/* 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);

 	}