• DOI:10.1145/1039488.1039489
• Corpus ID: 52827731

Concurrent zero-knowledge

@article{Dwork2004ConcurrentZ,
  title={Concurrent zero-knowledge},
  author={Cynthia Dwork and Moni Naor and Amit Sahai},
  journal={J. ACM},
  year={2004},
  volume={51},
  pages={851-898}
}

• C. Dwork, M. Naor, A. Sahai
• Published 1 November 2004
• Computer Science
• J. ACM

Concurrent executions of a zero-knowledge protocol by a single prover (with one or more verifiers) may leak information and may not be zero-knowledge <i>in toto</i>. In this article, we study the problem of maintaining zero-knowledge.We introduce the notion of an (α, β) <i>timing constraint</i>: for any two processors <i>P</i>₁ and <i>P</i>₂, if <i>P</i>₁ measures α elapsed time on its local clock and <i>P</i>₂ measures β elapsed time on its local clock, and <i>P</i>₂ starts <i>after</i> <i>P</i>₁ does, then <i>P</i>₂ will finish after <i>P</i>₁ does. We show that if the adversary is constrained by an (α, β) assumption then there exist four-round almost concurrent zero-knowledge interactive proofs and perfect concurrent zero-knowledge arguments for every language in <i>NP</i>. We also address the more specific problem of <i>Deniable Authentication</i>, for which we propose several particularly efficient solutions. Deniable Authentication is of independent interest, even in the sequential case; our concurrent solutions yield sequential solutions <i>without recourse to timing</i>, that is, in the standard model.