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Feasibility and Infeasibility of Secure Computation with Malicious - - PowerPoint PPT Presentation

Feasibility and Infeasibility of Secure Computation with Malicious PUFs Dana Dachman-Soled 1 Nils Fleischhacker 2 Jonathan Katz 1 Anna Lysyanskaya 3 oder 2 Dominique Schr 1 University of Maryland, College Park 2 Saarland University 3 Brown


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Feasibility and Infeasibility of Secure Computation with Malicious PUFs

Dana Dachman-Soled1 Nils Fleischhacker2 Jonathan Katz1 Anna Lysyanskaya3 Dominique Schr¨

  • der2

1University of Maryland, College Park 2Saarland University 3Brown University

August 20, 2014

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What are PUFs?

Physically Uncloneable Function

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What are PUFs?

Physically Uncloneable Function

x y

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What are PUFs?

Physically Uncloneable Function

x y x y′

=

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What are PUFs?

Physically Uncloneable Function

x y x y′

=

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What are PUFs...

... And why do we care?

  • 1. Avoiding cryptographic assumptions.

— ”Unconditional Security”

  • 2. UC from physical assumptions (and no trusted setup)
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Honest or Malicious PUFs? [BFSK11][OSVW13] Here’s my PUF!

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Honest or Malicious PUFs? [BFSK11][OSVW13] Here’s my PUF! Are you sure that thing works correctly?

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Maliciously generated PUFs Stateless Stateful

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Maliciously generated PUFs Stateless k x Fk(x) Stateful

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Maliciously generated PUFs Stateless k x Fk(x) Stateful x1 y1 x1 y1

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Maliciously generated PUFs Stateless k x Fk(x) Stateful x2 y2 x1 y1 x2 y2

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Maliciously generated PUFs Stateless k x Fk(x) Stateful x3 y3 x1 y1 x2 y2 x3 y3

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Secure Computation from PUFs [BFSK11] [OSVW13]

? ?

Honest Malicious Stateless Malicious Stateful Unconditional Under Assumptions

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Secure Computation from PUFs [BFSK11] [OSVW13] This Paper This Paper Honest Malicious Stateless Malicious Stateful Unconditional Under Assumptions

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Our Results

Stateless

There exists an unconditionally UC-secure OT-protocol if the attacker is limited to creating stateless malicious PUFs.

Stateful

If the attacker can create stateful malicious PUFs, then OT cannot exist without additional assumptions.

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Oblivious Transfer

BP

Did she choose 0 or 1? Ok, now what’s s1−b? s0, s1 b sb

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Stateless Malicious PUFs

[BFSK11] [OSVW13] This Paper This Paper Honest Malicious Stateless Malicious Stateful Unconditional Under Assumptions

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Oblivious Transfer from honest PUFs [BFSK11] S R Create PUF c ← {0, 1}λ r := PUF(c) PUF Setup Phase

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Oblivious Transfer from honest PUFs S(s0, s1) R(b) x0, x1 ← {0, 1}λ x0, x1 v := c ⊕ xb v S0 := s0 ⊕ PUF(v ⊕ x0) S1 := s1 ⊕ PUF(v ⊕ x1) S0, S1 sb := Sb ⊕ r Protocol Phase

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Oblivious Transfer from stateless malicious PUFs Protocol adapted from [BFSK11]: S R Create PUFS Create PUFR PUFS c ← {0, 1}λ r := PUFS(c) ⊕ PUFR(c) PUFS, PUFR Setup Phase

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Oblivious Transfer from stateless malicious PUFs S(s0, s1) R(b) x0, x1 ← {0, 1}λ x0, x1 v := c ⊕ xb v S0 := s0 ⊕ PUFS(v ⊕ x0) ⊕ PUFR(v ⊕ x0) S1 := s1 ⊕ PUFS(v ⊕ x1) ⊕ PUFR(v ⊕ x1) S0, S1 sb := Sb ⊕ r Protocol Phase

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Stateful Malicious PUFs

[BFSK11] [OSVW13] This Paper This Paper Honest Malicious Stateless Malicious Stateful Unconditional Under Assumptions

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Barak and Mahmoody for Key Exchange [BM09][IR89]

BP

RO

00101010010000011100011 0010000011111100001110 1011101100110001111001

B A P

0010101001000001110001 001000001111110000111 101110110011000111100

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Extending Barak and Mahmoody for OT

BP

RO

00101010010000011100011 0010000011111100001110 1011101100110001111001

B A P s0, s1 b sb

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Impossibility of OT

The Distribution of Alice’s Views...

B A P

B P
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Impossibility of OT

The Distribution of Alice’s Views...

B A P Views with b = 0 Views with b = 1

B P
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Impossibility of OT

The Distribution of Alice’s Views...

B A P Views with b = 0 Views with b = 1 s1 s0

B P
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Impossibility of OT

The Distribution of Alice’s Views...

B A P Views with b = 0 Views with b = 1 s1 s0

B P

Obviously Bob’s secrets are “s0” and “s1”!

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Impossibility of OT

The Distribution of Alice’s Views...

B A P Views with b = 0 Views with b = 1

B P
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SLIDE 31

Impossibility of OT

The Distribution of Alice’s Views...

B A P Views with b = 0 Views with b = 1

B P

8 1

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Impossibility of OT

The Distribution of Alice’s Views...

B A P Views with b = 0 Views with b = 1

B P

Clearly Alice used b = 1! 8 1

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Extending Barak and Mahmoody for OT

BP

RO

00101010010000011100011 0010000011111100001110 1011101100110001111001

B A P s0, s1 b sb

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Handling PUFs Constructed by Alice Constructed by Bob Currently held by Alice Currently held by Bob

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Handling PUFs Constructed by Alice Constructed by Bob Currently held by Alice Currently held by Bob t-wise independent function

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Handling PUFs Constructed by Alice Constructed by Bob Currently held by Alice Currently held by Bob t-wise independent function

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Handling PUFs Constructed by Alice Constructed by Bob Currently held by Alice Currently held by Bob State State

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Handling PUFs

Constructed by Alice Constructed by Bob Currently held by Alice Currently held by Bob

C B D A

“Intersection Queries”: All actual intersection queries made to B and C. + All queries made to A by Bob. + All queries made to D by Alice.

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Summary & Conclusion

Stateless

There exists an unconditionally UC-secure multiparty computation protocol if the attacker is limited to creating stateless malicious PUFs.

Stateful

If the attacker can create stateful malicious PUFs, then OT cannot exist without additional assumptions.

Thanks!

Nils Fleischhacker fleischhacker@cs.uni-saarland.de