Simple permutations mix well

  • Authors:
  • Shlomo Hoory;Avner Magen;Steven Myers;Charles Rackoff

  • Affiliations:
  • Department of Computer Science, University of British Columbia, Vancouver, BC, Canada;Department of Computer Science, University of Toronto, Toronto, ON, Canada;School of Informatics, Indiana University, Bloomington, IN;Department of Computer Science, University of Toronto, Toronto, ON, Canada

  • Venue:
  • Theoretical Computer Science - Automata, languages and programming: Algorithms and complexity (ICALP-A 2004)
  • Year:
  • 2005

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Abstract

We study the random composition of a small family of O(n3) simple permutations on {0, 1}n. Specifically, we ask what is the number of compositions needed to achieve a permutation that is close to k-wise independent. We improve on a result of Gowers [An almost m-wise independent random permutation of the cube, Combin. Probab. Comput. 5(2) (1996) 119-130] and show that up to a polylogarithmic factor, n3k3 compositions of random permutations from this family suffice. We further show that the result applies to the stronger notion of k-wise independence against adaptive adversaries. This question is essentially about the rapid mixing of the random walk on a certain graph, and we approach it using a new technique to construct canonical paths. We also show that if we are willing to use a much larger family of simple permutations then we can guarantee closeness to k-wise independence with fewer compositions and fewer random bits.