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93 lines
2.6 KiB
C
93 lines
2.6 KiB
C
/*
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* invmod.c
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*
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* Compute modular inverses
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*
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* ***** BEGIN LICENSE BLOCK *****
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* Version: MPL 1.1/GPL 2.0/LGPL 2.1
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*
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* The contents of this file are subject to the Mozilla Public License Version
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* 1.1 (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.mozilla.org/MPL/
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*
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* Software distributed under the License is distributed on an "AS IS" basis,
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* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
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* for the specific language governing rights and limitations under the
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* License.
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*
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* The Original Code is the MPI Arbitrary Precision Integer Arithmetic library.
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*
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* The Initial Developer of the Original Code is
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* Michael J. Fromberger.
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* Portions created by the Initial Developer are Copyright (C) 1997
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* the Initial Developer. All Rights Reserved.
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*
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* Contributor(s):
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*
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* Alternatively, the contents of this file may be used under the terms of
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* either the GNU General Public License Version 2 or later (the "GPL"), or
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* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
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* in which case the provisions of the GPL or the LGPL are applicable instead
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* of those above. If you wish to allow use of your version of this file only
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* under the terms of either the GPL or the LGPL, and not to allow others to
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* use your version of this file under the terms of the MPL, indicate your
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* decision by deleting the provisions above and replace them with the notice
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* and other provisions required by the GPL or the LGPL. If you do not delete
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* the provisions above, a recipient may use your version of this file under
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* the terms of any one of the MPL, the GPL or the LGPL.
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*
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* ***** END LICENSE BLOCK ***** */
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/* $Id: invmod.c,v 1.3 2004/04/27 23:04:37 gerv%gerv.net Exp $ */
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#include <stdio.h>
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#include <stdlib.h>
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#include "mpi.h"
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int main(int argc, char *argv[])
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{
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mp_int a, m;
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mp_err res;
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char *buf;
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int len, out = 0;
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if(argc < 3) {
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fprintf(stderr, "Usage: %s <a> <m>\n", argv[0]);
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return 1;
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}
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mp_init(&a); mp_init(&m);
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mp_read_radix(&a, argv[1], 10);
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mp_read_radix(&m, argv[2], 10);
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if(mp_cmp(&a, &m) > 0)
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mp_mod(&a, &m, &a);
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switch((res = mp_invmod(&a, &m, &a))) {
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case MP_OKAY:
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len = mp_radix_size(&a, 10);
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buf = malloc(len);
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mp_toradix(&a, buf, 10);
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printf("%s\n", buf);
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free(buf);
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break;
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case MP_UNDEF:
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printf("No inverse\n");
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out = 1;
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break;
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default:
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printf("error: %s (%d)\n", mp_strerror(res), res);
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out = 2;
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break;
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}
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mp_clear(&a);
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mp_clear(&m);
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return out;
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}
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