ahmed osama research assistant. presentation outline winc- nile university- privacy preserving over...

Privacy Preservation Over Network Coding

Ahmed Osama

Research Assistant

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Presentation Outline

Winc- Nile University- Privacy Preserving Over Network Coding

Introduction Network coding Applications of network coding: recent work

Primitives Linear Network Coding Traffic analysis

Privacy preserving Scheme Security proposed scheme

Future work References


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Network Coding

Network coding is a field of information theory and coding theory and is a method of attaining maximum information flow in a network [Wikipedia].

Pioneering work: [1] R. Ahlswede, N. Cai, S.-Y. R. Li, and R.W. Yeung, “Network information flow,” IEEE Trans. on Information Theory, vol. 46, no. 4, July 2000.


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Network CodingExample Simple store and forward Multicast rate of 1.5 bits per time unit


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Network Coding X-OR is one of the simplest form of data

coding Multicast rate of 2 bits per time unit

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Primitives Linear Network Coding Traffic analysis “Unobservability Vs Anonymity”




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Applications of network coding: recent work


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Application 1:Content DistributionDistribute content to millions of users, such as Software updates Music Films

Traditional MethodContent collected in servers, clients connect to servers to download the information.Problems:Not-scalable, expensive, slow and Single point of failure


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Application 1:Content Distribution P2P networks:

Capacity and computational power of thenetwork increases with the number of users

Avalanche

Example


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Application 2:Vehicular Networks Vehicles communicate with each other and

with roadside infrastructure to increase safety and optimize traffic.

[Y. Lin ;MobiOpp 2007]

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Linear Network Coding

The output flow at a given node is obtained as a linear combination of its input flows. The coefficients of the combination are, by definition, selected from a finite field

……

x1

x2

xn

n

iiixay

Paper Summary- WINC- Nile University

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Network Model

t

s

t

s ϵ V

T ϵ V ; t means one destinationAcyclic graph Is the multi

cast capacity and x1…..,xh

Edge symbols comes from a finite field Fq

y(e) is the symbol carried

on edge e

ᵝ(e) is the LEV

),( TsMinCuth

'

' )'()()(e

e eyeey


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Network Model

T ϵ V ; t means one destination

Acyclic graph By induction we can

calculate that

Global Encoding

Vector(GEV) g(e) = [g1(e),

….gh(e)]

h

iie xegey

1' )()(

'

' )'()()(e

e egeeg

t

s

t

s ϵ V


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Network Model

By induction we can

calculate that

Global Encoding

Vector(GEV) g(e) = [g1(e),

….gh(e)]

h

iie xegey

1' )()(

'

' )'()()(e

e egeeg

h

t

hhhh

h

h x

x

G

x

x

egeg

egeg

ey

ey

.

.

.

.

.

.

)(...)(

...

...

...

)(...)(

)(.

.

.)( 11

1

1111

Global Encoding Matrix

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Traffic analysis

Traffic analysis is the process of intercepting and examining messages in order to deduce information from patterns in communication. It can be performed even when the messages are encrypted and cannot be decrypted. In general, the greater the number of messages observed, or even intercepted and stored, the more can be inferred from the traffic.

Passive attack

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Security proposed schemeProblem Statement Privacy threats exist in network coding since

explicit GEVs provide a back door for adversaries.

We need to prevent flow tracing to protect source and destination from being revealed, Specially in multi-hop wireless network.


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Security proposed scheme Solution

Encoding Global Encoding Vectors using Homomorphic Functions

Homomorphism means operations on plain text can be performed by operating on corresponding cipher text. We need additive propertyE(x+y) = Add(E(x),E(y)) Also we need Scalar Multiplicative propertyE(t.x) = Mul(E(x),t)

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Future Work Propose a scheme that provide less

computational overhead. Authentication vs. privacy tradeoff


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References [1] Y. Lin, B. Liang, and B. Li, “Performance Modeling of

Network Coding in Epidemic Routing,” in Proc. of the First ACM International Workshop on Mobile Opportunistic Networking (MobiOpp), 2007.

[2] S.-Y. R. Li, R. W. Yeung, and N. Cai, “Linear network Coding”, IEEE Trans. on Information Theory, vol. 49, no. 2, Feb. 2003.

[3] R. Ahlswede, N. Cai, S.-Y. R. Li, and R.W. Yeung, “Network information flow,” IEEE Trans. on Information Theory, vol. 46, no. 4, July 2000.

[4] Y. Fan, Y. Jiang, H. Zhu, and X. Shen, "An Efficient Privacy-Preserving Scheme against Traffic Analysis Attacks in Network Coding", Proc.IEEE INFOCOM'09, Rio de Janeiro, Brazil, April 19-25, 2009.


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Thank you

Any Questions ?

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