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