Quadratic functions with prescribed spectra

  • Authors:
  • Wilfried Meidl;Alev Topuzoğlu

  • Affiliations:
  • Sabancı University MDBF, Tuzla, Turkey 34956;Sabancı University MDBF, Tuzla, Turkey 34956

  • Venue:
  • Designs, Codes and Cryptography
  • Year:
  • 2013

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Abstract

We study a class of quadratic p-ary functions $${{\mathcal{F}}_{p,n}}$$ from $${\mathbb{F}_{p^n}}$$ to $${\mathbb{F}_p, p \geq 2}$$ , which are well-known to have plateaued Walsh spectrum; i.e., for each $${b \in \mathbb{F}_{p^n}}$$ the Walsh transform $${\hat{f}(b)}$$ satisfies $${|\hat{f}(b)|^2 \in \{ 0, p^{(n+s)}\}}$$ for some integer 0 驴 s 驴 n 驴 1. For various types of integers n, we determine possible values of s, construct $${{\mathcal{F}}_{p,n}}$$ with prescribed spectrum, and present enumeration results. Our work generalizes some of the earlier results, in characteristic two, of Khoo et. al. (Des Codes Cryptogr, 38, 279---295, 2006) and Charpin et al. (IEEE Trans Inf Theory 51, 4286---4298, 2005) on semi-bent functions, and of Fitzgerald (Finite Fields Appl 15, 69---81, 2009) on quadratic forms.