.com/deep-kaixun/APA.
