On the nonlinearity of exponential welch costas functions

  • Authors:
  • Konstantinos Drakakis;Verónica Requena;Gary McGuire

  • Affiliations:
  • School of Electrical, Electronic and Mechanical Engineering, University College Dublin, Belfield, Dublin 4, Ireland and Claude Shannon Institute and UCD, CASL, Ireland;Departament de Ciència de la Computació i Intelligencia Artificial, Universitat d' Alacant, Alacant, Spain;School of Mathematical Sciences, University College, Dublin, Belfield, Dublin 4, Ireland and UCD, CASL, Ireland

  • Venue:
  • IEEE Transactions on Information Theory
  • Year:
  • 2010

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Abstract

We study the nonlinearity of the Exponential Welch Costas functions, using the Fourier Transform on Zm. These functions have been proposed for use in nonbinary cryptosystems. High nonlinearity is required to ensure resistance to linear cryptanalysis. We prove some properties of the nonlinearity of these functions, and we suggest a plausible connection of the nonlinearity to the class number of a quadratic field.