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-rw-r--r--src/lib/libcrypto/bn/bn_gcd.c204
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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);
64int BN_gcd(BIGNUM *r, BIGNUM *in_a, BIGNUM *in_b, BN_CTX *ctx)
65 {
66 BIGNUM *a,*b,*t;
67 int ret=0;
68
69 bn_check_top(in_a);
70 bn_check_top(in_b);
71
72 a= &(ctx->bn[ctx->tos]);
73 b= &(ctx->bn[ctx->tos+1]);
74
75 if (BN_copy(a,in_a) == NULL) goto err;
76 if (BN_copy(b,in_b) == NULL) goto err;
77
78 if (BN_cmp(a,b) < 0) { t=a; a=b; b=t; }
79 t=euclid(a,b);
80 if (t == NULL) goto err;
81
82 if (BN_copy(r,t) == NULL) goto err;
83 ret=1;
84err:
85 return(ret);
86 }
87
88static BIGNUM *euclid(BIGNUM *a, BIGNUM *b)
89 {
90 BIGNUM *t;
91 int shifts=0;
92
93 bn_check_top(a);
94 bn_check_top(b);
95
96 for (;;)
97 {
98 if (BN_is_zero(b))
99 break;
100
101 if (BN_is_odd(a))
102 {
103 if (BN_is_odd(b))
104 {
105 if (!BN_sub(a,a,b)) goto err;
106 if (!BN_rshift1(a,a)) goto err;
107 if (BN_cmp(a,b) < 0)
108 { t=a; a=b; b=t; }
109 }
110 else /* a odd - b even */
111 {
112 if (!BN_rshift1(b,b)) goto err;
113 if (BN_cmp(a,b) < 0)
114 { t=a; a=b; b=t; }
115 }
116 }
117 else /* a is even */
118 {
119 if (BN_is_odd(b))
120 {
121 if (!BN_rshift1(a,a)) goto err;
122 if (BN_cmp(a,b) < 0)
123 { t=a; a=b; b=t; }
124 }
125 else /* a even - b even */
126 {
127 if (!BN_rshift1(a,a)) goto err;
128 if (!BN_rshift1(b,b)) goto err;
129 shifts++;
130 }
131 }
132 }
133 if (shifts)
134 {
135 if (!BN_lshift(a,a,shifts)) goto err;
136 }
137 return(a);
138err:
139 return(NULL);
140 }
141
142/* solves ax == 1 (mod n) */
143BIGNUM *BN_mod_inverse(BIGNUM *in, BIGNUM *a, const BIGNUM *n, BN_CTX *ctx)
144 {
145 BIGNUM *A,*B,*X,*Y,*M,*D,*R;
146 BIGNUM *T,*ret=NULL;
147 int sign;
148
149 bn_check_top(a);
150 bn_check_top(n);
151
152 A= &(ctx->bn[ctx->tos]);
153 B= &(ctx->bn[ctx->tos+1]);
154 X= &(ctx->bn[ctx->tos+2]);
155 D= &(ctx->bn[ctx->tos+3]);
156 M= &(ctx->bn[ctx->tos+4]);
157 Y= &(ctx->bn[ctx->tos+5]);
158 ctx->tos+=6;
159 if (in == NULL)
160 R=BN_new();
161 else
162 R=in;
163 if (R == NULL) goto err;
164
165 BN_zero(X);
166 BN_one(Y);
167 if (BN_copy(A,a) == NULL) goto err;
168 if (BN_copy(B,n) == NULL) goto err;
169 sign=1;
170
171 while (!BN_is_zero(B))
172 {
173 if (!BN_div(D,M,A,B,ctx)) goto err;
174 T=A;
175 A=B;
176 B=M;
177 /* T has a struct, M does not */
178
179 if (!BN_mul(T,D,X,ctx)) goto err;
180 if (!BN_add(T,T,Y)) goto err;
181 M=Y;
182 Y=X;
183 X=T;
184 sign= -sign;
185 }
186 if (sign < 0)
187 {
188 if (!BN_sub(Y,n,Y)) goto err;
189 }
190
191 if (BN_is_one(A))
192 { if (!BN_mod(R,Y,n,ctx)) goto err; }
193 else
194 {
195 BNerr(BN_F_BN_MOD_INVERSE,BN_R_NO_INVERSE);
196 goto err;
197 }
198 ret=R;
199err:
200 if ((ret == NULL) && (in == NULL)) BN_free(R);
201 ctx->tos-=6;
202 return(ret);
203 }
204
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