1 /*
2 * Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining
5 * a copy of this software and associated documentation files (the
6 * "Software"), to deal in the Software without restriction, including
7 * without limitation the rights to use, copy, modify, merge, publish,
8 * distribute, sublicense, and/or sell copies of the Software, and to
9 * permit persons to whom the Software is furnished to do so, subject to
10 * the following conditions:
11 *
12 * The above copyright notice and this permission notice shall be
13 * included in all copies or substantial portions of the Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
16 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
18 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
19 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
20 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
21 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
22 * SOFTWARE.
23 */
24
25 #include "inner.h"
26
27 /* see inner.h */
28 void
br_i32_montymul(uint32_t * d,const uint32_t * x,const uint32_t * y,const uint32_t * m,uint32_t m0i)29 br_i32_montymul(uint32_t *d, const uint32_t *x, const uint32_t *y,
30 const uint32_t *m, uint32_t m0i)
31 {
32 size_t len, u, v;
33 uint64_t dh;
34
35 len = (m[0] + 31) >> 5;
36 br_i32_zero(d, m[0]);
37 dh = 0;
38 for (u = 0; u < len; u ++) {
39 uint32_t f, xu;
40 uint64_t r1, r2, zh;
41
42 xu = x[u + 1];
43 f = (d[1] + x[u + 1] * y[1]) * m0i;
44 r1 = 0;
45 r2 = 0;
46 for (v = 0; v < len; v ++) {
47 uint64_t z;
48 uint32_t t;
49
50 z = (uint64_t)d[v + 1] + MUL(xu, y[v + 1]) + r1;
51 r1 = z >> 32;
52 t = (uint32_t)z;
53 z = (uint64_t)t + MUL(f, m[v + 1]) + r2;
54 r2 = z >> 32;
55 if (v != 0) {
56 d[v] = (uint32_t)z;
57 }
58 }
59 zh = dh + r1 + r2;
60 d[len] = (uint32_t)zh;
61 dh = zh >> 32;
62 }
63
64 /*
65 * d[] may still be greater than m[] at that point; notably, the
66 * 'dh' word may be non-zero.
67 */
68 br_i32_sub(d, m, NEQ(dh, 0) | NOT(br_i32_sub(d, m, 0)));
69 }
70