AppleCSP/open_ssl/bn/bn_gcd.c

   1 /*
   2  * Copyright (c) 2000-2001 Apple Computer, Inc. All Rights Reserved.
   3  *
   4  * The contents of this file constitute Original Code as defined in and are
   5  * subject to the Apple Public Source License Version 1.2 (the 'License').
   6  * You may not use this file except in compliance with the License. Please obtain
   7  * a copy of the License at http://www.apple.com/publicsource and read it before
   8  * using this file.
   9  *
  10  * This Original Code and all software distributed under the License are
  11  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS
  12  * OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, INCLUDING WITHOUT
  13  * LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
  14  * PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. Please see the License for the
  15  * specific language governing rights and limitations under the License.
  16  */
  17
  18
  19 /* crypto/bn/bn_gcd.c */
  20 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  21  * All rights reserved.
  22  *
  23  * This package is an SSL implementation written
  24  * by Eric Young (eay@cryptsoft.com).
  25  * The implementation was written so as to conform with Netscapes SSL.
  26  *
  27  * This library is free for commercial and non-commercial use as long as
  28  * the following conditions are aheared to.  The following conditions
  29  * apply to all code found in this distribution, be it the RC4, RSA,
  30  * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
  31  * included with this distribution is covered by the same copyright terms
  32  * except that the holder is Tim Hudson (tjh@cryptsoft.com).
  33  *
  34  * Copyright remains Eric Young's, and as such any Copyright notices in
  35  * the code are not to be removed.
  36  * If this package is used in a product, Eric Young should be given attribution
  37  * as the author of the parts of the library used.
  38  * This can be in the form of a textual message at program startup or
  39  * in documentation (online or textual) provided with the package.
  40  *
  41  * Redistribution and use in source and binary forms, with or without
  42  * modification, are permitted provided that the following conditions
  43  * are met:
  44  * 1. Redistributions of source code must retain the copyright
  45  *    notice, this list of conditions and the following disclaimer.
  46  * 2. Redistributions in binary form must reproduce the above copyright
  47  *    notice, this list of conditions and the following disclaimer in the
  48  *    documentation and/or other materials provided with the distribution.
  49  * 3. All advertising materials mentioning features or use of this software
  50  *    must display the following acknowledgement:
  51  *    "This product includes cryptographic software written by
  52  *     Eric Young (eay@cryptsoft.com)"
  53  *    The word 'cryptographic' can be left out if the rouines from the library
  54  *    being used are not cryptographic related :-).
  55  * 4. If you include any Windows specific code (or a derivative thereof) from
  56  *    the apps directory (application code) you must include an acknowledgement:
  57  *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
  58  *
  59  * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
  60  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  61  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  62  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  63  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  64  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  65  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  66  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  67  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  68  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  69  * SUCH DAMAGE.
  70  *
  71  * The licence and distribution terms for any publically available version or
  72  * derivative of this code cannot be changed.  i.e. this code cannot simply be
  73  * copied and put under another distribution licence
  74  * [including the GNU Public Licence.]
  75  */
  76
  77 #include <stdio.h>
  78 #include "cryptlib.h"
  79 #include "bn_lcl.h"
  80
  81 static BIGNUM *euclid(BIGNUM *a, BIGNUM *b);
  82
  83 int BN_gcd(BIGNUM *r, BIGNUM *in_a, BIGNUM *in_b, BN_CTX *ctx)
  84         {
  85         BIGNUM *a,*b,*t;
  86         int ret=0;
  87
  88         bn_check_top(in_a);
  89         bn_check_top(in_b);
  90
  91         BN_CTX_start(ctx);
  92         a = BN_CTX_get(ctx);
  93         b = BN_CTX_get(ctx);
  94         if (a == NULL || b == NULL) goto err;
  95
  96         if (BN_copy(a,in_a) == NULL) goto err;
  97         if (BN_copy(b,in_b) == NULL) goto err;
  98
  99         if (BN_cmp(a,b) < 0) { t=a; a=b; b=t; }
 100         t=euclid(a,b);
 101         if (t == NULL) goto err;
 102
 103         if (BN_copy(r,t) == NULL) goto err;
 104         ret=1;
 105 err:
 106         BN_CTX_end(ctx);
 107         return(ret);
 108         }
 109
 110 static BIGNUM *euclid(BIGNUM *a, BIGNUM *b)
 111         {
 112         BIGNUM *t;
 113         int shifts=0;
 114
 115         bn_check_top(a);
 116         bn_check_top(b);
 117
 118         for (;;)
 119                 {
 120                 if (BN_is_zero(b))
 121                         break;
 122
 123                 if (BN_is_odd(a))
 124                         {
 125                         if (BN_is_odd(b))
 126                                 {
 127                                 if (!BN_sub(a,a,b)) goto err;
 128                                 if (!BN_rshift1(a,a)) goto err;
 129                                 if (BN_cmp(a,b) < 0)
 130                                         { t=a; a=b; b=t; }
 131                                 }
 132                         else            /* a odd - b even */
 133                                 {
 134                                 if (!BN_rshift1(b,b)) goto err;
 135                                 if (BN_cmp(a,b) < 0)
 136                                         { t=a; a=b; b=t; }
 137                                 }
 138                         }
 139                 else                    /* a is even */
 140                         {
 141                         if (BN_is_odd(b))
 142                                 {
 143                                 if (!BN_rshift1(a,a)) goto err;
 144                                 if (BN_cmp(a,b) < 0)
 145                                         { t=a; a=b; b=t; }
 146                                 }
 147                         else            /* a even - b even */
 148                                 {
 149                                 if (!BN_rshift1(a,a)) goto err;
 150                                 if (!BN_rshift1(b,b)) goto err;
 151                                 shifts++;
 152                                 }
 153                         }
 154                 }
 155         if (shifts)
 156                 {
 157                 if (!BN_lshift(a,a,shifts)) goto err;
 158                 }
 159         return(a);
 160 err:
 161         return(NULL);
 162         }
 163
 164 /* solves ax == 1 (mod n) */
 165 BIGNUM *BN_mod_inverse(BIGNUM *in, BIGNUM *a, const BIGNUM *n, BN_CTX *ctx)
 166         {
 167         BIGNUM *A,*B,*X,*Y,*M,*D,*R=NULL;
 168         BIGNUM *T,*ret=NULL;
 169         int sign;
 170
 171         bn_check_top(a);
 172         bn_check_top(n);
 173
 174         BN_CTX_start(ctx);
 175         A = BN_CTX_get(ctx);
 176         B = BN_CTX_get(ctx);
 177         X = BN_CTX_get(ctx);
 178         D = BN_CTX_get(ctx);
 179         M = BN_CTX_get(ctx);
 180         Y = BN_CTX_get(ctx);
 181         if (Y == NULL) goto err;
 182
 183         if (in == NULL)
 184                 R=BN_new();
 185         else
 186                 R=in;
 187         if (R == NULL) goto err;
 188
 189         BN_zero(X);
 190         BN_one(Y);
 191         if (BN_copy(A,a) == NULL) goto err;
 192         if (BN_copy(B,n) == NULL) goto err;
 193         sign=1;
 194
 195         while (!BN_is_zero(B))
 196                 {
 197                 if (!BN_div(D,M,A,B,ctx)) goto err;
 198                 T=A;
 199                 A=B;
 200                 B=M;
 201                 /* T has a struct, M does not */
 202
 203                 if (!BN_mul(T,D,X,ctx)) goto err;
 204                 if (!BN_add(T,T,Y)) goto err;
 205                 M=Y;
 206                 Y=X;
 207                 X=T;
 208                 sign= -sign;
 209                 }
 210         if (sign < 0)
 211                 {
 212                 if (!BN_sub(Y,n,Y)) goto err;
 213                 }
 214
 215         if (BN_is_one(A))
 216                 { if (!BN_mod(R,Y,n,ctx)) goto err; }
 217         else
 218                 {
 219                 BNerr(BN_F_BN_MOD_INVERSE,BN_R_NO_INVERSE);
 220                 goto err;
 221                 }
 222         ret=R;
 223 err:
 224         if ((ret == NULL) && (in == NULL)) BN_free(R);
 225         BN_CTX_end(ctx);
 226         return(ret);
 227         }
 228