/* crypto/bn/bn_lib.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.]

  */

  /*

  © Portions copyright (c) 2006 Nokia Corporation.  All rights reserved.

  */

 #ifndef BN_DEBUG

 # undef NDEBUG /* avoid conflicting definitions */

 # define NDEBUG

 #endif

 #include <assert.h>

 #include <limits.h>

 #include <stdio.h>

 #include "cryptlib.h"

 #include "bn_lcl.h"

 #if (defined(SYMBIAN) && (defined(__WINSCW__) || defined(__WINS__)))

 #include "libcrypto_wsd_macros.h"

 #include "libcrypto_wsd.h"

 #endif

 const char BN_version[]="Big Number" OPENSSL_VERSION_PTEXT;

 /* This stuff appears to be completely unused, so is deprecated */

 #ifndef OPENSSL_NO_DEPRECATED

 /* For a 32 bit machine

  * 2 -   4 ==  128

  * 3 -   8 ==  256

  * 4 -  16 ==  512

  * 5 -  32 == 1024

  * 6 -  64 == 2048

  * 7 - 128 == 4096

  * 8 - 256 == 8192

  */

 static int bn_limit_bits=0;

 static int bn_limit_num=8;        /* (1<<bn_limit_bits) */

 static int bn_limit_bits_low=0;

 static int bn_limit_num_low=8;    /* (1<<bn_limit_bits_low) */

 static int bn_limit_bits_high=0;

 static int bn_limit_num_high=8;   /* (1<<bn_limit_bits_high) */

 static int bn_limit_bits_mont=0;

 static int bn_limit_num_mont=8;   /* (1<<bn_limit_bits_mont) */

 EXPORT_C void BN_set_params(int mult, int high, int low, int mont)

 	{

 	if (mult >= 0)

 		{

 		if (mult > (int)(sizeof(int)*8)-1)

 			mult=sizeof(int)*8-1;

 		bn_limit_bits=mult;

 		bn_limit_num=1<<mult;

 		}

 	if (high >= 0)

 		{

 		if (high > (int)(sizeof(int)*8)-1)

 			high=sizeof(int)*8-1;

 		bn_limit_bits_high=high;

 		bn_limit_num_high=1<<high;

 		}

 	if (low >= 0)

 		{

 		if (low > (int)(sizeof(int)*8)-1)

 			low=sizeof(int)*8-1;

 		bn_limit_bits_low=low;

 		bn_limit_num_low=1<<low;

 		}

 	if (mont >= 0)

 		{

 		if (mont > (int)(sizeof(int)*8)-1)

 			mont=sizeof(int)*8-1;

 		bn_limit_bits_mont=mont;

 		bn_limit_num_mont=1<<mont;

 		}

 	}

 EXPORT_C int BN_get_params(int which)

 	{

 	if      (which == 0) return(bn_limit_bits);

 	else if (which == 1) return(bn_limit_bits_high);

 	else if (which == 2) return(bn_limit_bits_low);

 	else if (which == 3) return(bn_limit_bits_mont);

 	else return(0);

 	}

 #endif

 #ifdef EMULATOR

 GET_STATIC_VAR_FROM_TLS(data_one,bn_lib,BN_ULONG)

 #define data_one (*GET_WSD_VAR_NAME(data_one,bn_lib, s)())

 GET_STATIC_VAR_FROM_TLS(const_one,bn_lib,BIGNUM)

 #define const_one (*GET_WSD_VAR_NAME(const_one,bn_lib, s)())

 #endif

 EXPORT_C const BIGNUM *BN_value_one(void)

 	{

 #ifndef EMULATOR 	

 	static BN_ULONG data_one=1L;

 	static BIGNUM const_one={&data_one,1,1,0,BN_FLG_STATIC_DATA};

 #endif	

 	return(&const_one);

 	}

 #ifdef EMULATOR	

 GET_STATIC_ARRAY_FROM_TLS(data,bn_lib,char)

 #define data (GET_WSD_VAR_NAME(data,bn_lib, s)())

 GET_STATIC_VAR_FROM_TLS(init,bn_lib,int)

 #define init (*GET_WSD_VAR_NAME(init,bn_lib, s)())

 #endif	

 EXPORT_C char *BN_options(void)

 	{

 #ifndef EMULATOR	

 	static int init=0;

 	static char data[16];

 #endif	

 	if (!init)

 		{

 		init++;

 #ifdef BN_LLONG

 		BIO_snprintf(data,sizeof data,"bn(%d,%d)",

 			     (int)sizeof(BN_ULLONG)*8,(int)sizeof(BN_ULONG)*8);

 #else

 		BIO_snprintf(data,sizeof data,"bn(%d,%d)",

 			     (int)sizeof(BN_ULONG)*8,(int)sizeof(BN_ULONG)*8);

 #endif

 		}

 	return((char*)data);

 	}

 EXPORT_C int BN_num_bits_word(BN_ULONG l)

 	{

 	static const char bits[256]={

 		0,1,2,2,3,3,3,3,4,4,4,4,4,4,4,4,

 		5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,

 		6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,

 		6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,

 		7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,

 		7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,

 		7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,

 		7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,

 		8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,

 		8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,

 		8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,

 		8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,

 		8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,

 		8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,

 		8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,

 		8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,

 		};

 #if defined(SIXTY_FOUR_BIT_LONG)

 	if (l & 0xffffffff00000000L)

 		{

 		if (l & 0xffff000000000000L)

 			{

 			if (l & 0xff00000000000000L)

 				{

 				return(bits[(int)(l>>56)]+56);

 				}

 			else	return(bits[(int)(l>>48)]+48);

 			}

 		else

 			{

 			if (l & 0x0000ff0000000000L)

 				{

 				return(bits[(int)(l>>40)]+40);

 				}

 			else	return(bits[(int)(l>>32)]+32);

 			}

 		}

 	else

 #else

 #ifdef SIXTY_FOUR_BIT

 	if (l & 0xffffffff00000000LL)

 		{

 		if (l & 0xffff000000000000LL)

 			{

 			if (l & 0xff00000000000000LL)

 				{

 				return(bits[(int)(l>>56)]+56);

 				}

 			else	return(bits[(int)(l>>48)]+48);

 			}

 		else

 			{

 			if (l & 0x0000ff0000000000LL)

 				{

 				return(bits[(int)(l>>40)]+40);

 				}

 			else	return(bits[(int)(l>>32)]+32);

 			}

 		}

 	else

 #endif

 #endif

 		{

 #if defined(THIRTY_TWO_BIT) || defined(SIXTY_FOUR_BIT) || defined(SIXTY_FOUR_BIT_LONG)

 		if (l & 0xffff0000L)

 			{

 			if (l & 0xff000000L)

 				return(bits[(int)(l>>24L)]+24);

 			else	return(bits[(int)(l>>16L)]+16);

 			}

 		else

 #endif

 			{

 #if defined(SIXTEEN_BIT) || defined(THIRTY_TWO_BIT) || defined(SIXTY_FOUR_BIT) || defined(SIXTY_FOUR_BIT_LONG)

 			if (l & 0xff00L)

 				return(bits[(int)(l>>8)]+8);

 			else	

 #endif

 				return(bits[(int)(l   )]  );

 			}

 		}

 	}

 EXPORT_C int BN_num_bits(const BIGNUM *a)

 	{

 	int i = a->top - 1;

 	bn_check_top(a);

 	if (BN_is_zero(a)) return 0;

 	return ((i*BN_BITS2) + BN_num_bits_word(a->d[i]));

 	}

 EXPORT_C void BN_clear_free(BIGNUM *a)

 	{

 	int i;

 	if (a == NULL) return;

 	bn_check_top(a);

 	if (a->d != NULL)

 		{

 		OPENSSL_cleanse(a->d,a->dmax*sizeof(a->d[0]));

 		if (!(BN_get_flags(a,BN_FLG_STATIC_DATA)))

 			OPENSSL_free(a->d);

 		}

 	i=BN_get_flags(a,BN_FLG_MALLOCED);

 	OPENSSL_cleanse(a,sizeof(BIGNUM));

 	if (i)

 		OPENSSL_free(a);

 	}

 EXPORT_C void BN_free(BIGNUM *a)

 	{

 	if (a == NULL) return;

 	bn_check_top(a);

 	if ((a->d != NULL) && !(BN_get_flags(a,BN_FLG_STATIC_DATA)))

 		OPENSSL_free(a->d);

 	if (a->flags & BN_FLG_MALLOCED)

 		OPENSSL_free(a);

 	else

 		{

 #ifndef OPENSSL_NO_DEPRECATED

 		a->flags|=BN_FLG_FREE;

 #endif

 		a->d = NULL;

 		}

 	}

 EXPORT_C void BN_init(BIGNUM *a)

 	{

 	memset(a,0,sizeof(BIGNUM));

 	bn_check_top(a);

 	}

 EXPORT_C BIGNUM *BN_new(void)

 	{

 	BIGNUM *ret;

 	if ((ret=(BIGNUM *)OPENSSL_malloc(sizeof(BIGNUM))) == NULL)

 		{

 		BNerr(BN_F_BN_NEW,ERR_R_MALLOC_FAILURE);

 		return(NULL);

 		}

 	ret->flags=BN_FLG_MALLOCED;

 	ret->top=0;

 	ret->neg=0;

 	ret->dmax=0;

 	ret->d=NULL;

 	bn_check_top(ret);

 	return(ret);

 	}

 /* This is used both by bn_expand2() and bn_dup_expand() */

 /* The caller MUST check that words > b->dmax before calling this */

 static BN_ULONG *bn_expand_internal(const BIGNUM *b, int words)

 	{

 	BN_ULONG *A,*a = NULL;

 	const BN_ULONG *B;

 	int i;

 	bn_check_top(b);

 	if (words > (INT_MAX/(4*BN_BITS2)))

 		{

 		BNerr(BN_F_BN_EXPAND_INTERNAL,BN_R_BIGNUM_TOO_LONG);

 		return NULL;

 		}

 	if (BN_get_flags(b,BN_FLG_STATIC_DATA))

 		{

 		BNerr(BN_F_BN_EXPAND_INTERNAL,BN_R_EXPAND_ON_STATIC_BIGNUM_DATA);

 		return(NULL);

 		}

 	a=A=(BN_ULONG *)OPENSSL_malloc(sizeof(BN_ULONG)*words);

 	if (A == NULL)

 		{

 		BNerr(BN_F_BN_EXPAND_INTERNAL,ERR_R_MALLOC_FAILURE);

 		return(NULL);

 		}

 #if 1

 	B=b->d;

 	/* Check if the previous number needs to be copied */

 	if (B != NULL)

 		{

 		for (i=b->top>>2; i>0; i--,A+=4,B+=4)

 			{

 			/*

 			 * The fact that the loop is unrolled

 			 * 4-wise is a tribute to Intel. It's

 			 * the one that doesn't have enough

 			 * registers to accomodate more data.

 			 * I'd unroll it 8-wise otherwise:-)

 			 *

 			 *		<appro@fy.chalmers.se>

 			 */

 			BN_ULONG a0,a1,a2,a3;

 			a0=B[0]; a1=B[1]; a2=B[2]; a3=B[3];

 			A[0]=a0; A[1]=a1; A[2]=a2; A[3]=a3;

 			}

 		switch (b->top&3)

 			{

 		case 3:	A[2]=B[2];

 		case 2:	A[1]=B[1];

 		case 1:	A[0]=B[0];

 		case 0: /* workaround for ultrix cc: without 'case 0', the optimizer does

 		         * the switch table by doing a=top&3; a--; goto jump_table[a];

 		         * which fails for top== 0 */

 			;

 			}

 		}

 #else

 	memset(A,0,sizeof(BN_ULONG)*words);

 	memcpy(A,b->d,sizeof(b->d[0])*b->top);

 #endif

 	return(a);

 	}

 /* This is an internal function that can be used instead of bn_expand2()

  * when there is a need to copy BIGNUMs instead of only expanding the

  * data part, while still expanding them.

  * Especially useful when needing to expand BIGNUMs that are declared

  * 'const' and should therefore not be changed.

  * The reason to use this instead of a BN_dup() followed by a bn_expand2()

  * is memory allocation overhead.  A BN_dup() followed by a bn_expand2()

  * will allocate new memory for the BIGNUM data twice, and free it once,

  * while bn_dup_expand() makes sure allocation is made only once.

  */

 #ifndef OPENSSL_NO_DEPRECATED

 EXPORT_C BIGNUM *bn_dup_expand(const BIGNUM *b, int words)

 	{

 	BIGNUM *r = NULL;

 	bn_check_top(b);

 	/* This function does not work if

 	 *      words <= b->dmax && top < words

 	 * because BN_dup() does not preserve 'dmax'!

 	 * (But bn_dup_expand() is not used anywhere yet.)

 	 */

 	if (words > b->dmax)

 		{

 		BN_ULONG *a = bn_expand_internal(b, words);

 		if (a)

 			{

 			r = BN_new();

 			if (r)

 				{

 				r->top = b->top;

 				r->dmax = words;

 				r->neg = b->neg;

 				r->d = a;

 				}

 			else

 				{

 				/* r == NULL, BN_new failure */

 				OPENSSL_free(a);

 				}

 			}

 		/* If a == NULL, there was an error in allocation in

 		   bn_expand_internal(), and NULL should be returned */

 		}

 	else

 		{

 		r = BN_dup(b);

 		}

 	bn_check_top(r);

 	return r;

 	}

 #endif

 /* This is an internal function that should not be used in applications.

  * It ensures that 'b' has enough room for a 'words' word number

  * and initialises any unused part of b->d with leading zeros.

  * It is mostly used by the various BIGNUM routines. If there is an error,

  * NULL is returned. If not, 'b' is returned. */

 EXPORT_C BIGNUM *bn_expand2(BIGNUM *b, int words)

 	{

 	bn_check_top(b);

 	if (words > b->dmax)

 		{

 		BN_ULONG *a = bn_expand_internal(b, words);

 		if(!a) return NULL;

 		if(b->d) OPENSSL_free(b->d);

 		b->d=a;

 		b->dmax=words;

 		}

 /* None of this should be necessary because of what b->top means! */

 #if 0

 	/* NB: bn_wexpand() calls this only if the BIGNUM really has to grow */

 	if (b->top < b->dmax)

 		{

 		int i;

 		BN_ULONG *A = &(b->d[b->top]);

 		for (i=(b->dmax - b->top)>>3; i>0; i--,A+=8)

 			{

 			A[0]=0; A[1]=0; A[2]=0; A[3]=0;

 			A[4]=0; A[5]=0; A[6]=0; A[7]=0;

 			}

 		for (i=(b->dmax - b->top)&7; i>0; i--,A++)

 			A[0]=0;

 		assert(A == &(b->d[b->dmax]));

 		}

 #endif

 	bn_check_top(b);

 	return b;

 	}

 EXPORT_C BIGNUM *BN_dup(const BIGNUM *a)

 	{

 	BIGNUM *t;

 	if (a == NULL) return NULL;

 	bn_check_top(a);

 	t = BN_new();

 	if (t == NULL) return NULL;

 	if(!BN_copy(t, a))

 		{

 		BN_free(t);

 		return NULL;

 		}

 	bn_check_top(t);

 	return t;

 	}

 EXPORT_C BIGNUM *BN_copy(BIGNUM *a, const BIGNUM *b)

 	{

 	int i;

 	BN_ULONG *A;

 	const BN_ULONG *B;

 	bn_check_top(b);

 	if (a == b) return(a);

 	if (bn_wexpand(a,b->top) == NULL) return(NULL);

 #if 1

 	A=a->d;

 	B=b->d;

 	for (i=b->top>>2; i>0; i--,A+=4,B+=4)

 		{

 		BN_ULONG a0,a1,a2,a3;

 		a0=B[0]; a1=B[1]; a2=B[2]; a3=B[3];

 		A[0]=a0; A[1]=a1; A[2]=a2; A[3]=a3;

 		}

 	switch (b->top&3)

 		{

 		case 3: A[2]=B[2];

 		case 2: A[1]=B[1];

 		case 1: A[0]=B[0];

 		case 0: ; /* ultrix cc workaround, see comments in bn_expand_internal */

 		}

 #else

 	memcpy(a->d,b->d,sizeof(b->d[0])*b->top);

 #endif

 	a->top=b->top;

 	a->neg=b->neg;

 	bn_check_top(a);

 	return(a);

 	}

 EXPORT_C void BN_swap(BIGNUM *a, BIGNUM *b)

 	{

 	int flags_old_a, flags_old_b;

 	BN_ULONG *tmp_d;

 	int tmp_top, tmp_dmax, tmp_neg;

 	bn_check_top(a);

 	bn_check_top(b);

 	flags_old_a = a->flags;

 	flags_old_b = b->flags;

 	tmp_d = a->d;

 	tmp_top = a->top;

 	tmp_dmax = a->dmax;

 	tmp_neg = a->neg;

 	a->d = b->d;

 	a->top = b->top;

 	a->dmax = b->dmax;

 	a->neg = b->neg;

 	b->d = tmp_d;

 	b->top = tmp_top;

 	b->dmax = tmp_dmax;

 	b->neg = tmp_neg;

 	a->flags = (flags_old_a & BN_FLG_MALLOCED) | (flags_old_b & BN_FLG_STATIC_DATA);

 	b->flags = (flags_old_b & BN_FLG_MALLOCED) | (flags_old_a & BN_FLG_STATIC_DATA);

 	bn_check_top(a);

 	bn_check_top(b);

 	}

 EXPORT_C void BN_clear(BIGNUM *a)

 	{

 	bn_check_top(a);

 	if (a->d != NULL)

 		memset(a->d,0,a->dmax*sizeof(a->d[0]));

 	a->top=0;

 	a->neg=0;

 	}

 EXPORT_C BN_ULONG BN_get_word(const BIGNUM *a)

 	{

 	if (a->top > 1)

 		return BN_MASK2;

 	else if (a->top == 1)

 		return a->d[0];

 	/* a->top == 0 */

 	return 0;

 	}

 EXPORT_C int BN_set_word(BIGNUM *a, BN_ULONG w)

 	{

 	bn_check_top(a);

 	if (bn_expand(a,(int)sizeof(BN_ULONG)*8) == NULL) return(0);

 	a->neg = 0;

 	a->d[0] = w;

 	a->top = (w ? 1 : 0);

 	bn_check_top(a);

 	return(1);

 	}

 EXPORT_C BIGNUM *BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret)

 	{

 	unsigned int i,m;

 	unsigned int n;

 	BN_ULONG l;

 	BIGNUM  *bn = NULL;

 	if (ret == NULL)

 		ret = bn = BN_new();

 	if (ret == NULL) return(NULL);

 	bn_check_top(ret);

 	l=0;

 	n=len;

 	if (n == 0)

 		{

 		ret->top=0;

 		return(ret);

 		}

 	i=((n-1)/BN_BYTES)+1;

 	m=((n-1)%(BN_BYTES));

 	if (bn_wexpand(ret, (int)i) == NULL)

 		{

 		if (bn) BN_free(bn);

 		return NULL;

 		}

 	ret->top=i;

 	ret->neg=0;

 	while (n--)

 		{

 		l=(l<<8L)| *(s++);

 		if (m-- == 0)

 			{

 			ret->d[--i]=l;

 			l=0;

 			m=BN_BYTES-1;

 			}

 		}

 	/* need to call this due to clear byte at top if avoiding

 	 * having the top bit set (-ve number) */

 	bn_correct_top(ret);

 	return(ret);

 	}

 /* ignore negative */

 EXPORT_C int BN_bn2bin(const BIGNUM *a, unsigned char *to)

 	{

 	int n,i;

 	BN_ULONG l;

 	bn_check_top(a);

 	n=i=BN_num_bytes(a);

 	while (i--)

 		{

 		l=a->d[i/BN_BYTES];

 		*(to++)=(unsigned char)(l>>(8*(i%BN_BYTES)))&0xff;

 		}

 	return(n);

 	}

 EXPORT_C int BN_ucmp(const BIGNUM *a, const BIGNUM *b)

 	{

 	int i;

 	BN_ULONG t1,t2,*ap,*bp;

 	bn_check_top(a);

 	bn_check_top(b);

 	i=a->top-b->top;

 	if (i != 0) return(i);

 	ap=a->d;

 	bp=b->d;

 	for (i=a->top-1; i>=0; i--)

 		{

 		t1= ap[i];

 		t2= bp[i];

 		if (t1 != t2)

 			return((t1 > t2) ? 1 : -1);

 		}

 	return(0);

 	}

 EXPORT_C int BN_cmp(const BIGNUM *a, const BIGNUM *b)

 	{

 	int i;

 	int gt,lt;

 	BN_ULONG t1,t2;

 	if ((a == NULL) || (b == NULL))

 		{

 		if (a != NULL)

 			return(-1);

 		else if (b != NULL)

 			return(1);

 		else

 			return(0);

 		}

 	bn_check_top(a);

 	bn_check_top(b);

 	if (a->neg != b->neg)

 		{

 		if (a->neg)

 			return(-1);

 		else	return(1);

 		}

 	if (a->neg == 0)

 		{ gt=1; lt= -1; }

 	else	{ gt= -1; lt=1; }

 	if (a->top > b->top) return(gt);

 	if (a->top < b->top) return(lt);

 	for (i=a->top-1; i>=0; i--)

 		{

 		t1=a->d[i];

 		t2=b->d[i];

 		if (t1 > t2) return(gt);

 		if (t1 < t2) return(lt);

 		}

 	return(0);

 	}

 EXPORT_C int BN_set_bit(BIGNUM *a, int n)

 	{

 	int i,j,k;

 	if (n < 0)

 		return 0;

 	i=n/BN_BITS2;

 	j=n%BN_BITS2;

 	if (a->top <= i)

 		{

 		if (bn_wexpand(a,i+1) == NULL) return(0);

 		for(k=a->top; k<i+1; k++)

 			a->d[k]=0;

 		a->top=i+1;

 		}

 	a->d[i]|=(((BN_ULONG)1)<<j);

 	bn_check_top(a);

 	return(1);

 	}

 EXPORT_C int BN_clear_bit(BIGNUM *a, int n)

 	{

 	int i,j;

 	bn_check_top(a);

 	if (n < 0) return 0;

 	i=n/BN_BITS2;

 	j=n%BN_BITS2;

 	if (a->top <= i) return(0);

 	a->d[i]&=(~(((BN_ULONG)1)<<j));

 	bn_correct_top(a);

 	return(1);

 	}

 EXPORT_C int BN_is_bit_set(const BIGNUM *a, int n)

 	{

 	int i,j;

 	bn_check_top(a);

 	if (n < 0) return 0;

 	i=n/BN_BITS2;

 	j=n%BN_BITS2;

 	if (a->top <= i) return 0;

 	return(((a->d[i])>>j)&((BN_ULONG)1));

 	}

 EXPORT_C int BN_mask_bits(BIGNUM *a, int n)

 	{

 	int b,w;

 	bn_check_top(a);

 	if (n < 0) return 0;

 	w=n/BN_BITS2;

 	b=n%BN_BITS2;

 	if (w >= a->top) return 0;

 	if (b == 0)

 		a->top=w;

 	else

 		{

 		a->top=w+1;

 		a->d[w]&= ~(BN_MASK2<<b);

 		}

 	bn_correct_top(a);

 	return(1);

 	}

 EXPORT_C void BN_set_negative(BIGNUM *a, int b)

 	{

 	if (b && !BN_is_zero(a))

 		a->neg = 1;

 	else

 		a->neg = 0;

 	}

 EXPORT_C int bn_cmp_words(const BN_ULONG *a, const BN_ULONG *b, int n)

 	{

 	int i;

 	BN_ULONG aa,bb;

 	aa=a[n-1];

 	bb=b[n-1];

 	if (aa != bb) return((aa > bb)?1:-1);

 	for (i=n-2; i>=0; i--)

 		{

 		aa=a[i];

 		bb=b[i];

 		if (aa != bb) return((aa > bb)?1:-1);

 		}

 	return(0);

 	}

 /* Here follows a specialised variants of bn_cmp_words().  It has the

    property of performing the operation on arrays of different sizes.

    The sizes of those arrays is expressed through cl, which is the

    common length ( basicall, min(len(a),len(b)) ), and dl, which is the

    delta between the two lengths, calculated as len(a)-len(b).

    All lengths are the number of BN_ULONGs...  */

 EXPORT_C int bn_cmp_part_words(const BN_ULONG *a, const BN_ULONG *b,

 	int cl, int dl)

 	{

 	int n,i;

 	n = cl-1;

 	if (dl < 0)

 		{

 		for (i=dl; i<0; i++)

 			{

 			if (b[n-i] != 0)

 				return -1; /* a < b */

 			}

 		}

 	if (dl > 0)

 		{

 		for (i=dl; i>0; i--)

 			{

 			if (a[n+i] != 0)

 				return 1; /* a > b */

 			}

 		}

 	return bn_cmp_words(a,b,cl);

 	}