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Efficient Private Conjunctive Query Protocol Over Encrypted Data

Department of Computer Science and Engineering, Jatiya Kabi Kazi Nazrul Islam University, Trishal, Mymensingh 2224, Bangladesh
Faculty of Education and Integrated Arts and Sciences, Waseda University, Tokyo 169-8050, Japan
Author to whom correspondence should be addressed.
Appeared at Progress in Cryptology-AFRICACRYPT 2017 (Africacrypt2017). We extend the contribution of the paper by adding another efficient protocol for PCQ processing using an N-ary encoding, its homomorphic evaluation, and showing the corresponding results.
Received: 15 December 2020 / Revised: 7 January 2021 / Accepted: 12 January 2021 / Published: 18 January 2021
Conjunctive queries play a key role in retrieving data from a database. In a database, a query containing many conditions in its predicate, connected by an “and/&/∧” operator, is called a conjunctive query. Retrieving the outcome of a conjunctive query from thousands of records is a heavy computational task. Private data access to an outsourced database is required to keep the database secure from adversaries; thus, private conjunctive queries (PCQs) are indispensable. Cheon, Kim, and Kim (CKK) proposed a PCQ protocol using search-and-compute circuits in which they used somewhat homomorphic encryption (SwHE) for their protocol security. As their protocol is far from being able to be used practically, we propose a practical batch private conjunctive query (BPCQ) protocol by applying a batch technique for processing conjunctive queries over an outsourced database, in which both database and queries are encoded in binary format. As a main technique in our protocol, we develop a new data-packing method to pack many data into a single polynomial with the batch technique. We further enhance the performances of the binary-encoded BPCQ protocol by replacing the binary encoding with N-ary encoding. Finally, we compare the performance to assess the results obtained by the binary-encoded BPCQ protocol and the N-ary-encoded BPCQ protocol. View Full-Text
Keywords: private conjunctive query; encrypted data; packing method; homomorphic encryption private conjunctive query; encrypted data; packing method; homomorphic encryption
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MDPI and ACS Style

Saha, T.K.; Koshiba, T. Efficient Private Conjunctive Query Protocol Over Encrypted Data. Cryptography 2021, 5, 2.

AMA Style

Saha TK, Koshiba T. Efficient Private Conjunctive Query Protocol Over Encrypted Data. Cryptography. 2021; 5(1):2.

Chicago/Turabian Style

Saha, Tushar K., and Takeshi Koshiba. 2021. "Efficient Private Conjunctive Query Protocol Over Encrypted Data" Cryptography 5, no. 1: 2.

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