/* crypto/bn/bn_sqr.c */
/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
* All rights reserved.
*
* This package is an SSL implementation written
* by Eric Young (eay@cryptsoft.com).
* The implementation was written so as to conform with Netscapes SSL.
*
* This library is free for commercial and non-commercial use as long as
* the following conditions are aheared to. The following conditions
* apply to all code found in this distribution, be it the RC4, RSA,
* lhash, DES, etc., code; not just the SSL code. The SSL documentation
* included with this distribution is covered by the same copyright terms
* except that the holder is Tim Hudson (tjh@cryptsoft.com).
*
* Copyright remains Eric Young's, and as such any Copyright notices in
* the code are not to be removed.
* If this package is used in a product, Eric Young should be given attribution
* as the author of the parts of the library used.
* This can be in the form of a textual message at program startup or
* in documentation (online or textual) provided with the package.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* "This product includes cryptographic software written by
* Eric Young (eay@cryptsoft.com)"
* The word 'cryptographic' can be left out if the rouines from the library
* being used are not cryptographic related :-).
* 4. If you include any Windows specific code (or a derivative thereof) from
* the apps directory (application code) you must include an acknowledgement:
* "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
*
* THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* The licence and distribution terms for any publically available version or
* derivative of this code cannot be changed. i.e. this code cannot simply be
* copied and put under another distribution licence
* [including the GNU Public Licence.]
*/
#include <stdio.h>
#include "cryptlib.h"
#include "bn_lcl.h"
/* r must not be a */
/* I've just gone over this and it is now %20 faster on x86 - eay - 27 Jun 96 */
int BN_sqr(BIGNUM *r, const BIGNUM *a, BN_CTX *ctx)
{
int max,al;
int ret = 0;
BIGNUM *tmp,*rr;
#ifdef BN_COUNT
fprintf(stderr,"BN_sqr %d * %d\n",a->top,a->top);
#endif
bn_check_top(a);
al=a->top;
if (al <= 0)
{
r->top=0;
return 1;
}
BN_CTX_start(ctx);
rr=(a != r) ? r : BN_CTX_get(ctx);
tmp=BN_CTX_get(ctx);
if (!rr || !tmp) goto err;
max = 2 * al; /* Non-zero (from above) */
if (bn_wexpand(rr,max) == NULL) goto err;
if (al == 4)
{
#ifndef BN_SQR_COMBA
BN_ULONG t[8];
bn_sqr_normal(rr->d,a->d,4,t);
#else
bn_sqr_comba4(rr->d,a->d);
#endif
}
else if (al == 8)
{
#ifndef BN_SQR_COMBA
BN_ULONG t[16];
bn_sqr_normal(rr->d,a->d,8,t);
#else
bn_sqr_comba8(rr->d,a->d);
#endif
}
else
{
#if defined(BN_RECURSION)
if (al < BN_SQR_RECURSIVE_SIZE_NORMAL)
{
BN_ULONG t[BN_SQR_RECURSIVE_SIZE_NORMAL*2];
bn_sqr_normal(rr->d,a->d,al,t);
}
else
{
int j,k;
j=BN_num_bits_word((BN_ULONG)al);
j=1<<(j-1);
k=j+j;
if (al == j)
{
if (bn_wexpand(tmp,k*2) == NULL) goto err;
bn_sqr_recursive(rr->d,a->d,al,tmp->d);
}
else
{
if (bn_wexpand(tmp,max) == NULL) goto err;
bn_sqr_normal(rr->d,a->d,al,tmp->d);
}
}
#else
if (bn_wexpand(tmp,max) == NULL) goto err;
bn_sqr_normal(rr->d,a->d,al,tmp->d);
#endif
}
rr->neg=0;
/* If the most-significant half of the top word of 'a' is zero, then
* the square of 'a' will max-1 words. */
if(a->d[al - 1] == (a->d[al - 1] & BN_MASK2l))
rr->top = max - 1;
else
rr->top = max;
if (rr != r) BN_copy(r,rr);
ret = 1;
err:
bn_check_top(rr);
bn_check_top(tmp);
BN_CTX_end(ctx);
return(ret);
}
/* tmp must have 2*n words */
void bn_sqr_normal(BN_ULONG *r, const BN_ULONG *a, int n, BN_ULONG *tmp)
{
int i,j,max;
const BN_ULONG *ap;
BN_ULONG *rp;
max=n*2;
ap=a;
rp=r;
rp[0]=rp[max-1]=0;
rp++;
j=n;
if (--j > 0)
{
ap++;
rp[j]=bn_mul_words(rp,ap,j,ap[-1]);
rp+=2;
}
for (i=n-2; i>0; i--)
{
j--;
ap++;
rp[j]=bn_mul_add_words(rp,ap,j,ap[-1]);
rp+=2;
}
bn_add_words(r,r,r,max);
/* There will not be a carry */
bn_sqr_words(tmp,a,n);
bn_add_words(r,r,tmp,max);
}
#ifdef BN_RECURSION
/* r is 2*n words in size,
* a and b are both n words in size. (There's not actually a 'b' here ...)
* n must be a power of 2.
* We multiply and return the result.
* t must be 2*n words in size
* We calculate
* a[0]*b[0]
* a[0]*b[0]+a[1]*b[1]+(a[0]-a[1])*(b[1]-b[0])
* a[1]*b[1]
*/
void bn_sqr_recursive(BN_ULONG *r, const BN_ULONG *a, int n2, BN_ULONG *t)
{
int n=n2/2;
int zero,c1;
BN_ULONG ln,lo,*p;
#ifdef BN_COUNT
fprintf(stderr," bn_sqr_recursive %d * %d\n",n2,n2);
#endif
if (n2 == 4)
{
#ifndef BN_SQR_COMBA
bn_sqr_normal(r,a,4,t);
#else
bn_sqr_comba4(r,a);
#endif
return;
}
else if (n2 == 8)
{
#ifndef BN_SQR_COMBA
bn_sqr_normal(r,a,8,t);
#else
bn_sqr_comba8(r,a);
#endif
return;
}
if (n2 < BN_SQR_RECURSIVE_SIZE_NORMAL)
{
bn_sqr_normal(r,a,n2,t);
return;
}
/* r=(a[0]-a[1])*(a[1]-a[0]) */
c1=bn_cmp_words(a,&(a[n]),n);
zero=0;
if (c1 > 0)
bn_sub_words(t,a,&(a[n]),n);
else if (c1 < 0)
bn_sub_words(t,&(a[n]),a,n);
else
zero=1;
/* The result will always be negative unless it is zero */
p= &(t[n2*2]);
if (!zero)
bn_sqr_recursive(&(t[n2]),t,n,p);
else
memset(&(t[n2]),0,n2*sizeof(BN_ULONG));
bn_sqr_recursive(r,a,n,p);
bn_sqr_recursive(&(r[n2]),&(a[n]),n,p);
/* t[32] holds (a[0]-a[1])*(a[1]-a[0]), it is negative or zero
* r[10] holds (a[0]*b[0])
* r[32] holds (b[1]*b[1])
*/
c1=(int)(bn_add_words(t,r,&(r[n2]),n2));
/* t[32] is negative */
c1-=(int)(bn_sub_words(&(t[n2]),t,&(t[n2]),n2));
/* t[32] holds (a[0]-a[1])*(a[1]-a[0])+(a[0]*a[0])+(a[1]*a[1])
* r[10] holds (a[0]*a[0])
* r[32] holds (a[1]*a[1])
* c1 holds the carry bits
*/
c1+=(int)(bn_add_words(&(r[n]),&(r[n]),&(t[n2]),n2));
if (c1)
{
p= &(r[n+n2]);
lo= *p;
ln=(lo+c1)&BN_MASK2;
*p=ln;
/* The overflow will stop before we over write
* words we should not overwrite */
if (ln < (BN_ULONG)c1)
{
do {
p++;
lo= *p;
ln=(lo+1)&BN_MASK2;
*p=ln;
} while (ln == 0);
}
}
}
#endif