/security/nss/lib/freebl/mpi/utils/invmod.c

 1/*
 2 *  invmod.c
 3 *
 4 *  Compute modular inverses
 5 *
 6 * ***** BEGIN LICENSE BLOCK *****
 7 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 8 *
 9 * The contents of this file are subject to the Mozilla Public License Version
10 * 1.1 (the "License"); you may not use this file except in compliance with
11 * the License. You may obtain a copy of the License at
12 * http://www.mozilla.org/MPL/
13 *
14 * Software distributed under the License is distributed on an "AS IS" basis,
15 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
16 * for the specific language governing rights and limitations under the
17 * License.
18 *
19 * The Original Code is the MPI Arbitrary Precision Integer Arithmetic library.
20 *
21 * The Initial Developer of the Original Code is
22 * Michael J. Fromberger.
23 * Portions created by the Initial Developer are Copyright (C) 1997
24 * the Initial Developer. All Rights Reserved.
25 *
26 * Contributor(s):
27 *
28 * Alternatively, the contents of this file may be used under the terms of
29 * either the GNU General Public License Version 2 or later (the "GPL"), or
30 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
31 * in which case the provisions of the GPL or the LGPL are applicable instead
32 * of those above. If you wish to allow use of your version of this file only
33 * under the terms of either the GPL or the LGPL, and not to allow others to
34 * use your version of this file under the terms of the MPL, indicate your
35 * decision by deleting the provisions above and replace them with the notice
36 * and other provisions required by the GPL or the LGPL. If you do not delete
37 * the provisions above, a recipient may use your version of this file under
38 * the terms of any one of the MPL, the GPL or the LGPL.
39 *
40 * ***** END LICENSE BLOCK ***** */
41/* $Id: invmod.c,v 1.3 2004/04/27 23:04:37 gerv%gerv.net Exp $ */
42
43#include <stdio.h>
44#include <stdlib.h>
45
46#include "mpi.h"
47
48int main(int argc, char *argv[])
49{
50  mp_int    a, m;
51  mp_err    res;
52  char     *buf;
53  int       len, out = 0;
54
55  if(argc < 3) {
56    fprintf(stderr, "Usage: %s <a> <m>\n", argv[0]);
57    return 1;
58  }
59
60  mp_init(&a); mp_init(&m);
61  mp_read_radix(&a, argv[1], 10);
62  mp_read_radix(&m, argv[2], 10);
63
64  if(mp_cmp(&a, &m) > 0)
65    mp_mod(&a, &m, &a);
66
67  switch((res = mp_invmod(&a, &m, &a))) {
68  case MP_OKAY:
69    len = mp_radix_size(&a, 10);
70    buf = malloc(len);
71
72    mp_toradix(&a, buf, 10);
73    printf("%s\n", buf);
74    free(buf);
75    break;
76
77  case MP_UNDEF:
78    printf("No inverse\n");
79    out = 1;
80    break;
81
82  default:
83    printf("error: %s (%d)\n", mp_strerror(res), res);
84    out = 2;
85    break;
86  }
87
88  mp_clear(&a);
89  mp_clear(&m);
90
91  return out;
92}