UDK 512.624.2
POSSIBLE OPTIONS TO IMPROVE CRYPTOGRAPHIC RELIABILITY OF ALGORITHMS BASED ON NYBERG CONSTRUCTION
M. A. Dmitriev
Siberian Federal University 79, Svobodny Av., Krasnoyarsk, 660041, Russian Federation E-mail: makcmad@mail.ru
Nowadays one of the most used tools to protect data from unauthorized access is block symmetric-key cryptographic algorithms. The rapid growth of computer processing power and significant development of linear cryptanalysis actualize the task to continue increasing reliability of the existing algorithms, as well as developing new ones. An important component in determining the stability of a block symmetric-key cryptographic algorithm to the most common types of cryptanalysis is the quality of S-box substitution. This work was aimed at calculating and achieving all possible S-box substitutions, based on irreducible polynomials over the Galois field and their compositions. For this purpose a set of programs to obtain S-box substitutions which have different cryptographic characteristics with its help was developed. Calculation of the quantitative values of these characteristics was performed by presenting S-box substitutions in the form of sets of Boolean functions. Particular attention was paid to such characteristics as nonlinearity of Boolean functions, the maximum modulus of the correlation coefficients and the numbers of zeros of the correlation matrix of S-box substitutions, as those are the most important characteristics. These blocks substitutions can be the basis for further study of possible options to improve Rijndael algorithm’s cryptographic reliability.
Keywords: Rijndael algorithm, S-box, irreducible polynomial over the Galois field.
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Dmitriev Maksim Anatol’evich – postgraduate student, Siberian Federal University. E-mail: makcmad@mail.ru.