bn_recp.c revision 40f53fa8d9c6a4fc38c0014495e7a42b08f52481
/* crypto/bn/bn_recp.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 <config.h>
#include "../rename.h"
#include <stdio.h>
#include "cryptlib.h"
#include "bn_lcl.h"
void BN_RECP_CTX_init(BN_RECP_CTX *recp)
{
BN_init(&(recp->N));
BN_init(&(recp->Nr));
recp->num_bits=0;
recp->flags=0;
}
BN_RECP_CTX *BN_RECP_CTX_new(void)
{
BN_RECP_CTX *ret;
if ((ret=(BN_RECP_CTX *)Malloc(sizeof(BN_RECP_CTX))) == NULL)
return(NULL);
BN_RECP_CTX_init(ret);
ret->flags=BN_FLG_MALLOCED;
return(ret);
}
void BN_RECP_CTX_free(BN_RECP_CTX *recp)
{
if(recp == NULL)
return;
BN_free(&(recp->N));
BN_free(&(recp->Nr));
if (recp->flags & BN_FLG_MALLOCED)
Free(recp);
}
int BN_RECP_CTX_set(BN_RECP_CTX *recp, const BIGNUM *d, BN_CTX *ctx)
{
ctx = ctx; /* BEW - quiet the compiler */
BN_copy(&(recp->N),d);
BN_zero(&(recp->Nr));
recp->num_bits=BN_num_bits(d);
recp->shift=0;
return(1);
}
int BN_mod_mul_reciprocal(BIGNUM *r, BIGNUM *x, BIGNUM *y, BN_RECP_CTX *recp,
BN_CTX *ctx)
{
int ret=0;
BIGNUM *a;
BN_CTX_start(ctx);
if ((a = BN_CTX_get(ctx)) == NULL) goto err;
if (y != NULL)
{
if (x == y)
{ if (!BN_sqr(a,x,ctx)) goto err; }
else
{ if (!BN_mul(a,x,y,ctx)) goto err; }
}
else
a=x; /* Just do the mod */
BN_div_recp(NULL,r,a,recp,ctx);
ret=1;
err:
BN_CTX_end(ctx);
return(ret);
}
int BN_div_recp(BIGNUM *dv, BIGNUM *rem, BIGNUM *m, BN_RECP_CTX *recp,
BN_CTX *ctx)
{
int i,j,ret=0;
BIGNUM *a,*b,*d,*r;
BN_CTX_start(ctx);
a=BN_CTX_get(ctx);
b=BN_CTX_get(ctx);
if (dv != NULL)
d=dv;
else
d=BN_CTX_get(ctx);
if (rem != NULL)
r=rem;
else
r=BN_CTX_get(ctx);
if (a == NULL || b == NULL || d == NULL || r == NULL) goto err;
if (BN_ucmp(m,&(recp->N)) < 0)
{
BN_zero(d);
BN_copy(r,m);
BN_CTX_end(ctx);
return(1);
}
/* We want the remainder
* Given input of ABCDEF / ab
* we need multiply ABCDEF by 3 digests of the reciprocal of ab
*
*/
i=BN_num_bits(m);
j=recp->num_bits<<1;
if (j>i) i=j;
j>>=1;
if (i != recp->shift)
recp->shift=BN_reciprocal(&(recp->Nr),&(recp->N),
i,ctx);
if (!BN_rshift(a,m,j)) goto err;
if (!BN_mul(b,a,&(recp->Nr),ctx)) goto err;
if (!BN_rshift(d,b,i-j)) goto err;
d->neg=0;
if (!BN_mul(b,&(recp->N),d,ctx)) goto err;
if (!BN_usub(r,m,b)) goto err;
r->neg=0;
#if 1
j=0;
while (BN_ucmp(r,&(recp->N)) >= 0)
{
if (j++ > 2)
{
BNerr(BN_F_BN_MOD_MUL_RECIPROCAL,BN_R_BAD_RECIPROCAL);
goto err;
}
if (!BN_usub(r,r,&(recp->N))) goto err;
if (!BN_add_word(d,1)) goto err;
}
#endif
r->neg=BN_is_zero(r)?0:m->neg;
d->neg=m->neg^recp->N.neg;
ret=1;
err:
BN_CTX_end(ctx);
return(ret);
}
/* len is the expected size of the result
* We actually calculate with an extra word of precision, so
* we can do faster division if the remainder is not required.
*/
int BN_reciprocal(BIGNUM *r, BIGNUM *m, int len, BN_CTX *ctx)
{
int ret= -1;
BIGNUM t;
BN_init(&t);
BN_zero(&t);
if (!BN_set_bit(&t,len)) goto err;
if (!BN_div(r,NULL,&t,m,ctx)) goto err;
ret=len;
err:
BN_free(&t);
return(ret);
}