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396 lines
11 KiB
C
396 lines
11 KiB
C
/* crypto/bn/bn_exp.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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/* ====================================================================
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* Copyright (c) 1998-2000 The OpenSSL Project. All rights reserved.
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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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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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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
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* 3. All advertising materials mentioning features or use of this
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* software must display the following acknowledgment:
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* "This product includes software developed by the OpenSSL Project
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* for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
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*
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* 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
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* endorse or promote products derived from this software without
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* prior written permission. For written permission, please contact
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* openssl-core@openssl.org.
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*
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* 5. Products derived from this software may not be called "OpenSSL"
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* nor may "OpenSSL" appear in their names without prior written
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* permission of the OpenSSL Project.
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*
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* 6. Redistributions of any form whatsoever must retain the following
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* acknowledgment:
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* "This product includes software developed by the OpenSSL Project
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* for use in the OpenSSL Toolkit (http://www.openssl.org/)"
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*
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* THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
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* EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
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* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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* ====================================================================
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*
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* This product includes cryptographic software written by Eric Young
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* (eay@cryptsoft.com). This product includes software written by Tim
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* Hudson (tjh@cryptsoft.com).
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*
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*/
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#include <stdio.h>
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#include "bn_lcl.h"
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#define TABLE_SIZE 32
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/* slow but works */
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int BN_mod_mul(BIGNUM *ret, BIGNUM *a, BIGNUM *b, const BIGNUM *m, BN_CTX *ctx)
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{
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BIGNUM *t;
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int r=0;
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bn_check_top(a);
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bn_check_top(b);
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bn_check_top(m);
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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 (a == b)
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{ if (!BN_sqr(t,a,ctx)) goto err; }
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else
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{ if (!BN_mul(t,a,b,ctx)) goto err; }
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if (!BN_mod(ret,t,m,ctx)) goto err;
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r=1;
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err:
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BN_CTX_end(ctx);
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return(r);
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}
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int BN_mod_exp(BIGNUM *r, BIGNUM *a, const BIGNUM *p, const BIGNUM *m,
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BN_CTX *ctx)
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{
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int ret;
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bn_check_top(a);
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bn_check_top(p);
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bn_check_top(m);
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#ifdef MONT_MUL_MOD
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/* I have finally been able to take out this pre-condition of
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* the top bit being set. It was caused by an error in BN_div
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* with negatives. There was also another problem when for a^b%m
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* a >= m. eay 07-May-97 */
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/* if ((m->d[m->top-1]&BN_TBIT) && BN_is_odd(m)) */
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if (BN_is_odd(m))
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{
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if (a->top == 1)
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{
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BN_ULONG A = a->d[0];
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ret=BN_mod_exp_mont_word(r,A,p,m,ctx,NULL);
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}
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else
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ret=BN_mod_exp_mont(r,a,p,m,ctx,NULL);
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}
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else
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#endif
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#ifdef RECP_MUL_MOD
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{ ret=BN_mod_exp_recp(r,a,p,m,ctx); }
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#else
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{ ret=BN_mod_exp_simple(r,a,p,m,ctx); }
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#endif
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return(ret);
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}
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#ifdef RECP_MUL_MOD
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int BN_mod_exp_recp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
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const BIGNUM *m, BN_CTX *ctx)
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{
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int i,j,bits,ret=0,wstart,wend,window,wvalue;
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int start=1,ts=0;
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BIGNUM *aa;
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BIGNUM val[TABLE_SIZE];
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BN_RECP_CTX recp;
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bits=BN_num_bits(p);
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if (bits == 0)
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{
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BN_one(r);
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return(1);
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}
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BN_CTX_start(ctx);
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if ((aa = BN_CTX_get(ctx)) == NULL) goto err;
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BN_RECP_CTX_init(&recp);
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if (BN_RECP_CTX_set(&recp,m,ctx) <= 0) goto err;
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BN_init(&(val[0]));
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ts=1;
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if (!BN_mod(&(val[0]),a,m,ctx)) goto err; /* 1 */
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window = BN_window_bits_for_exponent_size(bits);
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if (window > 1)
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{
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if (!BN_mod_mul_reciprocal(aa,&(val[0]),&(val[0]),&recp,ctx))
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goto err; /* 2 */
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j=1<<(window-1);
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for (i=1; i<j; i++)
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{
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BN_init(&val[i]);
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if (!BN_mod_mul_reciprocal(&(val[i]),&(val[i-1]),aa,&recp,ctx))
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goto err;
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}
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ts=i;
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}
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start=1; /* This is used to avoid multiplication etc
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* when there is only the value '1' in the
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* buffer. */
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wvalue=0; /* The 'value' of the window */
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wstart=bits-1; /* The top bit of the window */
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wend=0; /* The bottom bit of the window */
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if (!BN_one(r)) goto err;
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for (;;)
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{
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if (BN_is_bit_set(p,wstart) == 0)
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{
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if (!start)
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if (!BN_mod_mul_reciprocal(r,r,r,&recp,ctx))
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goto err;
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if (wstart == 0) break;
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wstart--;
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continue;
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}
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/* We now have wstart on a 'set' bit, we now need to work out
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* how bit a window to do. To do this we need to scan
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* forward until the last set bit before the end of the
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* window */
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j=wstart;
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wvalue=1;
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wend=0;
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for (i=1; i<window; i++)
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{
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if (wstart-i < 0) break;
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if (BN_is_bit_set(p,wstart-i))
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{
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wvalue<<=(i-wend);
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wvalue|=1;
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wend=i;
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}
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}
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/* wend is the size of the current window */
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j=wend+1;
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/* add the 'bytes above' */
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if (!start)
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for (i=0; i<j; i++)
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{
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if (!BN_mod_mul_reciprocal(r,r,r,&recp,ctx))
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goto err;
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}
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/* wvalue will be an odd number < 2^window */
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if (!BN_mod_mul_reciprocal(r,r,&(val[wvalue>>1]),&recp,ctx))
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goto err;
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/* move the 'window' down further */
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wstart-=wend+1;
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wvalue=0;
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start=0;
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if (wstart < 0) break;
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}
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ret=1;
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err:
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BN_CTX_end(ctx);
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for (i=0; i<ts; i++)
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BN_clear_free(&(val[i]));
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BN_RECP_CTX_free(&recp);
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return(ret);
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}
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#else
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/* The old fallback, simple version :-) */
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int BN_mod_exp_simple(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
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const BIGNUM *m, BN_CTX *ctx)
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{
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int i,j,bits,ret=0,wstart,wend,window,wvalue,ts=0;
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int start=1;
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BIGNUM *d;
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BIGNUM val[TABLE_SIZE];
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bits=BN_num_bits(p);
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if (bits == 0)
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{
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BN_one(r);
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return(1);
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}
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BN_CTX_start(ctx);
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if ((d = BN_CTX_get(ctx)) == NULL) goto err;
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BN_init(&(val[0]));
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ts=1;
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if (!BN_mod(&(val[0]),a,m,ctx)) goto err; /* 1 */
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window = BN_window_bits_for_exponent_size(bits);
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if (window > 1)
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{
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if (!BN_mod_mul(d,&(val[0]),&(val[0]),m,ctx))
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goto err; /* 2 */
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j=1<<(window-1);
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for (i=1; i<j; i++)
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{
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BN_init(&(val[i]));
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if (!BN_mod_mul(&(val[i]),&(val[i-1]),d,m,ctx))
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goto err;
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}
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ts=i;
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}
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start=1; /* This is used to avoid multiplication etc
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* when there is only the value '1' in the
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* buffer. */
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wvalue=0; /* The 'value' of the window */
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wstart=bits-1; /* The top bit of the window */
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wend=0; /* The bottom bit of the window */
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if (!BN_one(r)) goto err;
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for (;;)
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{
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if (BN_is_bit_set(p,wstart) == 0)
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{
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if (!start)
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if (!BN_mod_mul(r,r,r,m,ctx))
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goto err;
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if (wstart == 0) break;
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wstart--;
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continue;
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}
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/* We now have wstart on a 'set' bit, we now need to work out
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* how bit a window to do. To do this we need to scan
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* forward until the last set bit before the end of the
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* window */
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j=wstart;
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wvalue=1;
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wend=0;
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for (i=1; i<window; i++)
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{
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if (wstart-i < 0) break;
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if (BN_is_bit_set(p,wstart-i))
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{
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wvalue<<=(i-wend);
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wvalue|=1;
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wend=i;
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}
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}
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/* wend is the size of the current window */
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j=wend+1;
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/* add the 'bytes above' */
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if (!start)
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for (i=0; i<j; i++)
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{
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if (!BN_mod_mul(r,r,r,m,ctx))
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goto err;
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}
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/* wvalue will be an odd number < 2^window */
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if (!BN_mod_mul(r,r,&(val[wvalue>>1]),m,ctx))
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goto err;
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/* move the 'window' down further */
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wstart-=wend+1;
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wvalue=0;
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start=0;
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if (wstart < 0) break;
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}
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ret=1;
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err:
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BN_CTX_end(ctx);
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for (i=0; i<ts; i++)
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BN_clear_free(&(val[i]));
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return(ret);
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}
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#endif
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