1 /* mpi-mpow.c - MPI functions
2 * Copyright (C) 1998, 1999, 2000 Free Software Foundation, Inc.
4 * This file is part of GnuPG.
6 * GnuPG is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
11 * GnuPG is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
21 #include "mpi-internal.h"
26 build_index(const MPI *exparray, int k, int i, int t )
32 for(j=k-1; j >= 0; j-- ) {
34 if( mpi_test_bit( exparray[j], bitno ) )
41 * RES = (BASE[0] ^ EXP[0]) * (BASE[1] ^ EXP[1]) * ... * mod M
44 mpi_mulpowm( MPI res, MPI *basearray, MPI *exparray, MPI m)
47 int k; /* number of elements */
48 int t; /* bit size of largest exponent */
50 MPI *G = NULL; /* table with precomputed values of size 2^k */
53 for(k=0; basearray[k]; k++ )
55 if (!k) { printk("mpi_mulpowm: assert(k) failed\n"); BUG(); }
56 for(t=0, i=0; (tmp=exparray[i]); i++ ) {
57 j = mpi_get_nbits(tmp);
61 if (i!=k) { printk("mpi_mulpowm: assert(i==k) failed\n"); BUG(); }
62 if (!t) { printk("mpi_mulpowm: assert(t) failed\n"); BUG(); }
63 if (k>=10) { printk("mpi_mulpowm: assert(k<10) failed\n"); BUG(); }
65 G = kmalloc( (1<<k) * sizeof *G, GFP_KERNEL );
67 memset(G,0,(1<<k) * sizeof *G);
69 tmp = mpi_alloc( mpi_get_nlimbs(m)+1 ); if (!tmp) goto nomem;
70 if (mpi_set_ui( res, 1 ) < 0) goto nomem;
71 for(i = 1; i <= t; i++ ) {
72 if (mpi_mulm(tmp, res, res, m ) < 0) goto nomem;
73 idx = build_index( exparray, k, i, t );
74 if (!(idx >= 0 && idx < (1<<k))) {
75 printk("mpi_mulpowm: assert(idx >= 0 && idx < (1<<k)) failed\n");
80 G[0] = mpi_alloc_set_ui( 1 );
81 if (!G[0]) goto nomem;
84 for(j=0; j < k; j++ ) {
85 if( (idx & (1<<j) ) ) {
87 if (mpi_copy( &G[idx], basearray[j] ) < 0)
91 if (mpi_mulm(G[idx],G[idx],basearray[j],m) < 0)
97 G[idx] = mpi_alloc(0);
98 if (!G[idx]) goto nomem;
102 if (mpi_mulm(res, tmp, G[idx], m ) < 0) goto nomem;
109 for(i=0; i < (1<<k); i++ )