122 lines
2.7 KiB
C
122 lines
2.7 KiB
C
/*
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Copyright 2009 Jason Moxham
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This file is part of the MPIR Library.
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The MPIR Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published
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by the Free Software Foundation; either version 2.1 of the License, or (at
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your option) any later version.
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The MPIR Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with the MPIR Library; see the file COPYING.LIB. If not, write
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to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
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Boston, MA 02110-1301, USA.
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*/
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#include "mpir.h"
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#include "gmp-impl.h"
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int
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mpz_probable_prime_p (mpz_srcptr N, gmp_randstate_t STATE, int PROB, mpir_ui td)
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{
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int d, t, i, r;
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mpz_t base, nm1, x, e, n;
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ALLOC(n) = ALLOC(N);
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SIZ(n) = ABSIZ(N);
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PTR(n) = PTR(N); /* fake up an absolute value that we dont have de-allocate */
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/* algorithm does not handle small values, get rid of them here */
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if (mpz_cmp_ui(n, 2) == 0 || mpz_cmp_ui(n, 3) == 0)
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return 1;
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if (mpz_cmp_ui(n, 5) < 0 || mpz_even_p(n))
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return 0;
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/*
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We assume we know nothing about N, i.e. it is a random integer
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So we try here anything which speeds up the average case
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We try some trial division
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*/
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#define LIM 1024
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d = mpz_trial_division(n, 3, LIM);
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if (d != 0)
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{
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if (mpz_cmp_ui(n, d) == 0)
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return 1;
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return 0;
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}
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if (mpz_cmp_ui(n, LIM * LIM) < 0)
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return 1;
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ASSERT (mpz_odd_p(n));
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ASSERT (mpz_cmp_ui(n, 5) >= 0);
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/* now do some random strong pseudoprime tests */
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mpz_init(base);
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mpz_init_set(nm1, n);
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mpz_sub_ui(nm1, nm1, 1);
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mpz_init(e);
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mpz_init(x);
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t = mpz_scan1(nm1, 0); /* 2^t divides nm1 */
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ASSERT (t > 0);
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mpz_tdiv_q_2exp (e, nm1, t); /* e = nm1/2^t */
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r = 1;
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while (PROB > 0)
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{
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PROB -= 2;
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do
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{
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mpz_urandomm (base, STATE, nm1);
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} while (mpz_cmp_ui (base, 1) <= 0);
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mpz_powm (x, base, e, n); /* x = base^e mod n */
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if (mpz_cmp_ui(x, 1) == 0 || mpz_cmp(x, nm1) == 0)
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continue;
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for (i = t - 1; i > 0; i--)
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{
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mpz_mul(x, x, x);
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mpz_mod(x, x, n);
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if (mpz_cmp(x, nm1) == 0)
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break;
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if (mpz_cmp_ui(x, 1) == 0)
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{
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r = 0;
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break;
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}
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}
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if (i == 0 || r == 0)
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{
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r = 0;
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break;
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}
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}
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mpz_clear (nm1);
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mpz_clear (x);
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mpz_clear (e);
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mpz_clear (base);
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return r;
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}
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