sl@0: /* crypto/bn/bn_recp.c */
sl@0: /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
sl@0:  * All rights reserved.
sl@0:  *
sl@0:  * This package is an SSL implementation written
sl@0:  * by Eric Young (eay@cryptsoft.com).
sl@0:  * The implementation was written so as to conform with Netscapes SSL.
sl@0:  * 
sl@0:  * This library is free for commercial and non-commercial use as long as
sl@0:  * the following conditions are aheared to.  The following conditions
sl@0:  * apply to all code found in this distribution, be it the RC4, RSA,
sl@0:  * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
sl@0:  * included with this distribution is covered by the same copyright terms
sl@0:  * except that the holder is Tim Hudson (tjh@cryptsoft.com).
sl@0:  * 
sl@0:  * Copyright remains Eric Young's, and as such any Copyright notices in
sl@0:  * the code are not to be removed.
sl@0:  * If this package is used in a product, Eric Young should be given attribution
sl@0:  * as the author of the parts of the library used.
sl@0:  * This can be in the form of a textual message at program startup or
sl@0:  * in documentation (online or textual) provided with the package.
sl@0:  * 
sl@0:  * Redistribution and use in source and binary forms, with or without
sl@0:  * modification, are permitted provided that the following conditions
sl@0:  * are met:
sl@0:  * 1. Redistributions of source code must retain the copyright
sl@0:  *    notice, this list of conditions and the following disclaimer.
sl@0:  * 2. Redistributions in binary form must reproduce the above copyright
sl@0:  *    notice, this list of conditions and the following disclaimer in the
sl@0:  *    documentation and/or other materials provided with the distribution.
sl@0:  * 3. All advertising materials mentioning features or use of this software
sl@0:  *    must display the following acknowledgement:
sl@0:  *    "This product includes cryptographic software written by
sl@0:  *     Eric Young (eay@cryptsoft.com)"
sl@0:  *    The word 'cryptographic' can be left out if the rouines from the library
sl@0:  *    being used are not cryptographic related :-).
sl@0:  * 4. If you include any Windows specific code (or a derivative thereof) from 
sl@0:  *    the apps directory (application code) you must include an acknowledgement:
sl@0:  *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
sl@0:  * 
sl@0:  * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
sl@0:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
sl@0:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
sl@0:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
sl@0:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
sl@0:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
sl@0:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
sl@0:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
sl@0:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
sl@0:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
sl@0:  * SUCH DAMAGE.
sl@0:  * 
sl@0:  * The licence and distribution terms for any publically available version or
sl@0:  * derivative of this code cannot be changed.  i.e. this code cannot simply be
sl@0:  * copied and put under another distribution licence
sl@0:  * [including the GNU Public Licence.]
sl@0:  */
sl@0: 
sl@0: #include <stdio.h>
sl@0: #include "cryptlib.h"
sl@0: #include "bn_lcl.h"
sl@0: 
sl@0: EXPORT_C void BN_RECP_CTX_init(BN_RECP_CTX *recp)
sl@0: 	{
sl@0: 	BN_init(&(recp->N));
sl@0: 	BN_init(&(recp->Nr));
sl@0: 	recp->num_bits=0;
sl@0: 	recp->flags=0;
sl@0: 	}
sl@0: 
sl@0: EXPORT_C BN_RECP_CTX *BN_RECP_CTX_new(void)
sl@0: 	{
sl@0: 	BN_RECP_CTX *ret;
sl@0: 
sl@0: 	if ((ret=(BN_RECP_CTX *)OPENSSL_malloc(sizeof(BN_RECP_CTX))) == NULL)
sl@0: 		return(NULL);
sl@0: 
sl@0: 	BN_RECP_CTX_init(ret);
sl@0: 	ret->flags=BN_FLG_MALLOCED;
sl@0: 	return(ret);
sl@0: 	}
sl@0: 
sl@0: EXPORT_C void BN_RECP_CTX_free(BN_RECP_CTX *recp)
sl@0: 	{
sl@0: 	if(recp == NULL)
sl@0: 	    return;
sl@0: 
sl@0: 	BN_free(&(recp->N));
sl@0: 	BN_free(&(recp->Nr));
sl@0: 	if (recp->flags & BN_FLG_MALLOCED)
sl@0: 		OPENSSL_free(recp);
sl@0: 	}
sl@0: 
sl@0: EXPORT_C int BN_RECP_CTX_set(BN_RECP_CTX *recp, const BIGNUM *d, BN_CTX *ctx)
sl@0: 	{
sl@0: 	if (!BN_copy(&(recp->N),d)) return 0;
sl@0: 	BN_zero(&(recp->Nr));
sl@0: 	recp->num_bits=BN_num_bits(d);
sl@0: 	recp->shift=0;
sl@0: 	return(1);
sl@0: 	}
sl@0: 
sl@0: EXPORT_C int BN_mod_mul_reciprocal(BIGNUM *r, const BIGNUM *x, const BIGNUM *y,
sl@0: 	BN_RECP_CTX *recp, BN_CTX *ctx)
sl@0: 	{
sl@0: 	int ret=0;
sl@0: 	BIGNUM *a;
sl@0: 	const BIGNUM *ca;
sl@0: 
sl@0: 	BN_CTX_start(ctx);
sl@0: 	if ((a = BN_CTX_get(ctx)) == NULL) goto err;
sl@0: 	if (y != NULL)
sl@0: 		{
sl@0: 		if (x == y)
sl@0: 			{ if (!BN_sqr(a,x,ctx)) goto err; }
sl@0: 		else
sl@0: 			{ if (!BN_mul(a,x,y,ctx)) goto err; }
sl@0: 		ca = a;
sl@0: 		}
sl@0: 	else
sl@0: 		ca=x; /* Just do the mod */
sl@0: 
sl@0: 	ret = BN_div_recp(NULL,r,ca,recp,ctx);
sl@0: err:
sl@0: 	BN_CTX_end(ctx);
sl@0: 	bn_check_top(r);
sl@0: 	return(ret);
sl@0: 	}
sl@0: 
sl@0: EXPORT_C int BN_div_recp(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m,
sl@0: 	BN_RECP_CTX *recp, BN_CTX *ctx)
sl@0: 	{
sl@0: 	int i,j,ret=0;
sl@0: 	BIGNUM *a,*b,*d,*r;
sl@0: 
sl@0: 	BN_CTX_start(ctx);
sl@0: 	a=BN_CTX_get(ctx);
sl@0: 	b=BN_CTX_get(ctx);
sl@0: 	if (dv != NULL)
sl@0: 		d=dv;
sl@0: 	else
sl@0: 		d=BN_CTX_get(ctx);
sl@0: 	if (rem != NULL)
sl@0: 		r=rem;
sl@0: 	else
sl@0: 		r=BN_CTX_get(ctx);
sl@0: 	if (a == NULL || b == NULL || d == NULL || r == NULL) goto err;
sl@0: 
sl@0: 	if (BN_ucmp(m,&(recp->N)) < 0)
sl@0: 		{
sl@0: 		BN_zero(d);
sl@0: 		if (!BN_copy(r,m)) return 0;
sl@0: 		BN_CTX_end(ctx);
sl@0: 		return(1);
sl@0: 		}
sl@0: 
sl@0: 	/* We want the remainder
sl@0: 	 * Given input of ABCDEF / ab
sl@0: 	 * we need multiply ABCDEF by 3 digests of the reciprocal of ab
sl@0: 	 *
sl@0: 	 */
sl@0: 
sl@0: 	/* i := max(BN_num_bits(m), 2*BN_num_bits(N)) */
sl@0: 	i=BN_num_bits(m);
sl@0: 	j=recp->num_bits<<1;
sl@0: 	if (j>i) i=j;
sl@0: 
sl@0: 	/* Nr := round(2^i / N) */
sl@0: 	if (i != recp->shift)
sl@0: 		recp->shift=BN_reciprocal(&(recp->Nr),&(recp->N),
sl@0: 			i,ctx); /* BN_reciprocal returns i, or -1 for an error */
sl@0: 	if (recp->shift == -1) goto err;
sl@0: 
sl@0: 	/* d := |round(round(m / 2^BN_num_bits(N)) * recp->Nr / 2^(i - BN_num_bits(N)))|
sl@0: 	 *    = |round(round(m / 2^BN_num_bits(N)) * round(2^i / N) / 2^(i - BN_num_bits(N)))|
sl@0: 	 *   <= |(m / 2^BN_num_bits(N)) * (2^i / N) * (2^BN_num_bits(N) / 2^i)|
sl@0: 	 *    = |m/N|
sl@0: 	 */
sl@0: 	if (!BN_rshift(a,m,recp->num_bits)) goto err;
sl@0: 	if (!BN_mul(b,a,&(recp->Nr),ctx)) goto err;
sl@0: 	if (!BN_rshift(d,b,i-recp->num_bits)) goto err;
sl@0: 	d->neg=0;
sl@0: 
sl@0: 	if (!BN_mul(b,&(recp->N),d,ctx)) goto err;
sl@0: 	if (!BN_usub(r,m,b)) goto err;
sl@0: 	r->neg=0;
sl@0: 
sl@0: #if 1
sl@0: 	j=0;
sl@0: 	while (BN_ucmp(r,&(recp->N)) >= 0)
sl@0: 		{
sl@0: 		if (j++ > 2)
sl@0: 			{
sl@0: 			BNerr(BN_F_BN_DIV_RECP,BN_R_BAD_RECIPROCAL);
sl@0: 			goto err;
sl@0: 			}
sl@0: 		if (!BN_usub(r,r,&(recp->N))) goto err;
sl@0: 		if (!BN_add_word(d,1)) goto err;
sl@0: 		}
sl@0: #endif
sl@0: 
sl@0: 	r->neg=BN_is_zero(r)?0:m->neg;
sl@0: 	d->neg=m->neg^recp->N.neg;
sl@0: 	ret=1;
sl@0: err:
sl@0: 	BN_CTX_end(ctx);
sl@0: 	bn_check_top(dv);
sl@0: 	bn_check_top(rem);
sl@0: 	return(ret);
sl@0: 	} 
sl@0: 
sl@0: /* len is the expected size of the result
sl@0:  * We actually calculate with an extra word of precision, so
sl@0:  * we can do faster division if the remainder is not required.
sl@0:  */
sl@0: /* r := 2^len / m */
sl@0: EXPORT_C int BN_reciprocal(BIGNUM *r, const BIGNUM *m, int len, BN_CTX *ctx)
sl@0: 	{
sl@0: 	int ret= -1;
sl@0: 	BIGNUM *t;
sl@0: 
sl@0: 	BN_CTX_start(ctx);
sl@0: 	if((t = BN_CTX_get(ctx)) == NULL) goto err;
sl@0: 
sl@0: 	if (!BN_set_bit(t,len)) goto err;
sl@0: 
sl@0: 	if (!BN_div(r,NULL,t,m,ctx)) goto err;
sl@0: 
sl@0: 	ret=len;
sl@0: err:
sl@0: 	bn_check_top(r);
sl@0: 	BN_CTX_end(ctx);
sl@0: 	return(ret);
sl@0: 	}