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comparison libtommath/bn_mp_reduce.c @ 1692:1051e4eea25a

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Update LibTomMath to 1.2.0 (#84) * update C files * update other files * update headers * update makefiles * remove mp_set/get_double() * use ltm 1.2.0 API * update ltm_desc * use bundled tommath if system-tommath is too old * XMALLOC etc. were changed to MP_MALLOC etc.
author Steffen Jaeckel <s@jaeckel.eu>
date Tue, 26 May 2020 17:36:47 +0200
parents f52919ffd3b1
children
comparison
equal deleted inserted replaced
1691:2d3745d58843 1692:1051e4eea25a
1 #include "tommath_private.h" 1 #include "tommath_private.h"
2 #ifdef BN_MP_REDUCE_C 2 #ifdef BN_MP_REDUCE_C
3 /* LibTomMath, multiple-precision integer library -- Tom St Denis 3 /* LibTomMath, multiple-precision integer library -- Tom St Denis */
4 * 4 /* SPDX-License-Identifier: Unlicense */
5 * LibTomMath is a library that provides multiple-precision
6 * integer arithmetic as well as number theoretic functionality.
7 *
8 * The library was designed directly after the MPI library by
9 * Michael Fromberger but has been written from scratch with
10 * additional optimizations in place.
11 *
12 * SPDX-License-Identifier: Unlicense
13 */
14 5
15 /* reduces x mod m, assumes 0 < x < m**2, mu is 6 /* reduces x mod m, assumes 0 < x < m**2, mu is
16 * precomputed via mp_reduce_setup. 7 * precomputed via mp_reduce_setup.
17 * From HAC pp.604 Algorithm 14.42 8 * From HAC pp.604 Algorithm 14.42
18 */ 9 */
19 int mp_reduce(mp_int *x, const mp_int *m, const mp_int *mu) 10 mp_err mp_reduce(mp_int *x, const mp_int *m, const mp_int *mu)
20 { 11 {
21 mp_int q; 12 mp_int q;
22 int res, um = m->used; 13 mp_err err;
14 int um = m->used;
23 15
24 /* q = x */ 16 /* q = x */
25 if ((res = mp_init_copy(&q, x)) != MP_OKAY) { 17 if ((err = mp_init_copy(&q, x)) != MP_OKAY) {
26 return res; 18 return err;
27 } 19 }
28 20
29 /* q1 = x / b**(k-1) */ 21 /* q1 = x / b**(k-1) */
30 mp_rshd(&q, um - 1); 22 mp_rshd(&q, um - 1);
31 23
32 /* according to HAC this optimization is ok */ 24 /* according to HAC this optimization is ok */
33 if ((mp_digit)um > ((mp_digit)1 << (DIGIT_BIT - 1))) { 25 if ((mp_digit)um > ((mp_digit)1 << (MP_DIGIT_BIT - 1))) {
34 if ((res = mp_mul(&q, mu, &q)) != MP_OKAY) { 26 if ((err = mp_mul(&q, mu, &q)) != MP_OKAY) {
27 goto CLEANUP;
28 }
29 } else if (MP_HAS(S_MP_MUL_HIGH_DIGS)) {
30 if ((err = s_mp_mul_high_digs(&q, mu, &q, um)) != MP_OKAY) {
31 goto CLEANUP;
32 }
33 } else if (MP_HAS(S_MP_MUL_HIGH_DIGS_FAST)) {
34 if ((err = s_mp_mul_high_digs_fast(&q, mu, &q, um)) != MP_OKAY) {
35 goto CLEANUP; 35 goto CLEANUP;
36 } 36 }
37 } else { 37 } else {
38 #ifdef BN_S_MP_MUL_HIGH_DIGS_C 38 err = MP_VAL;
39 if ((res = s_mp_mul_high_digs(&q, mu, &q, um)) != MP_OKAY) { 39 goto CLEANUP;
40 goto CLEANUP;
41 }
42 #elif defined(BN_FAST_S_MP_MUL_HIGH_DIGS_C)
43 if ((res = fast_s_mp_mul_high_digs(&q, mu, &q, um)) != MP_OKAY) {
44 goto CLEANUP;
45 }
46 #else
47 {
48 res = MP_VAL;
49 goto CLEANUP;
50 }
51 #endif
52 } 40 }
53 41
54 /* q3 = q2 / b**(k+1) */ 42 /* q3 = q2 / b**(k+1) */
55 mp_rshd(&q, um + 1); 43 mp_rshd(&q, um + 1);
56 44
57 /* x = x mod b**(k+1), quick (no division) */ 45 /* x = x mod b**(k+1), quick (no division) */
58 if ((res = mp_mod_2d(x, DIGIT_BIT * (um + 1), x)) != MP_OKAY) { 46 if ((err = mp_mod_2d(x, MP_DIGIT_BIT * (um + 1), x)) != MP_OKAY) {
59 goto CLEANUP; 47 goto CLEANUP;
60 } 48 }
61 49
62 /* q = q * m mod b**(k+1), quick (no division) */ 50 /* q = q * m mod b**(k+1), quick (no division) */
63 if ((res = s_mp_mul_digs(&q, m, &q, um + 1)) != MP_OKAY) { 51 if ((err = s_mp_mul_digs(&q, m, &q, um + 1)) != MP_OKAY) {
64 goto CLEANUP; 52 goto CLEANUP;
65 } 53 }
66 54
67 /* x = x - q */ 55 /* x = x - q */
68 if ((res = mp_sub(x, &q, x)) != MP_OKAY) { 56 if ((err = mp_sub(x, &q, x)) != MP_OKAY) {
69 goto CLEANUP; 57 goto CLEANUP;
70 } 58 }
71 59
72 /* If x < 0, add b**(k+1) to it */ 60 /* If x < 0, add b**(k+1) to it */
73 if (mp_cmp_d(x, 0uL) == MP_LT) { 61 if (mp_cmp_d(x, 0uL) == MP_LT) {
74 mp_set(&q, 1uL); 62 mp_set(&q, 1uL);
75 if ((res = mp_lshd(&q, um + 1)) != MP_OKAY) 63 if ((err = mp_lshd(&q, um + 1)) != MP_OKAY) {
76 goto CLEANUP; 64 goto CLEANUP;
77 if ((res = mp_add(x, &q, x)) != MP_OKAY) 65 }
66 if ((err = mp_add(x, &q, x)) != MP_OKAY) {
78 goto CLEANUP; 67 goto CLEANUP;
68 }
79 } 69 }
80 70
81 /* Back off if it's too big */ 71 /* Back off if it's too big */
82 while (mp_cmp(x, m) != MP_LT) { 72 while (mp_cmp(x, m) != MP_LT) {
83 if ((res = s_mp_sub(x, m, x)) != MP_OKAY) { 73 if ((err = s_mp_sub(x, m, x)) != MP_OKAY) {
84 goto CLEANUP; 74 goto CLEANUP;
85 } 75 }
86 } 76 }
87 77
88 CLEANUP: 78 CLEANUP:
89 mp_clear(&q); 79 mp_clear(&q);
90 80
91 return res; 81 return err;
92 } 82 }
93 #endif 83 #endif
94
95 /* ref: HEAD -> master, tag: v1.1.0 */
96 /* git commit: 08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */
97 /* commit time: 2019-01-28 20:32:32 +0100 */