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Querying Twice to Achieve Information-Theoretic Verifiability in Private Information Retrieval
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  • Stanislav Kruglik ,
  • Son Hoang Dau ,
  • Han Mao Kiah ,
  • Huaxiong Wang ,
  • Liang Feng Zhang
Stanislav Kruglik
Nanyang Technological University

Corresponding Author:[email protected]

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Son Hoang Dau
RMIT University
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Han Mao Kiah
Nanyang Technological University
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Huaxiong Wang
Nanyang Technological University
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Liang Feng Zhang
ShanghaiTech University
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Abstract

Private Information Retrieval (PIR) protocols allow a client to retrieve any file of interest while keeping the files’ identities hidden from the database servers. While most existing PIR protocols assume servers to be honest but curious, we investigate the scenario of dishonest servers that provide incorrect answers to mislead clients into obtaining wrong results. We propose a unified framework for polynomial PIR protocols encompassing various existing protocols that optimize the download rate or total communication cost. We introduce a way to transform a polynomial PIR to a verifiable one without increasing the number of involved servers by doubling the queries. The security guarantees can be information-theoretic or computational, and the verification keys can be public or private. Moreover, in one of our protocols, the ratio between the additional download overhead associated with verification and the normal download cost approaches zero as the file size goes to infinity.