5 * Modular exponentiation using Barrett reduction
7 * (c) 2004 Straylight/Edgeware
10 /*----- Licensing notice --------------------------------------------------*
12 * This file is part of Catacomb.
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.
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.
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,
30 /*----- Header files ------------------------------------------------------*/
33 #include "mpbarrett.h"
34 #include "mpbarrett-exp.h"
36 /*----- Main code ---------------------------------------------------------*/
38 /* --- @mpbarrett_exp@ --- *
40 * Arguments: @mpbarrett *mb@ = pointer to Barrett reduction context
41 * @mp *d@ = fake destination
45 * Returns: Result, %$a^e \bmod m$%.
48 mp *mpbarrett_exp(mpbarrett *mb, mp *d, mp *a, mp *e)
51 mp *spare = (e->f & MP_BURN) ? MP_NEWSEC : MP_NEW;
59 a = mp_modinv(a, a, mb->m);
60 if (MP_LEN(e) < EXP_THRESH)
71 /*----- Test rig ----------------------------------------------------------*/
75 static int vexp(dstr *v)
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;
85 mpbarrett_create(&mb, m);
87 mr = mpbarrett_exp(&mb, MP_NEW, a, b);
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);
105 mpbarrett_destroy(&mb);
106 assert(mparena_count(MPARENA_GLOBAL) == 0);
110 static test_chunk tests[] = {
111 { "mpbarrett-exp", vexp, { &type_mp, &type_mp, &type_mp, &type_mp, 0 } },
115 int main(int argc, char *argv[])
118 test_run(argc, argv, tests, SRCDIR "/tests/mpbarrett");
124 /*----- That's all, folks -------------------------------------------------*/