crypto/bn/old/bn_low.c

   1 /* crypto/bn/bn_mul.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
  63 static int bn_mm_low(BIGNUM *m,BIGNUM *A,BIGNUM *B, int num,
  64                 BIGNUM *sk,BN_CTX *ctx);
  65 int BN_mul_low(BIGNUM *r, BIGNUM *a, BIGNUM *b,int words);
  66
  67 /* r must be different to a and b */
  68 int BN_mul_low(BIGNUM *r, BIGNUM *a, BIGNUM *b, int num)
  69         {
  70         BN_ULONG *ap,*bp,*rp;
  71         BIGNUM *sk;
  72         int j,i,n,ret;
  73         int max,al,bl;
  74         BN_CTX ctx;
  75
  76         bn_check_top(a);
  77         bn_check_top(b);
  78
  79 #ifdef BN_MUL_DEBUG
  80 printf("BN_mul_low(%d,%d,%d)\n",a->top,b->top,num);
  81 #endif
  82
  83         al=a->top;
  84         bl=b->top;
  85         if ((al == 0) || (bl == 0))
  86                 {
  87                 r->top=0;
  88                 return(1);
  89                 }
  90
  91         if ((bn_limit_bits_low > 0) && (num > bn_limit_num_low))
  92                 {
  93                 n=BN_num_bits_word(num*2)-bn_limit_bits_low;
  94                 n*=2;
  95                 sk=(BIGNUM *)Malloc(sizeof(BIGNUM)*n);
  96                 memset(sk,0,sizeof(BIGNUM)*n);
  97                 memset(&ctx,0,sizeof(ctx));
  98
  99                 ret=bn_mm_low(r,a,b,num,&(sk[0]),&ctx);
 100                 for (i=0; i<n; i+=2)
 101                         {
 102                         BN_clear_free(&sk[i]);
 103                         BN_clear_free(&sk[i+1]);
 104                         }
 105                 Free(sk);
 106                 return(ret);
 107                 }
 108
 109         max=(al+bl);
 110         if (bn_wexpand(r,max) == NULL) return(0);
 111         r->neg=a->neg^b->neg;
 112         ap=a->d;
 113         bp=b->d;
 114         rp=r->d;
 115         r->top=(max > num)?num:max;
 116
 117         rp[al]=bn_mul_words(rp,ap,al,*(bp++));
 118         rp++;
 119         j=bl;
 120         for (i=1; i<j; i++)
 121                 {
 122                 if (al >= num--)
 123                         {
 124                         al--;
 125                         if (al <= 0) break;
 126                         }
 127                 rp[al]=bn_mul_add_words(rp,ap,al,*(bp++));
 128                 rp++;
 129                 }
 130
 131         while ((r->top > 0) && (r->d[r->top-1] == 0))
 132                 r->top--;
 133         return(1);
 134         }
 135
 136
 137 #define t1      (sk[0])
 138 #define t2      (sk[1])
 139
 140 /* r must be different to a and b */
 141 int bn_mm_low(BIGNUM *m, BIGNUM *A, BIGNUM *B, int num, BIGNUM *sk,
 142              BN_CTX *ctx)
 143         {
 144         int n; /* ,sqr=0; */
 145         int an,bn;
 146         BIGNUM ah,al,bh,bl;
 147
 148         bn_wexpand(m,num+3);
 149         an=A->top;
 150         bn=B->top;
 151
 152 #ifdef BN_MUL_DEBUG
 153 printf("bn_mm_low(%d,%d,%d)\n",A->top,B->top,num);
 154 #endif
 155
 156         n=(num+1)/2;
 157
 158         BN_init(&ah); BN_init(&al); BN_init(&bh); BN_init(&bl);
 159
 160         bn_set_low( &al,A,n);
 161         bn_set_high(&ah,A,n);
 162         bn_set_low( &bl,B,n);
 163         bn_set_high(&bh,B,n);
 164
 165         if (num <= (bn_limit_num_low+bn_limit_num_low))
 166                 {
 167                 BN_mul(m,&al,&bl);
 168                 BN_mul_low(&t1,&al,&bh,n);
 169                 BN_mul_low(&t2,&ah,&bl,n);
 170                 }
 171         else
 172                 {
 173                 bn_mm(m  ,&al,&bl,&(sk[2]),ctx);
 174                 bn_mm_low(&t1,&al,&bh,n,&(sk[2]),ctx);
 175                 bn_mm_low(&t2,&ah,&bl,n,&(sk[2]),ctx);
 176                 }
 177
 178         BN_add(&t1,&t1,&t2);
 179
 180         /* We will now do an evil hack instead of
 181          * BN_lshift(&t1,&t1,n*BN_BITS2);
 182          * BN_add(m,m,&t1);
 183          * BN_mask_bits(m,num*BN_BITS2);
 184          */
 185         bn_set_high(&ah,m,n); ah.max=num+2;
 186         BN_add(&ah,&ah,&t1);
 187         m->top=num;
 188
 189         m->neg=A->neg^B->neg;
 190         return(1);
 191         }
 192
 193 #undef t1       (sk[0])
 194 #undef t2       (sk[1])