3 * Modular exponentiation using Barrett reduction
5 * (c) 2004 Straylight/Edgeware
8 /*----- Licensing notice --------------------------------------------------*
10 * This file is part of Catacomb.
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.
17 * Catacomb is distributed in the hope that it will be useful,
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19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 * GNU Library General Public License for more details.
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,
28 /*----- Header files ------------------------------------------------------*/
31 #include "mpbarrett.h"
32 #include "mpbarrett-exp.h"
34 /*----- Main code ---------------------------------------------------------*/
36 /* --- @mpbarrett_exp@ --- *
38 * Arguments: @mpbarrett *mb@ = pointer to Barrett reduction context
39 * @mp *d@ = fake destination
43 * Returns: Result, %$a^e \bmod m$%.
46 mp *mpbarrett_exp(mpbarrett *mb, mp *d, mp *a, mp *e)
49 mp *spare = (e->f & MP_BURN) ? MP_NEWSEC : MP_NEW;
57 a = mp_modinv(a, a, mb->m);
58 if (MP_LEN(e) < EXP_THRESH)
69 /*----- Test rig ----------------------------------------------------------*/
73 static int vexp(dstr *v)
75 mp *m = *(mp **)v[0].buf;
76 mp *a = *(mp **)v[1].buf;
77 mp *b = *(mp **)v[2].buf;
78 mp *r = *(mp **)v[3].buf;
83 mpbarrett_create(&mb, m);
85 mr = mpbarrett_exp(&mb, MP_NEW, a, b);
88 fputs("\n*** barrett modexp failed", stderr);
89 fputs("\n m = ", stderr); mp_writefile(m, stderr, 10);
90 fputs("\n a = ", stderr); mp_writefile(a, stderr, 10);
91 fputs("\n e = ", stderr); mp_writefile(b, stderr, 10);
92 fputs("\n r = ", stderr); mp_writefile(r, stderr, 10);
93 fputs("\nmr = ", stderr); mp_writefile(mr, stderr, 10);
103 mpbarrett_destroy(&mb);
104 assert(mparena_count(MPARENA_GLOBAL) == 0);
108 static test_chunk tests[] = {
109 { "mpbarrett-exp", vexp, { &type_mp, &type_mp, &type_mp, &type_mp, 0 } },
113 int main(int argc, char *argv[])
116 test_run(argc, argv, tests, SRCDIR "/t/mpbarrett");
122 /*----- That's all, folks -------------------------------------------------*/