8da938fb7704594dba9d9cb47920d7d68dcb4fc4
2 * Copyright (c) 2017 Thomas Pornin <pornin@bolet.org>
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:
12 * The above copyright notice and this permission notice shall be
13 * included in all copies or substantial portions of the Software.
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
29 br_i15_montymul(uint16_t *d
, const uint16_t *x
, const uint16_t *y
,
30 const uint16_t *m
, uint16_t m0i
)
32 size_t len
, len4
, u
, v
;
35 len
= (m
[0] + 15) >> 4;
36 len4
= len
& ~(size_t)3;
39 for (u
= 0; u
< len
; u
++) {
40 uint32_t f
, xu
, r
, zh
;
43 f
= MUL15((d
[1] + MUL15(x
[u
+ 1], y
[1])) & 0x7FFF, m0i
)
47 for (v
= 0; v
< len4
; v
+= 4) {
50 z
= d
[v
+ 1] + MUL15(xu
, y
[v
+ 1])
51 + MUL15(f
, m
[v
+ 1]) + r
;
53 d
[v
+ 0] = z
& 0x7FFF;
54 z
= d
[v
+ 2] + MUL15(xu
, y
[v
+ 2])
55 + MUL15(f
, m
[v
+ 2]) + r
;
57 d
[v
+ 1] = z
& 0x7FFF;
58 z
= d
[v
+ 3] + MUL15(xu
, y
[v
+ 3])
59 + MUL15(f
, m
[v
+ 3]) + r
;
61 d
[v
+ 2] = z
& 0x7FFF;
62 z
= d
[v
+ 4] + MUL15(xu
, y
[v
+ 4])
63 + MUL15(f
, m
[v
+ 4]) + r
;
65 d
[v
+ 3] = z
& 0x7FFF;
67 for (; v
< len
; v
++) {
70 z
= d
[v
+ 1] + MUL15(xu
, y
[v
+ 1])
71 + MUL15(f
, m
[v
+ 1]) + r
;
73 d
[v
+ 0] = z
& 0x7FFF;
82 * Restore the bit length (it was overwritten in the loop above).
87 * d[] may be greater than m[], but it is still lower than twice
90 br_i15_sub(d
, m
, NEQ(dh
, 0) | NOT(br_i15_sub(d
, m
, 0)));