md4_round2
md4_round2(&A, B, C, D, X0, 3);
md4_round2(&D, A, B, C, X4, 5);
md4_round2(&C, D, A, B, X8, 9);
md4_round2(&B, C, D, A, X12, 13);
md4_round2(&A, B, C, D, X1, 3);
md4_round2(&D, A, B, C, X5, 5);
md4_round2(&C, D, A, B, X9, 9);
md4_round2(&B, C, D, A, X13, 13);
md4_round2(&A, B, C, D, X2, 3);
md4_round2(&D, A, B, C, X6, 5);
md4_round2(&C, D, A, B, X10, 9);
md4_round2(&B, C, D, A, X14, 13);
md4_round2(&A, B, C, D, X3, 3);
md4_round2(&D, A, B, C, X7, 5);
md4_round2(&C, D, A, B, X11, 9);
md4_round2(&B, C, D, A, X15, 13);