<p>The algebraic degree of a vectorial Boolean function is one of the main parameters driving the cost of its hardware implementation. Thus, finding decompositions of functions into sequences of functions of lower algebraic degrees has been explored to reduce the cost of implementations. In this paper, we consider such decompositions of permutations over <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="145_2025_9547_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="25" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathbb {F}_{2^n}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi mathvariant="double-struck">F</mi> <msup> <mn>2</mn> <mi>n</mi> </msup> </msub> </math></EquationSource> </InlineEquation>. We prove the existence of a decomposition of the inverse using quadratic and linear power permutations for all permutations when <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="145_2025_9547_Article_IEq2.gif" Format="GIF" Height="15" Rendition="HTML" Resolution="72" Type="Linedraw" Width="46" /> </InlineMediaObject> <EquationSource Format="TEX">\(2^n-1\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mn>2</mn> <mi>n</mi> </msup> <mo>-</mo> <mn>1</mn> </mrow> </math></EquationSource> </InlineEquation> is a prime, and we prove the non-existence of such decompositions for power permutations of differential uniformity strictly lower than 16 when 4|<i>n</i>. We also prove that any permutation admits a decomposition into quadratic power permutations and affine permutations of the form <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="145_2025_9547_Article_IEq3.gif" Format="GIF" Height="15" Rendition="HTML" Resolution="72" Type="Linedraw" Width="50" /> </InlineMediaObject> <EquationSource Format="TEX">\(ax+b\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>a</mi> <mi>x</mi> <mo>+</mo> <mi>b</mi> </mrow> </math></EquationSource> </InlineEquation> if <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="145_2025_9547_Article_IEq4.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="36" /> </InlineMediaObject> <EquationSource Format="TEX">\(4 \not \mid n\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>4</mn> <mo>∤</mo> <mi>n</mi> </mrow> </math></EquationSource> </InlineEquation>. Furthermore, we prove that any permutation admits a decomposition into cubic power permutations and affine permutations. Finally, we present a decomposition of the PRESENT S-Box using the power permutation <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="145_2025_9547_Article_IEq5.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="17" /> </InlineMediaObject> <EquationSource Format="TEX">\(x^7\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>x</mi> <mn>7</mn> </msup> </math></EquationSource> </InlineEquation> and affine permutations.</p>

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On Decompositions of Permutations in Quadratic Functions

  • Samuele Andreoli,
  • Enrico Piccione,
  • Lilya Budaghyan,
  • Pantelimon Stănică,
  • Svetla Nikova

摘要

The algebraic degree of a vectorial Boolean function is one of the main parameters driving the cost of its hardware implementation. Thus, finding decompositions of functions into sequences of functions of lower algebraic degrees has been explored to reduce the cost of implementations. In this paper, we consider such decompositions of permutations over \(\mathbb {F}_{2^n}\) F 2 n . We prove the existence of a decomposition of the inverse using quadratic and linear power permutations for all permutations when \(2^n-1\) 2 n - 1 is a prime, and we prove the non-existence of such decompositions for power permutations of differential uniformity strictly lower than 16 when 4|n. We also prove that any permutation admits a decomposition into quadratic power permutations and affine permutations of the form \(ax+b\) a x + b if \(4 \not \mid n\) 4 n . Furthermore, we prove that any permutation admits a decomposition into cubic power permutations and affine permutations. Finally, we present a decomposition of the PRESENT S-Box using the power permutation \(x^7\) x 7 and affine permutations.