Commit ec613387 authored by Niels Möller's avatar Niels Möller

Implemented _eddsa_verify. Almost correct.

parent 259f0d2b
2014-10-14 Niels Möller <nisse@lysator.liu.se>
* eddsa-verify.c (_eddsa_verify, eddsa_verify_itch): New file, new
functions.
* eddsa.h: Declare new functions.
* Makefile.in (hogweed_SOURCES): Added eddsa-verify.c.
2014-10-08 Niels Möller <nisse@lysator.liu.se>
* testsuite/eddsa-sign-test.c (test_eddsa_sign): Use
......
......@@ -177,7 +177,7 @@ hogweed_SOURCES = sexp.c sexp-format.c \
ecc-ecdsa-verify.c ecdsa-verify.c ecdsa-keygen.c \
curve25519-mul-g.c curve25519-mul.c curve25519-eh-to-x.c \
eddsa-compress.c eddsa-decompress.c eddsa-expand.c \
eddsa-hash.c eddsa-sign.c \
eddsa-hash.c eddsa-sign.c eddsa-verify.c \
$(OPT_HOGWEED_SOURCES)
HEADERS = aes.h arcfour.h arctwo.h asn1.h blowfish.h \
......
/* eddsa-verify.c
Copyright (C) 2014 Niels Möller
This file is part of GNU Nettle.
GNU Nettle is free software: you can redistribute it and/or
modify it under the terms of either:
* 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.
or
* the GNU General Public License as published by the Free
Software Foundation; either version 2 of the License, or (at your
option) any later version.
or both in parallel, as here.
GNU Nettle 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
General Public License for more details.
You should have received copies of the GNU General Public License and
the GNU Lesser General Public License along with this program. If
not, see http://www.gnu.org/licenses/.
*/
#if HAVE_CONFIG_H
# include "config.h"
#endif
#include <assert.h>
#include "eddsa.h"
#include "ecc.h"
#include "ecc-internal.h"
#include "nettle-meta.h"
/* FIXME: Use mpn_zero_p. Also duplicated in ecc-ecdsa-verify.c. */
static int
zero_p (const mp_limb_t *xp, mp_size_t n)
{
while (n > 0)
if (xp[--n] > 0)
return 0;
return 1;
}
mp_size_t
_eddsa_verify_itch (const struct ecc_curve *ecc)
{
return 8*ecc->p.size + ecc->mul_itch;
}
int
_eddsa_verify (const struct ecc_curve *ecc,
const struct nettle_hash *H,
const uint8_t *pub,
void *ctx,
const mp_limb_t *A,
size_t length,
const uint8_t *msg,
const uint8_t *signature,
mp_limb_t *scratch)
{
size_t nbytes;
#define R scratch
#define sp (scratch + 2*ecc->p.size)
#define hp (scratch + 3*ecc->p.size)
#define P (scratch + 5*ecc->p.size)
#define scratch_out (scratch + 8*ecc->p.size)
#define S R
#define hash ((uint8_t *) P)
nbytes = 1 + ecc->p.bit_size / 8;
/* Could maybe save some storage by delaying the R and S operations,
but it makes sense to check them for validity up front. */
if (!_eddsa_decompress (ecc, R, signature, R+2*ecc->p.size))
return 0;
mpn_set_base256_le (sp, ecc->q.size, signature + nbytes, nbytes);
/* Check that s < q */
if (mpn_cmp (sp, ecc->q.m, ecc->q.size) >= 0)
return 0;
H->init (ctx);
H->update (ctx, nbytes, signature);
H->update (ctx, nbytes, pub);
H->update (ctx, length, msg);
H->digest (ctx, 2*nbytes, hash);
_eddsa_hash (&ecc->q, hp, hash);
/* Compute h A + R - s G, which should be the neutral point */
ecc->mul (ecc, P, hp, A, scratch_out);
/* FIXME: Introduce an ecc->add method? */
ecc_add_eh (ecc, P, P, R, scratch_out);
/* Produces s in the range 1 <= s <= q, with no carry. */
mpn_sub_n (hp, ecc->q.m, sp, ecc->q.size);
ecc->mul_g (ecc, S, hp, scratch_out);
ecc_add_ehh (ecc, P, P, S, scratch_out);
/* Zero point iff x == 0 (mod p) iff (x == 0 or x == p) */
/* FIXME: Needs to differentiate between (0,1) and (0,-1). Implement
point compare instead of the above ecc_add_ehh?
/* FIXME: Introduce zero_p method? */
return (zero_p (P, ecc->p.size)
|| mpn_cmp (P, ecc->p.m, ecc->p.size) == 0);
#undef R
#undef sp
#undef hp
#undef P
#undef S
}
......@@ -50,6 +50,8 @@ extern "C" {
#define _eddsa_expand_key _nettle_eddsa_expand_key
#define _eddsa_sign _nettle_eddsa_sign
#define _eddsa_sign_itch _nettle_eddsa_sign_itch
#define _eddsa_verify _nettle_eddsa_verify
#define _eddsa_verify_itch _nettle_eddsa_verify_itch
#define ED25519_KEY_SIZE 32
......@@ -87,6 +89,20 @@ _eddsa_sign (const struct ecc_curve *ecc,
uint8_t *signature,
mp_limb_t *scratch);
mp_size_t
_eddsa_verify_itch (const struct ecc_curve *ecc);
int
_eddsa_verify (const struct ecc_curve *ecc,
const struct nettle_hash *H,
const uint8_t *pub,
void *ctx,
const mp_limb_t *A,
size_t length,
const uint8_t *msg,
const uint8_t *signature,
mp_limb_t *scratch);
mp_size_t
_eddsa_expand_key_itch (const struct ecc_curve *ecc);
......
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