Improved Upper Bound on the Nonlinearity of High Order Correlation Immune Functions

  • Authors:
  • Yuliang Zheng;Xian-Mo Zhang

  • Affiliations:
  • -;-

  • Venue:
  • SAC '00 Proceedings of the 7th Annual International Workshop on Selected Areas in Cryptography
  • Year:
  • 2000

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Abstract

It has recently been shown that when m 1/2n - 1, the nonlinearity Nf of an mth-order correlation immune function f with n variables satisfies the condition of Nf ≤ 2n-1 - 2m, and that when m 1/2n - 2 and f is a balanced function, the nonlinearity satisfies Nf ≤ 2n-1 - 2m+1. In this work we prove that the general inequality, namely Nf ≤ 2n-1 - 2m, can be improved to Nf ≤ 2n-1 - 2m+1 for m ≥ 0.6n - 0.4, regardless of the balance of the function. We also show that correlation immune functions achieving the maximum nonlinearity for these functions have close relationships with plateaued functions. The latter have a number of cryptographically desirable properties.