Geometric constructions of optimal linear perfect hash families

  • Authors:
  • S. G. Barwick;Wen-Ai Jackson

  • Affiliations:
  • School of Pure Mathematics, University of Adelaide, Adelaide 5005, Australia;School of Pure Mathematics, University of Adelaide, Adelaide 5005, Australia

  • Venue:
  • Finite Fields and Their Applications
  • Year:
  • 2008

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Abstract

A linear (q^d,q,t)-perfect hash family of size s in a vector space V of order q^d over a field F of order q consists of a sequence @f"1,...,@f"s of linear functions from V to F with the following property: for all t subsets X@?V there exists i@?{1,...,s} such that @f"i is injective when restricted to F. A linear (q^d,q,t)-perfect hash family of minimal size d(t-1) is said to be optimal. In this paper we use projective geometry techniques to completely determine the values of q for which optimal linear (q^3,q,3)-perfect hash families exist and give constructions in these cases. We also give constructions of optimal linear (q^2,q,5)-perfect hash families.