287 lines
7.5 KiB
C
287 lines
7.5 KiB
C
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/* $OpenBSD: bn_sqr.c,v 1.12 2015/02/09 15:49:22 jsing Exp $ */
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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 <string.h>
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#include "bn_lcl.h"
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/* r must not be a */
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/* I've just gone over this and it is now %20 faster on x86 - eay - 27 Jun 96 */
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int
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BN_sqr(BIGNUM *r, const BIGNUM *a, BN_CTX *ctx)
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{
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int max, al;
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int ret = 0;
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BIGNUM *tmp, *rr;
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#ifdef BN_COUNT
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fprintf(stderr, "BN_sqr %d * %d\n", a->top, a->top);
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#endif
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bn_check_top(a);
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al = a->top;
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if (al <= 0) {
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r->top = 0;
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r->neg = 0;
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return 1;
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}
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BN_CTX_start(ctx);
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rr = (a != r) ? r : BN_CTX_get(ctx);
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tmp = BN_CTX_get(ctx);
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if (rr == NULL || tmp == NULL)
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goto err;
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max = 2 * al; /* Non-zero (from above) */
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if (bn_wexpand(rr, max) == NULL)
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goto err;
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if (al == 4) {
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#ifndef BN_SQR_COMBA
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BN_ULONG t[8];
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bn_sqr_normal(rr->d, a->d, 4, t);
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#else
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bn_sqr_comba4(rr->d, a->d);
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#endif
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} else if (al == 8) {
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#ifndef BN_SQR_COMBA
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BN_ULONG t[16];
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bn_sqr_normal(rr->d, a->d, 8, t);
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#else
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bn_sqr_comba8(rr->d, a->d);
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#endif
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} else {
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#if defined(BN_RECURSION)
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if (al < BN_SQR_RECURSIVE_SIZE_NORMAL) {
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BN_ULONG t[BN_SQR_RECURSIVE_SIZE_NORMAL*2];
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bn_sqr_normal(rr->d, a->d, al, t);
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} else {
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int j, k;
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j = BN_num_bits_word((BN_ULONG)al);
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j = 1 << (j - 1);
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k = j + j;
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if (al == j) {
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if (bn_wexpand(tmp, k * 2) == NULL)
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goto err;
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bn_sqr_recursive(rr->d, a->d, al, tmp->d);
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} else {
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if (bn_wexpand(tmp, max) == NULL)
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goto err;
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bn_sqr_normal(rr->d, a->d, al, tmp->d);
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}
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}
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#else
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if (bn_wexpand(tmp, max) == NULL)
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goto err;
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bn_sqr_normal(rr->d, a->d, al, tmp->d);
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#endif
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}
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rr->neg = 0;
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/* If the most-significant half of the top word of 'a' is zero, then
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* the square of 'a' will max-1 words. */
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if (a->d[al - 1] == (a->d[al - 1] & BN_MASK2l))
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rr->top = max - 1;
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else
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rr->top = max;
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if (rr != r)
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BN_copy(r, rr);
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ret = 1;
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err:
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bn_check_top(rr);
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bn_check_top(tmp);
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BN_CTX_end(ctx);
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return (ret);
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}
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/* tmp must have 2*n words */
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void
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bn_sqr_normal(BN_ULONG *r, const BN_ULONG *a, int n, BN_ULONG *tmp)
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{
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int i, j, max;
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const BN_ULONG *ap;
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BN_ULONG *rp;
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max = n * 2;
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ap = a;
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rp = r;
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rp[0] = rp[max - 1] = 0;
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rp++;
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j = n;
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if (--j > 0) {
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ap++;
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rp[j] = bn_mul_words(rp, ap, j, ap[-1]);
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rp += 2;
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}
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for (i = n - 2; i > 0; i--) {
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j--;
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ap++;
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rp[j] = bn_mul_add_words(rp, ap, j, ap[-1]);
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rp += 2;
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}
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bn_add_words(r, r, r, max);
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/* There will not be a carry */
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bn_sqr_words(tmp, a, n);
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bn_add_words(r, r, tmp, max);
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}
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#ifdef BN_RECURSION
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/* r is 2*n words in size,
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* a and b are both n words in size. (There's not actually a 'b' here ...)
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* n must be a power of 2.
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* We multiply and return the result.
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* t must be 2*n words in size
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* We calculate
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* a[0]*b[0]
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* a[0]*b[0]+a[1]*b[1]+(a[0]-a[1])*(b[1]-b[0])
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* a[1]*b[1]
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*/
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void
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bn_sqr_recursive(BN_ULONG *r, const BN_ULONG *a, int n2, BN_ULONG *t)
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{
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int n = n2 / 2;
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int zero, c1;
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BN_ULONG ln, lo, *p;
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#ifdef BN_COUNT
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fprintf(stderr, " bn_sqr_recursive %d * %d\n", n2, n2);
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#endif
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if (n2 == 4) {
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#ifndef BN_SQR_COMBA
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bn_sqr_normal(r, a, 4, t);
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#else
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bn_sqr_comba4(r, a);
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#endif
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return;
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} else if (n2 == 8) {
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#ifndef BN_SQR_COMBA
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bn_sqr_normal(r, a, 8, t);
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#else
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bn_sqr_comba8(r, a);
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#endif
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return;
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}
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if (n2 < BN_SQR_RECURSIVE_SIZE_NORMAL) {
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bn_sqr_normal(r, a, n2, t);
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return;
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}
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/* r=(a[0]-a[1])*(a[1]-a[0]) */
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c1 = bn_cmp_words(a, &(a[n]), n);
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zero = 0;
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if (c1 > 0)
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bn_sub_words(t, a, &(a[n]), n);
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else if (c1 < 0)
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bn_sub_words(t, &(a[n]), a, n);
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else
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zero = 1;
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/* The result will always be negative unless it is zero */
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p = &(t[n2*2]);
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if (!zero)
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bn_sqr_recursive(&(t[n2]), t, n, p);
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else
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memset(&(t[n2]), 0, n2 * sizeof(BN_ULONG));
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bn_sqr_recursive(r, a, n, p);
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bn_sqr_recursive(&(r[n2]), &(a[n]), n, p);
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/* t[32] holds (a[0]-a[1])*(a[1]-a[0]), it is negative or zero
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* r[10] holds (a[0]*b[0])
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* r[32] holds (b[1]*b[1])
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*/
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c1 = (int)(bn_add_words(t, r, &(r[n2]), n2));
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/* t[32] is negative */
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c1 -= (int)(bn_sub_words(&(t[n2]), t, &(t[n2]), n2));
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/* t[32] holds (a[0]-a[1])*(a[1]-a[0])+(a[0]*a[0])+(a[1]*a[1])
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* r[10] holds (a[0]*a[0])
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* r[32] holds (a[1]*a[1])
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* c1 holds the carry bits
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*/
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c1 += (int)(bn_add_words(&(r[n]), &(r[n]), &(t[n2]), n2));
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if (c1) {
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p = &(r[n + n2]);
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lo= *p;
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ln = (lo + c1) & BN_MASK2;
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*p = ln;
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/* The overflow will stop before we over write
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* words we should not overwrite */
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if (ln < (BN_ULONG)c1) {
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do {
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p++;
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lo= *p;
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ln = (lo + 1) & BN_MASK2;
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*p = ln;
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} while (ln == 0);
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}
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}
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}
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#endif
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