Line data Source code
1 : /* crypto/bn/bn_sqr.c */
2 : /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
3 : * All rights reserved.
4 : *
5 : * This package is an SSL implementation written
6 : * by Eric Young (eay@cryptsoft.com).
7 : * The implementation was written so as to conform with Netscapes SSL.
8 : *
9 : * This library is free for commercial and non-commercial use as long as
10 : * the following conditions are aheared to. The following conditions
11 : * apply to all code found in this distribution, be it the RC4, RSA,
12 : * lhash, DES, etc., code; not just the SSL code. The SSL documentation
13 : * included with this distribution is covered by the same copyright terms
14 : * except that the holder is Tim Hudson (tjh@cryptsoft.com).
15 : *
16 : * Copyright remains Eric Young's, and as such any Copyright notices in
17 : * the code are not to be removed.
18 : * If this package is used in a product, Eric Young should be given attribution
19 : * as the author of the parts of the library used.
20 : * This can be in the form of a textual message at program startup or
21 : * in documentation (online or textual) provided with the package.
22 : *
23 : * Redistribution and use in source and binary forms, with or without
24 : * modification, are permitted provided that the following conditions
25 : * are met:
26 : * 1. Redistributions of source code must retain the copyright
27 : * notice, this list of conditions and the following disclaimer.
28 : * 2. Redistributions in binary form must reproduce the above copyright
29 : * notice, this list of conditions and the following disclaimer in the
30 : * documentation and/or other materials provided with the distribution.
31 : * 3. All advertising materials mentioning features or use of this software
32 : * must display the following acknowledgement:
33 : * "This product includes cryptographic software written by
34 : * Eric Young (eay@cryptsoft.com)"
35 : * The word 'cryptographic' can be left out if the rouines from the library
36 : * being used are not cryptographic related :-).
37 : * 4. If you include any Windows specific code (or a derivative thereof) from
38 : * the apps directory (application code) you must include an acknowledgement:
39 : * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
40 : *
41 : * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
42 : * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
43 : * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
44 : * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
45 : * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
46 : * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
47 : * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
48 : * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
49 : * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
50 : * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
51 : * SUCH DAMAGE.
52 : *
53 : * The licence and distribution terms for any publically available version or
54 : * derivative of this code cannot be changed. i.e. this code cannot simply be
55 : * copied and put under another distribution licence
56 : * [including the GNU Public Licence.]
57 : */
58 :
59 : #include <stdio.h>
60 : #include "cryptlib.h"
61 : #include "bn_lcl.h"
62 :
63 : /* r must not be a */
64 : /*
65 : * I've just gone over this and it is now %20 faster on x86 - eay - 27 Jun 96
66 : */
67 3220068 : int BN_sqr(BIGNUM *r, const BIGNUM *a, BN_CTX *ctx)
68 : {
69 : int max, al;
70 : int ret = 0;
71 : BIGNUM *tmp, *rr;
72 :
73 : #ifdef BN_COUNT
74 : fprintf(stderr, "BN_sqr %d * %d\n", a->top, a->top);
75 : #endif
76 : bn_check_top(a);
77 :
78 3220068 : al = a->top;
79 3220068 : if (al <= 0) {
80 0 : r->top = 0;
81 0 : r->neg = 0;
82 0 : return 1;
83 : }
84 :
85 3220068 : BN_CTX_start(ctx);
86 3220068 : rr = (a != r) ? r : BN_CTX_get(ctx);
87 3220068 : tmp = BN_CTX_get(ctx);
88 3220068 : if (!rr || !tmp)
89 : goto err;
90 :
91 3220068 : max = 2 * al; /* Non-zero (from above) */
92 3220068 : if (bn_wexpand(rr, max) == NULL)
93 : goto err;
94 :
95 3220068 : if (al == 4) {
96 : #ifndef BN_SQR_COMBA
97 : BN_ULONG t[8];
98 : bn_sqr_normal(rr->d, a->d, 4, t);
99 : #else
100 2788319 : bn_sqr_comba4(rr->d, a->d);
101 : #endif
102 431749 : } else if (al == 8) {
103 : #ifndef BN_SQR_COMBA
104 : BN_ULONG t[16];
105 : bn_sqr_normal(rr->d, a->d, 8, t);
106 : #else
107 405773 : bn_sqr_comba8(rr->d, a->d);
108 : #endif
109 : } else {
110 : #if defined(BN_RECURSION)
111 25976 : if (al < BN_SQR_RECURSIVE_SIZE_NORMAL) {
112 : BN_ULONG t[BN_SQR_RECURSIVE_SIZE_NORMAL * 2];
113 2352 : bn_sqr_normal(rr->d, a->d, al, t);
114 : } else {
115 : int j, k;
116 :
117 23624 : j = BN_num_bits_word((BN_ULONG)al);
118 23624 : j = 1 << (j - 1);
119 23624 : k = j + j;
120 23624 : if (al == j) {
121 23624 : if (bn_wexpand(tmp, k * 2) == NULL)
122 : goto err;
123 23624 : bn_sqr_recursive(rr->d, a->d, al, tmp->d);
124 : } else {
125 0 : if (bn_wexpand(tmp, max) == NULL)
126 : goto err;
127 0 : bn_sqr_normal(rr->d, a->d, al, tmp->d);
128 : }
129 : }
130 : #else
131 : if (bn_wexpand(tmp, max) == NULL)
132 : goto err;
133 : bn_sqr_normal(rr->d, a->d, al, tmp->d);
134 : #endif
135 : }
136 :
137 3220068 : rr->neg = 0;
138 : /*
139 : * If the most-significant half of the top word of 'a' is zero, then the
140 : * square of 'a' will max-1 words.
141 : */
142 3220068 : if (a->d[al - 1] == (a->d[al - 1] & BN_MASK2l))
143 2352 : rr->top = max - 1;
144 : else
145 3217716 : rr->top = max;
146 3220068 : if (rr != r)
147 0 : BN_copy(r, rr);
148 : ret = 1;
149 : err:
150 : bn_check_top(rr);
151 : bn_check_top(tmp);
152 3220068 : BN_CTX_end(ctx);
153 3220068 : return (ret);
154 : }
155 :
156 : /* tmp must have 2*n words */
157 2352 : void bn_sqr_normal(BN_ULONG *r, const BN_ULONG *a, int n, BN_ULONG *tmp)
158 : {
159 : int i, j, max;
160 : const BN_ULONG *ap;
161 : BN_ULONG *rp;
162 :
163 2352 : max = n * 2;
164 : ap = a;
165 : rp = r;
166 2352 : rp[0] = rp[max - 1] = 0;
167 2352 : rp++;
168 : j = n;
169 :
170 2352 : if (--j > 0) {
171 0 : ap++;
172 0 : rp[j] = bn_mul_words(rp, ap, j, ap[-1]);
173 0 : rp += 2;
174 : }
175 :
176 2352 : for (i = n - 2; i > 0; i--) {
177 0 : j--;
178 0 : ap++;
179 0 : rp[j] = bn_mul_add_words(rp, ap, j, ap[-1]);
180 0 : rp += 2;
181 : }
182 :
183 2352 : bn_add_words(r, r, r, max);
184 :
185 : /* There will not be a carry */
186 :
187 2352 : bn_sqr_words(tmp, a, n);
188 :
189 2352 : bn_add_words(r, r, tmp, max);
190 2352 : }
191 :
192 : #ifdef BN_RECURSION
193 : /*-
194 : * r is 2*n words in size,
195 : * a and b are both n words in size. (There's not actually a 'b' here ...)
196 : * n must be a power of 2.
197 : * We multiply and return the result.
198 : * t must be 2*n words in size
199 : * We calculate
200 : * a[0]*b[0]
201 : * a[0]*b[0]+a[1]*b[1]+(a[0]-a[1])*(b[1]-b[0])
202 : * a[1]*b[1]
203 : */
204 94496 : void bn_sqr_recursive(BN_ULONG *r, const BN_ULONG *a, int n2, BN_ULONG *t)
205 : {
206 94496 : int n = n2 / 2;
207 : int zero, c1;
208 : BN_ULONG ln, lo, *p;
209 :
210 : # ifdef BN_COUNT
211 : fprintf(stderr, " bn_sqr_recursive %d * %d\n", n2, n2);
212 : # endif
213 94496 : if (n2 == 4) {
214 : # ifndef BN_SQR_COMBA
215 : bn_sqr_normal(r, a, 4, t);
216 : # else
217 0 : bn_sqr_comba4(r, a);
218 : # endif
219 0 : return;
220 94496 : } else if (n2 == 8) {
221 : # ifndef BN_SQR_COMBA
222 : bn_sqr_normal(r, a, 8, t);
223 : # else
224 70872 : bn_sqr_comba8(r, a);
225 : # endif
226 70872 : return;
227 : }
228 23624 : if (n2 < BN_SQR_RECURSIVE_SIZE_NORMAL) {
229 0 : bn_sqr_normal(r, a, n2, t);
230 0 : return;
231 : }
232 : /* r=(a[0]-a[1])*(a[1]-a[0]) */
233 23624 : c1 = bn_cmp_words(a, &(a[n]), n);
234 : zero = 0;
235 23624 : if (c1 > 0)
236 13278 : bn_sub_words(t, a, &(a[n]), n);
237 10346 : else if (c1 < 0)
238 10346 : bn_sub_words(t, &(a[n]), a, n);
239 : else
240 : zero = 1;
241 :
242 : /* The result will always be negative unless it is zero */
243 23624 : p = &(t[n2 * 2]);
244 :
245 23624 : if (!zero)
246 23624 : bn_sqr_recursive(&(t[n2]), t, n, p);
247 : else
248 0 : memset(&(t[n2]), 0, n2 * sizeof(BN_ULONG));
249 23624 : bn_sqr_recursive(r, a, n, p);
250 23624 : bn_sqr_recursive(&(r[n2]), &(a[n]), n, p);
251 :
252 : /*-
253 : * t[32] holds (a[0]-a[1])*(a[1]-a[0]), it is negative or zero
254 : * r[10] holds (a[0]*b[0])
255 : * r[32] holds (b[1]*b[1])
256 : */
257 :
258 23624 : c1 = (int)(bn_add_words(t, r, &(r[n2]), n2));
259 :
260 : /* t[32] is negative */
261 23624 : c1 -= (int)(bn_sub_words(&(t[n2]), t, &(t[n2]), n2));
262 :
263 : /*-
264 : * t[32] holds (a[0]-a[1])*(a[1]-a[0])+(a[0]*a[0])+(a[1]*a[1])
265 : * r[10] holds (a[0]*a[0])
266 : * r[32] holds (a[1]*a[1])
267 : * c1 holds the carry bits
268 : */
269 23624 : c1 += (int)(bn_add_words(&(r[n]), &(r[n]), &(t[n2]), n2));
270 23624 : if (c1) {
271 11029 : p = &(r[n + n2]);
272 11029 : lo = *p;
273 11029 : ln = (lo + c1) & BN_MASK2;
274 11029 : *p = ln;
275 :
276 : /*
277 : * The overflow will stop before we over write words we should not
278 : * overwrite
279 : */
280 11029 : if (ln < (BN_ULONG)c1) {
281 : do {
282 0 : p++;
283 0 : lo = *p;
284 0 : ln = (lo + 1) & BN_MASK2;
285 0 : *p = ln;
286 0 : } while (ln == 0);
287 : }
288 : }
289 : }
290 : #endif
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