Cryptology ePrint Archive: Report 2019/1075

Private Information Retrieval with Sublinear Online Time

Henry Corrigan-Gibbs and Dmitry Kogan

Abstract: We present the first protocols for private information retrieval that allow fast (sublinear-time) database lookups without increasing the server-side storage requirements. To achieve these efficiency goals, our protocols work in an offline/online model. In an offline phase, which takes place before the client has decided which database bit it wants to read, the client fetches a short string from the servers. In a subsequent online phase, the client can privately retrieve its desired bit of the database by making a second query to the servers. By pushing the bulk of the server-side computation into the offline phase (which is independent of the client's query), our protocols allow the online phase to complete very quickly—in time sublinear in the size of the database. Our protocols can provide statistical security in the two-server setting and computational security in the single-server setting. Finally, we prove that, in this model, our protocols are optimal in terms of the trade-off they achieve between communication and running time.

Category / Keywords: cryptographic protocols / Private Information Retrieval

Original Publication (with major differences): IACR-EUROCRYPT-2020

Date: received 20 Sep 2019, last revised 4 Aug 2021

Contact author: henrycg at cs stanford edu, dkogan at cs stanford edu

Available format(s): PDF | BibTeX Citation

Note: This version fixes two typographical errors.

Version: 20210804:163930 (All versions of this report)

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