ecc-modp.c 3.55 KB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
/* ecc-modp.c

   Copyright (C) 2013 Niels Möller

   This file is part of GNU Nettle.

   GNU Nettle is free software: you can redistribute it and/or
   modify it under the terms of either:

     * the GNU Lesser General Public License as published by the Free
       Software Foundation; either version 3 of the License, or (at your
       option) any later version.

   or

     * 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.

   or both in parallel, as here.

   GNU Nettle 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 copies of the GNU General Public License and
   the GNU Lesser General Public License along with this program.  If
   not, see http://www.gnu.org/licenses/.
*/
Niels Möller's avatar
Niels Möller committed
31

32
/* Development of Nettle's ECC support was funded by the .SE Internet Fund. */
Niels Möller's avatar
Niels Möller committed
33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49

#if HAVE_CONFIG_H
# include "config.h"
#endif

#include <assert.h>

#include "ecc-internal.h"

/* Routines for modp arithmetic. All values are ecc->size limbs, but
   not necessarily < p. */

void
ecc_modp_add (const struct ecc_curve *ecc, mp_limb_t *rp,
	      const mp_limb_t *ap, const mp_limb_t *bp)
{
  mp_limb_t cy;
Niels Möller's avatar
Niels Möller committed
50 51 52
  cy = mpn_add_n (rp, ap, bp, ecc->p.size);
  cy = cnd_add_n (cy, rp, ecc->p.B, ecc->p.size);
  cy = cnd_add_n (cy, rp, ecc->p.B, ecc->p.size);
Niels Möller's avatar
Niels Möller committed
53 54 55 56 57 58 59 60
  assert (cy == 0);  
}

void
ecc_modp_sub (const struct ecc_curve *ecc, mp_limb_t *rp,
	      const mp_limb_t *ap, const mp_limb_t *bp)
{
  mp_limb_t cy;
Niels Möller's avatar
Niels Möller committed
61 62 63
  cy = mpn_sub_n (rp, ap, bp, ecc->p.size);
  cy = cnd_sub_n (cy, rp, ecc->p.B, ecc->p.size);
  cy = cnd_sub_n (cy, rp, ecc->p.B, ecc->p.size);
Niels Möller's avatar
Niels Möller committed
64 65 66 67 68 69 70 71 72 73
  assert (cy == 0);  
}

void
ecc_modp_mul_1 (const struct ecc_curve *ecc, mp_limb_t *rp,
		const mp_limb_t *ap, mp_limb_t b)
{
  mp_limb_t hi;

  assert (b <= 0xffffffff);
Niels Möller's avatar
Niels Möller committed
74 75
  hi = mpn_mul_1 (rp, ap, ecc->p.size, b);
  hi = mpn_addmul_1 (rp, ecc->p.B, ecc->p.size, hi);
Niels Möller's avatar
Niels Möller committed
76
  assert (hi <= 1);
Niels Möller's avatar
Niels Möller committed
77
  hi = cnd_add_n (hi, rp, ecc->p.B, ecc->p.size);
Niels Möller's avatar
Niels Möller committed
78 79 80 81 82 83 84 85 86 87 88
  /* Sufficient if b < B^size / p */
  assert (hi == 0);
}

void
ecc_modp_addmul_1 (const struct ecc_curve *ecc, mp_limb_t *rp,
		   const mp_limb_t *ap, mp_limb_t b)
{
  mp_limb_t hi;

  assert (b <= 0xffffffff);
Niels Möller's avatar
Niels Möller committed
89 90
  hi = mpn_addmul_1 (rp, ap, ecc->p.size, b);
  hi = mpn_addmul_1 (rp, ecc->p.B, ecc->p.size, hi);
Niels Möller's avatar
Niels Möller committed
91
  assert (hi <= 1);
Niels Möller's avatar
Niels Möller committed
92
  hi = cnd_add_n (hi, rp, ecc->p.B, ecc->p.size);
Niels Möller's avatar
Niels Möller committed
93 94 95 96 97 98 99 100 101 102 103
  /* Sufficient roughly if b < B^size / p */
  assert (hi == 0);
}
  
void
ecc_modp_submul_1 (const struct ecc_curve *ecc, mp_limb_t *rp,
		   const mp_limb_t *ap, mp_limb_t b)
{
  mp_limb_t hi;

  assert (b <= 0xffffffff);
Niels Möller's avatar
Niels Möller committed
104 105
  hi = mpn_submul_1 (rp, ap, ecc->p.size, b);
  hi = mpn_submul_1 (rp, ecc->p.B, ecc->p.size, hi);
Niels Möller's avatar
Niels Möller committed
106
  assert (hi <= 1);
Niels Möller's avatar
Niels Möller committed
107
  hi = cnd_sub_n (hi, rp, ecc->p.B, ecc->p.size);
Niels Möller's avatar
Niels Möller committed
108 109 110 111
  /* Sufficient roughly if b < B^size / p */
  assert (hi == 0);
}

Niels Möller's avatar
Niels Möller committed
112
/* NOTE: mul and sqr needs 2*ecc->p.size limbs at rp */
Niels Möller's avatar
Niels Möller committed
113 114 115 116
void
ecc_modp_mul (const struct ecc_curve *ecc, mp_limb_t *rp,
	      const mp_limb_t *ap, const mp_limb_t *bp)
{
Niels Möller's avatar
Niels Möller committed
117
  mpn_mul_n (rp, ap, bp, ecc->p.size);
118
  ecc->reduce (&ecc->p, rp);
Niels Möller's avatar
Niels Möller committed
119 120 121 122 123 124
}

void
ecc_modp_sqr (const struct ecc_curve *ecc, mp_limb_t *rp,
	      const mp_limb_t *ap)
{
Niels Möller's avatar
Niels Möller committed
125
  mpn_sqr (rp, ap, ecc->p.size);
126
  ecc->reduce (&ecc->p, rp);
Niels Möller's avatar
Niels Möller committed
127 128 129 130 131 132
}

void
ecc_modp_inv (const struct ecc_curve *ecc, mp_limb_t *rp, mp_limb_t *ap,
	      mp_limb_t *scratch)
{
Niels Möller's avatar
Niels Möller committed
133
  sec_modinv (rp, ap, ecc->p.size, ecc->p.m, ecc->pp1h, ecc->p.bit_size, scratch);
Niels Möller's avatar
Niels Möller committed
134 135
}