Mercurial > dropbear

annotate bn_mp_reduce_2k_l.c @ 190:d8254fc979e9 libtommath-orig LTM_0.35

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Initial import of libtommath 0.35
author Matt Johnston <matt@ucc.asn.au>
date Fri, 06 May 2005 08:59:30 +0000
parents
children 97db060d0ef5
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
190
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
1 #include <tommath.h>
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
2 #ifdef BN_MP_REDUCE_2K_L_C
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
3 /* LibTomMath, multiple-precision integer library -- Tom St Denis
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
4 *
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
5 * LibTomMath is a library that provides multiple-precision
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
6 * integer arithmetic as well as number theoretic functionality.
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
7 *
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
8 * The library was designed directly after the MPI library by
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
9 * Michael Fromberger but has been written from scratch with
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
10 * additional optimizations in place.
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
11 *
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
12 * The library is free for all purposes without any express
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
13 * guarantee it works.
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
14 *
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
15 * Tom St Denis, [email protected], http://math.libtomcrypt.org
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
16 */
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
17
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
18 /* reduces a modulo n where n is of the form 2**p - d
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
19 This differs from reduce_2k since "d" can be larger
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
20 than a single digit.
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
21 */
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
22 int mp_reduce_2k_l(mp_int *a, mp_int *n, mp_int *d)
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
23 {
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
24 mp_int q;
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
25 int p, res;
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
26
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
27 if ((res = mp_init(&q)) != MP_OKAY) {
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
28 return res;
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
29 }
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
30
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
31 p = mp_count_bits(n);
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
32 top:
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
33 /* q = a/2**p, a = a mod 2**p */
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
34 if ((res = mp_div_2d(a, p, &q, a)) != MP_OKAY) {
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
35 goto ERR;
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
36 }
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
37
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
38 /* q = q * d */
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
39 if ((res = mp_mul(&q, d, &q)) != MP_OKAY) {
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
40 goto ERR;
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
41 }
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
42
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
43 /* a = a + q */
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
44 if ((res = s_mp_add(a, &q, a)) != MP_OKAY) {
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
45 goto ERR;
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
46 }
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
47
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
48 if (mp_cmp_mag(a, n) != MP_LT) {
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
49 s_mp_sub(a, n, a);
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
50 goto top;
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
51 }
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
52
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
53 ERR:
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
54 mp_clear(&q);
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
55 return res;
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
56 }
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
57
d8254fc979e9 Initial import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
58 #endif