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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"
24 static int build_index(const MPI
*exparray
, int k
, int i
, int t
)
30 for (j
= k
- 1; j
>= 0; j
--) {
32 if (mpi_test_bit(exparray
[j
], bitno
))
39 * RES = (BASE[0] ^ EXP[0]) * (BASE[1] ^ EXP[1]) * ... * mod M
41 int mpi_mulpowm(MPI res
, MPI
*basearray
, MPI
*exparray
, MPI m
)
44 int k
; /* number of elements */
45 int t
; /* bit size of largest exponent */
47 MPI
*G
= NULL
; /* table with precomputed values of size 2^k */
50 for (k
= 0; basearray
[k
]; k
++)
53 pr_emerg("mpi_mulpowm: assert(k) failed\n");
56 for (t
= 0, i
= 0; (tmp
= exparray
[i
]); i
++) {
57 j
= mpi_get_nbits(tmp
);
62 pr_emerg("mpi_mulpowm: assert(i==k) failed\n");
66 pr_emerg("mpi_mulpowm: assert(t) failed\n");
70 pr_emerg("mpi_mulpowm: assert(k<10) failed\n");
74 G
= kzalloc((1 << k
) * sizeof *G
, GFP_KERNEL
);
79 tmp
= mpi_alloc(mpi_get_nlimbs(m
) + 1);
82 if (mpi_set_ui(res
, 1) < 0)
84 for (i
= 1; i
<= t
; i
++) {
85 if (mpi_mulm(tmp
, res
, res
, m
) < 0)
87 idx
= build_index(exparray
, k
, i
, t
);
88 if (!(idx
>= 0 && idx
< (1 << k
))) {
89 pr_emerg("mpi_mulpowm: assert(idx >= 0 && idx < (1<<k)) failed\n");
94 G
[0] = mpi_alloc_set_ui(1);
98 for (j
= 0; j
< k
; j
++) {
99 if ((idx
& (1 << j
))) {
115 G
[idx
] = mpi_alloc(0);
121 if (mpi_mulm(res
, tmp
, G
[idx
], m
) < 0)
129 for (i
= 0; i
< (1 << k
); i
++)