OblivCDN：一种具备不经意内容访问能力的实用型隐私保护CDN
OblivCDN: A Practical Privacy-preserving CDN with Oblivious Content Access
AI总结：
针对现有隐私保护CDN方案成本高、集成难的问题，研究提出OblivCDN系统，通过适配Range ORAM、定制不经意模块优化性能，无需边缘端可信硬件，流媒体下载速度较现有方案大幅提升。
摘要：
内容提供商越来越多地利用内容分发网络（CDN）来提升用户的内容下载体验。然而，由于第三方提供商的参与，这种部署场景引发了关于内容机密性和用户隐私的重大安全担忧。此前采用私有信息检索（PIR）和不经意随机存取存储器（ORAM）的方案已被证明不实用，原因是计算和通信成本高昂，且在分布式CDN架构中存在集成挑战。对此，我们提出了\textsf{OblivCDN}，这是一套精心设计的实用隐私保护系统，可与现有的真实互联网CDN基础设施无缝集成。我们的设计策略性地适配了Range ORAM（范围不经意随机存取存储器）原语，在源服务器和边缘服务器访问CDN内容的连续块时优化内存和磁盘寻道操作，同时保留内容机密性和用户访问模式隐藏特性。此外，我们精心定制了若干不经意构建模块，将分布式信任模型集成到ORAM客户端中，从而消除了源服务器的计算瓶颈，并降低了源服务器与边缘服务器之间的通信成本。不仅如此，新设计的ORAM客户端还消除了边缘服务器对可信硬件的需求，因此显著提升了对拥有大量遗留设备的网络的兼容性。在真实流媒体评估中，OblivCDN展现出了卓越的性能，仅用5.6秒就完成了256 MB视频的下载。这一成果相比基线方案（直接采用ORAM）实现了90倍的速度提升，相比现有技术OblivP2P则提升了366倍。
英文摘要：
Content providers increasingly utilise Content Delivery Networks (CDNs) to enhance users' content download experience. However, this deployment scenario raises significant security concerns regarding content confidentiality and user privacy due to the involvement of third-party providers. Prior proposals using private information retrieval (PIR) and oblivious RAM (ORAM) have proven impractical due to high computation and communication costs, as well as integration challenges within distributed CDN architectures. In response, we present \textsf{OblivCDN}, a practical privacy-preserving system meticulously designed for seamless integration with the existing real-world Internet-CDN infrastructure. Our design strategically adapts Range ORAM primitives to optimise memory and disk seeks when accessing contiguous blocks of CDN content, both at the origin and edge servers, while preserving both content confidentiality and user access pattern hiding features. Also, we carefully customise several oblivious building blocks that integrate the distributed trust model into the ORAM client, thereby eliminating the computational bottleneck in the origin server and reducing communication costs between the origin server and edge servers. Moreover, the newly-designed ORAM client also eliminates the need for trusted hardware on edge servers, and thus significantly ameliorates the compatibility towards networks with massive legacy devices.In real-world streaming evaluations, OblivCDN} demonstrates remarkable performance, downloading a $256$ MB video in just $5.6$ seconds. This achievement represents a speedup of $90\times$ compared to a strawman approach (direct ORAM adoption) and a $366\times$ improvement over the prior art, OblivP2P.
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