crypto/bn/bn_mul.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 #ifdef BN_RECURSION
  64 /* r is 2*n2 words in size,
  65  * a and b are both n2 words in size.
  66  * n2 must be a power of 2.
  67  * We multiply and return the result.
  68  * t must be 2*n2 words in size
  69  * We calculate
  70  * a[0]*b[0]
  71  * a[0]*b[0]+a[1]*b[1]+(a[0]-a[1])*(b[1]-b[0])
  72  * a[1]*b[1]
  73  */
  74 void bn_mul_recursive(BN_ULONG *r, BN_ULONG *a, BN_ULONG *b, int n2,
  75              BN_ULONG *t)
  76         {
  77         int n=n2/2,c1,c2;
  78         unsigned int neg,zero;
  79         BN_ULONG ln,lo,*p;
  80
  81 # ifdef BN_COUNT
  82         printf(" bn_mul_recursive %d * %d\n",n2,n2);
  83 # endif
  84 # ifdef BN_MUL_COMBA
  85 #  if 0
  86         if (n2 == 4)
  87                 {
  88                 bn_mul_comba4(r,a,b);
  89                 return;
  90                 }
  91 #  endif
  92         if (n2 == 8)
  93                 {
  94                 bn_mul_comba8(r,a,b);
  95                 return;
  96                 }
  97 # endif /* BN_MUL_COMBA */
  98         if (n2 < BN_MUL_RECURSIVE_SIZE_NORMAL)
  99                 {
 100                 /* This should not happen */
 101                 bn_mul_normal(r,a,n2,b,n2);
 102                 return;
 103                 }
 104         /* r=(a[0]-a[1])*(b[1]-b[0]) */
 105         c1=bn_cmp_words(a,&(a[n]),n);
 106         c2=bn_cmp_words(&(b[n]),b,n);
 107         zero=neg=0;
 108         switch (c1*3+c2)
 109                 {
 110         case -4:
 111                 bn_sub_words(t,      &(a[n]),a,      n); /* - */
 112                 bn_sub_words(&(t[n]),b,      &(b[n]),n); /* - */
 113                 break;
 114         case -3:
 115                 zero=1;
 116                 break;
 117         case -2:
 118                 bn_sub_words(t,      &(a[n]),a,      n); /* - */
 119                 bn_sub_words(&(t[n]),&(b[n]),b,      n); /* + */
 120                 neg=1;
 121                 break;
 122         case -1:
 123         case 0:
 124         case 1:
 125                 zero=1;
 126                 break;
 127         case 2:
 128                 bn_sub_words(t,      a,      &(a[n]),n); /* + */
 129                 bn_sub_words(&(t[n]),b,      &(b[n]),n); /* - */
 130                 neg=1;
 131                 break;
 132         case 3:
 133                 zero=1;
 134                 break;
 135         case 4:
 136                 bn_sub_words(t,      a,      &(a[n]),n);
 137                 bn_sub_words(&(t[n]),&(b[n]),b,      n);
 138                 break;
 139                 }
 140
 141 # ifdef BN_MUL_COMBA
 142         if (n == 4)
 143                 {
 144                 if (!zero)
 145                         bn_mul_comba4(&(t[n2]),t,&(t[n]));
 146                 else
 147                         memset(&(t[n2]),0,8*sizeof(BN_ULONG));
 148
 149                 bn_mul_comba4(r,a,b);
 150                 bn_mul_comba4(&(r[n2]),&(a[n]),&(b[n]));
 151                 }
 152         else if (n == 8)
 153                 {
 154                 if (!zero)
 155                         bn_mul_comba8(&(t[n2]),t,&(t[n]));
 156                 else
 157                         memset(&(t[n2]),0,16*sizeof(BN_ULONG));
 158
 159                 bn_mul_comba8(r,a,b);
 160                 bn_mul_comba8(&(r[n2]),&(a[n]),&(b[n]));
 161                 }
 162         else
 163 # endif /* BN_MUL_COMBA */
 164                 {
 165                 p= &(t[n2*2]);
 166                 if (!zero)
 167                         bn_mul_recursive(&(t[n2]),t,&(t[n]),n,p);
 168                 else
 169                         memset(&(t[n2]),0,n2*sizeof(BN_ULONG));
 170                 bn_mul_recursive(r,a,b,n,p);
 171                 bn_mul_recursive(&(r[n2]),&(a[n]),&(b[n]),n,p);
 172                 }
 173
 174         /* t[32] holds (a[0]-a[1])*(b[1]-b[0]), c1 is the sign
 175          * r[10] holds (a[0]*b[0])
 176          * r[32] holds (b[1]*b[1])
 177          */
 178
 179         c1=(int)(bn_add_words(t,r,&(r[n2]),n2));
 180
 181         if (neg) /* if t[32] is negative */
 182                 {
 183                 c1-=(int)(bn_sub_words(&(t[n2]),t,&(t[n2]),n2));
 184                 }
 185         else
 186                 {
 187                 /* Might have a carry */
 188                 c1+=(int)(bn_add_words(&(t[n2]),&(t[n2]),t,n2));
 189                 }
 190
 191         /* t[32] holds (a[0]-a[1])*(b[1]-b[0])+(a[0]*b[0])+(a[1]*b[1])
 192          * r[10] holds (a[0]*b[0])
 193          * r[32] holds (b[1]*b[1])
 194          * c1 holds the carry bits
 195          */
 196         c1+=(int)(bn_add_words(&(r[n]),&(r[n]),&(t[n2]),n2));
 197         if (c1)
 198                 {
 199                 p= &(r[n+n2]);
 200                 lo= *p;
 201                 ln=(lo+c1)&BN_MASK2;
 202                 *p=ln;
 203
 204                 /* The overflow will stop before we over write
 205                  * words we should not overwrite */
 206                 if (ln < (BN_ULONG)c1)
 207                         {
 208                         do      {
 209                                 p++;
 210                                 lo= *p;
 211                                 ln=(lo+1)&BN_MASK2;
 212                                 *p=ln;
 213                                 } while (ln == 0);
 214                         }
 215                 }
 216         }
 217
 218 /* n+tn is the word length
 219  * t needs to be n*4 is size, as does r */
 220 void bn_mul_part_recursive(BN_ULONG *r, BN_ULONG *a, BN_ULONG *b, int tn,
 221              int n, BN_ULONG *t)
 222         {
 223         int i,j,n2=n*2;
 224         unsigned int c1,c2,neg,zero;
 225         BN_ULONG ln,lo,*p;
 226
 227 # ifdef BN_COUNT
 228         printf(" bn_mul_part_recursive %d * %d\n",tn+n,tn+n);
 229 # endif
 230         if (n < 8)
 231                 {
 232                 i=tn+n;
 233                 bn_mul_normal(r,a,i,b,i);
 234                 return;
 235                 }
 236
 237         /* r=(a[0]-a[1])*(b[1]-b[0]) */
 238         c1=bn_cmp_words(a,&(a[n]),n);
 239         c2=bn_cmp_words(&(b[n]),b,n);
 240         zero=neg=0;
 241         switch (c1*3+c2)
 242                 {
 243         case -4:
 244                 bn_sub_words(t,      &(a[n]),a,      n); /* - */
 245                 bn_sub_words(&(t[n]),b,      &(b[n]),n); /* - */
 246                 break;
 247         case -3:
 248                 zero=1;
 249                 /* break; */
 250         case -2:
 251                 bn_sub_words(t,      &(a[n]),a,      n); /* - */
 252                 bn_sub_words(&(t[n]),&(b[n]),b,      n); /* + */
 253                 neg=1;
 254                 break;
 255         case -1:
 256         case 0:
 257         case 1:
 258                 zero=1;
 259                 /* break; */
 260         case 2:
 261                 bn_sub_words(t,      a,      &(a[n]),n); /* + */
 262                 bn_sub_words(&(t[n]),b,      &(b[n]),n); /* - */
 263                 neg=1;
 264                 break;
 265         case 3:
 266                 zero=1;
 267                 /* break; */
 268         case 4:
 269                 bn_sub_words(t,      a,      &(a[n]),n);
 270                 bn_sub_words(&(t[n]),&(b[n]),b,      n);
 271                 break;
 272                 }
 273                 /* The zero case isn't yet implemented here. The speedup
 274                    would probably be negligible. */
 275 # if 0
 276         if (n == 4)
 277                 {
 278                 bn_mul_comba4(&(t[n2]),t,&(t[n]));
 279                 bn_mul_comba4(r,a,b);
 280                 bn_mul_normal(&(r[n2]),&(a[n]),tn,&(b[n]),tn);
 281                 memset(&(r[n2+tn*2]),0,sizeof(BN_ULONG)*(n2-tn*2));
 282                 }
 283         else
 284 # endif
 285         if (n == 8)
 286                 {
 287                 bn_mul_comba8(&(t[n2]),t,&(t[n]));
 288                 bn_mul_comba8(r,a,b);
 289                 bn_mul_normal(&(r[n2]),&(a[n]),tn,&(b[n]),tn);
 290                 memset(&(r[n2+tn*2]),0,sizeof(BN_ULONG)*(n2-tn*2));
 291                 }
 292         else
 293                 {
 294                 p= &(t[n2*2]);
 295                 bn_mul_recursive(&(t[n2]),t,&(t[n]),n,p);
 296                 bn_mul_recursive(r,a,b,n,p);
 297                 i=n/2;
 298                 /* If there is only a bottom half to the number,
 299                  * just do it */
 300                 j=tn-i;
 301                 if (j == 0)
 302                         {
 303                         bn_mul_recursive(&(r[n2]),&(a[n]),&(b[n]),i,p);
 304                         memset(&(r[n2+i*2]),0,sizeof(BN_ULONG)*(n2-i*2));
 305                         }
 306                 else if (j > 0) /* eg, n == 16, i == 8 and tn == 11 */
 307                                 {
 308                                 bn_mul_part_recursive(&(r[n2]),&(a[n]),&(b[n]),
 309                                         j,i,p);
 310                                 memset(&(r[n2+tn*2]),0,
 311                                         sizeof(BN_ULONG)*(n2-tn*2));
 312                                 }
 313                 else /* (j < 0) eg, n == 16, i == 8 and tn == 5 */
 314                         {
 315                         memset(&(r[n2]),0,sizeof(BN_ULONG)*n2);
 316                         if (tn < BN_MUL_RECURSIVE_SIZE_NORMAL)
 317                                 {
 318                                 bn_mul_normal(&(r[n2]),&(a[n]),tn,&(b[n]),tn);
 319                                 }
 320                         else
 321                                 {
 322                                 for (;;)
 323                                         {
 324                                         i/=2;
 325                                         if (i < tn)
 326                                                 {
 327                                                 bn_mul_part_recursive(&(r[n2]),
 328                                                         &(a[n]),&(b[n]),
 329                                                         tn-i,i,p);
 330                                                 break;
 331                                                 }
 332                                         else if (i == tn)
 333                                                 {
 334                                                 bn_mul_recursive(&(r[n2]),
 335                                                         &(a[n]),&(b[n]),
 336                                                         i,p);
 337                                                 break;
 338                                                 }
 339                                         }
 340                                 }
 341                         }
 342                 }
 343
 344         /* t[32] holds (a[0]-a[1])*(b[1]-b[0]), c1 is the sign
 345          * r[10] holds (a[0]*b[0])
 346          * r[32] holds (b[1]*b[1])
 347          */
 348
 349         c1=(int)(bn_add_words(t,r,&(r[n2]),n2));
 350
 351         if (neg) /* if t[32] is negative */
 352                 {
 353                 c1-=(int)(bn_sub_words(&(t[n2]),t,&(t[n2]),n2));
 354                 }
 355         else
 356                 {
 357                 /* Might have a carry */
 358                 c1+=(int)(bn_add_words(&(t[n2]),&(t[n2]),t,n2));
 359                 }
 360
 361         /* t[32] holds (a[0]-a[1])*(b[1]-b[0])+(a[0]*b[0])+(a[1]*b[1])
 362          * r[10] holds (a[0]*b[0])
 363          * r[32] holds (b[1]*b[1])
 364          * c1 holds the carry bits
 365          */
 366         c1+=(int)(bn_add_words(&(r[n]),&(r[n]),&(t[n2]),n2));
 367         if (c1)
 368                 {
 369                 p= &(r[n+n2]);
 370                 lo= *p;
 371                 ln=(lo+c1)&BN_MASK2;
 372                 *p=ln;
 373
 374                 /* The overflow will stop before we over write
 375                  * words we should not overwrite */
 376                 if (ln < c1)
 377                         {
 378                         do      {
 379                                 p++;
 380                                 lo= *p;
 381                                 ln=(lo+1)&BN_MASK2;
 382                                 *p=ln;
 383                                 } while (ln == 0);
 384                         }
 385                 }
 386         }
 387
 388 /* a and b must be the same size, which is n2.
 389  * r needs to be n2 words and t needs to be n2*2
 390  */
 391 void bn_mul_low_recursive(BN_ULONG *r, BN_ULONG *a, BN_ULONG *b, int n2,
 392              BN_ULONG *t)
 393         {
 394         int n=n2/2;
 395
 396 # ifdef BN_COUNT
 397         printf(" bn_mul_low_recursive %d * %d\n",n2,n2);
 398 # endif
 399
 400         bn_mul_recursive(r,a,b,n,&(t[0]));
 401         if (n >= BN_MUL_LOW_RECURSIVE_SIZE_NORMAL)
 402                 {
 403                 bn_mul_low_recursive(&(t[0]),&(a[0]),&(b[n]),n,&(t[n2]));
 404                 bn_add_words(&(r[n]),&(r[n]),&(t[0]),n);
 405                 bn_mul_low_recursive(&(t[0]),&(a[n]),&(b[0]),n,&(t[n2]));
 406                 bn_add_words(&(r[n]),&(r[n]),&(t[0]),n);
 407                 }
 408         else
 409                 {
 410                 bn_mul_low_normal(&(t[0]),&(a[0]),&(b[n]),n);
 411                 bn_mul_low_normal(&(t[n]),&(a[n]),&(b[0]),n);
 412                 bn_add_words(&(r[n]),&(r[n]),&(t[0]),n);
 413                 bn_add_words(&(r[n]),&(r[n]),&(t[n]),n);
 414                 }
 415         }
 416
 417 /* a and b must be the same size, which is n2.
 418  * r needs to be n2 words and t needs to be n2*2
 419  * l is the low words of the output.
 420  * t needs to be n2*3
 421  */
 422 void bn_mul_high(BN_ULONG *r, BN_ULONG *a, BN_ULONG *b, BN_ULONG *l, int n2,
 423              BN_ULONG *t)
 424         {
 425         int i,n;
 426         int c1,c2;
 427         int neg,oneg,zero;
 428         BN_ULONG ll,lc,*lp,*mp;
 429
 430 # ifdef BN_COUNT
 431         printf(" bn_mul_high %d * %d\n",n2,n2);
 432 # endif
 433         n=n2/2;
 434
 435         /* Calculate (al-ah)*(bh-bl) */
 436         neg=zero=0;
 437         c1=bn_cmp_words(&(a[0]),&(a[n]),n);
 438         c2=bn_cmp_words(&(b[n]),&(b[0]),n);
 439         switch (c1*3+c2)
 440                 {
 441         case -4:
 442                 bn_sub_words(&(r[0]),&(a[n]),&(a[0]),n);
 443                 bn_sub_words(&(r[n]),&(b[0]),&(b[n]),n);
 444                 break;
 445         case -3:
 446                 zero=1;
 447                 break;
 448         case -2:
 449                 bn_sub_words(&(r[0]),&(a[n]),&(a[0]),n);
 450                 bn_sub_words(&(r[n]),&(b[n]),&(b[0]),n);
 451                 neg=1;
 452                 break;
 453         case -1:
 454         case 0:
 455         case 1:
 456                 zero=1;
 457                 break;
 458         case 2:
 459                 bn_sub_words(&(r[0]),&(a[0]),&(a[n]),n);
 460                 bn_sub_words(&(r[n]),&(b[0]),&(b[n]),n);
 461                 neg=1;
 462                 break;
 463         case 3:
 464                 zero=1;
 465                 break;
 466         case 4:
 467                 bn_sub_words(&(r[0]),&(a[0]),&(a[n]),n);
 468                 bn_sub_words(&(r[n]),&(b[n]),&(b[0]),n);
 469                 break;
 470                 }
 471
 472         oneg=neg;
 473         /* t[10] = (a[0]-a[1])*(b[1]-b[0]) */
 474         /* r[10] = (a[1]*b[1]) */
 475 # ifdef BN_MUL_COMBA
 476         if (n == 8)
 477                 {
 478                 bn_mul_comba8(&(t[0]),&(r[0]),&(r[n]));
 479                 bn_mul_comba8(r,&(a[n]),&(b[n]));
 480                 }
 481         else
 482 # endif
 483                 {
 484                 bn_mul_recursive(&(t[0]),&(r[0]),&(r[n]),n,&(t[n2]));
 485                 bn_mul_recursive(r,&(a[n]),&(b[n]),n,&(t[n2]));
 486                 }
 487
 488         /* s0 == low(al*bl)
 489          * s1 == low(ah*bh)+low((al-ah)*(bh-bl))+low(al*bl)+high(al*bl)
 490          * We know s0 and s1 so the only unknown is high(al*bl)
 491          * high(al*bl) == s1 - low(ah*bh+s0+(al-ah)*(bh-bl))
 492          * high(al*bl) == s1 - (r[0]+l[0]+t[0])
 493          */
 494         if (l != NULL)
 495                 {
 496                 lp= &(t[n2+n]);
 497                 c1=(int)(bn_add_words(lp,&(r[0]),&(l[0]),n));
 498                 }
 499         else
 500                 {
 501                 c1=0;
 502                 lp= &(r[0]);
 503                 }
 504
 505         if (neg)
 506                 neg=(int)(bn_sub_words(&(t[n2]),lp,&(t[0]),n));
 507         else
 508                 {
 509                 bn_add_words(&(t[n2]),lp,&(t[0]),n);
 510                 neg=0;
 511                 }
 512
 513         if (l != NULL)
 514                 {
 515                 bn_sub_words(&(t[n2+n]),&(l[n]),&(t[n2]),n);
 516                 }
 517         else
 518                 {
 519                 lp= &(t[n2+n]);
 520                 mp= &(t[n2]);
 521                 for (i=0; i<n; i++)
 522                         lp[i]=((~mp[i])+1)&BN_MASK2;
 523                 }
 524
 525         /* s[0] = low(al*bl)
 526          * t[3] = high(al*bl)
 527          * t[10] = (a[0]-a[1])*(b[1]-b[0]) neg is the sign
 528          * r[10] = (a[1]*b[1])
 529          */
 530         /* R[10] = al*bl
 531          * R[21] = al*bl + ah*bh + (a[0]-a[1])*(b[1]-b[0])
 532          * R[32] = ah*bh
 533          */
 534         /* R[1]=t[3]+l[0]+r[0](+-)t[0] (have carry/borrow)
 535          * R[2]=r[0]+t[3]+r[1](+-)t[1] (have carry/borrow)
 536          * R[3]=r[1]+(carry/borrow)
 537          */
 538         if (l != NULL)
 539                 {
 540                 lp= &(t[n2]);
 541                 c1= (int)(bn_add_words(lp,&(t[n2+n]),&(l[0]),n));
 542                 }
 543         else
 544                 {
 545                 lp= &(t[n2+n]);
 546                 c1=0;
 547                 }
 548         c1+=(int)(bn_add_words(&(t[n2]),lp,  &(r[0]),n));
 549         if (oneg)
 550                 c1-=(int)(bn_sub_words(&(t[n2]),&(t[n2]),&(t[0]),n));
 551         else
 552                 c1+=(int)(bn_add_words(&(t[n2]),&(t[n2]),&(t[0]),n));
 553
 554         c2 =(int)(bn_add_words(&(r[0]),&(r[0]),&(t[n2+n]),n));
 555         c2+=(int)(bn_add_words(&(r[0]),&(r[0]),&(r[n]),n));
 556         if (oneg)
 557                 c2-=(int)(bn_sub_words(&(r[0]),&(r[0]),&(t[n]),n));
 558         else
 559                 c2+=(int)(bn_add_words(&(r[0]),&(r[0]),&(t[n]),n));
 560
 561         if (c1 != 0) /* Add starting at r[0], could be +ve or -ve */
 562                 {
 563                 i=0;
 564                 if (c1 > 0)
 565                         {
 566                         lc=c1;
 567                         do      {
 568                                 ll=(r[i]+lc)&BN_MASK2;
 569                                 r[i++]=ll;
 570                                 lc=(lc > ll);
 571                                 } while (lc);
 572                         }
 573                 else
 574                         {
 575                         lc= -c1;
 576                         do      {
 577                                 ll=r[i];
 578                                 r[i++]=(ll-lc)&BN_MASK2;
 579                                 lc=(lc > ll);
 580                                 } while (lc);
 581                         }
 582                 }
 583         if (c2 != 0) /* Add starting at r[1] */
 584                 {
 585                 i=n;
 586                 if (c2 > 0)
 587                         {
 588                         lc=c2;
 589                         do      {
 590                                 ll=(r[i]+lc)&BN_MASK2;
 591                                 r[i++]=ll;
 592                                 lc=(lc > ll);
 593                                 } while (lc);
 594                         }
 595                 else
 596                         {
 597                         lc= -c2;
 598                         do      {
 599                                 ll=r[i];
 600                                 r[i++]=(ll-lc)&BN_MASK2;
 601                                 lc=(lc > ll);
 602                                 } while (lc);
 603                         }
 604                 }
 605         }
 606 #endif /* BN_RECURSION */
 607
 608 int BN_mul(BIGNUM *r, BIGNUM *a, BIGNUM *b, BN_CTX *ctx)
 609         {
 610         int top,al,bl;
 611         BIGNUM *rr;
 612         int ret = 0;
 613 #if defined(BN_MUL_COMBA) || defined(BN_RECURSION)
 614         int i;
 615 #endif
 616 #ifdef BN_RECURSION
 617         BIGNUM *t;
 618         int j,k;
 619 #endif
 620
 621 #ifdef BN_COUNT
 622         printf("BN_mul %d * %d\n",a->top,b->top);
 623 #endif
 624
 625         bn_check_top(a);
 626         bn_check_top(b);
 627         bn_check_top(r);
 628
 629         al=a->top;
 630         bl=b->top;
 631         r->neg=a->neg^b->neg;
 632
 633         if ((al == 0) || (bl == 0))
 634                 {
 635                 BN_zero(r);
 636                 return(1);
 637                 }
 638         top=al+bl;
 639
 640         BN_CTX_start(ctx);
 641         if ((r == a) || (r == b))
 642                 {
 643                 if ((rr = BN_CTX_get(ctx)) == NULL) goto err;
 644                 }
 645         else
 646                 rr = r;
 647
 648 #if defined(BN_MUL_COMBA) || defined(BN_RECURSION)
 649         i = al-bl;
 650 #endif
 651 #ifdef BN_MUL_COMBA
 652         if (i == 0)
 653                 {
 654 # if 0
 655                 if (al == 4)
 656                         {
 657                         if (bn_wexpand(rr,8) == NULL) goto err;
 658                         rr->top=8;
 659                         bn_mul_comba4(rr->d,a->d,b->d);
 660                         goto end;
 661                         }
 662 # endif
 663                 if (al == 8)
 664                         {
 665                         if (bn_wexpand(rr,16) == NULL) goto err;
 666                         rr->top=16;
 667                         bn_mul_comba8(rr->d,a->d,b->d);
 668                         goto end;
 669                         }
 670                 }
 671 #endif /* BN_MUL_COMBA */
 672 #ifdef BN_RECURSION
 673         if ((al >= BN_MULL_SIZE_NORMAL) && (bl >= BN_MULL_SIZE_NORMAL))
 674                 {
 675                 if (i == 1 && !BN_get_flags(b,BN_FLG_STATIC_DATA))
 676                         {
 677                         bn_wexpand(b,al);
 678                         b->d[bl]=0;
 679                         bl++;
 680                         i--;
 681                         }
 682                 else if (i == -1 && !BN_get_flags(a,BN_FLG_STATIC_DATA))
 683                         {
 684                         bn_wexpand(a,bl);
 685                         a->d[al]=0;
 686                         al++;
 687                         i++;
 688                         }
 689                 if (i == 0)
 690                         {
 691                         /* symmetric and > 4 */
 692                         /* 16 or larger */
 693                         j=BN_num_bits_word((BN_ULONG)al);
 694                         j=1<<(j-1);
 695                         k=j+j;
 696                         t = BN_CTX_get(ctx);
 697                         if (al == j) /* exact multiple */
 698                                 {
 699                                 bn_wexpand(t,k*2);
 700                                 bn_wexpand(rr,k*2);
 701                                 bn_mul_recursive(rr->d,a->d,b->d,al,t->d);
 702                                 }
 703                         else
 704                                 {
 705                                 bn_wexpand(a,k);
 706                                 bn_wexpand(b,k);
 707                                 bn_wexpand(t,k*4);
 708                                 bn_wexpand(rr,k*4);
 709                                 for (i=a->top; i<k; i++)
 710                                         a->d[i]=0;
 711                                 for (i=b->top; i<k; i++)
 712                                         b->d[i]=0;
 713                                 bn_mul_part_recursive(rr->d,a->d,b->d,al-j,j,t->d);
 714                                 }
 715                         rr->top=top;
 716                         goto end;
 717                         }
 718                 }
 719 #endif /* BN_RECURSION */
 720         if (bn_wexpand(rr,top) == NULL) goto err;
 721         rr->top=top;
 722         bn_mul_normal(rr->d,a->d,al,b->d,bl);
 723
 724 #if defined(BN_MUL_COMBA) || defined(BN_RECURSION)
 725 end:
 726 #endif
 727         bn_fix_top(rr);
 728         if (r != rr) BN_copy(r,rr);
 729         ret=1;
 730 err:
 731         BN_CTX_end(ctx);
 732         return(ret);
 733         }
 734
 735 void bn_mul_normal(BN_ULONG *r, BN_ULONG *a, int na, BN_ULONG *b, int nb)
 736         {
 737         BN_ULONG *rr;
 738
 739 #ifdef BN_COUNT
 740         printf(" bn_mul_normal %d * %d\n",na,nb);
 741 #endif
 742
 743         if (na < nb)
 744                 {
 745                 int itmp;
 746                 BN_ULONG *ltmp;
 747
 748                 itmp=na; na=nb; nb=itmp;
 749                 ltmp=a;   a=b;   b=ltmp;
 750
 751                 }
 752         rr= &(r[na]);
 753         rr[0]=bn_mul_words(r,a,na,b[0]);
 754
 755         for (;;)
 756                 {
 757                 if (--nb <= 0) return;
 758                 rr[1]=bn_mul_add_words(&(r[1]),a,na,b[1]);
 759                 if (--nb <= 0) return;
 760                 rr[2]=bn_mul_add_words(&(r[2]),a,na,b[2]);
 761                 if (--nb <= 0) return;
 762                 rr[3]=bn_mul_add_words(&(r[3]),a,na,b[3]);
 763                 if (--nb <= 0) return;
 764                 rr[4]=bn_mul_add_words(&(r[4]),a,na,b[4]);
 765                 rr+=4;
 766                 r+=4;
 767                 b+=4;
 768                 }
 769         }
 770
 771 void bn_mul_low_normal(BN_ULONG *r, BN_ULONG *a, BN_ULONG *b, int n)
 772         {
 773 #ifdef BN_COUNT
 774         printf(" bn_mul_low_normal %d * %d\n",n,n);
 775 #endif
 776         bn_mul_words(r,a,n,b[0]);
 777
 778         for (;;)
 779                 {
 780                 if (--n <= 0) return;
 781                 bn_mul_add_words(&(r[1]),a,n,b[1]);
 782                 if (--n <= 0) return;
 783                 bn_mul_add_words(&(r[2]),a,n,b[2]);
 784                 if (--n <= 0) return;
 785                 bn_mul_add_words(&(r[3]),a,n,b[3]);
 786                 if (--n <= 0) return;
 787                 bn_mul_add_words(&(r[4]),a,n,b[4]);
 788                 r+=4;
 789                 b+=4;
 790                 }
 791         }