International Association for Cryptologic Research

International Association
for Cryptologic Research


Paper: Private Join and Compute from PIR with Default

Tancrède Lepoint , Apple
Sarvar Patel , Google LLC
Mariana Raykova , Google LLC
Karn Seth , Google LLC
Ni Trieu , Arizona State University
DOI: 10.1007/978-3-030-92075-3_21
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Presentation: Slides
Conference: ASIACRYPT 2021
Abstract: The private join and compute (PJC) functionality enables secure computation over data distributed across different databases, and is applicable to a wide range of applications, many of which address settings where the input databases are of significantly different sizes. We introduce the notion of private information retrieval (PIR) with default, which enables two-party PJC functionalities in a way that hides the size of the intersection of the two databases and incurs sublinear communication cost in the size of the bigger database. We provide two constructions for this functionality, one of which requires offline linear communication, which can be amortized across queries, and one that provides sublinear cost for each query but relies on more computationally expensive tools. We construct inner-product PJC, which has applications to ads conversion measurement and contact tracing, relying on an extension of PIR with default. We evaluate the efficiency of our constructions, which can enable $\mathbf{2^{8}}$ PIR with default lookups on a database of size $\mathbf{2^{25}}$ (or inner-product PJC on databases with such sizes) with the communication of $\mathbf{44}$MB, which costs less than $\mathbf{0.17}$c. for the client and $\mathbf{26.48}$c. for the server.
Video from ASIACRYPT 2021
  title={Private Join and Compute from PIR with Default},
  author={Tancrède Lepoint and Sarvar Patel and Mariana Raykova and Karn Seth and Ni Trieu},