Abstract
The study of finite projective planes involves planar functions, namely, functions \(f:\mathbb {F}_q\rightarrow \mathbb {F}_q\) such that, for each \(a\in \mathbb {F}_q^*\), the function \(c\mapsto f(c+a)-f(c)\) is a bijection on \(\mathbb {F}_q\). Planar functions are also used in the construction of DES-like cryptosystems, where they are called perfect nonlinear functions. We determine all planar functions on \(\mathbb {F}_q\) of the form \(c\mapsto c^t\), under the assumption that \(q\ge (t-1)^4\). This resolves two conjectures of Hernando, McGuire and Monserrat. Our arguments also yield a new proof of a conjecture of Segre and Bartocci about monomial hyperovals in finite Desarguesian projective planes.
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Communicated by J. D. Key.
The author thanks Elodie Leducq and the referees for helpful remarks, and also thanks Gary McGuire and Peter Mueller for their interest. The author was partially supported by NSF Grant DMS-1162181.
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Zieve, M.E. Planar functions and perfect nonlinear monomials over finite fields. Des. Codes Cryptogr. 75, 71–80 (2015). https://doi.org/10.1007/s10623-013-9890-8
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DOI: https://doi.org/10.1007/s10623-013-9890-8