The influence of linear mapping reducibility on the choice of round constants

The influence of reducibility of linear mappings on the security of block ciphers is studied. It is shown that the replacement of only two key schedule constants of Khazad block cipher leads to the appearance of weak key classes. We study invariant subspaces of the Kuznyechik linear mapping and demonstrate that there are no weak key schedule constants similar to Khazad. But the choice of other linear mappings constructed similarly to the original Kuznyechik mapping and choice of other constants may results in the appearance of weak keys.