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39 results

ecdsa-verify.c

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  • Forked from Nettle / nettle
    1945 commits behind the upstream repository.
    ecdsa-verify.c 2.05 KiB
    /* 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
    }