crypto/bn/bn_mont.c

   1 /* crypto/bn/bn_mont.c */
   2 /* Copyright (C) 1995-1997 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 int BN_mod_mul_montgomery(r,a,b,mont,ctx)
  64 BIGNUM *r,*a,*b;
  65 BN_MONT_CTX *mont;
  66 BN_CTX *ctx;
  67         {
  68         BIGNUM *tmp;
  69
  70         tmp=ctx->bn[ctx->tos++];
  71
  72         if (a == b)
  73                 {
  74                 if (!BN_sqr(tmp,a,ctx)) goto err;
  75                 }
  76         else
  77                 {
  78                 if (!BN_mul(tmp,a,b)) goto err;
  79                 }
  80         /* reduce from aRR to aR */
  81         if (!BN_from_montgomery(r,tmp,mont,ctx)) goto err;
  82         ctx->tos--;
  83         return(1);
  84 err:
  85         return(0);
  86         }
  87
  88 #define MONT_WORD
  89
  90 #ifdef MONT_WORD
  91 int BN_from_montgomery(ret,a,mont,ctx)
  92 BIGNUM *ret;
  93 BIGNUM *a;
  94 BN_MONT_CTX *mont;
  95 BN_CTX *ctx;
  96         {
  97         BIGNUM *n,*t1,*r;
  98         BN_ULONG *ap,*np,*rp,k,n0,v,v2;
  99         int al,nl,max,i,x;
 100         int retn=0;
 101
 102         t1=ctx->bn[ctx->tos];
 103         r=ctx->bn[ctx->tos+1];
 104
 105         if (!BN_copy(r,a)) goto err;
 106         n=mont->N;
 107
 108         if (!BN_copy(t1,a)) goto err;
 109         BN_mask_bits(t1,mont->ri);
 110
 111         a=t1;
 112
 113         al=a->top;
 114         nl=n->top;
 115         if ((al == 0) || (nl == 0)) { r->top=0; return(1); }
 116
 117         max=(nl+al+1); /* allow for overflow (no?) XXX */
 118         if (bn_expand(r,(max)*BN_BITS2) == NULL) goto err;
 119
 120         r->neg=a->neg^n->neg;
 121         ap=a->d;
 122         np=n->d;
 123         rp=r->d;
 124
 125         /* clear the top bytes of T */
 126         for (i=r->top; i<max; i++) /* memset? XXX */
 127                 r->d[i]=0;
 128 /*      memset(&(r->d[r->top]),0,(max-r->top)*sizeof(BN_ULONG)); */
 129
 130         r->top=max;
 131         n0=mont->n0;
 132
 133         for (i=0; i<nl; i++)
 134                 {
 135                 /* This is were part words probably goes wrong */
 136                 k=(rp[0]*n0)&BN_MASK2;
 137                 v=bn_mul_add_word(rp,np,nl,k);
 138
 139                 for (x=nl; v; x++)
 140                         {
 141                         v2=rp[x];
 142                         v2+=v;
 143                         rp[x]=v2;
 144                         v=((v2&BN_MASK2) < v)?1:0; /* ever true? XXX */
 145                         }
 146                 rp++;
 147                 }
 148         while (r->d[r->top-1] == 0)
 149                 r->top--;
 150
 151         BN_rshift(ret,r,mont->ri);
 152
 153         if (BN_ucmp(ret,mont->N) >= 0)
 154                 {
 155                 bn_qsub(ret,ret,mont->N); /* XXX */
 156                 }
 157         retn=1;
 158 err:
 159         return(retn);
 160         }
 161 #else
 162 int BN_from_montgomery(r,a,mont,ctx)
 163 BIGNUM *r;
 164 BIGNUM *a;
 165 BN_MONT_CTX *mont;
 166 BN_CTX *ctx;
 167         {
 168         BIGNUM *t1,*t2;
 169
 170         t1=ctx->bn[ctx->tos];
 171         t2=ctx->bn[ctx->tos+1];
 172
 173         if (!BN_copy(t1,a)) goto err;
 174         /* can cheat */
 175         BN_mask_bits(t1,mont->ri);
 176
 177         if (!BN_mul(t2,t1,mont->Ni)) goto err;
 178         BN_mask_bits(t2,mont->ri);
 179
 180         if (!BN_mul(t1,t2,mont->N)) goto err;
 181         if (!BN_add(t2,a,t1)) goto err;
 182         BN_rshift(r,t2,mont->ri);
 183
 184         if (BN_ucmp(r,mont->N) >= 0)
 185                 bn_qsub(r,r,mont->N);
 186
 187         return(1);
 188 err:
 189         return(0);
 190         }
 191 #endif
 192
 193 BN_MONT_CTX *BN_MONT_CTX_new()
 194         {
 195         BN_MONT_CTX *ret;
 196
 197         if ((ret=(BN_MONT_CTX *)Malloc(sizeof(BN_MONT_CTX))) == NULL)
 198                 return(NULL);
 199         ret->ri=0;
 200         ret->RR=BN_new();
 201         ret->N=BN_new();
 202         ret->Ni=NULL;
 203         if ((ret->RR == NULL) || (ret->N == NULL))
 204                 {
 205                 BN_MONT_CTX_free(ret);
 206                 return(NULL);
 207                 }
 208         return(ret);
 209         }
 210
 211 void BN_MONT_CTX_free(mont)
 212 BN_MONT_CTX *mont;
 213         {
 214         if (mont->RR != NULL) BN_free(mont->RR);
 215         if (mont->N != NULL) BN_free(mont->N);
 216         if (mont->Ni != NULL) BN_free(mont->Ni);
 217         Free(mont);
 218         }
 219
 220 int BN_MONT_CTX_set(mont,mod,ctx)
 221 BN_MONT_CTX *mont;
 222 BIGNUM *mod;
 223 BN_CTX *ctx;
 224         {
 225         BIGNUM *Ri=NULL,*R=NULL;
 226
 227         if (mont->RR == NULL) mont->RR=BN_new();
 228         if (mont->N == NULL)  mont->N=BN_new();
 229
 230         R=mont->RR;                                     /* grab RR as a temp */
 231         BN_copy(mont->N,mod);                           /* Set N */
 232
 233 #ifdef MONT_WORD
 234 {
 235         BIGNUM tmod;
 236         BN_ULONG buf[2];
 237         /* int z; */
 238
 239         mont->ri=(BN_num_bits(mod)+(BN_BITS2-1))/BN_BITS2*BN_BITS2;
 240         BN_lshift(R,BN_value_one(),BN_BITS2);           /* R */
 241         /* I was bad, this modification of a passed variable was
 242          * breaking the multithreaded stuff :-(
 243          * z=mod->top;
 244          * mod->top=1; */
 245
 246         buf[0]=mod->d[0];
 247         buf[1]=0;
 248         tmod.d=buf;
 249         tmod.top=1;
 250         tmod.max=mod->max;
 251         tmod.neg=mod->neg;
 252
 253         if ((Ri=BN_mod_inverse(R,&tmod,ctx)) == NULL) goto err; /* Ri */
 254         BN_lshift(Ri,Ri,BN_BITS2);                      /* R*Ri */
 255         bn_qsub(Ri,Ri,BN_value_one());                  /* R*Ri - 1 */
 256         BN_div(Ri,NULL,Ri,&tmod,ctx);
 257         mont->n0=Ri->d[0];
 258         BN_free(Ri);
 259         /* mod->top=z; */
 260 }
 261 #else
 262         mont->ri=BN_num_bits(mod);
 263         BN_lshift(R,BN_value_one(),mont->ri);                   /* R */
 264         if ((Ri=BN_mod_inverse(R,mod,ctx)) == NULL) goto err;   /* Ri */
 265         BN_lshift(Ri,Ri,mont->ri);                              /* R*Ri */
 266         bn_qsub(Ri,Ri,BN_value_one());                          /* R*Ri - 1 */
 267         BN_div(Ri,NULL,Ri,mod,ctx);
 268         if (mont->Ni != NULL) BN_free(mont->Ni);
 269         mont->Ni=Ri;                                    /* Ni=(R*Ri-1)/N */
 270 #endif
 271
 272         /* setup RR for conversions */
 273         BN_lshift(mont->RR,BN_value_one(),mont->ri*2);
 274         BN_mod(mont->RR,mont->RR,mont->N,ctx);
 275
 276         return(1);
 277 err:
 278         return(0);
 279         }
 280