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/*
* Copyright (C) 2011 Free Software Foundation, Inc.
*
* This file is part of GNUTLS.
*
* The GNUTLS 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 3 of
* the License, or (at your option) any later version.
*
* This 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 this program. If not, see <http://www.gnu.org/licenses/>
*
*/
/* Based on public domain code of LibTomCrypt by Tom St Denis.
* Adapted to gmp and nettle by Nikos Mavrogiannopoulos.
*/
#include "ecc.h"
#include <nettle/dsa.h>
/*
@file ecc_sign_hash.c
ECC Crypto, Tom St Denis
*/
/*
Sign a message digest
@param in The message digest to sign
@param inlen The length of the digest
@param sign The destination for the signature
@param prng An active PRNG state
@param wprng The index of the PRNG you wish to use
@param key A private ECC key
@return 0 if successful
*/
int
ecc_sign_hash (const unsigned char *in, unsigned long inlen,
struct dsa_signature *sig,
void *random_ctx, nettle_random_func random, ecc_key * key)
{
ecc_key pubkey;
mpz_t e;
int err;
if (in == NULL || sig == NULL || key == NULL)
return -1;
/* is this a private key? */
if (key->type != PK_PRIVATE)
{
return -1;
}
/* get the hash and load it as a bignum into 'e' */
/* init the bignums */
if ((err = mp_init_multi (&e, NULL)) != 0)
{
return err;
}
nettle_mpz_set_str_256_u (e, inlen, in);
/* make up a key and export the public copy */
for (;;)
{
if ((err =
ecc_make_key_ex (random_ctx, random, &pubkey, key->prime,
key->order, key->A, key->B, key->Gx, key->Gy, 1)) != 0)
{
goto errnokey;
}
/* find r = x1 mod n */
mpz_mod (sig->r, pubkey.pubkey.x, pubkey.order);
if (mpz_cmp_ui (sig->r, 0) == 0)
{
ecc_free (&pubkey);
}
else
{
/* find s = (e + xr)/k */
mpz_invert (pubkey.k, pubkey.k, pubkey.order);
/* mulmod */
mpz_mul (sig->s, key->k, sig->r);
mpz_mod (sig->s, sig->s, pubkey.order);
mpz_add (sig->s, e, sig->s);
mpz_mod (sig->s, sig->s, pubkey.order);
mpz_mul (sig->s, sig->s, pubkey.k);
mpz_mod (sig->s, sig->s, pubkey.order);
ecc_free (&pubkey);
if (mpz_cmp_ui (sig->s, 0) != 0)
{
break;
}
}
}
errnokey:
mp_clear_multi (&e, NULL);
return err;
}
/* $Source: /cvs/libtom/libtomcrypt/src/pk/ecc/ecc_sign_hash.c,v $ */
/* $Revision: 1.11 $ */
/* $Date: 2007/05/12 14:32:35 $ */
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