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(nlimbs: wsize); |
49 | assign_wp = 1; |
50 | } else { |
51 | mpi_resize(a: w, nlimbs: 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(nlimbs: 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(nlimbs: 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(prodp: wp, up, usize, vp, vsize, result: &cy); |
75 | wsize -= cy ? 0:1; |
76 | } |
77 | |
78 | if (assign_wp) |
79 | mpi_assign_limb_space(a: w, ap: wp, nlimbs: wsize); |
80 | w->nlimbs = wsize; |
81 | w->sign = sign_product; |
82 | if (tmp_limb) |
83 | mpi_free_limb_space(a: 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(rem: w, num: w, den: m); |
91 | } |
92 | EXPORT_SYMBOL_GPL(mpi_mulm); |
93 | |