250 lines
7.2 KiB
C
250 lines
7.2 KiB
C
/* crypto/bn/bn_word.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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BN_ULONG BN_mod_word(const BIGNUM *a, BN_ULONG w)
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{
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#ifndef BN_LLONG
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BN_ULONG ret = 0;
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#else
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BN_ULLONG ret = 0;
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#endif
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int i;
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if (w == 0)
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return (BN_ULONG)-1;
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#ifndef BN_LLONG
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/*
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* If |w| is too long and we don't have BN_ULLONG then we need to fall
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* back to using BN_div_word
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*/
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if (w > ((BN_ULONG)1 << BN_BITS4)) {
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BIGNUM *tmp = BN_dup(a);
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if (tmp == NULL)
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return (BN_ULONG)-1;
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ret = BN_div_word(tmp, w);
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BN_free(tmp);
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return ret;
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}
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#endif
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bn_check_top(a);
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w &= BN_MASK2;
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for (i = a->top - 1; i >= 0; i--) {
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#ifndef BN_LLONG
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/*
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* We can assume here that | w <= ((BN_ULONG)1 << BN_BITS4) | and so
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* | ret < ((BN_ULONG)1 << BN_BITS4) | and therefore the shifts here are
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* safe and will not overflow
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*/
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ret = ((ret << BN_BITS4) | ((a->d[i] >> BN_BITS4) & BN_MASK2l)) % w;
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ret = ((ret << BN_BITS4) | (a->d[i] & BN_MASK2l)) % w;
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#else
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ret = (BN_ULLONG) (((ret << (BN_ULLONG) BN_BITS2) | a->d[i]) %
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(BN_ULLONG) w);
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#endif
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}
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return ((BN_ULONG)ret);
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}
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BN_ULONG BN_div_word(BIGNUM *a, BN_ULONG w)
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{
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BN_ULONG ret = 0;
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int i, j;
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bn_check_top(a);
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w &= BN_MASK2;
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if (!w)
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/* actually this an error (division by zero) */
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return (BN_ULONG)-1;
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if (a->top == 0)
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return 0;
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/* normalize input (so bn_div_words doesn't complain) */
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j = BN_BITS2 - BN_num_bits_word(w);
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w <<= j;
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if (!BN_lshift(a, a, j))
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return (BN_ULONG)-1;
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for (i = a->top - 1; i >= 0; i--) {
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BN_ULONG l, d;
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l = a->d[i];
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d = bn_div_words(ret, l, w);
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ret = (l - ((d * w) & BN_MASK2)) & BN_MASK2;
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a->d[i] = d;
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}
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if ((a->top > 0) && (a->d[a->top - 1] == 0))
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a->top--;
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ret >>= j;
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bn_check_top(a);
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return (ret);
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}
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int BN_add_word(BIGNUM *a, BN_ULONG w)
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{
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BN_ULONG l;
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int i;
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bn_check_top(a);
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w &= BN_MASK2;
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/* degenerate case: w is zero */
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if (!w)
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return 1;
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/* degenerate case: a is zero */
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if (BN_is_zero(a))
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return BN_set_word(a, w);
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/* handle 'a' when negative */
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if (a->neg) {
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a->neg = 0;
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i = BN_sub_word(a, w);
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if (!BN_is_zero(a))
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a->neg = !(a->neg);
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return (i);
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}
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for (i = 0; w != 0 && i < a->top; i++) {
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a->d[i] = l = (a->d[i] + w) & BN_MASK2;
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w = (w > l) ? 1 : 0;
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}
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if (w && i == a->top) {
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if (bn_wexpand(a, a->top + 1) == NULL)
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return 0;
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a->top++;
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a->d[i] = w;
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}
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bn_check_top(a);
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return (1);
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}
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int BN_sub_word(BIGNUM *a, BN_ULONG w)
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{
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int i;
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bn_check_top(a);
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w &= BN_MASK2;
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/* degenerate case: w is zero */
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if (!w)
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return 1;
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/* degenerate case: a is zero */
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if (BN_is_zero(a)) {
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i = BN_set_word(a, w);
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if (i != 0)
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BN_set_negative(a, 1);
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return i;
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}
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/* handle 'a' when negative */
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if (a->neg) {
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a->neg = 0;
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i = BN_add_word(a, w);
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a->neg = 1;
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return (i);
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}
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if ((a->top == 1) && (a->d[0] < w)) {
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a->d[0] = w - a->d[0];
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a->neg = 1;
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return (1);
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}
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i = 0;
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for (;;) {
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if (a->d[i] >= w) {
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a->d[i] -= w;
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break;
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} else {
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a->d[i] = (a->d[i] - w) & BN_MASK2;
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i++;
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w = 1;
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}
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}
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if ((a->d[i] == 0) && (i == (a->top - 1)))
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a->top--;
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bn_check_top(a);
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return (1);
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}
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int BN_mul_word(BIGNUM *a, BN_ULONG w)
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{
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BN_ULONG ll;
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bn_check_top(a);
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w &= BN_MASK2;
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if (a->top) {
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if (w == 0)
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BN_zero(a);
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else {
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ll = bn_mul_words(a->d, a->d, a->top, w);
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if (ll) {
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if (bn_wexpand(a, a->top + 1) == NULL)
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return (0);
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a->d[a->top++] = ll;
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}
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}
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}
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bn_check_top(a);
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return (1);
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}
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