This work addresses the problem of indexing encrypted data outsourced to an external cloud server to support server-side execution of multi-attribute queries. The described approach partitions the dataset in groups with the same number of tuples, and associates all tuples in a group with the same combination of index values, so to guarantee protection against static inferences. The proposed indexing approach does not require any modifications to the server-side software stack, and requires limited storage at the client for query support. The experimental evaluation considers, for the storage of the encrypted and indexed dataset, both a relational database (PostgreSQL) and a key-value database (Redis). The paper includes extensive experiments evaluating client-storage requirements and query performance. The experimental results confirm the efficiency of the solution. The proposal is supported by an open source implementation.

Authors:

Sabrina De Capitani di Vimercati, Dario Facchinetti, Sara Foresti, Gianluca Oldani, Stefano Paraboschi, Matthew Rossi, Pierangela Samarati

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