Setup Key Expansion (KX) Tables
Each subcipher has a KX (key expansion) table of size 256 words, generated from the key
Procedures of the kX table setup:
(1) Initializing the KX table
(2) The first 128 words of key xored into the KX table (KX[0] - KX[127])
(3) Perform stirring function to psudo-randomize the KX table.
Continue with step 2 and 3 with the second 128 words of key,until the entire key has been xored into the KX array