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Check large factor for being prime before applying Pollard's 

algorithm; fixes "factor 2147483647111311".  Correct comment;
algorithm is Pollard p-1, not Pollard rho.  Increase base if p-1
algorithm reaches 1; fixes "factor 99999999999991".  Testcases from
David A Bagley <bagleyd@tux.org>.
This commit is contained in:
jsm 2004-02-08 11:47:36 +00:00
parent acc00ca8a4
commit 4eec310a4f
1 changed files with 14 additions and 6 deletions
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20
games/factor/factor.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: factor.c,v 1.14 2003/08/07 09:37:12 agc Exp $ */
/* $NetBSD: factor.c,v 1.15 2004/02/08 11:47:36 jsm Exp $ */
/*
* Copyright (c) 1989, 1993
@ -42,7 +42,7 @@ __COPYRIGHT("@(#) Copyright (c) 1989, 1993\n\
#if 0
static char sccsid[] = "@(#)factor.c 8.4 (Berkeley) 5/4/95";
#else
__RCSID("$NetBSD: factor.c,v 1.14 2003/08/07 09:37:12 agc Exp $");
__RCSID("$NetBSD: factor.c,v 1.15 2004/02/08 11:47:36 jsm Exp $");
#endif
#endif /* not lint */
@ -228,7 +228,9 @@ pr_fact(BIGNUM *val)
bnfact = BN_new();
BN_set_word(bnfact, *(fact - 1));
BN_sqr(bnfact, bnfact, ctx);
if (BN_cmp(bnfact, val) > 0) {
if (BN_cmp(bnfact, val) > 0
|| BN_is_prime(val, PRIME_CHECKS, NULL, NULL,
NULL) == 1) {
putchar(' ');
BN_print_dec_fp(stdout, val);
} else
@ -277,23 +279,29 @@ usage(void)
#ifdef HAVE_OPENSSL
/* pollard rho, algorithm from Jim Gillogly, May 2000 */
/* pollard p-1, algorithm from Jim Gillogly, May 2000 */
void
pollard_pminus1(BIGNUM *val)
{
BIGNUM *base, *num, *i, *x;
BIGNUM *base, *rbase, *num, *i, *x;
base = BN_new();
rbase = BN_new();
num = BN_new();
i = BN_new();
x = BN_new();
BN_set_word(rbase, 1);
newbase:
BN_add_word(rbase, 1);
BN_set_word(i, 2);
BN_set_word(base, 2);
BN_copy(base, rbase);
for (;;) {
BN_mod_exp(base, base, i, val, ctx);
if (BN_is_one(base))
goto newbase;
BN_copy(x, base);
BN_sub_word(x, 1);