Data confidentiality is one of the biggest concerns that hinders enterprise customers from moving their workloads to the cloud. Thanks to the trusted execution environment (TEE), it is now feasible to build encrypted databases in the enclave that can process customers' data while keeping it confidential to the cloud. Though some enclave-based encrypted databases emerge recently, there remains a large unexplored area in between about how confidentiality can be achieved in different ways and what influences are implied by them. In this paper, we first provide a broad exploration of possible design choices in building encrypted database storage engines, rendering trade-offs in security, performance and functionality. We observe that choices on different dimensions can be independent and their combination determines the overall trade-off of the entire storage. We then propose Enclage , an encrypted storage engine that makes practical trade-offs. It adopts many enclave-native designs, such as page-level encryption, reduced enclave interaction, and hierarchical memory buffer, which offer high-level security guarantee and high performance at the same time. To make better use of the limited enclave memory, we derive the optimal page size in enclave and adopt delta decryption to access large data pages with low cost. Our experiments show that Enclage outperforms the baseline, a common storage design in many encrypted databases, by over 13x in throughput and about 5x in storage savings.

The past decade has witnessed the rapid development of cloud computing and data-centric applications. While these innovations offer numerous attractive features for data processing, they also bring in new issues about the loss of data ownership. Though some encrypted databases have emerged recently, they can not fully address these concerns for the data owner. In this paper, we propose an ownership-preserving database (OPDB), a new paradigm that characterizes different roles' responsibilities from nowadays applications and preserves data ownership throughout the entire application. We build Operon to follow the OPDB paradigm, which utilizes the trusted execution environment (TEE) and introduces a behavior control list (BCL). Different from access controls that merely handle accessibility permissions, BCL further makes data operation behaviors under control. Besides, we make Operon practical for real-world applications, by extending database capabilities towards flexibility, functionality and ease of use. Operon is the first database framework with which the data owner exclusively controls its data across different roles' subsystems. We have successfully integrated Operon with different TEEs, i.e. , Intel SGX and an FPGA-based implementation, and various database services on Alibaba Cloud, i.e. , PolarDB and RDS PostgreSQL. The evaluation shows that Operon achieves 71% - 97% of the performance of plaintext databases under the TPC-C benchmark while preserving the data ownership.