Release-Aware In-Out Encryption Adjustment In Mongodb Query Processing

Querying over encrypted data typically uses multi-layered (onion) encryption, which requires level adjustment when processing queries. Previous studies, such as on CryptDB, emphasize the importance of inward encryption adjustment, from outer layers to inner layers, releasing information necessary for query execution. Even though the idea of outward encryption adjustment, which is used to re-establish the outer layers after query processing, is very natural and appeared already in the early papers on CryptDB as a topic for future work, no prior studies have addressed it systematically. This paper extends previous work on intelligent, release-aware encryption adjustment for document-based databases querying with the outward adjustment policy. We define the resulting Release-Aware In-Out Encryption Adjustment principles and report on their empirical evaluation using both local and cloud deployment of MongoDB. The evaluation utilizing datasets of different sizes shows that the proposed method is efficient, scalable, and provides better data protection.