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comparison libtommath/bn_mp_reduce_2k_l.c @ 1437:871b18fd7065 fuzz

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merge from main (libtommath/libtomcrypt/curve25510-donna updates)
author Matt Johnston <matt@ucc.asn.au>
date Sat, 24 Jun 2017 22:51:45 +0800
parents 60fc6476e044
children 8bba51a55704
comparison
equal deleted inserted replaced
1432:41dca1e5ea34 1437:871b18fd7065
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 /* $Date$ */