Design Considerations
triple diffusion: one bit of change in data or spice propagates three times through the cipher state changing every bit
non-linearity of addition and exclusive OR to achieve mixing of the bits
The key expansion table lookup serves as an additional non-linear function, mapping 8 bits to 64 bits
The KX tables are firewalled: knowing a KX table won't help find the original key, or a KX table for a different subcipher.