Transcript Private Information Retrieval Benny Chor Oded Goldreich Eyal Kushilevitz

Private Information Retrieval
Benny Chor
Technion, Haifa, Istarel
Oded Goldreich
Weizmann Institute of Science, Rehovot, Israel
Eyal Kushilevitz
Technion, Haifa, Isarael
Madhu Sudan
Massachusetts Institute of Technology,
Cambridge, Massachusetts
Journal of the ACM, Vol.45, No.6,
November 1998, pp.965-982
Abstract
Today, a lot of research is devoted to methods that protect the
database against a “curious” user. While, there is no
method to protect the privacy of the User….
Public accessible database are an indispensable resource for retrieving
up to-date information. But they also pose a significant risk to the
privacy of the user, since a curious database operator can follow the
user’s queries and infer what the user is after.
To completely guarantee the privacy of the user, the whole database
should be down-loaded.
This paper investigated whether by replicating the database, more
efficient solution to the private retrieval problem can be obtained.
We describe schemes that enable a user to access k replicated copies of a
database(k>=2) and privately retrieve information stored in the
database. This means that each individual server gets no information
on the identity of the item retrieved by the user.
Organization
1.
2.
3.
4.
5.
Introduction
Model, Definitions and Discussion
Single bit PIR Schemes
Private Block Retrieval
Lower Bound
What is PIR?
We view the database as a binary string x =
x1…xn of length n. Identical copies of
this string are stored by k>=2 servers.
The user has some index i,and he is
interested in obtaining the value of the bit
xi.To achieve this goal, the user queries
each of the servers and gets replies from
which the desired bit xi can be computed.
The query to each server is distributed
independently of i and therefore each
server gains no information about i. A
scheme with these properties is called a
Private Information Retrieval(PIR)
scheme.
Main result of this paper
---some PIR schemes
1. A basic Two-server scheme
This scheme allows user to privately obtain some bits of database by
receiving a single bit from each of two servers so that none of the servers
know the identity information.It’s the basis of all the schemes.
2. A Multi-server scheme
This scheme allows user to obtain the desired bit by asking queries to
k=2^d servers.
3. The covering code scheme
a method based on covering codes that can reduce the number of server to
about 2^d/d while maintaining about the same communication cost
4. A Generic Transformation
a generic transformation which may be applied to reduce the
communication complexity of schemes.
Finally, about the paper…
 It take me quite a long time to
find a journal paper that is
formal and not too old .
 After I read this paper for 3
times, I found it so difficult to
understand thoroughly!
 I hope I can get through it
when I have time in the
future…
Wish you have a
wonderful
Thanksgiving!