Database Outsourcing with Hierarchical Authenticated Data Structures

In an outsourced database scheme, the data owner delegates the data management tasks to a remote service provider. At a later time, the remote service is supposed to answer any query on the database. The essential requirements are ensuring the data integrity and authenticity with efficient mechanisms. Current approaches employ authenticated data structures to store security information, generated by the client and used by the server, to compute proofs that show the answers to the queries are authentic. The existing solutions have shortcomings with multi-clause queries and duplicate values in a column. We propose a hierarchical authenticated data structure for storing security information, which alleviates the mentioned problems. We provide a unified formal definition of a secure outsourced database scheme, and prove that our proposed scheme is secure according to this definition, which captures previously separate properties such as correctness, completeness, and freshness. The performance evaluation based on our prototype implementation confirms the efficiency of the proposed outsourced database scheme, showing more than 50% decrease in proof size and proof generation time compared to previous work, and about 1-20% communication overhead compared to the query result size.