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authorcvs2svn <admin@example.com>2002-03-12 00:05:45 +0000
committercvs2svn <admin@example.com>2002-03-12 00:05:45 +0000
commit3779f2f4a8b544a7e4c362915322726b66cff114 (patch)
treeb6d77e66cbfdf6c0d8953fba2917f26f86fa50f6 /src/lib/libcrypto/bn/bn_gcd.c
parentf39945c2b3b0f9e4950384bdb8effdac6eed9199 (diff)
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diff --git a/src/lib/libcrypto/bn/bn_gcd.c b/src/lib/libcrypto/bn/bn_gcd.c
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1/* crypto/bn/bn_gcd.c */
2/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
3 * All rights reserved.
4 *
5 * This package is an SSL implementation written
6 * by Eric Young (eay@cryptsoft.com).
7 * The implementation was written so as to conform with Netscapes SSL.
8 *
9 * This library is free for commercial and non-commercial use as long as
10 * the following conditions are aheared to. The following conditions
11 * apply to all code found in this distribution, be it the RC4, RSA,
12 * lhash, DES, etc., code; not just the SSL code. The SSL documentation
13 * included with this distribution is covered by the same copyright terms
14 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
15 *
16 * Copyright remains Eric Young's, and as such any Copyright notices in
17 * the code are not to be removed.
18 * If this package is used in a product, Eric Young should be given attribution
19 * as the author of the parts of the library used.
20 * This can be in the form of a textual message at program startup or
21 * in documentation (online or textual) provided with the package.
22 *
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
25 * are met:
26 * 1. Redistributions of source code must retain the copyright
27 * notice, this list of conditions and the following disclaimer.
28 * 2. Redistributions in binary form must reproduce the above copyright
29 * notice, this list of conditions and the following disclaimer in the
30 * documentation and/or other materials provided with the distribution.
31 * 3. All advertising materials mentioning features or use of this software
32 * must display the following acknowledgement:
33 * "This product includes cryptographic software written by
34 * Eric Young (eay@cryptsoft.com)"
35 * The word 'cryptographic' can be left out if the rouines from the library
36 * being used are not cryptographic related :-).
37 * 4. If you include any Windows specific code (or a derivative thereof) from
38 * the apps directory (application code) you must include an acknowledgement:
39 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
40 *
41 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
42 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
43 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
44 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
45 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
46 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
47 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
48 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
49 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
50 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
51 * SUCH DAMAGE.
52 *
53 * The licence and distribution terms for any publically available version or
54 * derivative of this code cannot be changed. i.e. this code cannot simply be
55 * copied and put under another distribution licence
56 * [including the GNU Public Licence.]
57 */
58
59#include <stdio.h>
60#include "cryptlib.h"
61#include "bn_lcl.h"
62
63static BIGNUM *euclid(BIGNUM *a, BIGNUM *b);
64
65int BN_gcd(BIGNUM *r, BIGNUM *in_a, BIGNUM *in_b, BN_CTX *ctx)
66 {
67 BIGNUM *a,*b,*t;
68 int ret=0;
69
70 bn_check_top(in_a);
71 bn_check_top(in_b);
72
73 BN_CTX_start(ctx);
74 a = BN_CTX_get(ctx);
75 b = BN_CTX_get(ctx);
76 if (a == NULL || b == NULL) goto err;
77
78 if (BN_copy(a,in_a) == NULL) goto err;
79 if (BN_copy(b,in_b) == NULL) goto err;
80
81 if (BN_cmp(a,b) < 0) { t=a; a=b; b=t; }
82 t=euclid(a,b);
83 if (t == NULL) goto err;
84
85 if (BN_copy(r,t) == NULL) goto err;
86 ret=1;
87err:
88 BN_CTX_end(ctx);
89 return(ret);
90 }
91
92static BIGNUM *euclid(BIGNUM *a, BIGNUM *b)
93 {
94 BIGNUM *t;
95 int shifts=0;
96
97 bn_check_top(a);
98 bn_check_top(b);
99
100 for (;;)
101 {
102 if (BN_is_zero(b))
103 break;
104
105 if (BN_is_odd(a))
106 {
107 if (BN_is_odd(b))
108 {
109 if (!BN_sub(a,a,b)) goto err;
110 if (!BN_rshift1(a,a)) goto err;
111 if (BN_cmp(a,b) < 0)
112 { t=a; a=b; b=t; }
113 }
114 else /* a odd - b even */
115 {
116 if (!BN_rshift1(b,b)) goto err;
117 if (BN_cmp(a,b) < 0)
118 { t=a; a=b; b=t; }
119 }
120 }
121 else /* a is even */
122 {
123 if (BN_is_odd(b))
124 {
125 if (!BN_rshift1(a,a)) goto err;
126 if (BN_cmp(a,b) < 0)
127 { t=a; a=b; b=t; }
128 }
129 else /* a even - b even */
130 {
131 if (!BN_rshift1(a,a)) goto err;
132 if (!BN_rshift1(b,b)) goto err;
133 shifts++;
134 }
135 }
136 }
137 if (shifts)
138 {
139 if (!BN_lshift(a,a,shifts)) goto err;
140 }
141 return(a);
142err:
143 return(NULL);
144 }
145
146/* solves ax == 1 (mod n) */
147BIGNUM *BN_mod_inverse(BIGNUM *in, BIGNUM *a, const BIGNUM *n, BN_CTX *ctx)
148 {
149 BIGNUM *A,*B,*X,*Y,*M,*D,*R=NULL;
150 BIGNUM *T,*ret=NULL;
151 int sign;
152
153 bn_check_top(a);
154 bn_check_top(n);
155
156 BN_CTX_start(ctx);
157 A = BN_CTX_get(ctx);
158 B = BN_CTX_get(ctx);
159 X = BN_CTX_get(ctx);
160 D = BN_CTX_get(ctx);
161 M = BN_CTX_get(ctx);
162 Y = BN_CTX_get(ctx);
163 if (Y == NULL) goto err;
164
165 if (in == NULL)
166 R=BN_new();
167 else
168 R=in;
169 if (R == NULL) goto err;
170
171 BN_zero(X);
172 BN_one(Y);
173 if (BN_copy(A,a) == NULL) goto err;
174 if (BN_copy(B,n) == NULL) goto err;
175 sign=1;
176
177 while (!BN_is_zero(B))
178 {
179 if (!BN_div(D,M,A,B,ctx)) goto err;
180 T=A;
181 A=B;
182 B=M;
183 /* T has a struct, M does not */
184
185 if (!BN_mul(T,D,X,ctx)) goto err;
186 if (!BN_add(T,T,Y)) goto err;
187 M=Y;
188 Y=X;
189 X=T;
190 sign= -sign;
191 }
192 if (sign < 0)
193 {
194 if (!BN_sub(Y,n,Y)) goto err;
195 }
196
197 if (BN_is_one(A))
198 { if (!BN_mod(R,Y,n,ctx)) goto err; }
199 else
200 {
201 BNerr(BN_F_BN_MOD_INVERSE,BN_R_NO_INVERSE);
202 goto err;
203 }
204 ret=R;
205err:
206 if ((ret == NULL) && (in == NULL)) BN_free(R);
207 BN_CTX_end(ctx);
208 return(ret);
209 }
210
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