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/*
* invmod.c
*
* Compute modular inverses
*
* The contents of this file are subject to the Mozilla Public
* License Version 1.1 (the "License"); you may not use this file
* except in compliance with the License. You may obtain a copy of
* the License at http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS
* IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
* implied. See the License for the specific language governing
* rights and limitations under the License.
*
* The Original Code is the MPI Arbitrary Precision Integer Arithmetic
* library.
*
* The Initial Developer of the Original Code is Michael J. Fromberger.
* Portions created by Michael J. Fromberger are
* Copyright (C) 1997, 1998, 1999, 2000 Michael J. Fromberger.
* All Rights Reserved.
*
* Contributor(s):
*
* Alternatively, the contents of this file may be used under the
* terms of the GNU General Public License Version 2 or later (the
* "GPL"), in which case the provisions of the GPL are applicable
* instead of those above. If you wish to allow use of your
* version of this file only under the terms of the GPL and not to
* allow others to use your version of this file under the MPL,
* indicate your decision by deleting the provisions above and
* replace them with the notice and other provisions required by
* the GPL. If you do not delete the provisions above, a recipient
* may use your version of this file under either the MPL or the GPL.
*
* $Id$
*/
#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;
}
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