Plateaued Functions: Difference between revisions

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at <math>(a,b)</math>. If <math>\phi</math> is injective, resp. takes each value in its image set two times, then <math>f_{\phi,h}</math> is plateaued of amplitude <math>2^r</math>, resp. <math>2^{r+1}</math>.
at <math>(a,b)</math>. If <math>\phi</math> is injective, resp. takes each value in its image set two times, then <math>f_{\phi,h}</math> is plateaued of amplitude <math>2^r</math>, resp. <math>2^{r+1}</math>.
= Characterization of Plateaued Functions <ref name="carletPlateuaed">Carlet C. Boolean and vectorial plateaued functions and APN functions. IEEE Transactions on Information Theory. 2015 Nov;61(11):6272-89.</ref>  =
== Characterization by the Derivatives ==
Using the fact that a Boolean function <math>f</math> is plateaued if and only if the expression <math>\sum_{a,b \in \mathbb{F}_2^n} (-1)^{DaDbf(x)}</math> does not depend on <math>x \in \mathbb{F}_2^n</math>, one can derive the following characterization.
Let <math>F</math> be an <math>(n,m)</math>-function. Then:
* F is plateuaed if and only if, for every <math>v \in \mathbb{F}_2^m</math>, the size of the set
<div><math> \{ (a,b) \in (\mathbb{F}_2^n)^2 : D_aD_bF(x) = v \}</math></div>
does not depend on <math>x</math>;
* F is plateaued with single amplitude if and only if the size of the set depends neither on <math>x</math>, nor on <math>v \in \mathbb{F}_2^m</math> for <math>v \ne 0</math>.
Moreover:
* for every <math>F</math>, the value distribution of <math>D_aD_bF(x)</math> equals that of <math>D_aF(b) + D_aF(x)</math> when <math>(a,b)</math> ranges over <math>(\mathbb{F}_2^n)^2</math>;
* if two plateaued functions <math>F,G</math> have the same distribution, then all of their component functions <math>u \cdot F, u\cdot G</math> have the same amplitude.
=== Power Functions ===
Let <math>F(x) = x^d</math>. Then, for every $v,x,\lambda \in \mathbb{F}_{2^n}</math> with <math>\lambda \ne 0</math>, we have
<div><math> | \{ (a,b) \in \mathbb{F}_{2^n}^2 : D_aF(b) + D_aF(x) = v \} | = | \{ (a,b) \in \mathbb{F}_{2^n}^2 : D_aF(b) + D_aF(x/\lambda) = v/\lambda^d \}|.</math></div>
Then:
* <math>F</math> is plateaued if and only if, for every <math>v \in \mathbb{F}_{2^n}</math>, we have
<div><math>| \{ (a,b) \in \mathbb{F}_{2^n}^2 : D_aF(b) + D_aF(1) = v \} | = | \{ (a,b) \in \mathbb{F}_{2^n}^2 : D_aF(b) + D_aF(0) = v \}|;</math></div>
* <math>F</math> is plateaued with single amplitude if and only if the size above does not, in addition, depend on <math>v \ne 0</math>.
=== Functions with Unbalanced Components ===
Let <math>F</math> be an <math>(n,m)</math>-function. Then <math>F</math> is plateuaed with all components unbalanced if and only if, for every <math>v,x \in \mathbb{F}_{2}^n</math>, we have
<div><math> | \{ (a,b) \in (\mathbb{F}_2^n)^2 : D_aD_bF(x) = v \}| = | \{ (a,b) \in (\mathbb{F}_2^n)^2 : F(a) + F(b) = v \}|.</math></div>
Moreover, <math>F</math> is plateaued with single amplitude if and only if this value does not, in addition, depend on <math>v</math> for <math>v \ne 0</math>.

Revision as of 18:53, 7 February 2019

Background and Definition

A Boolean function is said to be plateaued if its Walsh transform takes at most three distinct values, viz. and Failed to parse (Conversion error. Server ("https://wikimedia.org/api/rest_") reported: "Cannot get mml. Server problem."): {\displaystyle \pm \mu } for some positive ineger Failed to parse (Conversion error. Server ("https://wikimedia.org/api/rest_") reported: "Cannot get mml. Server problem."): {\displaystyle \mu } called the amplitude of Failed to parse (Conversion error. Server ("https://wikimedia.org/api/rest_") reported: "Cannot get mml. Server problem."): {\displaystyle f} .

This notion can be naturally extended to vectorial Boolean functions by applying it to each component. More precisely, if is an -function, we say that is plateaued if all its component functions Failed to parse (Conversion error. Server ("https://wikimedia.org/api/rest_") reported: "Cannot get mml. Server problem."): {\displaystyle u\cdot F} for Failed to parse (Conversion error. Server ("https://wikimedia.org/api/rest_") reported: "Cannot get mml. Server problem."): {\displaystyle u\neq 0} are plateaued. If all of the component functions are plateaued and have the same amplitude, we say that is plateaued with single amplitude.

Equivalence relations

The class of functions that are plateaued with single amplitude is CCZ-invariant.

The class of plateaued functions is only EA-invariant.

Relations to other classes of functions

All bent and semi-bent Boolean functions are plateaued.

Any vectorial AB function is plateaued with single amplitude.

Constructions of Boolean plateaued functions

Primary constructons

Generalization of the Maiorana-MacFarland Functions [1]

The Maiorana-MacFarland class of bent functions can be generalized into the class of functions of the form

for , where Failed to parse (Conversion error. Server ("https://wikimedia.org/api/rest_") reported: "Cannot get mml. Server problem."): {\displaystyle r} and are any positive integers, Failed to parse (Conversion error. Server ("https://wikimedia.org/api/rest_") reported: "Cannot get mml. Server problem."): {\displaystyle n=r+s} , is arbitrary and Failed to parse (Conversion error. Server ("https://wikimedia.org/api/rest_") reported: "Cannot get mml. Server problem."): {\displaystyle h:\mathbb {F} _{2}^{s}\rightarrow \mathbb {F} _{2}} is any Boolean function.

The Walsh transform of takes the value

Failed to parse (Conversion error. Server ("https://wikimedia.org/api/rest_") reported: "Cannot get mml. Server problem."): {\displaystyle W_{f_{\phi ,h}}(a,b)=2^{r}\sum _{y\in \phi ^{-1}(a)}(-1)^{b\cdot y+h(y)}}

at . If is injective, resp. takes each value in its image set two times, then is plateaued of amplitude Failed to parse (Conversion error. Server ("https://wikimedia.org/api/rest_") reported: "Cannot get mml. Server problem."): {\displaystyle 2^{r}} , resp. Failed to parse (Conversion error. Server ("https://wikimedia.org/api/rest_") reported: "Cannot get mml. Server problem."): {\displaystyle 2^{r+1}} .

Characterization of Plateaued Functions [2]

Characterization by the Derivatives

Using the fact that a Boolean function Failed to parse (Conversion error. Server ("https://wikimedia.org/api/rest_") reported: "Cannot get mml. Server problem."): {\displaystyle f} is plateaued if and only if the expression does not depend on , one can derive the following characterization.

Let be an -function. Then:

  • F is plateuaed if and only if, for every Failed to parse (Conversion error. Server ("https://wikimedia.org/api/rest_") reported: "Cannot get mml. Server problem."): {\displaystyle v\in \mathbb {F} _{2}^{m}} , the size of the set
Failed to parse (Conversion error. Server ("https://wikimedia.org/api/rest_") reported: "Cannot get mml. Server problem."): {\displaystyle \{(a,b)\in (\mathbb {F} _{2}^{n})^{2}:D_{a}D_{b}F(x)=v\}}

does not depend on ;

  • F is plateaued with single amplitude if and only if the size of the set depends neither on , nor on Failed to parse (Conversion error. Server ("https://wikimedia.org/api/rest_") reported: "Cannot get mml. Server problem."): {\displaystyle v\in \mathbb {F} _{2}^{m}} for .

Moreover:

  • for every , the value distribution of equals that of Failed to parse (Conversion error. Server ("https://wikimedia.org/api/rest_") reported: "Cannot get mml. Server problem."): {\displaystyle D_{a}F(b)+D_{a}F(x)} when ranges over ;
  • if two plateaued functions Failed to parse (Conversion error. Server ("https://wikimedia.org/api/rest_") reported: "Cannot get mml. Server problem."): {\displaystyle F,G} have the same distribution, then all of their component functions Failed to parse (Conversion error. Server ("https://wikimedia.org/api/rest_") reported: "Cannot get mml. Server problem."): {\displaystyle u\cdot F,u\cdot G} have the same amplitude.

Power Functions

Let . Then, for every $v,x,\lambda \in \mathbb{F}_{2^n}</math> with Failed to parse (Conversion error. Server ("https://wikimedia.org/api/rest_") reported: "Cannot get mml. Server problem."): {\displaystyle \lambda \neq 0} , we have

Then:

  • is plateaued if and only if, for every Failed to parse (Conversion error. Server ("https://wikimedia.org/api/rest_") reported: "Cannot get mml. Server problem."): {\displaystyle v\in \mathbb {F} _{2^{n}}} , we have
Failed to parse (Conversion error. Server ("https://wikimedia.org/api/rest_") reported: "Cannot get mml. Server problem."): {\displaystyle |\{(a,b)\in \mathbb {F} _{2^{n}}^{2}:D_{a}F(b)+D_{a}F(1)=v\}|=|\{(a,b)\in \mathbb {F} _{2^{n}}^{2}:D_{a}F(b)+D_{a}F(0)=v\}|;}
  • Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle F} is plateaued with single amplitude if and only if the size above does not, in addition, depend on .

Functions with Unbalanced Components

Let Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle F} be an Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle (n,m)} -function. Then Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle F} is plateuaed with all components unbalanced if and only if, for every Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle v,x \in \mathbb{F}_{2}^n} , we have

Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle | \{ (a,b) \in (\mathbb{F}_2^n)^2 : D_aD_bF(x) = v \}| = | \{ (a,b) \in (\mathbb{F}_2^n)^2 : F(a) + F(b) = v \}|.}

Moreover, Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle F} is plateaued with single amplitude if and only if this value does not, in addition, depend on Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle v} for Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle v \ne 0} .

  1. ↑ Camion P, Carlet C, Charpin P, Sendrier N. On Correlation-immune functions. InAdvances in Cryptology—CRYPTO’91 1992 (pp. 86-100). Springer Berlin/Heidelberg.
  2. ↑ Carlet C. Boolean and vectorial plateaued functions and APN functions. IEEE Transactions on Information Theory. 2015 Nov;61(11):6272-89.