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comparison libtommath/bn_fast_mp_invmod.c @ 1436:60fc6476e044

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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_FAST_MP_INVMOD_C 2 #ifdef BN_FAST_MP_INVMOD_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 /* computes the modular inverse via binary extended euclidean algorithm, 18 /* computes the modular inverse via binary extended euclidean algorithm,
19 * that is c = 1/a mod b 19 * that is c = 1/a mod b
20 * 20 *
25 { 25 {
26 mp_int x, y, u, v, B, D; 26 mp_int x, y, u, v, B, D;
27 int res, neg; 27 int res, neg;
28 28
29 /* 2. [modified] b must be odd */ 29 /* 2. [modified] b must be odd */
30 if (mp_iseven (b) == 1) { 30 if (mp_iseven (b) == MP_YES) {
31 return MP_VAL; 31 return MP_VAL;
32 } 32 }
33 33
34 /* init all our temps */ 34 /* init all our temps */
35 if ((res = mp_init_multi(&x, &y, &u, &v, &B, &D, NULL)) != MP_OKAY) { 35 if ((res = mp_init_multi(&x, &y, &u, &v, &B, &D, NULL)) != MP_OKAY) {
55 } 55 }
56 mp_set (&D, 1); 56 mp_set (&D, 1);
57 57
58 top: 58 top:
59 /* 4. while u is even do */ 59 /* 4. while u is even do */
60 while (mp_iseven (&u) == 1) { 60 while (mp_iseven (&u) == MP_YES) {
61 /* 4.1 u = u/2 */ 61 /* 4.1 u = u/2 */
62 if ((res = mp_div_2 (&u, &u)) != MP_OKAY) { 62 if ((res = mp_div_2 (&u, &u)) != MP_OKAY) {
63 goto LBL_ERR; 63 goto LBL_ERR;
64 } 64 }
65 /* 4.2 if B is odd then */ 65 /* 4.2 if B is odd then */
66 if (mp_isodd (&B) == 1) { 66 if (mp_isodd (&B) == MP_YES) {
67 if ((res = mp_sub (&B, &x, &B)) != MP_OKAY) { 67 if ((res = mp_sub (&B, &x, &B)) != MP_OKAY) {
68 goto LBL_ERR; 68 goto LBL_ERR;
69 } 69 }
70 } 70 }
71 /* B = B/2 */ 71 /* B = B/2 */
73 goto LBL_ERR; 73 goto LBL_ERR;
74 } 74 }
75 } 75 }
76 76
77 /* 5. while v is even do */ 77 /* 5. while v is even do */
78 while (mp_iseven (&v) == 1) { 78 while (mp_iseven (&v) == MP_YES) {
79 /* 5.1 v = v/2 */ 79 /* 5.1 v = v/2 */
80 if ((res = mp_div_2 (&v, &v)) != MP_OKAY) { 80 if ((res = mp_div_2 (&v, &v)) != MP_OKAY) {
81 goto LBL_ERR; 81 goto LBL_ERR;
82 } 82 }
83 /* 5.2 if D is odd then */ 83 /* 5.2 if D is odd then */
84 if (mp_isodd (&D) == 1) { 84 if (mp_isodd (&D) == MP_YES) {
85 /* D = (D-x)/2 */ 85 /* D = (D-x)/2 */
86 if ((res = mp_sub (&D, &x, &D)) != MP_OKAY) { 86 if ((res = mp_sub (&D, &x, &D)) != MP_OKAY) {
87 goto LBL_ERR; 87 goto LBL_ERR;
88 } 88 }
89 } 89 }
113 goto LBL_ERR; 113 goto LBL_ERR;
114 } 114 }
115 } 115 }
116 116
117 /* if not zero goto step 4 */ 117 /* if not zero goto step 4 */
118 if (mp_iszero (&u) == 0) { 118 if (mp_iszero (&u) == MP_NO) {
119 goto top; 119 goto top;
120 } 120 }
121 121
122 /* now a = C, b = D, gcd == g*v */ 122 /* now a = C, b = D, gcd == g*v */
123 123
141 LBL_ERR:mp_clear_multi (&x, &y, &u, &v, &B, &D, NULL); 141 LBL_ERR:mp_clear_multi (&x, &y, &u, &v, &B, &D, NULL);
142 return res; 142 return res;
143 } 143 }
144 #endif 144 #endif
145 145
146 /* $Source: /cvs/libtom/libtommath/bn_fast_mp_invmod.c,v $ */ 146 /* $Source$ */
147 /* $Revision: 1.3 $ */ 147 /* $Revision$ */
148 /* $Date: 2006/03/31 14:18:44 $ */ 148 /* $Date$ */