s_mp_invmod_2d
mp_err s_mp_invmod_2d( const mp_int *a, mp_size k, mp_int *c);
return s_mp_invmod_2d(a, k, c);
MP_CHECKOK( s_mp_invmod_2d( a, k, &evenPart) );
MP_CHECKOK( s_mp_invmod_2d(&oddFactor, k, &C2) );