pqc/external/flint-2.4.3/ulong_extras/is_probabprime_fermat.c

39 lines
1.4 KiB
C

/*=============================================================================
This file is part of FLINT.
FLINT is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
FLINT is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with FLINT; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
=============================================================================*/
/******************************************************************************
Copyright (C) 2008 Peter Shrimpton
Copyright (C) 2009 William Hart
******************************************************************************/
#include <gmp.h>
#include "flint.h"
#include "ulong_extras.h"
int
n_is_probabprime_fermat(mp_limb_t n, mp_limb_t i)
{
if (FLINT_BIT_COUNT(n) <= FLINT_D_BITS)
return (n_powmod(i, n - 1, n) == UWORD(1));
else
return n_powmod2_ui_preinv(i, n - 1, n, n_preinvert_limb(n)) == UWORD(1);
}