crypto/bn/bn_mont.c

   1 /* crypto/bn/bn_mont.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 #define MONT_WORD
  64
  65 int BN_mod_mul_montgomery(r,a,b,mont,ctx)
  66 BIGNUM *r,*a,*b;
  67 BN_MONT_CTX *mont;
  68 BN_CTX *ctx;
  69         {
  70         BIGNUM *tmp,*tmp2;
  71
  72         tmp= &(ctx->bn[ctx->tos]);
  73         tmp2= &(ctx->bn[ctx->tos]);
  74         ctx->tos+=2;
  75
  76         bn_check_top(tmp);
  77         bn_check_top(tmp2);
  78
  79         if (a == b)
  80                 {
  81 #if 0
  82                 bn_wexpand(tmp,a->top*2);
  83                 bn_wexpand(tmp2,a->top*4);
  84                 bn_sqr_recursive(tmp->d,a->d,a->top,tmp2->d);
  85                 tmp->top=a->top*2;
  86                 if (tmp->d[tmp->top-1] == 0)
  87                         tmp->top--;
  88 #else
  89                 if (!BN_sqr(tmp,a,ctx)) goto err;
  90 #endif
  91                 }
  92         else
  93                 {
  94                 if (!BN_mul(tmp,a,b,ctx)) goto err;
  95                 }
  96         /* reduce from aRR to aR */
  97         if (!BN_from_montgomery(r,tmp,mont,ctx)) goto err;
  98         ctx->tos-=2;
  99         return(1);
 100 err:
 101         return(0);
 102         }
 103
 104 int BN_from_montgomery(ret,a,mont,ctx)
 105 BIGNUM *ret;
 106 BIGNUM *a;
 107 BN_MONT_CTX *mont;
 108 BN_CTX *ctx;
 109         {
 110 #ifdef BN_RECURSION
 111         if (mont->use_word)
 112 #endif
 113                 {
 114                 BIGNUM *n,*r;
 115                 BN_ULONG *ap,*np,*rp,n0,v,*nrp;
 116                 int al,nl,max,i,x,ri;
 117                 int retn=0;
 118
 119                 r= &(ctx->bn[ctx->tos]);
 120
 121                 if (!BN_copy(r,a)) goto err1;
 122                 n= &(mont->N);
 123
 124                 ap=a->d;
 125                 /* mont->ri is the size of mont->N in bits/words */
 126                 al=ri=mont->ri/BN_BITS2;
 127
 128                 nl=n->top;
 129                 if ((al == 0) || (nl == 0)) { r->top=0; return(1); }
 130
 131                 max=(nl+al+1); /* allow for overflow (no?) XXX */
 132                 if (bn_wexpand(r,max) == NULL) goto err1;
 133                 if (bn_wexpand(ret,max) == NULL) goto err1;
 134
 135                 r->neg=a->neg^n->neg;
 136                 np=n->d;
 137                 rp=r->d;
 138                 nrp= &(r->d[nl]);
 139
 140                 /* clear the top words of T */
 141 #if 1
 142                 for (i=r->top; i<max; i++) /* memset? XXX */
 143                         r->d[i]=0;
 144 #else
 145                 memset(&(r->d[r->top]),0,(max-r->top)*sizeof(BN_ULONG));
 146 #endif
 147
 148                 r->top=max;
 149                 n0=mont->n0;
 150
 151 #ifdef BN_COUNT
 152 printf("word BN_from_montgomery %d * %d\n",nl,nl);
 153 #endif
 154                 for (i=0; i<nl; i++)
 155                         {
 156                         v=bn_mul_add_words(rp,np,nl,(rp[0]*n0)&BN_MASK2);
 157                         nrp++;
 158                         rp++;
 159                         if (((nrp[-1]+=v)&BN_MASK2) >= v)
 160                                 continue;
 161                         else
 162                                 {
 163                                 if (((++nrp[0])&BN_MASK2) != 0) continue;
 164                                 if (((++nrp[1])&BN_MASK2) != 0) continue;
 165                                 for (x=2; (((++nrp[x])&BN_MASK2) == 0); x++) ;
 166                                 }
 167                         }
 168                 bn_fix_top(r);
 169
 170                 /* mont->ri will be a multiple of the word size */
 171 #if 0
 172                 BN_rshift(ret,r,mont->ri);
 173 #else
 174                 x=ri;
 175                 rp=ret->d;
 176                 ap= &(r->d[x]);
 177                 if (r->top < x)
 178                         al=0;
 179                 else
 180                         al=r->top-x;
 181                 ret->top=al;
 182                 al-=4;
 183                 for (i=0; i<al; i+=4)
 184                         {
 185                         BN_ULONG t1,t2,t3,t4;
 186
 187                         t1=ap[i+0];
 188                         t2=ap[i+1];
 189                         t3=ap[i+2];
 190                         t4=ap[i+3];
 191                         rp[i+0]=t1;
 192                         rp[i+1]=t2;
 193                         rp[i+2]=t3;
 194                         rp[i+3]=t4;
 195                         }
 196                 al+=4;
 197                 for (; i<al; i++)
 198                         rp[i]=ap[i];
 199 #endif
 200
 201                 if (BN_ucmp(ret, &(mont->N)) >= 0)
 202                         {
 203                         BN_usub(ret,ret,&(mont->N)); /* XXX */
 204                         }
 205                 retn=1;
 206 err1:
 207                 return(retn);
 208                 }
 209 #ifdef BN_RECURSION
 210         else /* bignum version */
 211                 {
 212                 BIGNUM *t1,*t2,*t3;
 213                 int j,i;
 214
 215 #ifdef BN_COUNT
 216 printf("number BN_from_montgomery\n");
 217 #endif
 218
 219                 t1= &(ctx->bn[ctx->tos]);
 220                 t2= &(ctx->bn[ctx->tos+1]);
 221                 t3= &(ctx->bn[ctx->tos+2]);
 222
 223                 i=mont->Ni.top;
 224                 bn_wexpand(ret,i); /* perhaps only i*2 */
 225                 bn_wexpand(t1,i*4); /* perhaps only i*2 */
 226                 bn_wexpand(t2,i*2); /* perhaps only i   */
 227
 228                 bn_mul_low_recursive(t2->d,a->d,mont->Ni.d,i,t1->d);
 229
 230                 BN_zero(t3);
 231                 BN_set_bit(t3,mont->N.top*BN_BITS2);
 232                 bn_sub_words(t3->d,t3->d,a->d,i);
 233                 bn_mul_high(ret->d,t2->d,mont->N.d,t3->d,i,t1->d);
 234
 235                 /* hmm... if a is between i and 2*i, things are bad */
 236                 if (a->top > i)
 237                         {
 238                         j=(int)(bn_add_words(ret->d,ret->d,&(a->d[i]),i));
 239                         if (j) /* overflow */
 240                                 bn_sub_words(ret->d,ret->d,mont->N.d,i);
 241                         }
 242                 ret->top=i;
 243                 bn_fix_top(ret);
 244                 if (a->d[0])
 245                         BN_add_word(ret,1); /* Always? */
 246                 else    /* Very very rare */
 247                         {
 248                         for (i=1; i<mont->N.top-1; i++)
 249                                 {
 250                                 if (a->d[i])
 251                                         {
 252                                         BN_add_word(ret,1); /* Always? */
 253                                         break;
 254                                         }
 255                                 }
 256                         }
 257
 258                 if (BN_ucmp(ret,&(mont->N)) >= 0)
 259                         BN_usub(ret,ret,&(mont->N));
 260
 261                 return(1);
 262                 }
 263 #endif
 264         }
 265
 266 BN_MONT_CTX *BN_MONT_CTX_new()
 267         {
 268         BN_MONT_CTX *ret;
 269
 270         if ((ret=(BN_MONT_CTX *)Malloc(sizeof(BN_MONT_CTX))) == NULL)
 271                 return(NULL);
 272
 273         BN_MONT_CTX_init(ret);
 274         ret->flags=BN_FLG_MALLOCED;
 275         return(ret);
 276         }
 277
 278 void BN_MONT_CTX_init(ctx)
 279 BN_MONT_CTX *ctx;
 280         {
 281         ctx->use_word=0;
 282         ctx->ri=0;
 283         BN_init(&(ctx->RR));
 284         BN_init(&(ctx->N));
 285         BN_init(&(ctx->Ni));
 286         ctx->flags=0;
 287         }
 288
 289 void BN_MONT_CTX_free(mont)
 290 BN_MONT_CTX *mont;
 291         {
 292         if(mont == NULL)
 293             return;
 294
 295         BN_free(&(mont->RR));
 296         BN_free(&(mont->N));
 297         BN_free(&(mont->Ni));
 298         if (mont->flags & BN_FLG_MALLOCED)
 299                 Free(mont);
 300         }
 301
 302 int BN_MONT_CTX_set(mont,mod,ctx)
 303 BN_MONT_CTX *mont;
 304 BIGNUM *mod;
 305 BN_CTX *ctx;
 306         {
 307         BIGNUM Ri,*R;
 308
 309         BN_init(&Ri);
 310         R= &(mont->RR);                                 /* grab RR as a temp */
 311         BN_copy(&(mont->N),mod);                        /* Set N */
 312
 313 #ifdef BN_RECURSION
 314         if (mont->N.top < BN_MONT_CTX_SET_SIZE_WORD)
 315 #endif
 316                 {
 317                 BIGNUM tmod;
 318                 BN_ULONG buf[2];
 319
 320                 mont->use_word=1;
 321
 322                 mont->ri=(BN_num_bits(mod)+(BN_BITS2-1))/BN_BITS2*BN_BITS2;
 323                 BN_zero(R);
 324                 BN_set_bit(R,BN_BITS2);
 325                 /* I was bad, this modification of a passed variable was
 326                  * breaking the multithreaded stuff :-(
 327                  * z=mod->top;
 328                  * mod->top=1; */
 329
 330                 buf[0]=mod->d[0];
 331                 buf[1]=0;
 332                 tmod.d=buf;
 333                 tmod.top=1;
 334                 tmod.max=mod->max;
 335                 tmod.neg=mod->neg;
 336
 337                 if ((BN_mod_inverse(&Ri,R,&tmod,ctx)) == NULL)
 338                         goto err;
 339                 BN_lshift(&Ri,&Ri,BN_BITS2);                    /* R*Ri */
 340                 if (!BN_is_zero(&Ri))
 341                         {
 342 #if 1
 343                         BN_sub_word(&Ri,1);
 344 #else
 345                         BN_usub(&Ri,&Ri,BN_value_one());        /* R*Ri - 1 */
 346 #endif
 347                         }
 348                 else
 349                         {
 350                         /* This is not common..., 1 in BN_MASK2,
 351                          * It happens when buf[0] was == 1.  So for 8 bit,
 352                          * this is 1/256, 16bit, 1 in 2^16 etc.
 353                          */
 354                         BN_set_word(&Ri,BN_MASK2);
 355                         }
 356                 BN_div(&Ri,NULL,&Ri,&tmod,ctx);
 357                 mont->n0=Ri.d[0];
 358                 BN_free(&Ri);
 359                 /* mod->top=z; */
 360                 }
 361 #ifdef BN_RECURSION
 362         else
 363                 {
 364                 mont->use_word=0;
 365                 mont->ri=(BN_num_bits(mod)+(BN_BITS2-1))/BN_BITS2*BN_BITS2;
 366 #if 1
 367                 BN_zero(R);
 368                 BN_set_bit(R,mont->ri);
 369 #else
 370                 BN_lshift(R,BN_value_one(),mont->ri);   /* R */
 371 #endif
 372                 if ((BN_mod_inverse(&Ri,R,mod,ctx)) == NULL)
 373                         goto err;
 374                 BN_lshift(&Ri,&Ri,mont->ri);            /* R*Ri */
 375 #if 1
 376                 BN_sub_word(&Ri,1);
 377 #else
 378                 BN_usub(&Ri,&Ri,BN_value_one());        /* R*Ri - 1 */
 379 #endif
 380                 BN_div(&(mont->Ni),NULL,&Ri,mod,ctx);
 381                 BN_free(&Ri);
 382                 }
 383 #endif
 384
 385         /* setup RR for conversions */
 386 #if 1
 387         BN_zero(&(mont->RR));
 388         BN_set_bit(&(mont->RR),mont->ri*2);
 389 #else
 390         BN_lshift(mont->RR,BN_value_one(),mont->ri*2);
 391 #endif
 392         BN_mod(&(mont->RR),&(mont->RR),&(mont->N),ctx);
 393
 394         return(1);
 395 err:
 396         return(0);
 397         }
 398
 399 BN_MONT_CTX *BN_MONT_CTX_copy(to, from)
 400 BN_MONT_CTX *to, *from;
 401         {
 402         if (to == from) return(to);
 403
 404         BN_copy(&(to->RR),&(from->RR));
 405         BN_copy(&(to->N),&(from->N));
 406         BN_copy(&(to->Ni),&(from->Ni));
 407         to->use_word=from->use_word;
 408         to->ri=from->ri;
 409         to->n0=from->n0;
 410         return(to);
 411         }
 412