On the impossibility of an invariant attack on Kuznyechik
Currently numerous cryptographic systems are based on SP-networks. These primitives are supposed to be secure but recent investigations show that some attacks are possible. The aim of this work is to study how secure the Russian standardized block cipher Kuznyechik over invariant attacks. We study the already known decompositions of its permutation and show the ways of constructing invariant subsets. A new approach to invariant attacks is presented and it proves that there are no subsets based on S-Box properties that are invariant under round functions of Kuznyechik.