1 /* mpi-mul.c - MPI functions
2 * Copyright (C) 1994, 1996, 1998, 2001, 2002,
3 * 2003 Free Software Foundation, Inc.
4 *
5 * This file is part of Libgcrypt.
6 *
7 * Note: This code is heavily based on the GNU MP Library.
8 * Actually it's the same code with only minor changes in the
9 * way the data is stored; this is to support the abstraction
10 * of an optional secure memory allocation which may be used
11 * to avoid revealing of sensitive data due to paging etc.
12 */
13
14 #include "mpi-internal.h"
15
16 void mpi_mul(MPI w, MPI u, MPI v)
17 {
18 mpi_size_t usize, vsize, wsize;
19 mpi_ptr_t up, vp, wp;
20 mpi_limb_t cy;
21 int usign, vsign, sign_product;
22 int assign_wp = 0;
23 mpi_ptr_t tmp_limb = NULL;
24
25 if (u->nlimbs < v->nlimbs) {
26 /* Swap U and V. */
27 usize = v->nlimbs;
28 usign = v->sign;
29 up = v->d;
30 vsize = u->nlimbs;
31 vsign = u->sign;
32 vp = u->d;
33 } else {
34 usize = u->nlimbs;
35 usign = u->sign;
36 up = u->d;
37 vsize = v->nlimbs;
38 vsign = v->sign;
39 vp = v->d;
40 }
41 sign_product = usign ^ vsign;
42 wp = w->d;
43
44 /* Ensure W has space enough to store the result. */
45 wsize = usize + vsize;
46 if (w->alloced < wsize) {
47 if (wp == up || wp == vp) {
48 wp = mpi_alloc_limb_space(wsize);
49 assign_wp = 1;
50 } else {
51 mpi_resize(w, wsize);
52 wp = w->d;
53 }
54 } else { /* Make U and V not overlap with W. */
55 if (wp == up) {
56 /* W and U are identical. Allocate temporary space for U. */
57 up = tmp_limb = mpi_alloc_limb_space(usize);
58 /* Is V identical too? Keep it identical with U. */
59 if (wp == vp)
60 vp = up;
61 /* Copy to the temporary space. */
62 MPN_COPY(up, wp, usize);
63 } else if (wp == vp) {
64 /* W and V are identical. Allocate temporary space for V. */
65 vp = tmp_limb = mpi_alloc_limb_space(vsize);
66 /* Copy to the temporary space. */
67 MPN_COPY(vp, wp, vsize);
68 }
69 }
70
71 if (!vsize)
72 wsize = 0;
73 else {
74 mpihelp_mul(wp, up, usize, vp, vsize, &cy);
75 wsize -= cy ? 0:1;
76 }
77
78 if (assign_wp)
79 mpi_assign_limb_space(w, wp, wsize);
80 w->nlimbs = wsize;
81 w->sign = sign_product;
82 if (tmp_limb)
83 mpi_free_limb_space(tmp_limb);
84 }
85 EXPORT_SYMBOL_GPL(mpi_mul);
86
87 void mpi_mulm(MPI w, MPI u, MPI v, MPI m)
88 {
89 mpi_mul(w, u, v);
90 mpi_tdiv_r(w, w, m);
91 }
92 EXPORT_SYMBOL_GPL(mpi_mulm);
93
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.