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/* ecdsa-sign.c */
/* nettle, low-level cryptographics library
*
* Copyright (C) 2013 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., 51 Franklin Street, Fifth Floor, Boston,
* MA 02111-1301, USA.
*/
/* Development of Nettle's ECC support was funded by the .SE Internet Fund. */
#if HAVE_CONFIG_H
# include "config.h"
#endif
#include <assert.h>
#include <stdlib.h>
#include "ecdsa.h"
#include "ecc-internal.h"
#include "nettle-internal.h"
void
ecdsa_sign (const struct ecc_scalar *key,
void *random_ctx, nettle_random_func *random,
size_t digest_length,
const uint8_t *digest,
struct dsa_signature *signature)
{
/* At most 936 bytes. */
TMP_DECL(k, mp_limb_t, ECC_MAX_SIZE + ECC_ECDSA_SIGN_ITCH (ECC_MAX_SIZE));
mp_limb_t size = key->ecc->size;
mp_limb_t *rp = mpz_limbs_write (signature->r, size);
mp_limb_t *sp = mpz_limbs_write (signature->s, size);
TMP_ALLOC (k, size + ECC_ECDSA_SIGN_ITCH (size));
/* Timing reveals the number of rounds through this loop, but the
timing is still independent of the secret k finally used. */
do
{
ecc_modq_random (key->ecc, k, random_ctx, random, k + size);
ecc_ecdsa_sign (key->ecc, key->p, k, digest_length, digest,
rp, sp, k + size);
mpz_limbs_finish (signature->r, size);
mpz_limbs_finish (signature->s, size);
}
while (mpz_sgn (signature->r) == 0 || mpz_sgn (signature->s) == 0);
}
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