EAGER: Protecting Data Access Pattern Privacy in Hybrid Cloud Storage Systems

基于云的存储服务因其有吸引力的即用即付模式以及高可用性、可靠性和经济效率而越来越受欢迎。与此同时，用户对这种存储模式的隐私意识越来越强。虽然加密为数据隐私提供了一些保护，但它无法保护数据访问模式，这可能会泄露有关云存储客户端的私人信息。特别地，云存储服务的好奇的所有者或雇员或者入侵系统的攻击者可以观察客户端的访问模式，开发将模式与客户端的活动相关联的模型，并且稍后使用模型和观察到的访问模式来推断或预测客户端的活动。尽管已经提出了几种方案来保护访问模式，特别是不经意随机存取存储器（RAM），但是由于它们引起的高通信、存储或计算开销，很难将这些方案付诸实践。为了解决这个问题，该项目旨在提供一个高效，可扩展和实用的解决方案，使用Oblivious RAM，可以保护访问模式的隐私，并可以与现有的云存储基础设施无缝集成。具体而言，该项目利用了新兴的混合云存储架构，该架构具有在客户端具有中等资源水平的云存储网关，众所周知的数据访问引用局部性原则，以及市场上多个独立云存储服务器的可用性。该项目将通过提高用户使用云服务时的安全和隐私风险意识，并为他们提供用户友好的保护工具，使他们放心地使用此类服务，从而造福社区。该项目设计了一个新的分层，不经意的RAM存储系统，包括多层的不经意的RAM模块，其中每一个都是优化不同的性能指标，这取决于其利基的层次结构;因此，层次结构作为一个整体可以同时实现高效率的通信，存储和计算。该项目形式化的问题，保护数据访问模式的整个层次结构的不经意RAM模块，并开发新的算法来解决这个问题。该项目还旨在提供一组可证明安全的不经意RAM算法，优化用于短数据访问延迟或低服务器端存储开销，以及一组可证明安全的算法，用于规划不经意RAM模块层次结构的最佳架构，配置层次结构并协调层次结构中所有不经意RAM模块的操作。该奖项反映了NSF的法定使命，并被认为是值得的通过使用基金会的知识价值和更广泛的影响审查标准进行评估来提供支持。

Cloud-based storage services are gaining increasing popularity for their attractive pay-as-you-go model and high availability, reliability and economic efficiency. Meanwhile, there is an increasing privacy consciousness among users regarding this storage paradigm. While encryption provides some protection for data privacy, it cannot protect data access patterns, which can reveal private information about cloud storage clients. In particular, a curious owner or employee of a cloud storage service or an attacker invading the system can observe a client's access patterns, develop a model relating the patterns to the client's activities and later on use the model and observed access patterns to infer or predict the client's activities. Although several schemes have been proposed to protect the access patterns, in particular Oblivious Random Access Memory (RAM), it is hard to put these into practice owing to the high communication, storage, or computational overheads they incur. Towards addressing this problem, the project aims to offer an efficient, scalable and practical solution using Oblivious RAM that can protect the privacy of access pattern and can seamlessly integrate with existing cloud storage infrastructures. Specifically, the project leverages the emerging hybrid cloud storage architecture that has a cloud storage gateway with a moderate level of resource at the client side, the well-known reference locality principle for data access, and the availability of multiple independent cloud storage servers in the market. The project would benefit the community by enhancing the users' awareness of security and privacy risks in using cloud services and providing them with user-friendly protection tools so that they benefit from using such services with confidence. The project designs a new hierarchical, Oblivious RAM storage system to include multiple layers of Oblivious RAM modules, each of which is optimized for different performance metrics depending on its niche on the hierarchy; hence, the hierarchy as whole can attain high efficiency in communication, storage and computation simultaneously. The project formalizes the problem of protecting the data access pattern for the whole hierarchy of Oblivious RAM modules, and develops novel algorithms to solve the problem. The project also aims to deliver a set of provably-secure Oblivious RAM algorithms optimized for short data access delay or low server-side storage overhead, and a set of provably-secure algorithms for planning an optimal architecture for a hierarchy of Oblivious RAM modules, configuring the hierarchy and coordinating the operations of all Oblivious RAM modules in the hierarchy.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.