/* crypto/bn/bn_exp2.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.]

 */

/* ====================================================================

 * Copyright (c) 1998-2000 The OpenSSL Project.  All rights reserved.

 *

 * 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 above 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 acknowledgment:

 *    "This product includes software developed by the OpenSSL Project

 *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"

 *

 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to

 *    endorse or promote products derived from this software without

 *    prior written permission. For written permission, please contact

 *    openssl-core@openssl.org.

 *

 * 5. Products derived from this software may not be called "OpenSSL"

 *    nor may "OpenSSL" appear in their names without prior written

 *    permission of the OpenSSL Project.

 *

 * 6. Redistributions of any form whatsoever must retain the following

 *    acknowledgment:

 *    "This product includes software developed by the OpenSSL Project

 *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"

 *

 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY

 * EXPRESSED 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 OpenSSL PROJECT OR

 * ITS 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.

 * ====================================================================

 *

 * This product includes cryptographic software written by Eric Young

 * (eay@cryptsoft.com).  This product includes software written by Tim

 * Hudson (tjh@cryptsoft.com).

 *

 */

#include <stdio.h>

#include "cryptlib.h"

#include "bn_lcl.h"

#define TABLE_SIZE	32

EXPORT_C int BN_mod_exp2_mont(BIGNUM *rr, const BIGNUM *a1, const BIGNUM *p1,

	const BIGNUM *a2, const BIGNUM *p2, const BIGNUM *m,

	BN_CTX *ctx, BN_MONT_CTX *in_mont)

	{

	int i,j,bits,b,bits1,bits2,ret=0,wpos1,wpos2,window1,window2,wvalue1,wvalue2;

	int r_is_one=1;

	BIGNUM *d,*r;

	const BIGNUM *a_mod_m;

	/* Tables of variables obtained from 'ctx' */

	BIGNUM *val1[TABLE_SIZE], *val2[TABLE_SIZE];

	BN_MONT_CTX *mont=NULL;

	bn_check_top(a1);

	bn_check_top(p1);

	bn_check_top(a2);

	bn_check_top(p2);

	bn_check_top(m);

	if (!(m->d[0] & 1))

		{

		BNerr(BN_F_BN_MOD_EXP2_MONT,BN_R_CALLED_WITH_EVEN_MODULUS);

		return(0);

		}

	bits1=BN_num_bits(p1);

	bits2=BN_num_bits(p2);

	if ((bits1 == 0) && (bits2 == 0))

		{

		ret = BN_one(rr);

		return ret;

		}

	bits=(bits1 > bits2)?bits1:bits2;

	BN_CTX_start(ctx);

	d = BN_CTX_get(ctx);

	r = BN_CTX_get(ctx);

	val1[0] = BN_CTX_get(ctx);

	val2[0] = BN_CTX_get(ctx);

	if(!d || !r || !val1[0] || !val2[0]) goto err;

	if (in_mont != NULL)

		mont=in_mont;

	else

		{

		if ((mont=BN_MONT_CTX_new()) == NULL) goto err;

		if (!BN_MONT_CTX_set(mont,m,ctx)) goto err;

		}

	window1 = BN_window_bits_for_exponent_size(bits1);

	window2 = BN_window_bits_for_exponent_size(bits2);

	/*

	 * Build table for a1:   val1[i] := a1^(2*i + 1) mod m  for i = 0 .. 2^(window1-1)

	 */

	if (a1->neg || BN_ucmp(a1,m) >= 0)

		{

		if (!BN_mod(val1[0],a1,m,ctx))

			goto err;

		a_mod_m = val1[0];

		}

	else

		a_mod_m = a1;

	if (BN_is_zero(a_mod_m))

		{

		BN_zero(rr);

		ret = 1;

		goto err;

		}

	if (!BN_to_montgomery(val1[0],a_mod_m,mont,ctx)) goto err;

	if (window1 > 1)

		{

		if (!BN_mod_mul_montgomery(d,val1[0],val1[0],mont,ctx)) goto err;

		j=1<<(window1-1);

		for (i=1; i<j; i++)

			{

			if(((val1[i] = BN_CTX_get(ctx)) == NULL) ||

					!BN_mod_mul_montgomery(val1[i],val1[i-1],

						d,mont,ctx))

				goto err;

			}

		}

	/*

	 * Build table for a2:   val2[i] := a2^(2*i + 1) mod m  for i = 0 .. 2^(window2-1)

	 */

	if (a2->neg || BN_ucmp(a2,m) >= 0)

		{

		if (!BN_mod(val2[0],a2,m,ctx))

			goto err;

		a_mod_m = val2[0];

		}

	else

		a_mod_m = a2;

	if (BN_is_zero(a_mod_m))

		{

		BN_zero(rr);

		ret = 1;

		goto err;

		}

	if (!BN_to_montgomery(val2[0],a_mod_m,mont,ctx)) goto err;

	if (window2 > 1)

		{

		if (!BN_mod_mul_montgomery(d,val2[0],val2[0],mont,ctx)) goto err;

		j=1<<(window2-1);

		for (i=1; i<j; i++)

			{

			if(((val2[i] = BN_CTX_get(ctx)) == NULL) ||

					!BN_mod_mul_montgomery(val2[i],val2[i-1],

						d,mont,ctx))

				goto err;

			}

		}

	/* Now compute the power product, using independent windows. */

	r_is_one=1;

	wvalue1=0;  /* The 'value' of the first window */

	wvalue2=0;  /* The 'value' of the second window */

	wpos1=0;    /* If wvalue1 > 0, the bottom bit of the first window */

	wpos2=0;    /* If wvalue2 > 0, the bottom bit of the second window */

	if (!BN_to_montgomery(r,BN_value_one(),mont,ctx)) goto err;

	for (b=bits-1; b>=0; b--)

		{

		if (!r_is_one)

			{

			if (!BN_mod_mul_montgomery(r,r,r,mont,ctx))

				goto err;

			}

		if (!wvalue1)

			if (BN_is_bit_set(p1, b))

				{

				/* consider bits b-window1+1 .. b for this window */

				i = b-window1+1;

				while (!BN_is_bit_set(p1, i)) /* works for i<0 */

					i++;

				wpos1 = i;

				wvalue1 = 1;

				for (i = b-1; i >= wpos1; i--)

					{

					wvalue1 <<= 1;

					if (BN_is_bit_set(p1, i))

						wvalue1++;

					}

				}

		if (!wvalue2)

			if (BN_is_bit_set(p2, b))

				{

				/* consider bits b-window2+1 .. b for this window */

				i = b-window2+1;

				while (!BN_is_bit_set(p2, i))

					i++;

				wpos2 = i;

				wvalue2 = 1;

				for (i = b-1; i >= wpos2; i--)

					{

					wvalue2 <<= 1;

					if (BN_is_bit_set(p2, i))

						wvalue2++;

					}

				}

		if (wvalue1 && b == wpos1)

			{

			/* wvalue1 is odd and < 2^window1 */

			if (!BN_mod_mul_montgomery(r,r,val1[wvalue1>>1],mont,ctx))

				goto err;

			wvalue1 = 0;

			r_is_one = 0;

			}

		if (wvalue2 && b == wpos2)

			{

			/* wvalue2 is odd and < 2^window2 */

			if (!BN_mod_mul_montgomery(r,r,val2[wvalue2>>1],mont,ctx))

				goto err;

			wvalue2 = 0;

			r_is_one = 0;

			}

		}

	BN_from_montgomery(rr,r,mont,ctx);

	ret=1;

err:

	if ((in_mont == NULL) && (mont != NULL)) BN_MONT_CTX_free(mont);

	BN_CTX_end(ctx);

	bn_check_top(rr);

	return(ret);

	}