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-rw-r--r--lib/mpi/mpi-mpow.c134
1 files changed, 134 insertions, 0 deletions
diff --git a/lib/mpi/mpi-mpow.c b/lib/mpi/mpi-mpow.c
new file mode 100644
index 0000000..7328d0d
--- /dev/null
+++ b/lib/mpi/mpi-mpow.c
@@ -0,0 +1,134 @@
+/* mpi-mpow.c - MPI functions
+ * Copyright (C) 1998, 1999, 2000 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 "mpi-internal.h"
+#include "longlong.h"
+
+static int build_index(const 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;
+ }
+ return index;
+}
+
+/****************
+ * RES = (BASE[0] ^ EXP[0]) * (BASE[1] ^ EXP[1]) * ... * mod M
+ */
+int mpi_mulpowm(MPI res, MPI *basearray, MPI *exparray, MPI m)
+{
+ int rc = -ENOMEM;
+ int k; /* number of elements */
+ int t; /* bit size of largest exponent */
+ int i, j, idx;
+ MPI *G = NULL; /* table with precomputed values of size 2^k */
+ MPI tmp = NULL;
+
+ for (k = 0; basearray[k]; k++)
+ ;
+ if (!k) {
+ pr_emerg("mpi_mulpowm: assert(k) failed\n");
+ BUG();
+ }
+ for (t = 0, i = 0; (tmp = exparray[i]); i++) {
+ j = mpi_get_nbits(tmp);
+ if (j > t)
+ t = j;
+ }
+ if (i != k) {
+ pr_emerg("mpi_mulpowm: assert(i==k) failed\n");
+ BUG();
+ }
+ if (!t) {
+ pr_emerg("mpi_mulpowm: assert(t) failed\n");
+ BUG();
+ }
+ if (k >= 10) {
+ pr_emerg("mpi_mulpowm: assert(k<10) failed\n");
+ BUG();
+ }
+
+ G = kzalloc((1 << k) * sizeof *G, GFP_KERNEL);
+ if (!G)
+ goto err_out;
+
+ /* and calculate */
+ tmp = mpi_alloc(mpi_get_nlimbs(m) + 1);
+ if (!tmp)
+ goto nomem;
+ if (mpi_set_ui(res, 1) < 0)
+ goto nomem;
+ for (i = 1; i <= t; i++) {
+ if (mpi_mulm(tmp, res, res, m) < 0)
+ goto nomem;
+ idx = build_index(exparray, k, i, t);
+ if (!(idx >= 0 && idx < (1 << k))) {
+ pr_emerg("mpi_mulpowm: assert(idx >= 0 && idx < (1<<k)) failed\n");
+ BUG();
+ }
+ if (!G[idx]) {
+ if (!idx) {
+ G[0] = mpi_alloc_set_ui(1);
+ if (!G[0])
+ goto nomem;
+ } else {
+ for (j = 0; j < k; j++) {
+ if ((idx & (1 << j))) {
+ if (!G[idx]) {
+ if (mpi_copy
+ (&G[idx],
+ basearray[j]) < 0)
+ goto nomem;
+ } else {
+ if (mpi_mulm
+ (G[idx], G[idx],
+ basearray[j],
+ m) < 0)
+ goto nomem;
+ }
+ }
+ }
+ if (!G[idx]) {
+ G[idx] = mpi_alloc(0);
+ if (!G[idx])
+ goto nomem;
+ }
+ }
+ }
+ if (mpi_mulm(res, tmp, G[idx], m) < 0)
+ goto nomem;
+ }
+
+ rc = 0;
+nomem:
+ /* cleanup */
+ mpi_free(tmp);
+ for (i = 0; i < (1 << k); i++)
+ mpi_free(G[i]);
+ kfree(G);
+err_out:
+ return rc;
+}
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