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34e4f738 | 1 | /* -*-c-*- |
2 | * | |
a69a3efd | 3 | * $Id$ |
34e4f738 | 4 | * |
5 | * Modular exponentiation using Barrett reduction | |
6 | * | |
7 | * (c) 2004 Straylight/Edgeware | |
8 | */ | |
9 | ||
45c0fd36 | 10 | /*----- Licensing notice --------------------------------------------------* |
34e4f738 | 11 | * |
12 | * This file is part of Catacomb. | |
13 | * | |
14 | * Catacomb is free software; you can redistribute it and/or modify | |
15 | * it under the terms of the GNU Library General Public License as | |
16 | * published by the Free Software Foundation; either version 2 of the | |
17 | * License, or (at your option) any later version. | |
45c0fd36 | 18 | * |
34e4f738 | 19 | * Catacomb is distributed in the hope that it will be useful, |
20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
22 | * GNU Library General Public License for more details. | |
45c0fd36 | 23 | * |
34e4f738 | 24 | * You should have received a copy of the GNU Library General Public |
25 | * License along with Catacomb; if not, write to the Free | |
26 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, | |
27 | * MA 02111-1307, USA. | |
28 | */ | |
29 | ||
34e4f738 | 30 | /*----- Header files ------------------------------------------------------*/ |
31 | ||
32 | #include "mp.h" | |
33 | #include "mpbarrett.h" | |
34 | #include "mpbarrett-exp.h" | |
35 | ||
36 | /*----- Main code ---------------------------------------------------------*/ | |
37 | ||
38 | /* --- @mpbarrett_exp@ --- * | |
39 | * | |
40 | * Arguments: @mpbarrett *mb@ = pointer to Barrett reduction context | |
45c0fd36 MW |
41 | * @mp *d@ = fake destination |
42 | * @mp *a@ = base | |
43 | * @mp *e@ = exponent | |
34e4f738 | 44 | * |
45c0fd36 | 45 | * Returns: Result, %$a^e \bmod m$%. |
34e4f738 | 46 | */ |
47 | ||
48 | mp *mpbarrett_exp(mpbarrett *mb, mp *d, mp *a, mp *e) | |
49 | { | |
50 | mp *x = MP_ONE; | |
51 | mp *spare = (e->f & MP_BURN) ? MP_NEWSEC : MP_NEW; | |
52 | ||
53 | MP_COPY(a); | |
54 | MP_SHRINK(e); | |
a69a3efd | 55 | if (MP_ZEROP(e)) |
34e4f738 | 56 | ; |
a69a3efd | 57 | else { |
58 | if (MP_NEGP(e)) | |
59 | a = mp_modinv(a, a, mb->m); | |
60 | if (MP_LEN(e) < EXP_THRESH) | |
61 | EXP_SIMPLE(x, a, e); | |
62 | else | |
63 | EXP_WINDOW(x, a, e); | |
64 | } | |
34e4f738 | 65 | mp_drop(d); |
66 | mp_drop(spare); | |
67 | mp_drop(a); | |
68 | return (x); | |
69 | } | |
70 | ||
71 | /*----- Test rig ----------------------------------------------------------*/ | |
72 | ||
73 | #ifdef TEST_RIG | |
74 | ||
75 | static int vexp(dstr *v) | |
76 | { | |
77 | mp *m = *(mp **)v[0].buf; | |
78 | mp *a = *(mp **)v[1].buf; | |
79 | mp *b = *(mp **)v[2].buf; | |
80 | mp *r = *(mp **)v[3].buf; | |
81 | mp *mr; | |
82 | int ok = 1; | |
83 | ||
84 | mpbarrett mb; | |
85 | mpbarrett_create(&mb, m); | |
86 | ||
87 | mr = mpbarrett_exp(&mb, MP_NEW, a, b); | |
88 | ||
89 | if (!MP_EQ(mr, r)) { | |
90 | fputs("\n*** barrett modexp failed", stderr); | |
91 | fputs("\n m = ", stderr); mp_writefile(m, stderr, 10); | |
92 | fputs("\n a = ", stderr); mp_writefile(a, stderr, 10); | |
93 | fputs("\n e = ", stderr); mp_writefile(b, stderr, 10); | |
94 | fputs("\n r = ", stderr); mp_writefile(r, stderr, 10); | |
95 | fputs("\nmr = ", stderr); mp_writefile(mr, stderr, 10); | |
96 | fputc('\n', stderr); | |
97 | ok = 0; | |
98 | } | |
99 | ||
100 | mp_drop(m); | |
101 | mp_drop(a); | |
102 | mp_drop(b); | |
103 | mp_drop(r); | |
104 | mp_drop(mr); | |
105 | mpbarrett_destroy(&mb); | |
106 | assert(mparena_count(MPARENA_GLOBAL) == 0); | |
107 | return ok; | |
108 | } | |
109 | ||
110 | static test_chunk tests[] = { | |
111 | { "mpbarrett-exp", vexp, { &type_mp, &type_mp, &type_mp, &type_mp, 0 } }, | |
112 | { 0, 0, { 0 } } | |
113 | }; | |
114 | ||
115 | int main(int argc, char *argv[]) | |
116 | { | |
117 | sub_init(); | |
118 | test_run(argc, argv, tests, SRCDIR "/tests/mpbarrett"); | |
119 | return (0); | |
120 | } | |
121 | ||
122 | #endif | |
123 | ||
124 | /*----- That's all, folks -------------------------------------------------*/ |