crypto/openssl-0.9.7d/crypto/bn/bn_sqr.c

   1 /* crypto/bn/bn_sqr.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 /* r must not be a */
  64 /* I've just gone over this and it is now %20 faster on x86 - eay - 27 Jun 96 */
  65 int BN_sqr(BIGNUM *r, const BIGNUM *a, BN_CTX *ctx)
  66         {
  67         int max,al;
  68         int ret = 0;
  69         BIGNUM *tmp,*rr;
  70
  71 #ifdef BN_COUNT
  72         fprintf(stderr,"BN_sqr %d * %d\n",a->top,a->top);
  73 #endif
  74         bn_check_top(a);
  75
  76         al=a->top;
  77         if (al <= 0)
  78                 {
  79                 r->top=0;
  80                 return(1);
  81                 }
  82
  83         BN_CTX_start(ctx);
  84         rr=(a != r) ? r : BN_CTX_get(ctx);
  85         tmp=BN_CTX_get(ctx);
  86         if (tmp == NULL) goto err;
  87
  88         max=(al+al);
  89         if (bn_wexpand(rr,max+1) == NULL) goto err;
  90
  91         if (al == 4)
  92                 {
  93 #ifndef BN_SQR_COMBA
  94                 BN_ULONG t[8];
  95                 bn_sqr_normal(rr->d,a->d,4,t);
  96 #else
  97                 bn_sqr_comba4(rr->d,a->d);
  98 #endif
  99                 }
 100         else if (al == 8)
 101                 {
 102 #ifndef BN_SQR_COMBA
 103                 BN_ULONG t[16];
 104                 bn_sqr_normal(rr->d,a->d,8,t);
 105 #else
 106                 bn_sqr_comba8(rr->d,a->d);
 107 #endif
 108                 }
 109         else
 110                 {
 111 #if defined(BN_RECURSION)
 112                 if (al < BN_SQR_RECURSIVE_SIZE_NORMAL)
 113                         {
 114                         BN_ULONG t[BN_SQR_RECURSIVE_SIZE_NORMAL*2];
 115                         bn_sqr_normal(rr->d,a->d,al,t);
 116                         }
 117                 else
 118                         {
 119                         int j,k;
 120
 121                         j=BN_num_bits_word((BN_ULONG)al);
 122                         j=1<<(j-1);
 123                         k=j+j;
 124                         if (al == j)
 125                                 {
 126                                 if (bn_wexpand(tmp,k*2) == NULL) goto err;
 127                                 bn_sqr_recursive(rr->d,a->d,al,tmp->d);
 128                                 }
 129                         else
 130                                 {
 131                                 if (bn_wexpand(tmp,max) == NULL) goto err;
 132                                 bn_sqr_normal(rr->d,a->d,al,tmp->d);
 133                                 }
 134                         }
 135 #else
 136                 if (bn_wexpand(tmp,max) == NULL) goto err;
 137                 bn_sqr_normal(rr->d,a->d,al,tmp->d);
 138 #endif
 139                 }
 140
 141         rr->top=max;
 142         rr->neg=0;
 143         if ((max > 0) && (rr->d[max-1] == 0)) rr->top--;
 144         if (rr != r) BN_copy(r,rr);
 145         ret = 1;
 146  err:
 147         BN_CTX_end(ctx);
 148         return(ret);
 149         }
 150
 151 /* tmp must have 2*n words */
 152 void bn_sqr_normal(BN_ULONG *r, const BN_ULONG *a, int n, BN_ULONG *tmp)
 153         {
 154         int i,j,max;
 155         const BN_ULONG *ap;
 156         BN_ULONG *rp;
 157
 158         max=n*2;
 159         ap=a;
 160         rp=r;
 161         rp[0]=rp[max-1]=0;
 162         rp++;
 163         j=n;
 164
 165         if (--j > 0)
 166                 {
 167                 ap++;
 168                 rp[j]=bn_mul_words(rp,ap,j,ap[-1]);
 169                 rp+=2;
 170                 }
 171
 172         for (i=n-2; i>0; i--)
 173                 {
 174                 j--;
 175                 ap++;
 176                 rp[j]=bn_mul_add_words(rp,ap,j,ap[-1]);
 177                 rp+=2;
 178                 }
 179
 180         bn_add_words(r,r,r,max);
 181
 182         /* There will not be a carry */
 183
 184         bn_sqr_words(tmp,a,n);
 185
 186         bn_add_words(r,r,tmp,max);
 187         }
 188
 189 #ifdef BN_RECURSION
 190 /* r is 2*n words in size,
 191  * a and b are both n words in size.    (There's not actually a 'b' here ...)
 192  * n must be a power of 2.
 193  * We multiply and return the result.
 194  * t must be 2*n words in size
 195  * We calculate
 196  * a[0]*b[0]
 197  * a[0]*b[0]+a[1]*b[1]+(a[0]-a[1])*(b[1]-b[0])
 198  * a[1]*b[1]
 199  */
 200 void bn_sqr_recursive(BN_ULONG *r, const BN_ULONG *a, int n2, BN_ULONG *t)
 201         {
 202         int n=n2/2;
 203         int zero,c1;
 204         BN_ULONG ln,lo,*p;
 205
 206 #ifdef BN_COUNT
 207         fprintf(stderr," bn_sqr_recursive %d * %d\n",n2,n2);
 208 #endif
 209         if (n2 == 4)
 210                 {
 211 #ifndef BN_SQR_COMBA
 212                 bn_sqr_normal(r,a,4,t);
 213 #else
 214                 bn_sqr_comba4(r,a);
 215 #endif
 216                 return;
 217                 }
 218         else if (n2 == 8)
 219                 {
 220 #ifndef BN_SQR_COMBA
 221                 bn_sqr_normal(r,a,8,t);
 222 #else
 223                 bn_sqr_comba8(r,a);
 224 #endif
 225                 return;
 226                 }
 227         if (n2 < BN_SQR_RECURSIVE_SIZE_NORMAL)
 228                 {
 229                 bn_sqr_normal(r,a,n2,t);
 230                 return;
 231                 }
 232         /* r=(a[0]-a[1])*(a[1]-a[0]) */
 233         c1=bn_cmp_words(a,&(a[n]),n);
 234         zero=0;
 235         if (c1 > 0)
 236                 bn_sub_words(t,a,&(a[n]),n);
 237         else if (c1 < 0)
 238                 bn_sub_words(t,&(a[n]),a,n);
 239         else
 240                 zero=1;
 241
 242         /* The result will always be negative unless it is zero */
 243         p= &(t[n2*2]);
 244
 245         if (!zero)
 246                 bn_sqr_recursive(&(t[n2]),t,n,p);
 247         else
 248                 memset(&(t[n2]),0,n2*sizeof(BN_ULONG));
 249         bn_sqr_recursive(r,a,n,p);
 250         bn_sqr_recursive(&(r[n2]),&(a[n]),n,p);
 251
 252         /* t[32] holds (a[0]-a[1])*(a[1]-a[0]), it is negative or zero
 253          * r[10] holds (a[0]*b[0])
 254          * r[32] holds (b[1]*b[1])
 255          */
 256
 257         c1=(int)(bn_add_words(t,r,&(r[n2]),n2));
 258
 259         /* t[32] is negative */
 260         c1-=(int)(bn_sub_words(&(t[n2]),t,&(t[n2]),n2));
 261
 262         /* t[32] holds (a[0]-a[1])*(a[1]-a[0])+(a[0]*a[0])+(a[1]*a[1])
 263          * r[10] holds (a[0]*a[0])
 264          * r[32] holds (a[1]*a[1])
 265          * c1 holds the carry bits
 266          */
 267         c1+=(int)(bn_add_words(&(r[n]),&(r[n]),&(t[n2]),n2));
 268         if (c1)
 269                 {
 270                 p= &(r[n+n2]);
 271                 lo= *p;
 272                 ln=(lo+c1)&BN_MASK2;
 273                 *p=ln;
 274
 275                 /* The overflow will stop before we over write
 276                  * words we should not overwrite */
 277                 if (ln < (BN_ULONG)c1)
 278                         {
 279                         do      {
 280                                 p++;
 281                                 lo= *p;
 282                                 ln=(lo+1)&BN_MASK2;
 283                                 *p=ln;
 284                                 } while (ln == 0);
 285                         }
 286                 }
 287         }
 288 #endif