Commit 501bb26e authored by Niels Möller's avatar Niels Möller
Browse files

New files.

Rev: src/nettle/dsa-sign.c:1.1
Rev: src/nettle/dsa-verify.c:1.1
Rev: src/nettle/dsa.c:1.1
Rev: src/nettle/dsa.h:1.1
parent 3f0c8f74
/* dsa-sign.c
*
* The DSA publickey algorithm.
*/
/* nettle, low-level cryptographics library
*
* Copyright (C) 2002 Niels Mller
*
* 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
#if WITH_PUBLIC_KEY
#include "dsa.h"
#include "bignum.h"
#include <stdlib.h>
/* Returns a number x, almost uniformly random in the range
* 0 <= x < n. */
static void
nettle_mpz_random(mpz_t x, const mpz_t n,
void *ctx, nettle_random_func random)
{
/* FIXME: This leaves some bias, which may be bad for DSA. A better
* way might to generate a random number of mpz_sizeinbase(n, 2)
* bits, and loop until one smaller than n is found. */
/* From Daniel Bleichenbacher (via coderpunks):
*
* There is still a theoretical attack possible with 8 extra bits.
* But, the attack would need about 2^66 signatures 2^66 memory and
* 2^66 time (if I remember that correctly). Compare that to DSA,
* where the attack requires 2^22 signatures 2^40 memory and 2^64
* time. And of course, the numbers above are not a real threat for
* PGP. Using 16 extra bits (i.e. generating a 176 bit random number
* and reducing it modulo q) will defeat even this theoretical
* attack.
*
* More generally log_2(q)/8 extra bits are enough to defeat my
* attack. NIST also plans to update the standard.
*/
/* Add a few bits extra, to decrease the bias from the final modulo
* operation. */
unsigned ndigits = (mpz_sizeinbase(n, 2) + 7) / 8 + 2;
uint8_t *digits = alloca(ndigits);
random(ctx, ndigits, digits);
nettle_mpz_set_str_256(x, ndigits, digits);
mpz_fdiv_r(x, x, n);
}
void
dsa_sign(struct dsa_private_key *key,
void *random_ctx, nettle_random_func random,
struct sha1_ctx *hash,
struct dsa_signature *signature)
{
mpz_t k;
mpz_t h;
mpz_t tmp;
/* Select k, 0<k<q, randomly */
mpz_init_set(tmp, key->pub.q);
mpz_sub_ui(tmp, tmp, 1);
mpz_init(k);
nettle_mpz_random(k, tmp, random_ctx, random);
mpz_add_ui(k, k, 1);
/* Compute r = (g^k (mod p)) (mod q) */
mpz_powm(tmp, key->pub.g, k, key->pub.p);
mpz_fdiv_r(signature->r, tmp, key->pub.q);
/* Compute hash */
_dsa_hash(h, hash);
/* Compute k^-1 (mod q) */
if (!mpz_invert(k, k, key->pub.q))
/* What do we do now? The key is invalid. */
abort();
/* Compute signature s = k^-1(h + xr) (mod q) */
mpz_mul(tmp, signature->r, key->x);
mpz_fdiv_r(tmp, tmp, key->pub.q);
mpz_add(tmp, tmp, h);
mpz_mul(tmp, tmp, k);
mpz_fdiv_r(signature->s, tmp, key->pub.q);
mpz_clear(k);
mpz_clear(h);
mpz_clear(tmp);
}
#endif /* WITH_PUBLIC_KEY */
/* dsa-verify.c
*
* The DSA publickey algorithm.
*/
/* nettle, low-level cryptographics library
*
* Copyright (C) 2002 Niels Mller
*
* 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
#if WITH_PUBLIC_KEY
#include "dsa.h"
#include <stdlib.h>
int
dsa_verify(struct dsa_public_key *key,
struct sha1_ctx *hash,
const struct dsa_signature *signature)
{
mpz_t w;
mpz_t tmp;
mpz_t v;
int res;
/* Check that r and s are in the proper range */
if (mpz_sgn(signature->r) <= 0 || mpz_cmp(signature->r, key->q) >= 0)
return 0;
if (mpz_sgn(signature->s) <= 0 || mpz_cmp(signature->s, key->q) >= 0)
return 0;
mpz_init(w);
/* Compute w = s^-1 (mod q) */
/* NOTE: In gmp-2, mpz_invert sometimes generates negative inverses,
* so we need gmp-3 or better. */
if (!mpz_invert(w, signature->s, key->q))
{
mpz_clear(w);
return 0;
}
mpz_init(tmp);
mpz_init(v);
/* Compute hash */
_dsa_hash(tmp, hash);
/* v = g^{w * h (mod q)} (mod p) */
mpz_mul(tmp, tmp, w);
mpz_fdiv_r(tmp, tmp, key->q);
mpz_powm(v, key->g, tmp, key->p);
/* y^{w * r (mod q) } (mod p) */
mpz_mul(tmp, signature->r, w);
mpz_fdiv_r(tmp, tmp, key->q);
mpz_powm(tmp, key->y, tmp, key->p);
/* v = (g^{w * h} * y^{w * r} (mod p) ) (mod q) */
mpz_mul(v, v, tmp);
mpz_fdiv_r(v, v, key->p);
mpz_fdiv_r(v, v, key->q);
res = !mpz_cmp(v, signature->r);
mpz_clear(w);
mpz_clear(tmp);
mpz_clear(v);
return res;
}
#endif /* WITH_PUBLIC_KEY */
/* dsa.h
*
* The DSA publickey algorithm.
*/
/* nettle, low-level cryptographics library
*
* Copyright (C) 2002 Niels Mller
*
* 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
#if WITH_PUBLIC_KEY
#include "dsa.h"
#include "bignum.h"
void
dsa_public_key_init(struct dsa_public_key *key)
{
mpz_init(key->p);
mpz_init(key->q);
mpz_init(key->g);
mpz_init(key->y);
}
void
dsa_public_key_clear(struct dsa_public_key *key)
{
mpz_clear(key->p);
mpz_clear(key->q);
mpz_clear(key->g);
mpz_clear(key->y);
}
void
dsa_private_key_init(struct dsa_private_key *key)
{
dsa_public_key_init(&key->pub);
mpz_init(key->x);
}
void
dsa_private_key_clear(struct dsa_private_key *key)
{
dsa_public_key_clear(&key->pub);
mpz_clear(key->x);
}
void
dsa_signature_init(struct dsa_signature *signature)
{
mpz_init(signature->r);
mpz_init(signature->s);
}
void
dsa_signature_clear(struct dsa_signature *signature)
{
mpz_clear(signature->r);
mpz_clear(signature->s);
}
void
_dsa_hash(mpz_t x, struct sha1_ctx *hash)
{
uint8_t digest[SHA1_DIGEST_SIZE];
sha1_digest(hash, sizeof(digest), digest);
nettle_mpz_set_str_256(x, sizeof(digest), digest);
}
#endif /* WITH_PUBLIC_KEY */
/* dsa.h
*
* The DSA publickey algorithm.
*/
/* nettle, low-level cryptographics library
*
* Copyright (C) 2002 Niels Mller
*
* 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.
*/
#ifndef NETTLE_DSA_H_INCLUDED
#define NETTLE_DSA_H_INCLUDED
#include <inttypes.h>
#include <gmp.h>
#include "sha.h"
/* For nettle_random_func */
#include "nettle-meta.h"
struct dsa_public_key
{
/* Modulo */
mpz_t p;
/* Group order */
mpz_t q;
/* Generator */
mpz_t g;
/* Public value */
mpz_t y;
};
struct dsa_private_key
{
/* Unlike an rsa public key, all the public information is needed,
* in addition to the private information. */
struct dsa_public_key pub;
mpz_t x;
};
struct dsa_signature
{
mpz_t r;
mpz_t s;
};
/* Signing a message works as follows:
*
* Store the private key in a dsa_private_key struct.
*
* Initialize a hashing context, by callling
* sha1_init
*
* Hash the message by calling
* sha1_update
*
* Create the signature by calling
* dsa_sign
*
* The signature is represented as two mpz_t bignums. This call also
* resets the hashing context.
*
* When done with the key and signature, don't forget to call
* mpz_clear.
*/
/* Calls mpz_init to initialize bignum storage. */
void
dsa_public_key_init(struct dsa_public_key *key);
/* Calls mpz_clear to deallocate bignum storage. */
void
dsa_public_key_clear(struct dsa_public_key *key);
/* Calls mpz_init to initialize bignum storage. */
void
dsa_private_key_init(struct dsa_private_key *key);
/* Calls mpz_clear to deallocate bignum storage. */
void
dsa_private_key_clear(struct dsa_private_key *key);
/* Calls mpz_init to initialize bignum storage. */
void
dsa_signature_init(struct dsa_signature *signature);
/* Calls mpz_clear to deallocate bignum storage. */
void
dsa_signature_clear(struct dsa_signature *signature);
void
_dsa_hash(mpz_t x, struct sha1_ctx *hash);
void
dsa_sign(struct dsa_private_key *key,
void *random_ctx, nettle_random_func random,
struct sha1_ctx *hash,
struct dsa_signature *signature);
int
dsa_verify(struct dsa_public_key *key,
struct sha1_ctx *hash,
const struct dsa_signature *signature);
/* Key generation */
#if 0
/* Note that the key structs must be initialized first. */
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,
/* Desired size of modulo, in bits */
unsigned n_size,
/* Desired size of public exponent, in bits. If
* zero, the passed in value pub->e is used. */
unsigned e_size);
#define DSA_SIGN(key, algorithm, ctx, length, data, signature) ( \
algorithm##_update(ctx, length, data), \
dsa_##algorithm##_sign(key, ctx, signature) \
)
#define DSA_VERIFY(key, algorithm, ctx, length, data, signature) ( \
algorithm##_update(ctx, length, data), \
dsa_##algorithm##_verify(key, ctx, signature) \
)
#endif
#endif /* NETTLE_DSA_H_INCLUDED */
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