Coverage Report

Created: 2024-11-25 06:29

/src/nettle/ecc-mod-arith.c
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/* ecc-mod-arith.c
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   Copyright (C) 2013, 2014 Niels Möller
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   This file is part of GNU Nettle.
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   GNU Nettle is free software: you can redistribute it and/or
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   modify it under the terms of either:
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     * the GNU Lesser General Public License as published by the Free
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       Software Foundation; either version 3 of the License, or (at your
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       option) any later version.
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   or
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     * the GNU General Public License as published by the Free
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       Software Foundation; either version 2 of the License, or (at your
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       option) any later version.
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   or both in parallel, as here.
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   GNU Nettle is distributed in the hope that it will be useful,
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   but WITHOUT ANY WARRANTY; without even the implied warranty of
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   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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   General Public License for more details.
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   You should have received copies of the GNU General Public License and
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   the GNU Lesser General Public License along with this program.  If
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   not, see http://www.gnu.org/licenses/.
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*/
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/* Development of Nettle's ECC support was funded by the .SE Internet Fund. */
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#if HAVE_CONFIG_H
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# include "config.h"
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#endif
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#include <assert.h>
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#include "ecc-internal.h"
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/* Routines for modp arithmetic. All values are ecc->size limbs, but
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   not necessarily < p. */
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int
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ecc_mod_zero_p (const struct ecc_modulo *m, const mp_limb_t *xp_in)
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0
{
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0
  volatile mp_limb_t is_non_zero, is_not_p;
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0
  const volatile mp_limb_t *xp;
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0
  mp_size_t i;
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  for (xp = xp_in, i = 0, is_non_zero = is_not_p = 0; i < m->size; i++)
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0
    {
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0
      is_non_zero |= xp[i];
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0
      is_not_p |= (xp[i] ^ m->m[i]);
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0
    }
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  return is_zero_limb (is_non_zero) | is_zero_limb (is_not_p);
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0
}
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int
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ecc_mod_equal_p (const struct ecc_modulo *m, const mp_limb_t *a,
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     const mp_limb_t *ref, mp_limb_t *scratch)
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0
{
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0
  mp_limb_t cy;
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0
  cy = mpn_sub_n (scratch, a, ref, m->size);
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  /* If cy > 0, i.e., a < ref, then they can't be equal mod m. */
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  return (1 - cy) & ecc_mod_zero_p (m, scratch);
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0
}
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void
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ecc_mod_add (const struct ecc_modulo *m, mp_limb_t *rp,
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       const mp_limb_t *ap, const mp_limb_t *bp)
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526k
{
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  mp_limb_t cy;
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526k
  cy = mpn_add_n (rp, ap, bp, m->size);
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526k
  cy = mpn_cnd_add_n (cy, rp, rp, m->B, m->size);
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526k
  cy = mpn_cnd_add_n (cy, rp, rp, m->B, m->size);
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  assert_maybe (cy == 0);
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}
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void
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ecc_mod_sub (const struct ecc_modulo *m, mp_limb_t *rp,
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       const mp_limb_t *ap, const mp_limb_t *bp)
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945k
{
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  mp_limb_t cy;
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945k
  cy = mpn_sub_n (rp, ap, bp, m->size);
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  /* The adjustments for this function work differently depending on
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     the value of the most significant bit of m.
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     If m has a most significant bit of zero, then the first
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     adjustment step conditionally adds 2m. If in addition, inputs are
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     in the 0 <= a,b < 2m range, then the first adjustment guarantees
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     that result is in that same range. The second adjustment step is
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     needed only if b > 2m, it then ensures output is correct modulo
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     m, but nothing more.
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     If m has a most significant bit of one, Bm2m and B are the same,
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     and this function works analogously to ecc_mod_add.
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   */
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945k
  cy = mpn_cnd_sub_n (cy, rp, rp, m->Bm2m, m->size);
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  cy = mpn_cnd_sub_n (cy, rp, rp, m->B, m->size);
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  assert_maybe (cy == 0);
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}
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void
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ecc_mod_mul_1 (const struct ecc_modulo *m, mp_limb_t *rp,
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         const mp_limb_t *ap, mp_limb_t b)
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219k
{
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  mp_limb_t hi;
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  assert (b <= 0xffffffff);
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  hi = mpn_mul_1 (rp, ap, m->size, b);
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  hi = mpn_addmul_1 (rp, m->B, m->size, hi);
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  assert_maybe (hi <= 1);
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  hi = mpn_cnd_add_n (hi, rp, rp, m->B, m->size);
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  /* Sufficient if b < B^size / p */
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  assert_maybe (hi == 0);
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}
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void
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ecc_mod_addmul_1 (const struct ecc_modulo *m, mp_limb_t *rp,
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      const mp_limb_t *ap, mp_limb_t b)
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55.5k
{
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55.5k
  mp_limb_t hi;
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  assert (b <= 0xffffffff);
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  hi = mpn_addmul_1 (rp, ap, m->size, b);
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  hi = mpn_addmul_1 (rp, m->B, m->size, hi);
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  assert_maybe (hi <= 1);
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  hi = mpn_cnd_add_n (hi, rp, rp, m->B, m->size);
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  /* Sufficient roughly if b < B^size / p */
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  assert_maybe (hi == 0);
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}
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void
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ecc_mod_submul_1 (const struct ecc_modulo *m, mp_limb_t *rp,
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      const mp_limb_t *ap, mp_limb_t b)
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291k
{
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  mp_limb_t hi;
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  assert (b <= 0xffffffff);
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  hi = mpn_submul_1 (rp, ap, m->size, b);
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  hi = mpn_submul_1 (rp, m->B, m->size, hi);
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  assert_maybe (hi <= 1);
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  hi = mpn_cnd_sub_n (hi, rp, rp, m->B, m->size);
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  /* Sufficient roughly if b < B^size / p */
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  assert_maybe (hi == 0);
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}
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void
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ecc_mod_mul (const struct ecc_modulo *m, mp_limb_t *rp,
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       const mp_limb_t *ap, const mp_limb_t *bp, mp_limb_t *tp)
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1.13M
{
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1.13M
  mpn_mul_n (tp, ap, bp, m->size);
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1.13M
  m->reduce (m, rp, tp);
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1.13M
}
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void
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ecc_mod_sqr (const struct ecc_modulo *m, mp_limb_t *rp,
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       const mp_limb_t *ap, mp_limb_t *tp)
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1.30M
{
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1.30M
  mpn_sqr (tp, ap, m->size);
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1.30M
  m->reduce (m, rp, tp);
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1.30M
}
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void
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ecc_mod_mul_canonical (const struct ecc_modulo *m, mp_limb_t *rp,
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           const mp_limb_t *ap, const mp_limb_t *bp, mp_limb_t *tp)
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{
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  mp_limb_t cy;
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  mpn_mul_n (tp, ap, bp, m->size);
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  m->reduce (m, tp + m->size, tp);
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  cy = mpn_sub_n (rp, tp + m->size, m->m, m->size);
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  cnd_copy (cy, rp, tp + m->size, m->size);
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}
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void
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ecc_mod_sqr_canonical (const struct ecc_modulo *m, mp_limb_t *rp,
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           const mp_limb_t *ap, mp_limb_t *tp)
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{
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  mp_limb_t cy;
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  mpn_sqr (tp, ap, m->size);
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  m->reduce (m, tp + m->size, tp);
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  cy = mpn_sub_n (rp, tp + m->size, m->m, m->size);
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  cnd_copy (cy, rp, tp + m->size, m->size);
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}
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void
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ecc_mod_pow_2k (const struct ecc_modulo *m,
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    mp_limb_t *rp, const mp_limb_t *xp,
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    unsigned k, mp_limb_t *tp)
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12.7k
{
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  ecc_mod_sqr (m, rp, xp, tp);
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  while (--k > 0)
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    ecc_mod_sqr (m, rp, rp, tp);
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}
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void
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ecc_mod_pow_2k_mul (const struct ecc_modulo *m,
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        mp_limb_t *rp, const mp_limb_t *xp,
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        unsigned k, const mp_limb_t *yp,
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        mp_limb_t *tp)
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12.7k
{
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12.7k
  ecc_mod_pow_2k (m, rp, xp, k, tp);
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12.7k
  ecc_mod_mul (m, rp, rp, yp, tp);
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12.7k
}