Factorize bignums using the Pollard Rho algorithm. The code comes
from NetBSD, altered to retain the FreeBSD -h feature and various stylistic improvements and avoid regressions. In the absence of OpenSSL (and therefore bignums) the old code is used. PR: 43831 Reviewed by: kris, markm, obrien Obtained from: NetBSD MFC after: 2 weeks
This commit is contained in:
Tony Finch
parent
add448e4e7
commit
63f7eaa932
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=104722
@ -4,6 +4,13 @@
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PROG= factor
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SRCS= factor.c pr_tbl.c
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CFLAGS+=-I${.CURDIR}/../primes
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.if exists(${.CURDIR}/../../crypto) && !defined(NO_OPENSSL)
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CFLAGS+=-DHAVE_OPENSSL
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LDADD+= -lcrypto
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DPADD+= ${LIBCRYPTO}
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.endif
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MAN= factor.6
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MLINKS+=factor.6 primes.6
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.PATH: ${.CURDIR}/../primes
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@ -43,6 +43,7 @@ static const char copyright[] =
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#ifndef lint
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#if 0
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static char sccsid[] = "@(#)factor.c 8.4 (Berkeley) 5/4/95";
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__RCSID("$NetBSD: factor.c,v 1.13 2002/06/18 23:07:36 simonb Exp $");
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#endif
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static const char rcsid[] =
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"$FreeBSD$";
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@ -77,18 +78,54 @@ static const char rcsid[] =
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#include "primes.h"
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static int hflag;
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#ifdef HAVE_OPENSSL
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static void pr_fact(ubig); /* print factors of a value */
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#include <openssl/bn.h>
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#define PRIME_CHECKS 5
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static void pollard_pminus1(BIGNUM *); /* print factors for big numbers */
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#else
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typedef ubig BIGNUM;
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typedef u_long BN_ULONG;
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#define BN_CTX int
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#define BN_CTX_new() NULL
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#define BN_new() ((BIGNUM *)calloc(sizeof(BIGNUM), 1))
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#define BN_is_zero(v) (*(v) == 0)
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#define BN_is_one(v) (*(v) == 1)
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#define BN_mod_word(a, b) (*(a) % (b))
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static int BN_dec2bn(BIGNUM **a, const char *str);
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static int BN_hex2bn(BIGNUM **a, const char *str);
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static BN_ULONG BN_div_word(BIGNUM *, BN_ULONG);
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static void BN_print_fp(FILE *, const BIGNUM *);
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#endif
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static void BN_print_dec_fp(FILE *, const BIGNUM *);
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static void pr_fact(BIGNUM *); /* print factors of a value */
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static void pr_print(BIGNUM *); /* print a prime */
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static void usage(void);
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static BN_CTX *ctx; /* just use a global context */
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static int hflag;
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int
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main(int argc, char *argv[])
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{
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ubig val;
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BIGNUM *val;
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int ch;
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char *p, buf[LINE_MAX]; /* > max number of digits. */
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ctx = BN_CTX_new();
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val = BN_new();
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if (val == NULL)
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errx(1, "can't initialise bignum");
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while ((ch = getopt(argc, argv, "h")) != -1)
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switch (ch) {
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case 'h':
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@ -114,11 +151,8 @@ main(int argc, char *argv[])
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continue;
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if (*p == '-')
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errx(1, "negative numbers aren't permitted.");
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errno = 0;
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val = strtoul(buf, &p, 0);
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if (errno)
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err(1, "%s", buf);
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if (*p != '\n')
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if (BN_dec2bn(&val, buf) == 0 &&
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BN_hex2bn(&val, buf) == 0)
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errx(1, "%s: illegal numeric format.", buf);
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pr_fact(val);
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}
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@ -127,11 +161,8 @@ main(int argc, char *argv[])
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for (; *argv != NULL; ++argv) {
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if (argv[0][0] == '-')
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errx(1, "negative numbers aren't permitted.");
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errno = 0;
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val = strtoul(argv[0], &p, 0);
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if (errno)
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err(1, "%s", argv[0]);
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if (*p != '\0')
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if (BN_dec2bn(&val, argv[0]) == 0 &&
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BN_hex2bn(&val, argv[0]) == 0)
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errx(1, "%s: illegal numeric format.", argv[0]);
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pr_fact(val);
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}
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@ -148,38 +179,56 @@ main(int argc, char *argv[])
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* Factors are printed with leading tabs.
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*/
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static void
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pr_fact(ubig val)
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pr_fact(BIGNUM *val)
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{
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const ubig *fact; /* The factor found. */
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/* Firewall - catch 0 and 1. */
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if (val == 0) /* Historical practice; 0 just exits. */
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if (BN_is_zero(val)) /* Historical practice; 0 just exits. */
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exit(0);
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if (val == 1) {
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if (BN_is_one(val)) {
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printf("1: 1\n");
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return;
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}
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/* Factor value. */
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printf(hflag ? "0x%lx:" : "%lu:", val);
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for (fact = &prime[0]; val > 1; ++fact) {
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if (hflag) {
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fputs("0x", stdout);
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BN_print_fp(stdout, val);
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} else
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BN_print_dec_fp(stdout, val);
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putchar(':');
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for (fact = &prime[0]; !BN_is_one(val); ++fact) {
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/* Look for the smallest factor. */
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do {
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if (val % *fact == 0)
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if (BN_mod_word(val, (BN_ULONG)*fact) == 0)
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break;
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} while (++fact <= pr_limit);
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/* Watch for primes larger than the table. */
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if (fact > pr_limit) {
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printf(hflag ? " 0x%lx" : " %lu", val);
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#ifdef HAVE_OPENSSL
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BIGNUM *bnfact;
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bnfact = BN_new();
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BN_set_word(bnfact, *(fact - 1));
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BN_sqr(bnfact, bnfact, ctx);
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if (BN_cmp(bnfact, val) > 0)
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pr_print(val);
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else
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pollard_pminus1(val);
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#else
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pr_print(val);
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#endif
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break;
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}
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/* Divide factor out until none are left. */
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do {
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printf(hflag ? " 0x%lx" : " %lu", *fact);
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val /= *fact;
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} while ((val % *fact) == 0);
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BN_div_word(val, (BN_ULONG)*fact);
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} while (BN_mod_word(val, (BN_ULONG)*fact) == 0);
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/* Let the user know we're doing something. */
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fflush(stdout);
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@ -187,9 +236,128 @@ pr_fact(ubig val)
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putchar('\n');
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}
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static void
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pr_print(BIGNUM *val)
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{
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if (hflag) {
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fputs(" 0x", stdout);
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BN_print_fp(stdout, val);
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} else {
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putchar(' ');
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BN_print_dec_fp(stdout, val);
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}
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}
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static void
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usage(void)
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{
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fprintf(stderr, "usage: factor [-h] [value ...]\n");
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exit(1);
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}
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#ifdef HAVE_OPENSSL
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/* pollard rho, algorithm from Jim Gillogly, May 2000 */
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static void
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pollard_pminus1(BIGNUM *val)
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{
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BIGNUM *base, *num, *i, *x;
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base = BN_new();
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num = BN_new();
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i = BN_new();
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x = BN_new();
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BN_set_word(i, 2);
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BN_set_word(base, 2);
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for (;;) {
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BN_mod_exp(base, base, i, val, ctx);
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BN_copy(x, base);
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BN_sub_word(x, 1);
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BN_gcd(x, x, val, ctx);
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if (!BN_is_one(x)) {
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if (BN_is_prime(x, PRIME_CHECKS, NULL, NULL,
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NULL) == 1)
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pr_print(x);
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else
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pollard_pminus1(x);
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fflush(stdout);
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BN_div(num, NULL, val, x, ctx);
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if (BN_is_one(num))
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return;
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if (BN_is_prime(num, PRIME_CHECKS, NULL, NULL,
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NULL) == 1) {
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pr_print(num);
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fflush(stdout);
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return;
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}
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BN_copy(val, num);
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}
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BN_add_word(i, 1);
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}
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}
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/*
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* Sigh.. No _decimal_ output to file functions in BN.
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*/
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static void
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BN_print_dec_fp(FILE *fp, const BIGNUM *num)
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{
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char *buf;
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buf = BN_bn2dec(num);
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if (buf == NULL)
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return; /* XXX do anything here? */
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fprintf(fp, buf);
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free(buf);
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}
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#else
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static void
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BN_print_fp(FILE *fp, const BIGNUM *num)
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{
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fprintf(fp, "%lx", (unsigned long)*num);
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}
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static void
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BN_print_dec_fp(FILE *fp, const BIGNUM *num)
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{
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fprintf(fp, "%lu", (unsigned long)*num);
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}
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static int
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BN_dec2bn(BIGNUM **a, const char *str)
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{
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char *p;
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errno = 0;
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**a = strtoul(str, &p, 10);
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return (errno == 0 && (*p == '\n' || *p == '\0'));
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}
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static int
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BN_hex2bn(BIGNUM **a, const char *str)
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{
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char *p;
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errno = 0;
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**a = strtoul(str, &p, 16);
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return (errno == 0 && (*p == '\n' || *p == '\0'));
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}
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static BN_ULONG
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BN_div_word(BIGNUM *a, BN_ULONG b)
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{
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BN_ULONG mod;
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mod = *a % b;
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*a /= b;
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return mod;
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}
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#endif
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