bn_sqr.c revision 59191
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 */ 65int BN_sqr(BIGNUM *r, BIGNUM *a, BN_CTX *ctx) 66 { 67 int max,al; 68 int ret = 0; 69 BIGNUM *tmp,*rr; 70 71#ifdef BN_COUNT 72printf("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 (tmp == NULL) goto err; 87 88 max=(al+al); 89 if (bn_wexpand(rr,max+1) == NULL) goto err; 90 91 r->neg=0; 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(a,k*2) == NULL) goto err; 128 if (bn_wexpand(tmp,k*2) == NULL) goto err; 129 bn_sqr_recursive(rr->d,a->d,al,tmp->d); 130 } 131 else 132 { 133 if (bn_wexpand(tmp,max) == NULL) goto err; 134 bn_sqr_normal(rr->d,a->d,al,tmp->d); 135 } 136 } 137#else 138 if (bn_wexpand(tmp,max) == NULL) goto err; 139 bn_sqr_normal(rr->d,a->d,al,tmp->d); 140#endif 141 } 142 143 rr->top=max; 144 if ((max > 0) && (rr->d[max-1] == 0)) rr->top--; 145 if (rr != r) BN_copy(r,rr); 146 ret = 1; 147 err: 148 BN_CTX_end(ctx); 149 return(ret); 150 } 151 152/* tmp must have 2*n words */ 153void bn_sqr_normal(BN_ULONG *r, BN_ULONG *a, int n, BN_ULONG *tmp) 154 { 155 int i,j,max; 156 BN_ULONG *ap,*rp; 157 158 max=n*2; 159 ap=a; 160 rp=r; 161 rp[0]=rp[max-1]=0; 162 rp++; 163 j=n; 164 165 if (--j > 0) 166 { 167 ap++; 168 rp[j]=bn_mul_words(rp,ap,j,ap[-1]); 169 rp+=2; 170 } 171 172 for (i=n-2; i>0; i--) 173 { 174 j--; 175 ap++; 176 rp[j]=bn_mul_add_words(rp,ap,j,ap[-1]); 177 rp+=2; 178 } 179 180 bn_add_words(r,r,r,max); 181 182 /* There will not be a carry */ 183 184 bn_sqr_words(tmp,a,n); 185 186 bn_add_words(r,r,tmp,max); 187 } 188 189#ifdef BN_RECURSION 190/* r is 2*n words in size, 191 * a and b are both n words in size. 192 * n must be a power of 2. 193 * We multiply and return the result. 194 * t must be 2*n words in size 195 * We calculate 196 * a[0]*b[0] 197 * a[0]*b[0]+a[1]*b[1]+(a[0]-a[1])*(b[1]-b[0]) 198 * a[1]*b[1] 199 */ 200void bn_sqr_recursive(BN_ULONG *r, BN_ULONG *a, int n2, BN_ULONG *t) 201 { 202 int n=n2/2; 203 int zero,c1; 204 BN_ULONG ln,lo,*p; 205 206#ifdef BN_COUNT 207printf(" bn_sqr_recursive %d * %d\n",n2,n2); 208#endif 209 if (n2 == 4) 210 { 211#ifndef BN_SQR_COMBA 212 bn_sqr_normal(r,a,4,t); 213#else 214 bn_sqr_comba4(r,a); 215#endif 216 return; 217 } 218 else if (n2 == 8) 219 { 220#ifndef BN_SQR_COMBA 221 bn_sqr_normal(r,a,8,t); 222#else 223 bn_sqr_comba8(r,a); 224#endif 225 return; 226 } 227 if (n2 < BN_SQR_RECURSIVE_SIZE_NORMAL) 228 { 229 bn_sqr_normal(r,a,n2,t); 230 return; 231 } 232 /* r=(a[0]-a[1])*(a[1]-a[0]) */ 233 c1=bn_cmp_words(a,&(a[n]),n); 234 zero=0; 235 if (c1 > 0) 236 bn_sub_words(t,a,&(a[n]),n); 237 else if (c1 < 0) 238 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 p= &(t[n2*2]); 244 245 if (!zero) 246 bn_sqr_recursive(&(t[n2]),t,n,p); 247 else 248 memset(&(t[n2]),0,n*sizeof(BN_ULONG)); 249 bn_sqr_recursive(r,a,n,p); 250 bn_sqr_recursive(&(r[n2]),&(a[n]),n,p); 251 252 /* t[32] holds (a[0]-a[1])*(a[1]-a[0]), it is negative or zero 253 * r[10] holds (a[0]*b[0]) 254 * r[32] holds (b[1]*b[1]) 255 */ 256 257 c1=(int)(bn_add_words(t,r,&(r[n2]),n2)); 258 259 /* t[32] is negative */ 260 c1-=(int)(bn_sub_words(&(t[n2]),t,&(t[n2]),n2)); 261 262 /* t[32] holds (a[0]-a[1])*(a[1]-a[0])+(a[0]*a[0])+(a[1]*a[1]) 263 * r[10] holds (a[0]*a[0]) 264 * r[32] holds (a[1]*a[1]) 265 * c1 holds the carry bits 266 */ 267 c1+=(int)(bn_add_words(&(r[n]),&(r[n]),&(t[n2]),n2)); 268 if (c1) 269 { 270 p= &(r[n+n2]); 271 lo= *p; 272 ln=(lo+c1)&BN_MASK2; 273 *p=ln; 274 275 /* The overflow will stop before we over write 276 * words we should not overwrite */ 277 if (ln < (BN_ULONG)c1) 278 { 279 do { 280 p++; 281 lo= *p; 282 ln=(lo+1)&BN_MASK2; 283 *p=ln; 284 } while (ln == 0); 285 } 286 } 287 } 288#endif 289