Commit | Line | Data |
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34e4f738 | 1 | /* -*-c-*- |
2 | * | |
34e4f738 | 3 | * Modular exponentiation with Montgomery reduction |
4 | * | |
5 | * (c) 2004 Straylight/Edgeware | |
6 | */ | |
7 | ||
45c0fd36 | 8 | /*----- Licensing notice --------------------------------------------------* |
34e4f738 | 9 | * |
10 | * This file is part of Catacomb. | |
11 | * | |
12 | * Catacomb is free software; you can redistribute it and/or modify | |
13 | * it under the terms of the GNU Library General Public License as | |
14 | * published by the Free Software Foundation; either version 2 of the | |
15 | * License, or (at your option) any later version. | |
45c0fd36 | 16 | * |
34e4f738 | 17 | * Catacomb is distributed in the hope that it will be useful, |
18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
20 | * GNU Library General Public License for more details. | |
45c0fd36 | 21 | * |
34e4f738 | 22 | * You should have received a copy of the GNU Library General Public |
23 | * License along with Catacomb; if not, write to the Free | |
24 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, | |
25 | * MA 02111-1307, USA. | |
26 | */ | |
27 | ||
34e4f738 | 28 | /*----- Header files ------------------------------------------------------*/ |
29 | ||
30 | #include "mp.h" | |
31 | #include "mpmont.h" | |
32 | #include "mpmont-exp.h" | |
33 | ||
34 | /*----- Exponentiation ----------------------------------------------------*/ | |
35 | ||
36 | /* --- @mpmont_expr@ --- * | |
37 | * | |
295f4f90 | 38 | * Arguments: @const mpmont *mm@ = pointer to Montgomery reduction context |
34e4f738 | 39 | * @mp *d@ = fake destination |
40 | * @mp *a@ = base | |
41 | * @mp *e@ = exponent | |
42 | * | |
43 | * Returns: Result, %$(a R^{-1})^e R \bmod m$%. | |
44 | */ | |
45 | ||
295f4f90 | 46 | mp *mpmont_expr(const mpmont *mm, mp *d, mp *a, mp *e) |
34e4f738 | 47 | { |
48 | mp *x = MP_COPY(mm->r); | |
49 | mp *spare = (e->f & MP_BURN) ? MP_NEWSEC : MP_NEW; | |
50 | ||
51 | MP_COPY(a); | |
52 | MP_SHRINK(e); | |
a69a3efd | 53 | if (MP_ZEROP(e)) |
34e4f738 | 54 | ; |
a69a3efd | 55 | else { |
56 | if (MP_NEGP(e)) { | |
57 | a = mpmont_reduce(mm, a, a); | |
58 | a = mp_modinv(a, a, mm->m); | |
59 | a = mpmont_mul(mm, a, a, mm->r2); | |
60 | } | |
61 | if (MP_LEN(e) < EXP_THRESH) | |
62 | EXP_SIMPLE(x, a, e); | |
63 | else | |
64 | EXP_WINDOW(x, a, e); | |
65 | } | |
34e4f738 | 66 | mp_drop(d); |
67 | mp_drop(spare); | |
68 | mp_drop(a); | |
69 | return (x); | |
70 | } | |
71 | ||
72 | /* --- @mpmont_exp@ --- * | |
73 | * | |
295f4f90 | 74 | * Arguments: @const mpmont *mm@ = pointer to Montgomery reduction context |
34e4f738 | 75 | * @mp *d@ = fake destination |
76 | * @mp *a@ = base | |
77 | * @mp *e@ = exponent | |
78 | * | |
79 | * Returns: Result, %$a^e \bmod m$%. | |
80 | */ | |
81 | ||
295f4f90 | 82 | mp *mpmont_exp(const mpmont *mm, mp *d, mp *a, mp *e) |
34e4f738 | 83 | { |
84 | e = MP_COPY(e); | |
85 | d = mpmont_mul(mm, d, a, mm->r2); | |
86 | d = mpmont_expr(mm, d, d, e); | |
87 | d = mpmont_reduce(mm, d, d); | |
88 | MP_DROP(e); | |
89 | return (d); | |
90 | } | |
91 | ||
92 | /*----- Test rig ----------------------------------------------------------*/ | |
93 | ||
94 | #ifdef TEST_RIG | |
95 | ||
416b8869 MW |
96 | #ifdef ENABLE_ASM_DEBUG |
97 | # include "regdump.h" | |
98 | #endif | |
99 | ||
34e4f738 | 100 | static int texp(dstr *v) |
101 | { | |
102 | mp *m = *(mp **)v[0].buf; | |
103 | mp *a = *(mp **)v[1].buf; | |
104 | mp *b = *(mp **)v[2].buf; | |
105 | mp *r = *(mp **)v[3].buf; | |
106 | mp *mr; | |
107 | int ok = 1; | |
108 | ||
109 | mpmont mm; | |
110 | mpmont_create(&mm, m); | |
111 | ||
112 | mr = mpmont_exp(&mm, MP_NEW, a, b); | |
113 | ||
114 | if (!MP_EQ(mr, r)) { | |
115 | fputs("\n*** montgomery modexp failed", stderr); | |
116 | fputs("\n m = ", stderr); mp_writefile(m, stderr, 10); | |
117 | fputs("\n a = ", stderr); mp_writefile(a, stderr, 10); | |
118 | fputs("\n e = ", stderr); mp_writefile(b, stderr, 10); | |
119 | fputs("\n r = ", stderr); mp_writefile(r, stderr, 10); | |
120 | fputs("\nmr = ", stderr); mp_writefile(mr, stderr, 10); | |
121 | fputc('\n', stderr); | |
122 | ok = 0; | |
123 | } | |
124 | ||
125 | MP_DROP(m); | |
126 | MP_DROP(a); | |
127 | MP_DROP(b); | |
128 | MP_DROP(r); | |
129 | MP_DROP(mr); | |
130 | mpmont_destroy(&mm); | |
131 | assert(mparena_count(MPARENA_GLOBAL) == 0); | |
132 | return ok; | |
133 | } | |
134 | ||
34e4f738 | 135 | static test_chunk tests[] = { |
136 | { "exp", texp, { &type_mp, &type_mp, &type_mp, &type_mp, 0 } }, | |
137 | { 0, 0, { 0 } }, | |
138 | }; | |
139 | ||
140 | int main(int argc, char *argv[]) | |
141 | { | |
142 | sub_init(); | |
416b8869 MW |
143 | #ifdef ENABLE_ASM_DEBUG |
144 | regdump_init(); | |
145 | #endif | |
0f00dc4c | 146 | test_run(argc, argv, tests, SRCDIR "/t/mpmont"); |
34e4f738 | 147 | return (0); |
148 | } | |
149 | ||
150 | #endif | |
151 | ||
152 | /*----- That's all, folks -------------------------------------------------*/ |