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comparison libtommath/bn_mp_gcd.c @ 1655:f52919ffd3b1

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update ltm to 1.1.0 and enable FIPS 186.4 compliant key-generation (#79) * make key-generation compliant to FIPS 186.4 * fix includes in tommath_class.h * update fuzzcorpus instead of error-out * fixup fuzzing make-targets * update Makefile.in * apply necessary patches to ltm sources * clean-up not required ltm files * update to vanilla ltm 1.1.0 this already only contains the required files * remove set/get double
author Steffen Jaeckel <s_jaeckel@gmx.de>
date Mon, 16 Sep 2019 15:50:38 +0200
parents 8bba51a55704
children 1051e4eea25a
comparison
equal deleted inserted replaced
1654:cc0fc5131c5c 1655:f52919ffd3b1
1 #include <tommath_private.h> 1 #include "tommath_private.h"
2 #ifdef BN_MP_GCD_C 2 #ifdef BN_MP_GCD_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.
7 * 7 *
8 * The library was designed directly after the MPI library by 8 * The library was designed directly after the MPI library by
9 * Michael Fromberger but has been written from scratch with 9 * Michael Fromberger but has been written from scratch with
10 * additional optimizations in place. 10 * additional optimizations in place.
11 * 11 *
12 * The library is free for all purposes without any express 12 * SPDX-License-Identifier: Unlicense
13 * guarantee it works.
14 *
15 * Tom St Denis, [email protected], http://libtom.org
16 */ 13 */
17 14
18 /* Greatest Common Divisor using the binary method */ 15 /* Greatest Common Divisor using the binary method */
19 int mp_gcd (mp_int * a, mp_int * b, mp_int * c) 16 int mp_gcd(const mp_int *a, const mp_int *b, mp_int *c)
20 { 17 {
21 mp_int u, v; 18 mp_int u, v;
22 int k, u_lsb, v_lsb, res; 19 int k, u_lsb, v_lsb, res;
23 20
24 /* either zero than gcd is the largest */ 21 /* either zero than gcd is the largest */
25 if (mp_iszero (a) == MP_YES) { 22 if (mp_iszero(a) == MP_YES) {
26 return mp_abs (b, c); 23 return mp_abs(b, c);
27 } 24 }
28 if (mp_iszero (b) == MP_YES) { 25 if (mp_iszero(b) == MP_YES) {
29 return mp_abs (a, c); 26 return mp_abs(a, c);
30 } 27 }
31 28
32 /* get copies of a and b we can modify */ 29 /* get copies of a and b we can modify */
33 if ((res = mp_init_copy (&u, a)) != MP_OKAY) { 30 if ((res = mp_init_copy(&u, a)) != MP_OKAY) {
34 return res; 31 return res;
35 } 32 }
36 33
37 if ((res = mp_init_copy (&v, b)) != MP_OKAY) { 34 if ((res = mp_init_copy(&v, b)) != MP_OKAY) {
38 goto LBL_U; 35 goto LBL_U;
39 } 36 }
40 37
41 /* must be positive for the remainder of the algorithm */ 38 /* must be positive for the remainder of the algorithm */
42 u.sign = v.sign = MP_ZPOS; 39 u.sign = v.sign = MP_ZPOS;
43 40
44 /* B1. Find the common power of two for u and v */ 41 /* B1. Find the common power of two for u and v */
45 u_lsb = mp_cnt_lsb(&u); 42 u_lsb = mp_cnt_lsb(&u);
46 v_lsb = mp_cnt_lsb(&v); 43 v_lsb = mp_cnt_lsb(&v);
47 k = MIN(u_lsb, v_lsb); 44 k = MIN(u_lsb, v_lsb);
48 45
49 if (k > 0) { 46 if (k > 0) {
50 /* divide the power of two out */ 47 /* divide the power of two out */
51 if ((res = mp_div_2d(&u, k, &u, NULL)) != MP_OKAY) { 48 if ((res = mp_div_2d(&u, k, &u, NULL)) != MP_OKAY) {
52 goto LBL_V; 49 goto LBL_V;
53 } 50 }
54 51
55 if ((res = mp_div_2d(&v, k, &v, NULL)) != MP_OKAY) { 52 if ((res = mp_div_2d(&v, k, &v, NULL)) != MP_OKAY) {
56 goto LBL_V; 53 goto LBL_V;
57 } 54 }
58 } 55 }
59 56
60 /* divide any remaining factors of two out */ 57 /* divide any remaining factors of two out */
61 if (u_lsb != k) { 58 if (u_lsb != k) {
62 if ((res = mp_div_2d(&u, u_lsb - k, &u, NULL)) != MP_OKAY) { 59 if ((res = mp_div_2d(&u, u_lsb - k, &u, NULL)) != MP_OKAY) {
63 goto LBL_V; 60 goto LBL_V;
64 } 61 }
65 } 62 }
66 63
67 if (v_lsb != k) { 64 if (v_lsb != k) {
68 if ((res = mp_div_2d(&v, v_lsb - k, &v, NULL)) != MP_OKAY) { 65 if ((res = mp_div_2d(&v, v_lsb - k, &v, NULL)) != MP_OKAY) {
69 goto LBL_V; 66 goto LBL_V;
70 } 67 }
71 } 68 }
72 69
73 while (mp_iszero(&v) == MP_NO) { 70 while (mp_iszero(&v) == MP_NO) {
74 /* make sure v is the largest */ 71 /* make sure v is the largest */
75 if (mp_cmp_mag(&u, &v) == MP_GT) { 72 if (mp_cmp_mag(&u, &v) == MP_GT) {
76 /* swap u and v to make sure v is >= u */ 73 /* swap u and v to make sure v is >= u */
77 mp_exch(&u, &v); 74 mp_exch(&u, &v);
78 } 75 }
79
80 /* subtract smallest from largest */
81 if ((res = s_mp_sub(&v, &u, &v)) != MP_OKAY) {
82 goto LBL_V;
83 }
84
85 /* Divide out all factors of two */
86 if ((res = mp_div_2d(&v, mp_cnt_lsb(&v), &v, NULL)) != MP_OKAY) {
87 goto LBL_V;
88 }
89 }
90 76
91 /* multiply by 2**k which we divided out at the beginning */ 77 /* subtract smallest from largest */
92 if ((res = mp_mul_2d (&u, k, c)) != MP_OKAY) { 78 if ((res = s_mp_sub(&v, &u, &v)) != MP_OKAY) {
93 goto LBL_V; 79 goto LBL_V;
94 } 80 }
95 c->sign = MP_ZPOS; 81
96 res = MP_OKAY; 82 /* Divide out all factors of two */
97 LBL_V:mp_clear (&u); 83 if ((res = mp_div_2d(&v, mp_cnt_lsb(&v), &v, NULL)) != MP_OKAY) {
98 LBL_U:mp_clear (&v); 84 goto LBL_V;
99 return res; 85 }
86 }
87
88 /* multiply by 2**k which we divided out at the beginning */
89 if ((res = mp_mul_2d(&u, k, c)) != MP_OKAY) {
90 goto LBL_V;
91 }
92 c->sign = MP_ZPOS;
93 res = MP_OKAY;
94 LBL_V:
95 mp_clear(&u);
96 LBL_U:
97 mp_clear(&v);
98 return res;
100 } 99 }
101 #endif 100 #endif
102 101
103 /* ref: $Format:%D$ */ 102 /* ref: HEAD -> master, tag: v1.1.0 */
104 /* git commit: $Format:%H$ */ 103 /* git commit: 08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */
105 /* commit time: $Format:%ai$ */ 104 /* commit time: 2019-01-28 20:32:32 +0100 */