Title
Trims and extensions of quadratic APN functions
Abstract
In this work, we study functions that can be obtained by restricting a vectorial Boolean function $$F :\mathbb {F}_{2}^n \rightarrow \mathbb {F}_{2}^n$$ to an affine hyperplane of dimension $$n-1$$ and then projecting the output to an $$n-1$$ -dimensional space. We show that a multiset of $$2 \cdot (2^n-1)^2$$ EA-equivalence classes of such restrictions defines an EA-invariant for vectorial Boolean functions on $$\mathbb {F}_{2}^n$$ . Further, for all of the known quadratic APN functions in dimension $$n < 10$$ , we determine the restrictions that are also APN. Moreover, we construct 6368 new quadratic APN functions in dimension eight up to EA-equivalence by extending a quadratic APN function in dimension seven. A special focus of this work is on quadratic APN functions with maximum linearity. In particular, we characterize a quadratic APN function $$F :\mathbb {F}_{2}^n \rightarrow \mathbb {F}_{2}^n$$ with linearity of $$2^{n-1}$$ by a property of the ortho-derivative of its restriction to a linear hyperplane. Using the fact that all quadratic APN functions in dimension seven are classified, we are able to obtain a classification of all quadratic 8-bit APN functions with linearity $$2^7$$ up to EA-equivalence.
Year
DOI
Venue
2022
10.1007/s10623-022-01024-4
Designs, Codes and Cryptography
Keywords
DocType
Volume
Almost perfect nonlinear, EA-equivalence, EA-invariant, Linearity, Restriction, Extension, 06E30, 94A60
Journal
90
Issue
ISSN
Citations 
4
0925-1022
0
PageRank 
References 
Authors
0.34
13
3
Name
Order
Citations
PageRank
Christof Beierle100.34
Gregor Leander2128777.03
Léo Perrin300.34