Melnychuk I. Cryptographic suitability assessing methods for substitution units of symmetric block ciphers

Thesis for a Ph.D. science degree by specialty 05.13.21 - information security systems. - Kharkiv National University of Radioelectronics of the MESYouthsport of Ukraine, Kharkiv, 2013. The thesis is devoted to additional justification of one of the central positions of the new method that in contrast to existing approaches is based on the following idea: the stability indices of modern ciphers do not depend on the properties of used S-blocks. The thesis represents a complex of research with small and full-scale cipher models, in particular the study of differential and linear parameters for ciphers using different types of substitutions, including random S-boxes. The research results indicate the validity of the original point. Keywords: the block symmetric cipher, differential cryptanalysis, linear cryptanalysis, provable security, the maximum differential probabilities.