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comparison libtommath/bn_mp_montgomery_calc_normalization.c @ 1739:13d834efc376 fuzz

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merge from main
author Matt Johnston <matt@ucc.asn.au>
date Thu, 15 Oct 2020 19:55:15 +0800
parents 1051e4eea25a
children
comparison
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1562:768ebf737aa0 1739:13d834efc376
1 #include <tommath_private.h> 1 #include "tommath_private.h"
2 #ifdef BN_MP_MONTGOMERY_CALC_NORMALIZATION_C 2 #ifdef BN_MP_MONTGOMERY_CALC_NORMALIZATION_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 * The library is free for all purposes without any express
13 * guarantee it works.
14 *
15 * Tom St Denis, [email protected], http://libtom.org
16 */
17 5
18 /* 6 /*
19 * shifts with subtractions when the result is greater than b. 7 * shifts with subtractions when the result is greater than b.
20 * 8 *
21 * The method is slightly modified to shift B unconditionally upto just under 9 * The method is slightly modified to shift B unconditionally upto just under
22 * the leading bit of b. This saves alot of multiple precision shifting. 10 * the leading bit of b. This saves alot of multiple precision shifting.
23 */ 11 */
24 int mp_montgomery_calc_normalization (mp_int * a, mp_int * b) 12 mp_err mp_montgomery_calc_normalization(mp_int *a, const mp_int *b)
25 { 13 {
26 int x, bits, res; 14 int x, bits;
15 mp_err err;
27 16
28 /* how many bits of last digit does b use */ 17 /* how many bits of last digit does b use */
29 bits = mp_count_bits (b) % DIGIT_BIT; 18 bits = mp_count_bits(b) % MP_DIGIT_BIT;
30 19
31 if (b->used > 1) { 20 if (b->used > 1) {
32 if ((res = mp_2expt (a, ((b->used - 1) * DIGIT_BIT) + bits - 1)) != MP_OKAY) { 21 if ((err = mp_2expt(a, ((b->used - 1) * MP_DIGIT_BIT) + bits - 1)) != MP_OKAY) {
33 return res; 22 return err;
34 } 23 }
35 } else { 24 } else {
36 mp_set(a, 1); 25 mp_set(a, 1uL);
37 bits = 1; 26 bits = 1;
38 } 27 }
39 28
40 29
41 /* now compute C = A * B mod b */ 30 /* now compute C = A * B mod b */
42 for (x = bits - 1; x < (int)DIGIT_BIT; x++) { 31 for (x = bits - 1; x < (int)MP_DIGIT_BIT; x++) {
43 if ((res = mp_mul_2 (a, a)) != MP_OKAY) { 32 if ((err = mp_mul_2(a, a)) != MP_OKAY) {
44 return res; 33 return err;
45 }
46 if (mp_cmp_mag (a, b) != MP_LT) {
47 if ((res = s_mp_sub (a, b, a)) != MP_OKAY) {
48 return res;
49 } 34 }
50 } 35 if (mp_cmp_mag(a, b) != MP_LT) {
51 } 36 if ((err = s_mp_sub(a, b, a)) != MP_OKAY) {
37 return err;
38 }
39 }
40 }
52 41
53 return MP_OKAY; 42 return MP_OKAY;
54 } 43 }
55 #endif 44 #endif
56
57 /* ref: $Format:%D$ */
58 /* git commit: $Format:%H$ */
59 /* commit time: $Format:%ai$ */