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/** \ingroup DSA_m
* \file dsa.c
*
* Digital Signature Algorithm signature scheme, code.
*
* DSA Signature:
* - Signing equation:
* - r = (g^k mod p) mod q and
* - s = (inv(k) * (h(m) + x*r)) mod q
* - Verifying equation:
* - check 0 < r < q and 0 < s < q
* - w = inv(s) mod q
* - u1 = (h(m)*w) mod q
* - u2 = (r*w) mod q
* - v = ((g^u1 * y^u2) mod p) mod q
* - check v == r
*
* For more information on this algorithm, see:
* NIST FIPS 186-1
*/
/*
* Copyright (c) 2001 Virtual Unlimited B.V.
*
* Author: Bob Deblier <bob@virtualunlimited.com>
*
* This 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.
*
* 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 library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*
*/
#include "system.h"
#include "dsa.h"
#include "dldp.h"
#include "mp32.h"
#include "debug.h"
/*@unchecked@*/
static int _debug = 0;
int dsasign(const mp32barrett* p, const mp32barrett* q, const mp32number* g, randomGeneratorContext* rgc, const mp32number* hm, const mp32number* x, mp32number* r, mp32number* s)
{
register uint32 psize = p->size;
register uint32 qsize = q->size;
register uint32* ptemp;
register uint32* qtemp;
register uint32* pwksp;
register uint32* qwksp;
register int rc = -1; /* assume failure */
ptemp = (uint32*) malloc((5*psize+2) * sizeof(*ptemp));
if (ptemp == NULL)
return rc;
qtemp = (uint32*) malloc((14*qsize+11) * sizeof(*qtemp));
if (qtemp == NULL) {
free(ptemp);
return rc;
}
pwksp = ptemp+psize;
qwksp = qtemp+3*qsize;
/* allocate r */
mp32nfree(r);
mp32nsize(r, qsize);
/* get a random k, invertible modulo q */
mp32brndinv_w(q, rgc, qtemp, qtemp+qsize, qwksp);
/* FIPS 186 test vectors
qtemp[0] = 0x358dad57;
qtemp[1] = 0x1462710f;
qtemp[2] = 0x50e254cf;
qtemp[3] = 0x1a376b2b;
qtemp[4] = 0xdeaadfbf;
mp32binv_w(q, qsize, qtemp, qtemp+qsize, qwksp);
*/
/* g^k mod p */
mp32bpowmod_w(p, g->size, g->data, qsize, qtemp, ptemp, pwksp);
/* (g^k mod p) mod q - simple modulo */
mp32nmod(qtemp+2*qsize, psize, ptemp, qsize, q->modl, pwksp);
mp32copy(qsize, r->data, qtemp+psize+qsize);
/* allocate s */
mp32nfree(s);
mp32nsize(s, qsize);
/* x*r mod q */
mp32bmulmod_w(q, x->size, x->data, r->size, r->data, qtemp, qwksp);
/* add h(m) mod q */
mp32baddmod_w(q, qsize, qtemp, hm->size, hm->data, qtemp+2*qsize, qwksp);
/* multiply inv(k) mod q */
mp32bmulmod_w(q, qsize, qtemp+qsize, qsize, qtemp+2*qsize, s->data, qwksp);
rc = 0;
free(qtemp);
free(ptemp);
return rc;
}
int dsavrfy(const mp32barrett* p, const mp32barrett* q, const mp32number* g, const mp32number* hm, const mp32number* y, const mp32number* r, const mp32number* s)
{
register uint32 psize = p->size;
register uint32 qsize = q->size;
register uint32* ptemp;
register uint32* qtemp;
register uint32* pwksp;
register uint32* qwksp;
register int rc = 0; /* XXX shouldn't this be -1 ?*/
if (mp32z(r->size, r->data))
return rc;
if (mp32gex(r->size, r->data, qsize, q->modl))
return rc;
if (mp32z(s->size, s->data))
return rc;
if (mp32gex(s->size, s->data, qsize, q->modl))
return rc;
ptemp = (uint32*) malloc((6*psize+2) * sizeof(*ptemp));
if (ptemp == NULL)
return rc;
qtemp = (uint32*) malloc((13*qsize+11) * sizeof(*qtemp));
if (qtemp == NULL) {
free(ptemp);
return rc;
}
pwksp = ptemp+2*psize;
qwksp = qtemp+2*qsize;
/* compute w = inv(s) mod q */
if (mp32binv_w(q, s->size, s->data, qtemp, qwksp))
{
/* compute u1 = h(m)*w mod q */
mp32bmulmod_w(q, hm->size, hm->data, qsize, qtemp, qtemp+qsize, qwksp);
/* compute u2 = r*w mod q */
mp32bmulmod_w(q, r->size, r->data, qsize, qtemp, qtemp, qwksp);
/* compute g^u1 mod p */
mp32bpowmod_w(p, g->size, g->data, qsize, qtemp+qsize, ptemp, pwksp);
/* compute y^u2 mod p */
mp32bpowmod_w(p, y->size, y->data, qsize, qtemp, ptemp+psize, pwksp);
/* multiply mod p */
mp32bmulmod_w(p, psize, ptemp, psize, ptemp+psize, ptemp, pwksp);
/* modulo q */
mp32nmod(ptemp+psize, psize, ptemp, qsize, q->modl, pwksp);
rc = mp32eqx(r->size, r->data, psize, ptemp+psize);
}
free(qtemp);
free(ptemp);
return rc;
}
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