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Secure Multiterminal Source Codingwith Side Information at the Eavesdropper

Joffrey Villard and Pablo Piantanida

SUPELEC, Dpt. of Telecommunications, Gif-sur-Yvette, France.

Email: {joffrey.villard, pablo.piantanida}@supelec.fr

1st International ICST Workshop on Secure Wireless Networks

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 1 / 31

Introduction

Context

An Alice Bob E[d(An, An)

]. D

J (rate RA)

En Eve 1n H(An|JEn) & ∆

Cn CharlieK (rate RC)

Tradeoff: Min. rates + Min. distortion + Max. equivocation

Our Aim: Find all achievable tuples (RA,RC,D,∆)

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 2 / 31

Introduction

Context

An Alice Bob E[d(An, An)

]. D

J (rate RA)

En Eve 1n H(An|JEn) & ∆

Cn CharlieK (rate RC)

Tradeoff: Min. rates + Min. distortion + Max. equivocation

Our Aim: Find all achievable tuples (RA,RC,D,∆)

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 2 / 31

Introduction

Context

An Alice BobE[d(An, An)

]. D

(+Cn)

J (rate RA)

En Eve 1n H(An|JEn) & ∆

Cn CharlieK (rate RC)

Tradeoff: Min. rates + Min. distortion + Max. equivocation

Our Aim: Find all achievable tuples (RA,RC,D,∆)

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 2 / 31

Introduction

Context

An Alice BobE[d(An, An)

]. D

(+Cn)

J (rate RA)

En Eve 1n H(An|JEn) & ∆

Cn CharlieK (rate RC)

Tradeoff: Min. rates + Min. distortion + Max. equivocation

Our Aim: Find all achievable tuples (RA,RC,D,∆)

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 2 / 31

Introduction

ReferencesMultiterminal source coding.D. Slepian and J. Wolf. Noiseless coding of correlated information sources. IEEE Trans. IT, 19(4):471–480, 1973.

T. Berger. Multiterminal source coding. in The information theory approach to communications, 1977.

Source coding with side-information.A. Wyner and J. Ziv. The rate-distortion function for source coding with side information at the decoder. IEEE Trans. IT,22(1):1–10, 1976.

Information-theoretic security.C.E. Shannon. Communication theory of secrecy systems. BSTJ, 28:656–715, 1949.

A.D. Wyner. The wire-tap channel. BSTJ, 54(8):1355–1387, 1975.

I. Csiszar and J. Korner. Broadcast channels with confidential messages. , 24(3):339–348, 1978.

Y. Liang, H.V. Poor, and S. Shamai. Information theoretic security. Now Publishers, 2009.

Secure source coding.H. Yamamoto. Rate-distortion theory for the Shannon cipher system. IEEE Trans. IT, 43(3):827–835, 1997.

V. Prabhakaran and K. Ramchandran. On secure distributed source coding. In Proc. ITW, p. 442–447, 2007.

D. Gunduz, E. Erkip, and H.V. Poor. Lossless compression with security constraints. In Proc. ISIT, p. 111–115, 2008.

R. Tandon, S. Ulukus, and K. Ramchandran. Secure source coding with a helper. In Proc. Allerton, p. 1061–1068, 2009.

N. Merhav. Shannon’s secrecy system with informed receivers and its application to systematic coding for wiretappedchannels. IEEE Trans. IT, 54(6):2723–2734, 2008.

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 3 / 31

Introduction

Outline

1 Definitions and First ResultsDefinitionsInner and Outer BoundsInner Bound–Insight

2 Results of OptimalityUncoded Side InformationLossless Compression of Both SourcesAlternative Characterizations

3 Application Example (Uncoded Side Information)

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 4 / 31

Definitions and First Results Definitions

Outline

1 Definitions and First ResultsDefinitionsInner and Outer BoundsInner Bound–Insight

2 Results of OptimalityUncoded Side InformationLossless Compression of Both SourcesAlternative Characterizations

3 Application Example (Uncoded Side Information)

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 5 / 31

Definitions and First Results Definitions

Definitions

A, C and E : three finite sets

(Ai,Ci,Ei)i≥1: i.i.d random variables on A× C × Ewith known joint distribution p(a, b, e)

d : A×A → [0 ; dmax]: a finite distortion measure

An (n,RA,RC)-code for source coding in this setup is defined by

Two encoding functions at Alice and CharliefA : An → {1, . . . , 2nRA} and fC : Cn → {1, . . . , 2nRC}, resp.

A decoding function at Bobg : {1, . . . , 2nRA} × {1, . . . , 2nRC} → An

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 6 / 31

Definitions and First Results Definitions

Definitions (cont.)

An Alice Bob E[d(An, An)

]. D

J (rate RA)

En Eve 1n H(An|JEn) & ∆

Cn CharlieK (rate RC)

A tuple (RA,RC,D,∆) ∈ R4+ is achievable if,

for any ε > 0, there exists an (n,RA + ε,RC + ε)-code (fA, fC, g)such that:

E[d(An, g(fA(An), fC(Cn)))

]≤ D + ε

1n

H(An|fA(An),En) ≥ ∆− ε

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 7 / 31

Definitions and First Results Inner and Outer Bounds

Outline

1 Definitions and First ResultsDefinitionsInner and Outer BoundsInner Bound–Insight

2 Results of OptimalityUncoded Side InformationLossless Compression of Both SourcesAlternative Characterizations

3 Application Example (Uncoded Side Information)

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 8 / 31

Definitions and First Results Inner and Outer Bounds

Inner and Outer Bounds

Theorem (Inner bound)

If

(RA,RC,D,∆) ∈ R4+ is achievable if there exist

r.v. U, V, W on some finite sets U , V,W, resp., s.t.p(uvwace) = p(u|v)p(v|a)p(w|c)p(ace) ,

a function A : V ×W → A, s.t.

RA ≥ I(V; A|W)

RC ≥ I(W; C|V)

RA + RC ≥ I(VW; AC)

D ≥ E[d(A, A(V,W))

]∆ ≤ H(A|UE)− I(V; A|UW)

∆− RC ≤ H(A|V)− I(A; E|U)− I(W; C|V)

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 9 / 31

Definitions and First Results Inner and Outer Bounds

Inner and Outer Bounds

Theorem (Inner bound)

If

(RA,RC,D,∆) ∈ R4+ is achievable if there exist

r.v. U, V, W on some finite sets U , V,W, resp., s.t.p(uvwace) = p(u|v)p(v|a)p(w|c)p(ace) ,

a function A : V ×W → A, s.t.

RA ≥ I(V; A|W)

RC ≥ I(W; C|V)

RA + RC ≥ I(VW; AC)

D ≥ E[d(A, A(V,W))

]∆ ≤ H(A|UE)− I(V; A|UW)

∆− RC ≤ H(A|V)− I(A; E|U)− I(W; C|V)

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 9 / 31

Definitions and First Results Inner and Outer Bounds

Inner and Outer Bounds

Theorem (Inner bound)

If

(RA,RC,D,∆) ∈ R4+ is achievable if there exist

r.v. U, V, W on some finite sets U , V,W, resp., s.t.p(uvwace) = p(u|v)p(v|a)p(w|c)p(ace) ,

a function A : V ×W → A, s.t.

RA ≥ I(V; A|W)

RC ≥ I(W; C|V)

RA + RC ≥ I(VW; AC)

D ≥ E[d(A, A(V,W))

]∆ ≤ H(A|UE)− I(V; A|UW)

∆− RC ≤ H(A|V)− I(A; E|U)− I(W; C|V)

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 9 / 31

Definitions and First Results Inner and Outer Bounds

Inner and Outer Bounds

Theorem (Inner bound)

If

(RA,RC,D,∆) ∈ R4+ is achievable if there exist

r.v. U, V, W on some finite sets U , V,W, resp., s.t.p(uvwace) = p(u|v)p(v|a)p(w|c)p(ace) ,

a function A : V ×W → A, s.t.

RA ≥ I(V; A|W)

RC ≥ I(W; C|V)

RA + RC ≥ I(VW; AC)

D ≥ E[d(A, A(V,W))

]∆ ≤ H(A|UE)− I(V; A|UW)

∆− RC ≤ H(A|V)− I(A; E|U)− I(W; C|V)

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 9 / 31

Definitions and First Results Inner and Outer Bounds

Inner and Outer Bounds

Theorem (Inner bound)

If

(RA,RC,D,∆) ∈ R4+ is achievable if there exist

r.v. U, V, W on some finite sets U , V,W, resp., s.t.p(uvwace) = p(u|v)p(v|a)p(w|c)p(ace) ,

a function A : V ×W → A, s.t.

RA ≥ I(V; A|W)

RC ≥ I(W; C|V)

RA + RC ≥ I(VW; AC)

D ≥ E[d(A, A(V,W))

]∆ ≤ H(A|UE)− I(V; A|UW)

∆− RC ≤ H(A|V)− I(A; E|U)− I(W; C|V)

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 9 / 31

Definitions and First Results Inner and Outer Bounds

Inner and Outer Bounds

Theorem (Outer bound)

If (RA,RC,D,∆) ∈ R4+ is achievable, then there exist

r.v. U, V, W on some finite sets U , V,W, resp., s.t.p(wace) = p(w|c)p(ace), p(uvace) = p(u|v)p(v|a)p(ace) ,

a function A : V ×W → A, s.t.

RA ≥ I(V; A|W)

RC ≥ I(W; C|V)

RA + RC ≥ I(VW; AC)

D ≥ E[d(A, A(V,W))

]∆ ≤ H(A|UE)− I(V; A|UW)

∆− RC ≤ H(A|V)− I(A; E|U)− I(W; C|V)

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 9 / 31

Definitions and First Results Inner and Outer Bounds

Auxiliary Variables

Inner Bound

U V A E

CW

Outer Bound

U V A E

C

A E

CW

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 10 / 31

Definitions and First Results Inner Bound–Insight

Outline

1 Definitions and First ResultsDefinitionsInner and Outer BoundsInner Bound–Insight

2 Results of OptimalityUncoded Side InformationLossless Compression of Both SourcesAlternative Characterizations

3 Application Example (Uncoded Side Information)

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 11 / 31

Definitions and First Results Inner Bound–Insight

Three Corner Points

3 three-step schemes to deliver (U,V) and W, usingsuperposition coding (U − V − A− C −W)previously received information used as side informationrandom binningtime-sharing

Corner point (I)

(II) (III)

Comm. order W, U, V

U, W, V U, V, W

RA I(V; A|W)

I(U; A) + I(V; A|UW) I(V; A)

RC I(W; C)

I(W; C|U) I(W; C|V)

D E[d(A, A(V,W))

]

— —

∆ H(A|UE)− I(V; A|UW)

H(A|UE)− I(V; A|UW) H(A|UE)− I(V; A|U)

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 12 / 31

Definitions and First Results Inner Bound–Insight

Three Corner Points

3 three-step schemes to deliver (U,V) and W, usingsuperposition coding (U − V − A− C −W)previously received information used as side informationrandom binningtime-sharing

Corner point (I) (II)

(III)

Comm. order W, U, V U, W, V

U, V, W

RA I(V; A|W) I(U; A) + I(V; A|UW)

I(V; A)

RC I(W; C) I(W; C|U)

I(W; C|V)

D E[d(A, A(V,W))

]—

∆ H(A|UE)− I(V; A|UW) H(A|UE)− I(V; A|UW)

H(A|UE)− I(V; A|U)

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 12 / 31

Definitions and First Results Inner Bound–Insight

Three Corner Points

3 three-step schemes to deliver (U,V) and W, usingsuperposition coding (U − V − A− C −W)previously received information used as side informationrandom binningtime-sharing

Corner point (I) (II) (III)

Comm. order W, U, V U, W, V U, V, W

RA I(V; A|W) I(U; A) + I(V; A|UW) I(V; A)

RC I(W; C) I(W; C|U) I(W; C|V)

D E[d(A, A(V,W))

]— —

∆ H(A|UE)− I(V; A|UW) H(A|UE)− I(V; A|UW) H(A|UE)− I(V; A|U)

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 12 / 31

Definitions and First Results Inner Bound–Insight

Time-Sharing

Segment (I)–(II)

D = E[d(A, A(V,W))

]∆ = H(A|UE)− I(V; A|UW)

RA + RC = I(VW; AC)

(I)

(II)

(III)RA

RC

Segment (II)–(III)

D = E[d(A, A(V,W))

]∆− RC = H(A|UE)− I(V; A|U)− I(W; C|V)

RA + RC = I(VW; AC)

(I)

(II)

(III)

RC

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 13 / 31

Definitions and First Results Inner Bound–Insight

Time-Sharing

Segment (I)–(II)

D = E[d(A, A(V,W))

]∆ = H(A|UE)− I(V; A|UW)

RA + RC = I(VW; AC)

(I)

(II)

(III)RA

RC

Segment (II)–(III)

D = E[d(A, A(V,W))

]∆− RC = H(A|UE)− I(V; A|U)− I(W; C|V)

RA + RC = I(VW; AC)

(I)

(II)

(III)

RC

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 13 / 31

Definitions and First Results Inner Bound–Insight

Achievable Region for Some Fixed D

(I)

(II)

(III)

RA

RC

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 14 / 31

Results of Optimality Uncoded Side Information

Outline

1 Definitions and First ResultsDefinitionsInner and Outer BoundsInner Bound–Insight

2 Results of OptimalityUncoded Side InformationLossless Compression of Both SourcesAlternative Characterizations

3 Application Example (Uncoded Side Information)

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 15 / 31

Results of Optimality Uncoded Side Information

Context

An Alice Bob E[d(An, An)

]. D

J (rate RA)

En Eve 1n H(An|JEn) & ∆

Cn

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 16 / 31

Results of Optimality Uncoded Side Information

Auxiliary Variables

Inner Bound

U V A E

CW

Outer Bound

U V A E

C

A E

CW

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 17 / 31

Results of Optimality Uncoded Side Information

Uncoded Side Information

Theorem (Rate-Distortion-Equivocation Region)

If

(RA, D,∆) ∈ R3+ is achievable i.f.f. there exist

r.v. U, V

, W

on some finite sets U , V

,W

, resp., s.t.p(uvace) = p(u|v)p(v|a)p(ace) ,

a function A : V × C → A, s.t.

RA ≥ I(V; A|C)

D ≥ E[d(A, A(V,C))

]∆ ≤ H(A|UE)− I(V; A|UC)

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 18 / 31

Results of Optimality Uncoded Side Information

Uncoded Side Information (cont.)

Achievability: point (I) with W = C

(I)(II)

(III)

RA

Converse: new proof

Wyner-Ziv coding achieves the optimal performanceif one side information is less noisy than the other(optimal choice: U∗ = ∅ or U∗ = V)

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 19 / 31

Results of Optimality Lossless Compression of Both Sources

Outline

1 Definitions and First ResultsDefinitionsInner and Outer BoundsInner Bound–Insight

2 Results of OptimalityUncoded Side InformationLossless Compression of Both SourcesAlternative Characterizations

3 Application Example (Uncoded Side Information)

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 20 / 31

Results of Optimality Lossless Compression of Both Sources

Context

An Alice Bob (An, Cn) ≈ (An,Cn)J (rate RA)

En Eve 1n H(An|JEn) & ∆

Cn CharlieK (rate RC)

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 21 / 31

Results of Optimality Lossless Compression of Both Sources

Auxiliary Variables

Inner Bound

U V A E

CW

Outer Bound

U V A E

C

A E

CW

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 22 / 31

Results of Optimality Lossless Compression of Both Sources

Lossless Compression of Both Sources

Theorem (Compression-Equivocation Rates Region)

If

(RA,RC, ∆) ∈ R3+ is achievable i.f.f. there exists

r.v. U

, V, W

on some finite set

s

U

, V,W, resp.,

s.t.p(uace) = p(u|a)p(ace),

a function A : V ×W → A, s.t.

RA ≥ H(A|C)

RC ≥ H(C|U)

RA + RC ≥ H(AC)

∆ ≤ H(A|UE)− H(A|UC)

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 23 / 31

Results of Optimality Lossless Compression of Both Sources

Lossless Compression of Both Sources (cont.)

Achievability: points (I) and (II) with V = A and W = C

(I)

(II)

(III)RA

RC

Converse: new proof

Slepian-Wolf coding is sufficientif E is less noisy than C (U∗ = A, and ∆ = 0)

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 24 / 31

Results of Optimality Alternative Characterizations

Outline

1 Definitions and First ResultsDefinitionsInner and Outer BoundsInner Bound–Insight

2 Results of OptimalityUncoded Side InformationLossless Compression of Both SourcesAlternative Characterizations

3 Application Example (Uncoded Side Information)

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 25 / 31

Results of Optimality Alternative Characterizations

Giving U to Eve is also optimal

Alice can enable Eve to decode the common message U:

RA ≥ (·) + [I(U; C)− I(U; E)]+ ,

with no loss on secrecy

Achievability: OKConverse: new proof

cf. broadcast channel with confidential messages[Csiszàr & Körner–1978]

optimal choice U∗:part of V which conveys “more information” about E than C

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 26 / 31

Application Example (Uncoded Side Information)

Outline

1 Definitions and First ResultsDefinitionsInner and Outer BoundsInner Bound–Insight

2 Results of OptimalityUncoded Side InformationLossless Compression of Both SourcesAlternative Characterizations

3 Application Example (Uncoded Side Information)

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 27 / 31

Application Example (Uncoded Side Information)

Binary Source with BEC and BSC Side Informations

A0

1

C0

e

1

E0

1

1− p

pp

1− p

1− ε

εε

1− ε

(1/2)

(1/2)

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 28 / 31

Application Example (Uncoded Side Information)

Binary Source with BEC and BSC Side Informations

A0

1

C0

e

1

E0

1

1− p

pp

1− p

1− ε

εε

1− ε

(1/2)

(1/2)

Neither Bob nor Eve is a lessnoisy decoder for all values of (p, ε):

0 2p 4p(1− p) h2(p) 1 ε

E stoch. degr.A − C − E

C less noisyU − A− (C,E)⇒I(U; C) ≥ I(U; E)

C more capableI(A; C) ≥ I(A; E)

X

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 28 / 31

Application Example (Uncoded Side Information)

Binary Source with BEC and BSC Side Informations

A0

1

C0

e

1

E0

1

1− p

pp

1− p

1− ε

εε

1− ε

(1/2)

(1/2)

Neither Bob nor Eve is a lessnoisy decoder for all values of (p, ε):

0 2p 4p(1− p) h2(p) 1 ε

E stoch. degr.

A − C − E

C less noisy

U − A− (C,E)⇒I(U; C) ≥ I(U; E)

C more capable

I(A; C) ≥ I(A; E)

X

Wyner-Ziv is optimal Wyner-Ziv is insufficient

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 28 / 31

Application Example (Uncoded Side Information)

Binary Source with BEC and BSC Side Informations

A0

1

C0

e

1

E0

1

1− p

pp

1− p

1− ε

εε

1− ε

(1/2)

(1/2)

distortion d: Hamming distance

source A: uniformly distributed

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 28 / 31

Application Example (Uncoded Side Information)

Illustration (p = 0.1, ε = h2(p) ≈ 0.469)

10−4 10−3 10−2 10−1

10−2

10−1

D

Optimal U, VWyner-Ziv

Equivocation rate at Eve as a function of the distortion level at Bob

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 29 / 31

Conclusion

Summary and Discussion

Single-letter inner and outer bounds on the generalrates-distortion-equivocation region

Results of optimalityuncoded side informationdistributed lossless compression

Ongoing work:

Source-channel coding with security constraints

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 30 / 31

This is the end...

with P. PiantanidaSecure Multiterminal Source Coding with Side Information at the Eavesdroppersubmitted to IEEE Trans. on Inf. Theory, available on arXiv:1105.1658.

with P. Piantanida and S. ShamaiSecure Lossy Source-Channel Wiretapping with Side Information at theReceiving Terminalsto be presented at ISIT 2011.

Thank you for your attention.

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 31 / 31

This is the end...

with P. PiantanidaSecure Multiterminal Source Coding with Side Information at the Eavesdroppersubmitted to IEEE Trans. on Inf. Theory, available on arXiv:1105.1658.

with P. Piantanida and S. ShamaiSecure Lossy Source-Channel Wiretapping with Side Information at theReceiving Terminalsto be presented at ISIT 2011.

Thank you for your attention.

Securenets 2011 Secure Multiterminal Source Coding with SI at Eve 31 / 31

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