Software-modeling complex cryptographic AES-like primitives nonlinear substitutions
Олександр Анатолійович Білецький, Анатолій Якович Білецький, Денис Александрович Навроцкий, Олександр Іванович Семенюк · Ukrainian Information Security Research Journal · 2014
Any iterative block cipher should contain one non-linear primitive at least. Lack of a nonlinear transformations significantly reduces the cryptographic cipher strength because of any combination of linear primitives could be reduced to the equivalent one, so as a consequence leads to the cipher compromise. In this paper method of nonlinear substitution primitives synthesis is proposed, grounded on S-box construction accordingly to Rijndael algorithm. Three different classes of primitives have evaluated with regard to cryptograms entropy. First class consists of primitives for which an encrypted data is represented by one-dimensional binary vector(bytes), for the second one — data represented by square matrices with an order of eight, for the third one- by three-dimensional matrices (binary fourth-order cubes). Provided possibilities of optimizing the S-box parameters in order to achieve both a minimum correlation coefficient between input and output variables of a primitives and the maximum block response dissipation entropy