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/* ecc-ecdsa-verify.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"
int
ecdsa_verify (const struct ecc_point *pub,
size_t length, const uint8_t *digest,
const struct dsa_signature *signature)
{
mp_limb_t size = pub->ecc->size;
mp_size_t itch = 2*size + ECC_ECDSA_VERIFY_ITCH (size);
/* For ECC_MUL_A_WBITS == 0, at most 1512 bytes. With
ECC_MUL_A_WBITS == 4, currently needs 67 * ecc->size, at most
4824 bytes. Don't use stack allocation for this. */
mp_limb_t *scratch = gmp_alloc_limbs (itch);
int res;
#define rp scratch
#define sp (scratch + size)
#define scratch_out (scratch + 2*size)
if (mpz_sgn (signature->r) <= 0 || mpz_size (signature->r) > size
|| mpz_sgn (signature->s) <= 0 || mpz_size (signature->s) > size)
return 0;
mpz_limbs_copy (rp, signature->r, size);
mpz_limbs_copy (sp, signature->s, size);
res = ecc_ecdsa_verify (pub->ecc, pub->p, length, digest, rp, sp, scratch_out);
gmp_free_limbs (scratch, itch);
return res;
#undef rp
#undef sp
#undef scratch_out
}
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