Kaidalov D. Methods for analyzing properties of high-level constructions and key-expansion schemes of block symmetric ciphers

The thesis is devoted to the analysis of properties of modern block symmetric ciphers. In particular the efficiency of basic high-level constructions for block ciphers is being analyzed. Security of block SPN-structure against related-key attacks has also been researched. The thesis represents a complex of researches with the main three high-level constructions: Feistel scheme, Lai-Massey scheme and SPN-structure. Research results confirm that the SPN-structure is the most efficient high-level construction according to the criteria of distinguishing with the random function. Research on security analysis of the block ciphers on the base of SPN-structure against related-key attacks was also made (practical criteria). The developed method proved that this cipher is secure against such attacks.