1 /* mpi-mul.c - MPI functions 1
2 * Copyright (C) 1994, 1996, 1998, 2001, 2002,
3 * 2003 Free Software Foundation
4 *
5 * This file is part of Libgcrypt.
6 *
7 * Note: This code is heavily based on the GNU
8 * Actually it's the same code with only
9 * way the data is stored; this is to su
10 * of an optional secure memory allocati
11 * to avoid revealing of sensitive data
12 */
13
14 #include "mpi-internal.h"
15
16 int 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 int err = 0;
25
26 if (u->nlimbs < v->nlimbs) {
27 /* Swap U and V. */
28 usize = v->nlimbs;
29 usign = v->sign;
30 up = v->d;
31 vsize = u->nlimbs;
32 vsign = u->sign;
33 vp = u->d;
34 } else {
35 usize = u->nlimbs;
36 usign = u->sign;
37 up = u->d;
38 vsize = v->nlimbs;
39 vsign = v->sign;
40 vp = v->d;
41 }
42 sign_product = usign ^ vsign;
43 wp = w->d;
44
45 /* Ensure W has space enough to store
46 wsize = usize + vsize;
47 if (w->alloced < wsize) {
48 if (wp == up || wp == vp) {
49 wp = mpi_alloc_limb_sp
50 if (!wp)
51 return -ENOMEM
52 assign_wp = 1;
53 } else {
54 err = mpi_resize(w, ws
55 if (err)
56 return err;
57 wp = w->d;
58 }
59 } else { /* Make U and V not overlap w
60 if (wp == up) {
61 /* W and U are identic
62 up = tmp_limb = mpi_al
63 if (!up)
64 return -ENOMEM
65 /* Is V identical too?
66 if (wp == vp)
67 vp = up;
68 /* Copy to the tempora
69 MPN_COPY(up, wp, usize
70 } else if (wp == vp) {
71 /* W and V are identic
72 vp = tmp_limb = mpi_al
73 if (!vp)
74 return -ENOMEM
75 /* Copy to the tempora
76 MPN_COPY(vp, wp, vsize
77 }
78 }
79
80 if (!vsize)
81 wsize = 0;
82 else {
83 err = mpihelp_mul(wp, up, usiz
84 if (err) {
85 if (assign_wp)
86 mpi_free_limb_
87 goto free_tmp_limb;
88 }
89 wsize -= cy ? 0:1;
90 }
91
92 if (assign_wp)
93 mpi_assign_limb_space(w, wp, w
94 w->nlimbs = wsize;
95 w->sign = sign_product;
96
97 free_tmp_limb:
98 if (tmp_limb)
99 mpi_free_limb_space(tmp_limb);
100 return err;
101 }
102 EXPORT_SYMBOL_GPL(mpi_mul);
103
104 int mpi_mulm(MPI w, MPI u, MPI v, MPI m)
105 {
106 return mpi_mul(w, u, v) ?:
107 mpi_tdiv_r(w, w, m);
108 }
109 EXPORT_SYMBOL_GPL(mpi_mulm);
110
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