261 research outputs found
Single-Server Single-Message Online Private Information Retrieval with Side Information
In many practical settings, the user needs to retrieve information from a
server in a periodic manner, over multiple rounds of communication. In this
paper, we discuss the setting in which this information needs to be retrieved
privately, such that the identity of all the information retrieved until the
current round is protected. This setting can occur in practical situations in
which the user needs to retrieve items from the server or a periodic basis,
such that the privacy needs to be guaranteed for all the items been retrieved
until the current round. We refer to this setting as an \emph{online private
information retrieval} as the user does not know the identities of the future
items that need to be retrieved from the server.
Following the previous line of work by Kadhe \emph{et al.}~we assume that the
user knows a random subset of messages in the database as a side
information which are unknown to the server. Focusing on scalar-linear
settings, we characterize the \emph{per-round capacity}, i.e., the maximum
achievable download rate at each round, and present a coding scheme that
achieves this capacity. The key idea of our scheme is to utilize the data
downloaded during the current round as a side information for the subsequent
rounds. We show for the setting with messages stored at the server, the
per-round capacity of the scalar-linear setting is for round
and for round , provided that
is a power of .Comment: 7 pages; This work is a long version of an article submitted to IEEE
for possible publicatio
Single-Server Multi-Message Private Information Retrieval with Side Information
We study the problem of single-server multi-message private information
retrieval with side information. One user wants to recover out of
independent messages which are stored at a single server. The user initially
possesses a subset of messages as side information. The goal of the user is
to download the demand messages while not leaking any information about the
indices of these messages to the server. In this paper, we characterize the
minimum number of required transmissions. We also present the optimal linear
coding scheme which enables the user to download the demand messages and
preserves the privacy of their indices. Moreover, we show that the trivial MDS
coding scheme with transmissions is optimal if or .
This means if one wishes to privately download more than the square-root of the
number of files in the database, then one must effectively download the full
database (minus the side information), irrespective of the amount of side
information one has available.Comment: 12 pages, submitted to the 56th Allerton conferenc
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