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148 lines
4.3 KiB
C
148 lines
4.3 KiB
C
/*
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* makeprime.c
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*
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* A simple prime generator function (and test driver). Prints out the
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* first prime it finds greater than or equal to the starting value.
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*
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* Usage: makeprime <start>
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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) 1998
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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: makeprime.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 <ctype.h>
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/* These two must be included for make_prime() to work */
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#include "mpi.h"
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#include "mpprime.h"
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/*
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make_prime(p, nr)
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Find the smallest prime integer greater than or equal to p, where
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primality is verified by 'nr' iterations of the Rabin-Miller
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probabilistic primality test. The caller is responsible for
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generating the initial value of p.
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Returns MP_OKAY if a prime has been generated, otherwise the error
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code indicates some other problem. The value of p is clobbered; the
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caller should keep a copy if the value is needed.
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*/
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mp_err make_prime(mp_int *p, int nr);
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/* The main() is not required -- it's just a test driver */
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int main(int argc, char *argv[])
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{
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mp_int start;
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mp_err res;
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if(argc < 2) {
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fprintf(stderr, "Usage: %s <start-value>\n", argv[0]);
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return 1;
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}
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mp_init(&start);
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if(argv[1][0] == '0' && tolower(argv[1][1]) == 'x') {
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mp_read_radix(&start, argv[1] + 2, 16);
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} else {
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mp_read_radix(&start, argv[1], 10);
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}
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mp_abs(&start, &start);
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if((res = make_prime(&start, 5)) != MP_OKAY) {
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fprintf(stderr, "%s: error: %s\n", argv[0], mp_strerror(res));
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mp_clear(&start);
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return 1;
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} else {
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char *buf = malloc(mp_radix_size(&start, 10));
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mp_todecimal(&start, buf);
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printf("%s\n", buf);
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free(buf);
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mp_clear(&start);
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return 0;
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}
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} /* end main() */
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/*------------------------------------------------------------------------*/
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mp_err make_prime(mp_int *p, int nr)
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{
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mp_err res;
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if(mp_iseven(p)) {
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mp_add_d(p, 1, p);
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}
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do {
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mp_digit which = prime_tab_size;
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/* First test for divisibility by a few small primes */
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if((res = mpp_divis_primes(p, &which)) == MP_YES)
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continue;
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else if(res != MP_NO)
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goto CLEANUP;
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/* If that passes, try one iteration of Fermat's test */
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if((res = mpp_fermat(p, 2)) == MP_NO)
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continue;
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else if(res != MP_YES)
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goto CLEANUP;
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/* If that passes, run Rabin-Miller as often as requested */
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if((res = mpp_pprime(p, nr)) == MP_YES)
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break;
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else if(res != MP_NO)
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goto CLEANUP;
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} while((res = mp_add_d(p, 2, p)) == MP_OKAY);
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CLEANUP:
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return res;
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} /* end make_prime() */
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/*------------------------------------------------------------------------*/
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/* HERE THERE BE DRAGONS */
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