Low differentially uniform permutations from Dobbertin APN function over 𝔽_2^n
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Block ciphers use S-boxes to create confusion in the cryptosystems. Such S-boxes are functions over 𝔽_2^n. These functions should have low differential uniformity, high nonlinearity, and high algebraic degree in order to resist differential attacks, linear attacks, and higher order differential attacks, respectively. In this paper, we construct new classes of differentially 4 and 6-uniform permutations by modifying the image of the Dobbertin APN function x^d with d=2^4k+2^3k+2^2k+2^k-1 over a subfield of 𝔽_2^n. Furthermore, the algebraic degree and the lower bound of the nonlinearity of the constructed functions are given.
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