{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,11,25]],"date-time":"2025-11-25T20:46:49Z","timestamp":1764103609361,"version":"3.40.5"},"reference-count":0,"publisher":"Privacy Enhancing Technologies Symposium Advisory Board","issue":"3","license":[{"start":{"date-parts":[[2025,7,1]],"date-time":"2025-07-01T00:00:00Z","timestamp":1751328000000},"content-version":"unspecified","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["PoPETs"],"abstract":"<jats:p>Private Information Retrieval (PIR) permits clients to query data entries from a public database hosted on untrusted servers while preserving client privacy. Traditional PIR models suffer from high computation and\/or bandwidth overhead due to linear database processing. Recently, Online-Offline PIR (OO-PIR) has been proposed to improve PIR practicality by precomputing query-independent materials to accelerate online access. While state-of-the-art OO-PIR schemes (e.g., S&amp;P\u201924, CRYPTO\u201923) successfully reduce online processing cost to sublinear levels, they still impose substantial bandwidth and storage burdens on the client, especially when operating on large databases.\n\nIn this paper, we propose Pirex, a new two-server OO-PIR scheme with semi-honest security that offers minimal client-side inbound bandwidth and storage costs while retaining sublinear processing efficiency. The Pirex design is simple, with most operations being naturally low-cost and streamlined (e.g., XOR, PRF, modular arithmetic). We have fully implemented Pirex and evaluated its real-world performance using commodity hardware. Our results show that Pirex outperforms existing OO-PIR schemes by at least two orders of magnitude. With a 1 TB database, Pirex takes only 55 ms to retrieve a 4 KB entry, compared to 9\u201330 seconds for state-of-the-art approaches. For practical databases with billions of 4 KB entries, Pirex requires just 16 KB of inbound bandwidth\u2014up to three orders of magnitude more efficient.<\/jats:p>","DOI":"10.56553\/popets-2025-0095","type":"journal-article","created":{"date-parts":[[2025,5,19]],"date-time":"2025-05-19T03:14:51Z","timestamp":1747624491000},"page":"192-212","source":"Crossref","is-referenced-by-count":1,"title":["Client-Efficient Online-Offline Private Information Retrieval"],"prefix":"10.56553","volume":"2025","author":[{"given":"Hoang-Dung","family":"Nguyen","sequence":"first","affiliation":[{"name":"Virginia Tech"}]},{"given":"Jorge","family":"Guajardo","sequence":"additional","affiliation":[{"name":"Robert Bosch LLC --- RTC"}]},{"given":"Thang","family":"Hoang","sequence":"additional","affiliation":[{"name":"Virginia Tech"}]}],"member":"35752","published-online":{"date-parts":[[2025,7]]},"container-title":["Proceedings on Privacy Enhancing Technologies"],"original-title":[],"deposited":{"date-parts":[[2025,5,19]],"date-time":"2025-05-19T03:14:55Z","timestamp":1747624495000},"score":1,"resource":{"primary":{"URL":"https:\/\/petsymposium.org\/popets\/2025\/popets-2025-0095.php"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,7]]},"references-count":0,"journal-issue":{"issue":"3","published-online":{"date-parts":[[2025,7]]}},"alternative-id":["10.56553\/popets-2025-0095"],"URL":"https:\/\/doi.org\/10.56553\/popets-2025-0095","relation":{},"ISSN":["2299-0984"],"issn-type":[{"value":"2299-0984","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,7]]}}}