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Published byMervyn Wright Modified over 3 years ago

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Nir Bitansky, Ran Canetti, Omer Paneth, Alon Rosen

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Largest Known Prime 2 57,885,161 − 1 Electronic Frontier Foundation offers $250,000 prize for a prime with at least a billion digits

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Knowledge Algorithm Knowledge Polynomial Time Extraction Procedure

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Proofs of Knowledge Witness Extraction Hide the Witness Secrecy : Zero-Knowledge \ Witness indistinguishability Goal: Extract knowledge that is not publicly available

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CCA Encryption Reduction To CPA Extraction

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More Knowledge Zero-knowledge Proofs, Signatures, Non-malleable Commitments, Multi-party Computation, Obfuscation,… Reduction Extraction

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How to Extract? Algorithm Knowledge Extraction?

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Extraction by Interaction Or : Black-Box Extraction Adversary Extraction Public Parameters

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Out of Reach Applications 3-Message Zero-Knowledge 2-Message Succinct Argument (SNARG)

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Out of Reach Applications [Goldreich-Krawczyk][Gentry-Wichs] Black-Box Security Proof is Impossible

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Knowledge of Exponent Adversary Extraction [Damgård 92] Non-Black-Box Extraction

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Applications of KEA 3-Message Zero-Knowledge 2-Message Succinct Argument (SNARG) Knowledge of Exponent Assumption* (KEA) * and variants [HT98,BP04,Mie08,G10,L12,BCCT13,GGPR13,BCIOP13]

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Extractable Functions Adversary Extraction [Canetti-Dakdouk 08]

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Remarks on EF Adversary Extraction OWF, CRHF

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Applications of EF 3-Message Zero-Knowledge 2-Message Succinct Argument (Privately Verifiable) Knowledge of Exponent Extractable One-Way Functions (EOWF) Extractable Collision-Resistant Hash Functions (ECRH) [BCCT12,GLR12,DFH12]

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What is missing? Clean assumptions Candidates Strong applications

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A Reduction Using EF Reduction

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Do Extractable One-Way Functions with an Explicit Extractor Exist?

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It depends on the Auxiliary Input.

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Example: Zero-Knowledge Auxiliary input

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Definition of EF with A.I.

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Types of A.I. Individual \ Common Bounded \ Unbounded

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What type of A.I. do we need?

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Example: Zero-Knowledge

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PossibleImpossibleOpen Subexp-LWEIndistinguishability Obfuscation Explicit Extractor Delegation for P from Subexp-PIR [Kalai-Raz-Rothblum13]

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Generalized EOWF EOWF* = Privately-Verifiable Generalized EOWF 1.EOWF* suffices for applications of EOWF. 2.The impossibility results holds also for EOWF* 3.Can remove * assuming publicly-verifiable delegation for P (P-certificates)

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Application 3-Message Zero-Knowledge EOWF 3-Message Zero-Knowledge For verifiers w. bounded A.I. EOWF with bounded A.I. EOWF* with bounded A.I. [BCCGLRT13]

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Construction Survey Impossibility

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Construction EOWF* with Bounded A.I from Privately-Verifiable Delegation for P EOWF with Bounded A.I from Publicly-Verifiable Delegation for P

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First Attempt

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Extraction

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One-Wayness

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Problem Solution: Delegation for P (following the protocols of [B01,BLV03])

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Delegation for P

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Final Construction

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Extraction

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One-Wayness

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Generalized EOWF

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Impossibility Assuming indistinguishability obfuscation, there is not EOWF with unbounded common auxiliary input

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Intuition Adversary Non-Black-Box Extractor

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Plan 1.Assuming virtual black-box obfuscation [Goldreich, Hada-Tanaka] 2.Assuming indistinguishability obfuscation

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Common A.I.

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Universal Extraction Universal Extractor Universal Adversary

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Black-Box Extraction Universal Extractor Universal Adversary Black-box obfuscation

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Black-Box Extraction Black-Box Extractor Adversary

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Indistinguishability Obfuscation Compute the same function

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Indistinguishability Obfuscation Extractor Adversary

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Indistinguishability Obfuscation Extractor Alternative adversary

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Alternative Adversary Using the Sahai-Waters puncturing technique

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Indistinguishability Obfuscation Extractor

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Back to the Construction?Construction

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PossibleImpossibleOpen Extractable CRHF\COM\1-to-1 OWF

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Thank You

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