[Resource Topic] 1998/004: Universal Service Providers for Database Private Information Retrieval

Welcome to the resource topic for 1998/004

Universal Service Providers for Database Private Information Retrieval

Authors: Giovanni Di-Crescenzo, Yuval Ishai, Rafail Ostrovsky


We consider the question of private information retrieval in the
so-called commodity-based'' model. This model was recently proposed by Beaver for practically-oriented service-provider internet applications. In this paper, we show the following, somewhat surprising, results regarding this model for the problem of private-information retrieval: (1) the service-provider model allows to dramatically reduce the overall communication involving the user, using off-line pre-processing messages from service-providers’’ to
databases, where the service-providers do not need to know the
database contents, nor the future user’s requests; (2) our
service-provider solutions are resilient against more than a majority
(in fact, all-but-one) coalitions of service-providers; and (3) these
results hold for {\em both} the computational and the
information-theoretic setting.

More specifically, we exhibit a service-provider algorithm which can
sell'' (i.e., generate and send) commodities’’ to users and
databases, that subsequently allow users to retrieve database contents
in a way which hides from the database which particular item the user
retrieves. The service-providers need not know anything about the
contents of the databases nor the nature of the user’s requests in
order to generate commodities. Our commodity-based solution
significantly improves communication complexity of the users (i.e.,
counting both the size of commodities bought by the user from the
service-providers and the subsequent communication with the databases)
compared to all previously known on-line private information retrieval
protocols (i.e., without the help of the service-providers).
Moreover, we show how commodities from different service-providers can
be {\em combined} in such a way that even if all-but-one'' of the service-providers collude with the database, the user's privacy remains intact. Finally, we show how to re-use commodities in case of multiple requests (i.e., in the amortized sense), how to check’’
commodity-correctness, and how some of the solutions can be extended
to the related problem of {\em Private Information Storage}.

ePrint: https://eprint.iacr.org/1998/004

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