On weakly APN functions and 4-bit S-Boxes
S-Boxes are important security components of block ciphers. We provide theoretical results on necessary or sufficient criteria for an (invertible) 4-bit S-Box to be weakly APN. Thanks to a classification of 4-bit invertible S-Boxes achieved independently by De Canniére and Leander-Poschmann, we can strengthen our results with a computer-aided proof.
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