/* 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 <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 *)OPENSSL_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)		OPENSSL_free(recp);	}int BN_RECP_CTX_set(BN_RECP_CTX *recp, const BIGNUM *d, BN_CTX *ctx)	{	if (!BN_copy(&(recp->N),d)) return 0;	if (!BN_zero(&(recp->Nr))) return 0;	recp->num_bits=BN_num_bits(d);	recp->shift=0;	return(1);	}int BN_mod_mul_reciprocal(BIGNUM *r, const BIGNUM *x, const BIGNUM *y,	BN_RECP_CTX *recp, BN_CTX *ctx)	{	int ret=0;	BIGNUM *a;	const BIGNUM *ca;	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; }		ca = a;		}	else		ca=x; /* Just do the mod */	ret = BN_div_recp(NULL,r,ca,recp,ctx);err:	BN_CTX_end(ctx);	return(ret);	}int BN_div_recp(BIGNUM *dv, BIGNUM *rem, const 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)		{		if (!BN_zero(d)) return 0;		if (!BN_copy(r,m)) return 0;		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 := max(BN_num_bits(m), 2*BN_num_bits(N)) */	i=BN_num_bits(m);	j=recp->num_bits<<1;	if (j>i) i=j;	/* Nr := round(2^i / N) */	if (i != recp->shift)		recp->shift=BN_reciprocal(&(recp->Nr),&(recp->N),			i,ctx); /* BN_reciprocal returns i, or -1 for an error */	if (recp->shift == -1) goto err;	/* d := |round(round(m / 2^BN_num_bits(N)) * recp->Nr / 2^(i - BN_num_bits(N)))|	 *    = |round(round(m / 2^BN_num_bits(N)) * round(2^i / N) / 2^(i - BN_num_bits(N)))|	 *   <= |(m / 2^BN_num_bits(N)) * (2^i / N) * (2^BN_num_bits(N) / 2^i)|	 *    = |m/N|	 */	if (!BN_rshift(a,m,recp->num_bits)) goto err;	if (!BN_mul(b,a,&(recp->Nr),ctx)) goto err;	if (!BN_rshift(d,b,i-recp->num_bits)) 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. *//* r := 2^len / m */int BN_reciprocal(BIGNUM *r, const BIGNUM *m, int len, BN_CTX *ctx)	{	int ret= -1;	BIGNUM t;	BN_init(&t);	if (!BN_zero(&t)) goto err;	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);	}