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