Proofs of Partial Knowledge and Simplified Design of Witness Hiding Protocols

  • Authors:
  • Ronald Cramer;Ivan Damgård;Berry Schoenmakers

  • Affiliations:
  • -;-;-

  • Venue:
  • CRYPTO '94 Proceedings of the 14th Annual International Cryptology Conference on Advances in Cryptology
  • Year:
  • 1994

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Abstract

Suppose we are given a proof of knowledge P in which a prover demonstrates that he knows a solution to a given problem instance. Suppose also that we have a secret sharing scheme S on n participants. Then under certain assumptions on P and S, we show how to transform P into a witness indistinguishable protocol, in which the prover demonstrates knowledge of the solution to some subset of n problem instances out of a collection of subsets denned by S. For example, using a threshold scheme, the prover can show that he knows at least d out of n solutions without revealing which d instances are involved. If the instances axe independently generated, we get a witness hiding protocol, even if P did not have this property. Our results can be used to efficiently implement general forms of group oriented identification and signatures. Our transformation produces a protocol with the same number of rounds as P and communication complexity n times that of P. Our results use no unproven complexity assumptions.