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/* dsa-keygen.c
*
* Generation of DSA keypairs
*/
/* nettle, low-level cryptographics library
*
* Copyright (C) 2002 Niels Möller
*
* The nettle library is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or (at your
* option) any later version.
*
* The nettle library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
* License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with the nettle library; see the file COPYING.LIB. If not, write to
* the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
* MA 02111-1307, USA.
*/
#if HAVE_CONFIG_H
# include "config.h"
#endif
#include <assert.h>
#include <stdlib.h>
#include "dsa.h"
#include "bignum.h"
#include "memxor.h"
#include "nettle-internal.h"
/* Valid sizes, according to FIPS 186-3 are (1024, 160), (2048. 224),
(2048, 256), (3072, 256). Currenty, we use only q_bits of 160 or
256. */
int
dsa_generate_keypair(struct dsa_public_key *pub,
struct dsa_private_key *key,
void *random_ctx, nettle_random_func random,
void *progress_ctx, nettle_progress_func progress,
unsigned p_bits, unsigned q_bits)
{
mpz_t p0, p0q, r;
unsigned p0_bits;
unsigned a;
switch (q_bits)
{
case 160:
if (p_bits < 512)
return 0;
break;
case 256:
if (p_bits < 1024)
return 0;
break;
default:
return 0;
}
mpz_init (p0);
mpz_init (p0q);
mpz_init (r);
nettle_random_prime (pub->q, q_bits, 0, random_ctx, random,
progress_ctx, progress);
p0_bits = (p_bits + 3)/2;
nettle_random_prime (p0, p0_bits, 0,
random_ctx, random,
progress_ctx, progress);
if (progress)
progress (progress_ctx, 'q');
/* Generate p = 2 r q p0 + 1, such that 2^{n-1} < p < 2^n.
*
* We select r in the range i + 1 < r <= 2i, with i = floor (2^{n-2} / (p0 q). */
mpz_mul (p0q, p0, pub->q);
_nettle_generate_pocklington_prime (pub->p, r, p_bits, 0,
random_ctx, random,
p0, pub->q, p0q);
if (progress)
progress (progress_ctx, 'p');
mpz_mul (r, r, p0);
for (a = 2; ; a++)
{
mpz_set_ui (pub->g, a);
mpz_powm (pub->g, pub->g, r, pub->p);
if (mpz_cmp_ui (pub->g, 1) != 0)
break;
}
if (progress)
progress (progress_ctx, 'g');
mpz_init_set(r, pub->q);
mpz_sub_ui(r, r, 2);
nettle_mpz_random(key->x, random_ctx, random, r);
mpz_add_ui(key->x, key->x, 1);
mpz_powm(pub->y, pub->g, key->x, pub->p);
if (progress)
progress (progress_ctx, '\n');
mpz_clear (p0);
mpz_clear (p0q);
mpz_clear (r);
return 1;
}
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