Random selection with an adversarial majority

  • Authors:
  • Ronen Gradwohl;Salil Vadhan;David Zuckerman

  • Affiliations:
  • Department of Computer Science and Applied Math, Weizmann Institute of Science;Division of Engineering & Applied Sciences, Harvard University;Department of Computer Science, University of Texas at Austin

  • Venue:
  • CRYPTO'06 Proceedings of the 26th annual international conference on Advances in Cryptology
  • Year:
  • 2006

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Abstract

We consider the problem of random selection, where p players follow a protocol to jointly select a random element of a universe of size n. However, some of the players may be adversarial and collude to force the output to lie in a small subset of the universe. We describe essentially the first protocols that solve this problem in the presence of a dishonest majority in the full-information model (where the adversary is computationally unbounded and all communication is via non-simultaneous broadcast). Our protocols are nearly optimal in several parameters, including the round complexity (as a function of n), the randomness complexity, the communication complexity, and the tradeoffs between the fraction of honest players, the probability that the output lies in a small subset of the universe, and the density of this subset.