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
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
|
/*
* invmod.c
*
* Compute modular inverses
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include <stdio.h>
#include <stdlib.h>
#include "mpi.h"
int
main(int argc, char *argv[])
{
mp_int a, m;
mp_err res;
char *buf;
int len, out = 0;
if (argc < 3) {
fprintf(stderr, "Usage: %s <a> <m>\n", argv[0]);
return 1;
}
mp_init(&a);
mp_init(&m);
mp_read_radix(&a, argv[1], 10);
mp_read_radix(&m, argv[2], 10);
if (mp_cmp(&a, &m) > 0)
mp_mod(&a, &m, &a);
switch ((res = mp_invmod(&a, &m, &a))) {
case MP_OKAY:
len = mp_radix_size(&a, 10);
buf = malloc(len);
mp_toradix(&a, buf, 10);
printf("%s\n", buf);
free(buf);
break;
case MP_UNDEF:
printf("No inverse\n");
out = 1;
break;
default:
printf("error: %s (%d)\n", mp_strerror(res), res);
out = 2;
break;
}
mp_clear(&a);
mp_clear(&m);
return out;
}
|
