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=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         BN_free(&(mont->RR));
 293         BN_free(&(mont->N));
 294         BN_free(&(mont->Ni));
 295         if (mont->flags & BN_FLG_MALLOCED)
 296                 Free(mont);
 297         }
 298
 299 int BN_MONT_CTX_set(mont,mod,ctx)
 300 BN_MONT_CTX *mont;
 301 BIGNUM *mod;
 302 BN_CTX *ctx;
 303         {
 304         BIGNUM Ri,*R;
 305
 306         BN_init(&Ri);
 307         R= &(mont->RR);                                 /* grab RR as a temp */
 308         BN_copy(&(mont->N),mod);                        /* Set N */
 309
 310 #ifdef BN_RECURSION
 311         if (mont->N.top < BN_MONT_CTX_SET_SIZE_WORD)
 312 #endif
 313                 {
 314                 BIGNUM tmod;
 315                 BN_ULONG buf[2];
 316
 317                 mont->use_word=1;
 318
 319                 mont->ri=(BN_num_bits(mod)+(BN_BITS2-1))/BN_BITS2*BN_BITS2;
 320                 BN_zero(R);
 321                 BN_set_bit(R,BN_BITS2);
 322                 /* I was bad, this modification of a passed variable was
 323                  * breaking the multithreaded stuff :-(
 324                  * z=mod->top;
 325                  * mod->top=1; */
 326
 327                 buf[0]=mod->d[0];
 328                 buf[1]=0;
 329                 tmod.d=buf;
 330                 tmod.top=1;
 331                 tmod.max=mod->max;
 332                 tmod.neg=mod->neg;
 333
 334                 if ((BN_mod_inverse(&Ri,R,&tmod,ctx)) == NULL)
 335                         goto err;
 336                 BN_lshift(&Ri,&Ri,BN_BITS2);                    /* R*Ri */
 337                 if (!BN_is_zero(&Ri))
 338                         {
 339 #if 1
 340                         BN_sub_word(&Ri,1);
 341 #else
 342                         BN_usub(&Ri,&Ri,BN_value_one());        /* R*Ri - 1 */
 343 #endif
 344                         }
 345                 else
 346                         {
 347                         /* This is not common..., 1 in BN_MASK2,
 348                          * It happens when buf[0] was == 1.  So for 8 bit,
 349                          * this is 1/256, 16bit, 1 in 2^16 etc.
 350                          */
 351                         BN_set_word(&Ri,BN_MASK2);
 352                         }
 353                 BN_div(&Ri,NULL,&Ri,&tmod,ctx);
 354                 mont->n0=Ri.d[0];
 355                 BN_free(&Ri);
 356                 /* mod->top=z; */
 357                 }
 358 #ifdef BN_RECURSION
 359         else
 360                 {
 361                 mont->use_word=0;
 362                 mont->ri=(BN_num_bits(mod)+(BN_BITS2-1))/BN_BITS2*BN_BITS2;
 363 #if 1
 364                 BN_zero(R);
 365                 BN_set_bit(R,mont->ri);
 366 #else
 367                 BN_lshift(R,BN_value_one(),mont->ri);   /* R */
 368 #endif
 369                 if ((BN_mod_inverse(&Ri,R,mod,ctx)) == NULL)
 370                         goto err;
 371                 BN_lshift(&Ri,&Ri,mont->ri);            /* R*Ri */
 372 #if 1
 373                 BN_sub_word(&Ri,1);
 374 #else
 375                 BN_usub(&Ri,&Ri,BN_value_one());        /* R*Ri - 1 */
 376 #endif
 377                 BN_div(&(mont->Ni),NULL,&Ri,mod,ctx);
 378                 BN_free(&Ri);
 379                 }
 380 #endif
 381
 382         /* setup RR for conversions */
 383 #if 1
 384         BN_zero(&(mont->RR));
 385         BN_set_bit(&(mont->RR),mont->ri*2);
 386 #else
 387         BN_lshift(mont->RR,BN_value_one(),mont->ri*2);
 388 #endif
 389         BN_mod(&(mont->RR),&(mont->RR),&(mont->N),ctx);
 390
 391         return(1);
 392 err:
 393         return(0);
 394         }
 395
 396 BN_MONT_CTX *BN_MONT_CTX_copy(to, from)
 397 BN_MONT_CTX *to, *from;
 398         {
 399         if (to == from) return(to);
 400
 401         BN_copy(&(to->RR),&(from->RR));
 402         BN_copy(&(to->N),&(from->N));
 403         BN_copy(&(to->Ni),&(from->Ni));
 404         to->use_word=from->use_word;
 405         to->ri=from->ri;
 406         to->n0=from->n0;
 407         return(to);
 408         }
 409