One Server for the Price of Two: Simple and Fast Single-Server Private Information Retrieval


Alexandra Henzinger, Matthew M. Hong, and Henry Corrigan-Gibbs, MIT; Sarah Meiklejohn, Google; Vinod Vaikuntanathan, MIT


We present SimplePIR, the fastest single-server private information retrieval scheme known to date. SimplePIR’s security holds under the learning-with-errors assumption. To answer a client’s query, the SimplePIR server performs fewer than one 32-bit multiplication and one 32-bit addition per database byte. SimplePIR achieves 10 GB/s/core server throughput, which approaches the memory bandwidth of the machine and the performance of the fastest two-server private-information-retrieval schemes (which require non-colluding servers). SimplePIR has relatively large communication costs: to make queries to a 1 GB database, the client must download a 121 MB "hint" about the database contents; thereafter, the client may make an unbounded number of queries, each requiring 242 KB of communication. We present a second single-server scheme, DoublePIR, that shrinks the hint to 16 MB at the cost of slightly higher per-query communication (345 KB) and slightly lower throughput (7.4 GB/s/core). Finally, we apply our new private-information-retrieval schemes, together with a novel data structure for approximate set membership, to the task of private auditing in Certificate Transparency. We achieve a strictly stronger notion of privacy than Google Chrome’s current approach with 13x more communication: 16 MB of download per week, along with 1.5 KB per TLS connection.

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@inproceedings {285367,
author = {Alexandra Henzinger and Matthew M. Hong and Henry Corrigan-Gibbs and Sarah Meiklejohn and Vinod Vaikuntanathan},
title = {One Server for the Price of Two: Simple and Fast {Single-Server} Private Information Retrieval},
booktitle = {32nd USENIX Security Symposium (USENIX Security 23)},
year = {2023},
isbn = {978-1-939133-37-3},
address = {Anaheim, CA},
pages = {3889--3905},
url = {},
publisher = {USENIX Association},
month = aug