Private Membership Testing (PMT) protocols enable clients to verify whether a certain data item is included in a database without revealing the item to the database operator or other external parties. This paper examines Source-assisted PMT (SPMT), in which clients leverage compact data source-provided information issued when the data item is first submitted to the database. SPMT is relevant in applications such as certificate transparency and supply-chain auditing; yet, designing an approach that is efficient, scalable, and privacy-preserving remains a challenge. This work presents Gyokuro, which takes a different approach to conventional membership testing schemes. Instead of requesting the server to produce a proof attesting that a certain data item exists in the database, we leverage Trusted Execution Environments (TEEs) to produce proofs demonstrating that the server has made enough progress to add the data item to the database. With the help of existing monitoring services, clients can infer that no items have been removed from the database. This allows Gyokuro to provide strong privacy guaranties and achieve high efficiency, as a client's membership testing query does not include any information regarding their interests, and eliminates the need for complex and inefficient protection mechanisms. Additionally, this approach enables membership testing on large-scale databases, since the communication and computation required are independent of the database size. Our evaluations show practical feasibility, achieving 7 ms membership testing latency and throughput of around 1400 requests/sec/core.

翻译：私有成员检测（PMT）协议使客户端能够验证特定数据项是否包含在数据库中，同时不向数据库操作员或外部第三方泄露该数据项。本文研究了源辅助私有成员检测（SPMT），其中客户端利用数据项首次提交至数据库时由数据源提供的紧凑信息。SPMT相关于证书透明度和供应链审计等应用；然而，设计一种高效、可扩展且保护隐私的方法仍面临挑战。本研究提出了“玉露”（Gyokuro），该方法不同于传统的成员检测方案。我们不要求服务器生成证明以证明特定数据项存在于数据库中，而是利用可信执行环境（TEE）生成证明，表明服务器已取得足够进展以将数据项添加至数据库。借助现有的监控服务，客户端可以推断数据库中未移除任何数据项。这使得Gyokuro能够提供强大的隐私保障并实现高效率，因为客户端的成员检测查询不包含任何与自身兴趣相关的信息，且消除了对复杂低效保护机制的需求。此外，该方法支持大规模数据库的成员检测，因为所需的通信和计算量与数据库大小无关。我们的评估显示了实际可行性，实现了7毫秒的成员检测延迟和约1400请求/秒/核心的吞吐量。