Strengthening zero-knowledge protocols using signatures

  • Authors:
  • Juan A. Garay;Philip MacKenzie;Ke Yang

  • Affiliations:
  • Bell Labs, Lucent Technologies, Murray Hill, NJ;Bell Labs, Lucent Technologies, Murray Hill, NJ;Computer Science Dept., Carnegie Mellon University, Pittsburgh, PA

  • Venue:
  • EUROCRYPT'03 Proceedings of the 22nd international conference on Theory and applications of cryptographic techniques
  • Year:
  • 2003

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Abstract

Recently there has been an interest in zero-knowledge protocols with stronger properties, such as concurrency, unbounded simulation soundness, non-malleability, and universal composability. In this paper, we show a novel technique to convert a large class of existing honest-verifier zero-knowledge protocols into ones with these stronger properties in the common reference string model. More precisely, our technique utilizes a signature scheme existentially unforgeable against adaptive chosen-message attacks, and transforms any Σ-protocol (which is honest-verifier zero-knowledge) into an unbounded simulation sound concurrent zero-knowledge protocol. We also introduce Ω-protocols, a variant of Σ-protocols for which our technique further achieves the properties of non-malleability and/or universal composability. In addition to its conceptual simplicity, a main advantage of this new technique over previous ones is that it avoids the Cook-Levin theorem, which tends to be rather inefficient. Indeed, our technique allows for very efficient instantiation based on the security of some efficient signature schemes and standard number-theoretic assumptions. For instance, one instantiation of our technique yields a universally composable zero-knowledge protocol under the Strong RSA assumption, incurring an overhead of a small constant number of exponentiations, plus the generation of two signatures.