Mercurial > dropbear
comparison libtommath/bn_mp_reduce_2k_l.c @ 1436:60fc6476e044
Update to libtommath v1.0
author | Matt Johnston <matt@ucc.asn.au> |
---|---|
date | Sat, 24 Jun 2017 22:37:14 +0800 |
parents | 5ff8218bcee9 |
children | 8bba51a55704 |
comparison
equal
deleted
inserted
replaced
1435:f849a5ca2efc | 1436:60fc6476e044 |
---|---|
1 #include <tommath.h> | 1 #include <tommath_private.h> |
2 #ifdef BN_MP_REDUCE_2K_L_C | 2 #ifdef BN_MP_REDUCE_2K_L_C |
3 /* LibTomMath, multiple-precision integer library -- Tom St Denis | 3 /* LibTomMath, multiple-precision integer library -- Tom St Denis |
4 * | 4 * |
5 * LibTomMath is a library that provides multiple-precision | 5 * LibTomMath is a library that provides multiple-precision |
6 * integer arithmetic as well as number theoretic functionality. | 6 * integer arithmetic as well as number theoretic functionality. |
10 * additional optimizations in place. | 10 * additional optimizations in place. |
11 * | 11 * |
12 * The library is free for all purposes without any express | 12 * The library is free for all purposes without any express |
13 * guarantee it works. | 13 * guarantee it works. |
14 * | 14 * |
15 * Tom St Denis, [email protected], http://math.libtomcrypt.com | 15 * Tom St Denis, [email protected], http://libtom.org |
16 */ | 16 */ |
17 | 17 |
18 /* reduces a modulo n where n is of the form 2**p - d | 18 /* reduces a modulo n where n is of the form 2**p - d |
19 This differs from reduce_2k since "d" can be larger | 19 This differs from reduce_2k since "d" can be larger |
20 than a single digit. | 20 than a single digit. |
21 */ | 21 */ |
22 int mp_reduce_2k_l(mp_int *a, mp_int *n, mp_int *d) | 22 int mp_reduce_2k_l(mp_int *a, mp_int *n, mp_int *d) |
23 { | 23 { |
24 mp_int q; | 24 mp_int q; |
25 int p, res; | 25 int p, res; |
26 | 26 |
27 if ((res = mp_init(&q)) != MP_OKAY) { | 27 if ((res = mp_init(&q)) != MP_OKAY) { |
28 return res; | 28 return res; |
29 } | 29 } |
30 | 30 |
31 p = mp_count_bits(n); | 31 p = mp_count_bits(n); |
32 top: | 32 top: |
33 /* q = a/2**p, a = a mod 2**p */ | 33 /* q = a/2**p, a = a mod 2**p */ |
34 if ((res = mp_div_2d(a, p, &q, a)) != MP_OKAY) { | 34 if ((res = mp_div_2d(a, p, &q, a)) != MP_OKAY) { |
35 goto ERR; | 35 goto ERR; |
36 } | 36 } |
37 | 37 |
38 /* q = q * d */ | 38 /* q = q * d */ |
39 if ((res = mp_mul(&q, d, &q)) != MP_OKAY) { | 39 if ((res = mp_mul(&q, d, &q)) != MP_OKAY) { |
40 goto ERR; | 40 goto ERR; |
41 } | 41 } |
42 | 42 |
43 /* a = a + q */ | 43 /* a = a + q */ |
44 if ((res = s_mp_add(a, &q, a)) != MP_OKAY) { | 44 if ((res = s_mp_add(a, &q, a)) != MP_OKAY) { |
45 goto ERR; | 45 goto ERR; |
46 } | 46 } |
47 | 47 |
48 if (mp_cmp_mag(a, n) != MP_LT) { | 48 if (mp_cmp_mag(a, n) != MP_LT) { |
49 s_mp_sub(a, n, a); | 49 if ((res = s_mp_sub(a, n, a)) != MP_OKAY) { |
50 goto ERR; | |
51 } | |
50 goto top; | 52 goto top; |
51 } | 53 } |
52 | 54 |
53 ERR: | 55 ERR: |
54 mp_clear(&q); | 56 mp_clear(&q); |
55 return res; | 57 return res; |
56 } | 58 } |
57 | 59 |
58 #endif | 60 #endif |
59 | 61 |
60 /* $Source: /cvs/libtom/libtommath/bn_mp_reduce_2k_l.c,v $ */ | 62 /* $Source$ */ |
61 /* $Revision: 1.3 $ */ | 63 /* $Revision$ */ |
62 /* $Date: 2006/03/31 14:18:44 $ */ | 64 /* $Date$ */ |