Key Generation

We need 40 sub-keys
- 8 used in input/output whitening
- 2 used in each of the 16 rounds
- Sub-keys are generated in pairs.

To generate key 2i and 2i+1, replace
- 0,0,0,0 with 2i,2i,2i,2i
- 1,1,1,1 with 2i+1,2i+1,2i+1,2i+1
- 0 ? i < 20

We need 40 sub-keys