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Protecting the Privacy of Users in e-Commerce Environment

Protecting the Privacy of Users in e-Commerce Environment

Date ： 2010.10.27Reporter:Chien-Wen Huang

Author:Chun-Hua Chen and Gwoboa Horng出處 :CCCT2004, Aug, 2004.

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Outline

INTRODUCTION1

BASIC DEFINITION OF OS-PIR AND OUR OS-PIR SCHEME2

33 THEOREM AND PROOF

2

COMPARISONS TO OTHER PIR SCHEMES4

CONCLUSIONS5

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INTRODUCTION

Private Information Retrieval: PIR A user to keep his preferences private from

everybody including the server. EX:Patent Databases 、 Pharmaceutical

Databases.

1.The first research of PIR was done by Chor et al. in 1995.(communication complexity:O(n1/k))

2.To improve the complexity, Chor et al. introduced the notation of Computational PIR(CPIR)

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Private Information Retrieval

EX:使用者隨機選取 S = {5,15,47} (假定 n=10000 , index i = 15, S i = {5,47})⊕

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We propose a simple one-server PIR(OS-PIR) scheme to provide privacy protection for online users in e-commerce

1.The scheme is more practical than previous PIR schemes in e-commerce environment.

2.The scheme has theoretical security to user privacy.

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多媒體網路安全實驗室 BASIC DEFINITION OF OS-PIR

AND OUR OS-PIR SCHEME

1. The user produces a query: to database server.

2. The database server responds

3. The user reconstructs the desired bit xi .(by reconstruction function )

Correctness: For every ,

Privacy: For every 6

},...,3,2,1{][ nni n

nxxX }1,0{...1

nX }1,0{ ][ni

))(Pr())(Pr( qjQqiQ ][, nji

)(iQ))(,( iQXA

)))(,(),(,( iQXAiQiR

ixiQXAiQiR )))(,(),(,(

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OS-PIR scheme(1)

1. The user randomly choose a small prime P1(e.g 19 or 101) and sends P1 to the database server. In other words, =P1.

2. The database server calculates and sends it back to the user.

1)

2) For k=2 to n do

(a)Calculate the next bigger prime Pk

(b) (xk is the value of k bit of X)

3)

7

)(iQ))(,( iQXA

)( 11 Q(i) PPa

kxaa )P(* kaiQXA ))(,(

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OS-PIR scheme(2)3) The user reconstructs the desired bit

1) Calculate the Pi (the user knows P1 already)

2) If mod Pi =0

Then =1

Else =0

EX: The Database [0,1,0,0,1,0,0,1] ,and user choose randam prime P1=19

1. P1= =19

2.

3.

8

ix

))(,( iQXAixix

)(iQ...*)29P(*)23P(*19 32

32xxa

,...)0,0,1,0 retrieve,1(0mod 依序開始由iPa

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THEOREM AND PROOFOur scheme proposed is OS-PIR,has

information-theoretic security in the property of privacy.1. Match the form of the OS-PIR scheme.

2. the user and the database server can calculate the value of Pi both.

3. Satisfy the property of privacy: Because the is P1, a small prime randomly chosen by user.

9

)(iQ

))(Pr())(Pr( qjQqiQ

多媒體網路安全實驗室 COMPARISONS TO OTHER PIR

SCHEMES

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CONCLUSIONS

The OS-PIR scheme was proposed which has practical feasibility and it can be easily implemented.

It avoids the large management overheads of multi-servers and has theoretical security to users’ privacy.

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