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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; | |
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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. */ | |
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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. */ | |
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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 | } | |
f145d411 | 85 | EXPORT_SYMBOL_GPL(mpi_mul); |
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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); |