InkShield：抵御未授权笔迹模仿的书写风格保护
InkShield: Writing Style Protection Against Unauthorized Handwriting Mimicry
- University of Electronic Science and Technology of China（电子科技大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
InkShield是一种主动书写风格防御方案，通过限制扰动在墨迹笔画边缘保护手写参考图像，可降低未授权笔迹模仿的检索率，且视觉质量与可读性良好。
AI中文摘要：
近期的手写文本生成器可从公开参考资料中复现书写者的风格，带来文件伪造与身份滥用风险。攻击者可能利用公开的手写笔记或签名样本生成伪造的推荐信或授权书，引发文件欺诈、身份滥用及决策误导。然而，现有针对未授权图像编辑或合成的防护措施难以适配笔迹模仿场景，这些措施针对含复杂背景的自然图像设计，通常对整幅图像优化扰动；对于稀疏的手写图像，此类全局扰动会在空白背景区域变得显眼，大幅降低视觉质量。本研究提出InkShield，一种在参考图像发布前提供保护的主动书写风格防御方案。InkShield选择一名诱饵书写者定义风格偏移方向，利用冻结的手写生成代理模型优化扰动，并将扰动限制在墨迹笔画边缘，以避免产生显眼的背景伪影。在IAM数据集上，两名独立书写者评估器将生成样本检索为目标书写者的平均Top-1/Top-5率从11.94%/36.52%降至2.03%/8.79%；同时，受保护的参考图像与原始图像视觉相似度高（LPIPS为0.0078），生成文本仍保持可读性，且InkShield对其他手写生成器也具备可迁移性，总体上能为抵御未授权笔迹风格模仿提供实用保护。
英文摘要：
Recent handwritten text generators can reproduce a writer's style from publicly available references, posing risks of document forgery and identity misuse. An attacker may use a publicly available handwritten note or signature sample to generate forged recommendation letters or authorization forms, leading to document fraud, identity misuse, and misleading decisions. However, existing protections against unauthorized image editing or synthesis transfer poorly to handwriting style mimicry. Designed for natural images with complex backgrounds, they often optimize perturbations over the whole image. For sparse handwriting images, such global perturbations become conspicuous in blank background regions and largely degrade the visual quality. In this work, we propose InkShield, a proactive writing-style defense that protects reference images before release. InkShield selects a decoy writer to define a style-displacement direction, optimizes perturbations with a frozen handwriting-generation surrogate, and confines them to ink-stroke edges to avoid conspicuous background artifacts. On IAM, the average Top-1/Top-5 rates at which generated samples are retrieved as the target writer by two independent writer evaluators decrease from 11.94%/36.52% to 2.03%/8.79%. Meanwhile, the protected references remain visually close to the originals (LPIPS 0.0078), and the generated text remains readable. InkShield also exhibits transferability to other handwriting generators. Overall, InkShield provides practical protection against unauthorized handwriting style mimicry.
