As database deployments shift toward cloud platforms and edge devices, thin clients need to securely retrieve sensitive records without leaking their query intent or metadata to the proxies that mediate access. Oblivious Transfer (OT) is a core tool for private retrieval, yet existing OTs assume direct client-database interaction and lack support for delegated querying or lightweight clients. We present Oblivis, a modular framework of new OT protocols that enable delegated, privacy-preserving query execution. Oblivis allows clients to retrieve database records without direct access, protects against leakage to both databases and proxies, and is designed with practical efficiency in mind. Its components include: (1) Delegated-Query OT, which permits secure outsourcing of query generation; (2) Multi-Receiver OT for merged, cloud-hosted databases; (3) a compiler producing constant-size responses suitable for thin clients; and (4) Supersonic OT, a proxy-based, informationtheoretic, and highly efficient 1-out-of-2 OT. The protocols are formally defined and proven secure in the simulation-based paradigm, under non-colluding assumption. We implement and empirically evaluate Supersonic OT. It achieves at least a 92x speedup over a highly efficient 1-out-of-2 OT, and a 2.6x-106x speedup over a standard OT extension across 200-100,000 invocations. Our implementation further shows that Supersonic OT remains efficient even on constrained hardware, e.g., it completes an end-to-end transfer in 1.36 ms on a Raspberry Pi 4.

翻译：随着数据库部署向云平台和边缘设备转移，轻量级客户端需要安全地检索敏感记录，同时避免将查询意图或元数据泄露给中介访问的代理服务器。不经意传输（OT）是隐私检索的核心工具，然而现有OT方案均假设客户端与数据库直接交互，缺乏对委托查询或轻量级客户端的支持。本文提出Oblivis——一个模块化的新型OT协议框架，能够实现委托式隐私保护查询执行。Oblivis允许客户端在无需直接访问数据库的情况下检索记录，防止信息泄露给数据库和代理双方，并兼顾实际运行效率。其核心组件包括：（1）支持安全外包查询生成的委托查询OT；（2）适用于合并托管数据库的多接收方OT；（3）能为轻量级客户端生成恒定大小响应的编译器；（4）基于代理的、信息论安全且高效的1选2不经意传输协议Supersonic OT。所有协议均在模拟安全范式下进行形式化定义与安全性证明，并基于非共谋假设。我们实现了Supersonic OT并进行实证评估：相较于高效1选2 OT方案加速比达92倍以上，在200至100,000次调用范围内较标准OT扩展方案加速2.6-106倍。实验进一步表明该协议在受限硬件上仍保持高效，例如在树莓派4上端到端传输仅需1.36毫秒。