crypto/bn/bn_sqr.c

   1 /* crypto/bn/bn_sqr.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 /* 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(r, a, ctx)
  66 BIGNUM *r;
  67 BIGNUM *a;
  68 BN_CTX *ctx;
  69         {
  70         int i,j,max,al;
  71         BIGNUM *tmp;
  72         BN_ULONG *ap,*rp,c;
  73
  74         tmp=ctx->bn[ctx->tos];
  75
  76         al=a->top;
  77         if (al == 0)
  78                 {
  79                 r->top=0;
  80                 return(1);
  81                 }
  82
  83         max=(al*2);
  84         if (bn_expand(r,max*BN_BITS2) == NULL) return(0);
  85         if (bn_expand(tmp,max*BN_BITS2) == NULL) return(0);
  86
  87         r->neg=0;
  88
  89         ap=a->d;
  90         rp=r->d;
  91         rp[0]=rp[max-1]=0;
  92         rp++;
  93         j=al;
  94
  95         if (--j > 0)
  96                 {
  97                 ap++;
  98                 rp[j]=bn_mul_word(rp,ap,j,ap[-1]);
  99                 rp+=2;
 100                 }
 101
 102         for (i=2; i<al; i++)
 103                 {
 104                 j--;
 105                 ap++;
 106                 rp[j]=bn_mul_add_word(rp,ap,j,ap[-1]);
 107                 rp+=2;
 108                 }
 109
 110         /* inlined shift, 2 words at once */
 111         j=max;
 112         rp=r->d;
 113         c=0;
 114         for (i=0; i<j; i++)
 115                 {
 116                 BN_ULONG t;
 117
 118                 t= *rp;
 119                 *(rp++)=((t<<1)|c)&BN_MASK2;
 120                 c=(t & BN_TBIT)?1:0;
 121
 122 #if 0
 123                 t= *rp;
 124                 *(rp++)=((t<<1)|c)&BN_MASK2;
 125                 c=(t & BN_TBIT)?1:0;
 126 #endif
 127                 }
 128         /* there will not be a carry */
 129
 130         bn_sqr_words(tmp->d,a->d,al);
 131
 132         /* inlined add */
 133         ap=tmp->d;
 134         rp=r->d;
 135         c=0;
 136         j=max;
 137         for (i=0; i<j; i++)
 138                 {
 139                 BN_ULONG t1,t2;
 140
 141                 t1= *(ap++);
 142                 t2= *rp;
 143                 if (c)
 144                         {
 145                         c=(t2 >= ((~t1)&BN_MASK2));
 146                         t2=(t1+t2+1)&BN_MASK2;
 147                         }
 148                 else
 149                         {
 150                         t2=(t1+t2)&BN_MASK2;
 151                         c=(t2<t1);
 152                         }
 153                 *(rp++)=t2;
 154                 }
 155         /* there will be no carry */
 156
 157         r->top=max;
 158         if (r->d[max-1] == 0) r->top--;
 159         return(1);
 160         }
 161