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 /* I've just gone over this and it is now %20 faster on x86 - eay - 27 Jun 96 */
65 int BN_sqr(BIGNUM *r, const BIGNUM *a, BN_CTX *ctx)
66 {
67 int max,al;
68 int ret = 0;
69 BIGNUM *tmp,*rr;
70
71 #ifdef BN_COUNT
72 fprintf(stderr,"BN_sqr %d * %d\n",a->top,a->top);
73 #endif
74 bn_check_top(a);
75
76 al=a->top;
77 if (al <= 0)
78 {
79 r->top=0;
80 r->neg = 0;
81 return 1;
82 }
83
84 BN_CTX_start(ctx);
85 rr=(a != r) ? r : BN_CTX_get(ctx);
86 tmp=BN_CTX_get(ctx);
87 if (!rr || !tmp) goto err;
88
89 max = 2 * al; /* Non-zero (from above) */
90 if (bn_wexpand(rr,max) == NULL) goto err;
91
92 if (al == 4)
93 {
94 #ifndef BN_SQR_COMBA
95 BN_ULONG t[8];
96 bn_sqr_normal(rr->d,a->d,4,t);
97 #else
98 bn_sqr_comba4(rr->d,a->d);
99 #endif
100 }
101 else if (al == 8)
102 {
103 #ifndef BN_SQR_COMBA
104 BN_ULONG t[16];
105 bn_sqr_normal(rr->d,a->d,8,t);
106 #else
107 bn_sqr_comba8(rr->d,a->d);
108 #endif
109 }
110 else
111 {
112 #if defined(BN_RECURSION)
113 if (al < BN_SQR_RECURSIVE_SIZE_NORMAL)
114 {
115 BN_ULONG t[BN_SQR_RECURSIVE_SIZE_NORMAL*2];
116 bn_sqr_normal(rr->d,a->d,al,t);
117 }
118 else
119 {
120 int j,k;
121
122 j=BN_num_bits_word((BN_ULONG)al);
123 j=1<<(j-1);
124 k=j+j;
125 if (al == j)
126 {
127 if (bn_wexpand(tmp,k*2) == NULL) goto err;
128 bn_sqr_recursive(rr->d,a->d,al,tmp->d);
129 }
130 else
131 {
132 if (bn_wexpand(tmp,max) == NULL) goto err;
133 bn_sqr_normal(rr->d,a->d,al,tmp->d);
134 }
135 }
136 #else
137 if (bn_wexpand(tmp,max) == NULL) goto err;
138 bn_sqr_normal(rr->d,a->d,al,tmp->d);
139 #endif
140 }
141
142 rr->neg=0;
143 /* If the most-significant half of the top word of 'a' is zero, then
144 * the square of 'a' will max-1 words. */
145 if(a->d[al - 1] == (a->d[al - 1] & BN_MASK2l))
146 rr->top = max - 1;
147 else
148 rr->top = max;
149 if (rr != r) BN_copy(r,rr);
150 ret = 1;
151 err:
152 bn_check_top(rr);
153 bn_check_top(tmp);
154 BN_CTX_end(ctx);
155 return(ret);
156 }
157
158 /* tmp must have 2*n words */
159 void bn_sqr_normal(BN_ULONG *r, const BN_ULONG *a, int n, BN_ULONG *tmp)
160 {
161 int i,j,max;
162 const BN_ULONG *ap;
163 BN_ULONG *rp;
164
165 max=n*2;
166 ap=a;
167 rp=r;
168 rp[0]=rp[max-1]=0;
169 rp++;
170 j=n;
171
172 if (--j > 0)
173 {
174 ap++;
175 rp[j]=bn_mul_words(rp,ap,j,ap[-1]);
176 rp+=2;
177 }
178
179 for (i=n-2; i>0; i--)
180 {
181 j--;
182 ap++;
183 rp[j]=bn_mul_add_words(rp,ap,j,ap[-1]);
184 rp+=2;
185 }
186
187 bn_add_words(r,r,r,max);
188
189 /* There will not be a carry */
190
191 bn_sqr_words(tmp,a,n);
192
193 bn_add_words(r,r,tmp,max);
194 }
195
196 #ifdef BN_RECURSION
197 /* r is 2*n words in size,
198 * a and b are both n words in size. (There's not actually a 'b' here ...)
199 * n must be a power of 2.
200 * We multiply and return the result.
201 * t must be 2*n words in size
202 * We calculate
203 * a[0]*b[0]
204 * a[0]*b[0]+a[1]*b[1]+(a[0]-a[1])*(b[1]-b[0])
205 * a[1]*b[1]
206 */
207 void bn_sqr_recursive(BN_ULONG *r, const BN_ULONG *a, int n2, BN_ULONG *t)
208 {
209 int n=n2/2;
210 int zero,c1;
211 BN_ULONG ln,lo,*p;
212
213 #ifdef BN_COUNT
214 fprintf(stderr," bn_sqr_recursive %d * %d\n",n2,n2);
215 #endif
216 if (n2 == 4)
217 {
218 #ifndef BN_SQR_COMBA
219 bn_sqr_normal(r,a,4,t);
220 #else
221 bn_sqr_comba4(r,a);
222 #endif
223 return;
224 }
225 else if (n2 == 8)
226 {
227 #ifndef BN_SQR_COMBA
228 bn_sqr_normal(r,a,8,t);
229 #else
230 bn_sqr_comba8(r,a);
231 #endif
232 return;
233 }
234 if (n2 < BN_SQR_RECURSIVE_SIZE_NORMAL)
235 {
236 bn_sqr_normal(r,a,n2,t);
237 return;
238 }
239 /* r=(a[0]-a[1])*(a[1]-a[0]) */
240 c1=bn_cmp_words(a,&(a[n]),n);
241 zero=0;
242 if (c1 > 0)
243 bn_sub_words(t,a,&(a[n]),n);
244 else if (c1 < 0)
245 bn_sub_words(t,&(a[n]),a,n);
246 else
247 zero=1;
248
249 /* The result will always be negative unless it is zero */
250 p= &(t[n2*2]);
251
252 if (!zero)
253 bn_sqr_recursive(&(t[n2]),t,n,p);
254 else
255 memset(&(t[n2]),0,n2*sizeof(BN_ULONG));
256 bn_sqr_recursive(r,a,n,p);
257 bn_sqr_recursive(&(r[n2]),&(a[n]),n,p);
258
259 /* t[32] holds (a[0]-a[1])*(a[1]-a[0]), it is negative or zero
260 * r[10] holds (a[0]*b[0])
261 * r[32] holds (b[1]*b[1])
262 */
263
264 c1=(int)(bn_add_words(t,r,&(r[n2]),n2));
265
266 /* t[32] is negative */
267 c1-=(int)(bn_sub_words(&(t[n2]),t,&(t[n2]),n2));
268
269 /* t[32] holds (a[0]-a[1])*(a[1]-a[0])+(a[0]*a[0])+(a[1]*a[1])
270 * r[10] holds (a[0]*a[0])
271 * r[32] holds (a[1]*a[1])
272 * c1 holds the carry bits
273 */
274 c1+=(int)(bn_add_words(&(r[n]),&(r[n]),&(t[n2]),n2));
275 if (c1)
276 {
277 p= &(r[n+n2]);
278 lo= *p;
279 ln=(lo+c1)&BN_MASK2;
280 *p=ln;
281
282 /* The overflow will stop before we over write
283 * words we should not overwrite */
284 if (ln < (BN_ULONG)c1)
285 {
286 do {
287 p++;
288 lo= *p;
289 ln=(lo+1)&BN_MASK2;
290 *p=ln;
291 } while (ln == 0);
292 }
293 }
294 }
295 #endif