The proliferation of cloud computing has greatly spurred the popularity of outsourced database storage and management, in which the cloud holding outsourced databases can process database queries on demand. Among others, skyline queries play an important role in the database field due to its prominent usefulness in multi-criteria decision support systems. To accommodate the tailored needs of users, user-defined skyline query has recently emerged as an intriguing advanced type of skyline query, which allows users to define custom preferences in their skyline queries (including the target attributes, preferred dominance relations, and range constraints on the target attributes). However, user-defined skyline query services, if deployed in the cloud, may raise critical privacy concerns as the outsourced databases and skyline queries may contain proprietary/privacy-sensitive information, and the cloud might even suffer from data breaches. In light of the above, this paper presents ObliuSky, a new system framework enabling oblivious user-defined skyline query processing in the cloud. ObliuSky departs from the state-of-the-art prior work by not only providing confidentiality protection for the content of the outsourced database, the user-defined skyline query, and the query results, but also making the cloud oblivious to the data patterns (e.g., user-defined dominance relations among database points and search access patterns) which may indirectly cause data leakages. We formally analyze the security guarantees and conduct extensive performance evaluations. The results show that while achieving much stronger security guarantees than the state-of-the-art prior work, ObliuSky is superior in database and query encryption efficiency, with practically affordable query latency.

翻译：云计算的发展极大地推动了外包数据库存储和管理的普及，云服务器持有外包数据库，可按需处理数据库查询。在天际线查询中，由于其在多准则决策支持系统中的突出实用性，在数据库领域占据重要地位。为满足用户的个性化需求，用户自定义天际线查询近期成为一种引人注目的高级天际线查询类型，允许用户在天际线查询中定义自定义偏好（包括目标属性、偏好的支配关系以及目标属性的范围约束）。然而，若将用户自定义天际线查询服务部署于云端，可能引发严重的隐私问题，因为外包数据库和天际线查询可能包含专有/隐私敏感信息，且云服务器甚至可能遭受数据泄露。鉴于此，本文提出ObliuSky，一种支持云端 oblivious 用户自定义天际线查询处理的新系统框架。ObliuSky 与现有最先进工作的不同之处在于，它不仅为外包数据库内容、用户自定义天际线查询及查询结果提供机密性保护，还使云服务器对数据模式（例如，数据库点之间用户定义的支配关系和搜索访问模式） oblivious，这些模式可能间接导致数据泄露。我们正式分析了其安全保障，并进行了广泛的性能评估。结果表明，ObliuSky 在实现比现有最先进工作更强的安全保障的同时，在数据库和查询加密效率上具有优势，且查询延迟在实际可接受范围内。