nist_set_256
nist_set_256(t_d, buf.bn, 0, 0, 0, 0, 0, 23 - 4, 22 - 4, 21 - 4);
nist_set_256(t_d, buf.bn, 15, 14, 13, 12, 11, 0, 0, 0);
nist_set_256(c_d, buf.bn, 0, 15, 14, 13, 12, 0, 0, 0);
nist_set_256(t_d, buf.bn, 15, 14, 0, 0, 0, 10, 9, 8);
nist_set_256(t_d, buf.bn, 8, 13, 15, 14, 13, 11, 10, 9);
nist_set_256(t_d, buf.bn, 10, 8, 0, 0, 0, 13, 12, 11);
nist_set_256(t_d, buf.bn, 11, 9, 0, 0, 15, 14, 13, 12);
nist_set_256(t_d, buf.bn, 12, 0, 10, 9, 8, 15, 14, 13);
nist_set_256(t_d, buf.bn, 13, 0, 11, 10, 9, 0, 15, 14);