mirror of
git://git.gnupg.org/gnupg.git
synced 2024-11-09 21:28:51 +01:00
120 lines
2.9 KiB
C
120 lines
2.9 KiB
C
/* mpi-mpow.c - MPI functions
|
|
* Copyright (C) 1998 Free Software Foundation, Inc.
|
|
*
|
|
* This file is part of GNUPG.
|
|
*
|
|
* GNUPG is free software; you can redistribute it and/or modify
|
|
* it under the terms of 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.
|
|
*
|
|
* GNUPG 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 a copy of the GNU General Public License
|
|
* along with this program; if not, write to the Free Software
|
|
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
|
|
*/
|
|
|
|
#include <config.h>
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
#include "mpi-internal.h"
|
|
#include "longlong.h"
|
|
#include <assert.h>
|
|
|
|
static int
|
|
build_index( MPI *exparray, int k, int i, int t )
|
|
{
|
|
int j, bitno;
|
|
int index = 0;
|
|
|
|
bitno = t-i;
|
|
for(j=k-1; j >= 0; j-- ) {
|
|
index <<= 1;
|
|
if( mpi_test_bit( exparray[j], bitno ) )
|
|
index |= 1;
|
|
}
|
|
/*log_debug("t=%d i=%d index=%d\n", t, i, index );*/
|
|
return index;
|
|
}
|
|
|
|
/****************
|
|
* RES = (BASE[0] ^ EXP[0]) * (BASE[1] ^ EXP[1]) * ... * mod M
|
|
*/
|
|
void
|
|
mpi_mulpowm( MPI res, MPI *basearray, MPI *exparray, MPI m)
|
|
{
|
|
int k; /* number of elements */
|
|
int t; /* bit size of largest exponent */
|
|
int i, j, idx;
|
|
MPI *G; /* table with precomputed values of size 2^k */
|
|
MPI tmp;
|
|
|
|
for(k=0; basearray[k]; k++ )
|
|
;
|
|
assert(k);
|
|
for(t=0, i=0; (tmp=exparray[i]); i++ ) {
|
|
/*log_mpidump("exp: ", tmp );*/
|
|
j = mpi_get_nbits(tmp);
|
|
if( j > t )
|
|
t = j;
|
|
}
|
|
/*log_mpidump("mod: ", m );*/
|
|
assert(i==k);
|
|
assert(t);
|
|
assert( k < 10 );
|
|
|
|
G = m_alloc_clear( (1<<k) * sizeof *G );
|
|
#if 0
|
|
/* do the precomputation */
|
|
G[0] = mpi_alloc_set_ui( 1 );
|
|
for(i=1; i < (1<<k); i++ ) {
|
|
for(j=0; j < k; j++ ) {
|
|
if( (i & (1<<j) ) ) {
|
|
if( !G[i] )
|
|
G[i] = mpi_copy( basearray[j] );
|
|
else
|
|
mpi_mulm( G[i], G[i], basearray[j], m );
|
|
}
|
|
}
|
|
if( !G[i] )
|
|
G[i] = mpi_alloc(0);
|
|
}
|
|
#endif
|
|
/* and calculate */
|
|
tmp = mpi_alloc( mpi_get_nlimbs(m)+1 );
|
|
mpi_set_ui( res, 1 );
|
|
for(i = 1; i <= t; i++ ) {
|
|
mpi_mulm(tmp, res, res, m );
|
|
idx = build_index( exparray, k, i, t );
|
|
assert( idx >= 0 && idx < (1<<k) );
|
|
if( !G[idx] ) {
|
|
if( !idx )
|
|
G[0] = mpi_alloc_set_ui( 1 );
|
|
else {
|
|
for(j=0; j < k; j++ ) {
|
|
if( (idx & (1<<j) ) ) {
|
|
if( !G[idx] )
|
|
G[idx] = mpi_copy( basearray[j] );
|
|
else
|
|
mpi_mulm( G[idx], G[idx], basearray[j], m );
|
|
}
|
|
}
|
|
if( !G[idx] )
|
|
G[idx] = mpi_alloc(0);
|
|
}
|
|
}
|
|
mpi_mulm(res, tmp, G[idx], m );
|
|
}
|
|
|
|
/* cleanup */
|
|
mpi_free(tmp);
|
|
for(i=0; i < (1<<k); i++ )
|
|
mpi_free(G[i]);
|
|
m_free(G);
|
|
}
|
|
|