The gradual fusion of intelligent transportation systems with metaverse technologies is giving rise to vehicular metaverses, which blend virtual spaces with physical space. As indispensable components for vehicular metaverses, Vehicular Twins (VTs) are digital replicas of Vehicular Metaverse Users (VMUs) and facilitate customized metaverse services to VMUs. VTs are established and maintained in RoadSide Units (RSUs) with sufficient computing and storage resources. Due to the limited communication coverage of RSUs and the high mobility of VMUs, VTs need to be migrated among RSUs to ensure real-time and seamless services for VMUs. However, during VT migrations, physical-virtual synchronization and massive communications among VTs may cause identity and location privacy disclosures of VMUs and VTs. In this article, we study privacy issues and the corresponding defenses for VT migrations in vehicular metaverses. We first present four kinds of specific privacy attacks during VT migrations. Then, we propose a VMU-VT dual pseudonym scheme and a synchronous pseudonym change framework to defend against these attacks. Additionally, we evaluate average privacy entropy for pseudonym changes and optimize the number of pseudonym distribution based on inventory theory. Numerical results show that the average utility of VMUs under our proposed schemes is 33.8% higher than that under the equal distribution scheme, demonstrating the superiority of our schemes.

翻译：智能交通系统与元宇宙技术的渐进融合催生了车辆元宇宙，该概念将虚拟空间与物理空间相结合。作为车辆元宇宙不可或缺的组成部分，车辆孪生（VT）是车辆元宇宙用户（VMU）的数字副本，为VMU提供定制化元宇宙服务。VT在具备充足计算与存储资源的路侧单元（RSU）中创建和维护。由于RSU通信覆盖范围有限以及VMU的高机动性，VT需要在各RSU之间迁移，以确保为VMU提供实时且不间断的服务。然而，在VT迁移过程中，物理-虚拟同步及VT间的大规模通信可能导致VMU和VT的身份及位置隐私泄露。本文研究了车辆元宇宙中VT迁移的隐私问题及相应防御策略。我们首先提出了VT迁移过程中四类具体的隐私攻击。进而提出了一种VMU-VT双伪名方案及一种同步伪名更换框架以抵御这些攻击。此外，我们评估了伪名更换的平均隐私熵，并基于库存理论优化了伪名分发数量。数值结果表明，所提方案下VMU的平均效用比均等分发方案提升了33.8%，验证了本方案的优越性。