Kuznyechik encryption is executed as follows. A 128-bit
plain text block is fed to the input. This plain text is added
with the first round subkey modulo two. This is followed
by 9 rounds of transform. Each round consists on three
operations: S transform, L transform, and addition with
the respective subkey. The output of the ninth round is a
128-bit cipher text. The decryption algorithm uses inverse
operations with reverse order of round subkeys. The general
data flow chart of Kuznyechik is shown in Fig. 1.