1 /* crypto/bn/bn_sqr.c */ 2 /* Copyright (C) 1995-1998 Eric Young (eay (at) cryptsoft.com) 3 * All rights reserved. 4 * 5 * This package is an SSL implementation written 6 * by Eric Young (eay (at) 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 (at) 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 (at) 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 (at) 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 296
