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Perfect Non-interactive Zero-Knowledge for NP

Perfect Non-interactive Zero-Knowledge for NP. Jens Groth Rafail Ostrovsky Amit Sahai UCLA. Will appear on ePrint archive shortly. Non-Interactive Zero-Knowledge. common reference string σ. C ( w )=1 circuit C. P. V. proof/argument π. Problems

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Perfect Non-interactive Zero-Knowledge for NP

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  1. Perfect Non-interactive Zero-Knowledge for NP Jens Groth Rafail Ostrovsky Amit Sahai UCLA Will appear on ePrint archive shortly

  2. Non-Interactive Zero-Knowledge common reference string σ C(w)=1 circuit C P V proof/argument π • Problems • even computational NIZK inefficient • no statistical NIZK arguments for NP • no UC NIZK arguments for NP

  3. Our contributions • Computational NIZK proof for Circuit SAT- O(k)-bit common reference string- O(|C|k)-bit proofs • Perfect NIZK argument for Circuit SAT- non-adaptive soundness- adaptive soundness (restrictions) • Perfect zero-knowledge UC NIZK argument for Circuit SAT

  4. BGN cryptosystem (TCC 2005) Setup G group of order n = pq bilinear map e: G  G  G1 pk = (n, G, G1, e, g, h) ord(g) = n, ord(h) = q Additively homomorphic gm1hr1gm2hr2 = gm1+m2hr1+r2 Multiplication-mapping e(gm1hr1, gm2hr2) = e(g,g)m1m2e(h,gm1r2+m2r1hr1r2) Decision subgroup problem ord(h) = q or ord(h) = n ?

  5. NIZK proof NIZK for Circuit SAT (NAND-gates) BGN-encrypt all wires NIZK proof 0 or 1 plaintexts * - e(c, cg-1) encrypts 0 NIZK proof encrypted bits respect NAND-gates Zero-knowledge simulation ord(g) = ord(h) = n gmhr is perfectly hiding

  6. Perfect zero-knowledge Perfect NIZK argument ord(g) = ord(h) = n Adaptive soundness problem - C satisfiable on ord(h) = q reference string - C unsatisfiable on ord(h) = n ref. string Solution restrict ourselves to circuits of small size so 2|C|log|C|Adv-SD(k) is negligible

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