- _y ^= f[_x ^ U8(k >> 0)]; \
- _x ^= f[_y ^ U8(k >> 8)]; \
- _y ^= f[_x ^ U8(k >> 16)]; \
- _x ^= f[_y ^ U8(k >> 24)]; \
+ _y ^= skipjack_s[_x ^ U8(k >> 0)]; \
+ _x ^= skipjack_s[_y ^ U8(k >> 8)]; \
+ _y ^= skipjack_s[_x ^ U8(k >> 16)]; \
+ _x ^= skipjack_s[_y ^ U8(k >> 24)]; \