ecc-modp.c 3.56 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->p.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->p.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
}