_S_
P1K[0] += _S_(P1K[4] ^ TK16((i & 1) + 0));
P1K[1] += _S_(P1K[0] ^ TK16((i & 1) + 2));
P1K[2] += _S_(P1K[1] ^ TK16((i & 1) + 4));
P1K[3] += _S_(P1K[2] ^ TK16((i & 1) + 6));
P1K[4] += _S_(P1K[3] ^ TK16((i & 1) + 0));
PPK[0] += _S_(PPK[5] ^ TK16(0)); /* Mix key in each "round" */
PPK[1] += _S_(PPK[0] ^ TK16(1));
PPK[2] += _S_(PPK[1] ^ TK16(2));
PPK[3] += _S_(PPK[2] ^ TK16(3));
PPK[4] += _S_(PPK[3] ^ TK16(4));
PPK[5] += _S_(PPK[4] ^ TK16(5)); /* Total # S-box lookups == 6 */