bn_sqr.c revision 55714
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 BIGNUM *tmp,*rr; 69 70#ifdef BN_COUNT 71printf("BN_sqr %d * %d\n",a->top,a->top); 72#endif 73 bn_check_top(a); 74 tmp= &(ctx->bn[ctx->tos]); 75 rr=(a != r)?r: (&ctx->bn[ctx->tos+1]); 76 77 al=a->top; 78 if (al <= 0) 79 { 80 r->top=0; 81 return(1); 82 } 83 84 max=(al+al); 85 if (bn_wexpand(rr,max+1) == NULL) return(0); 86 87 r->neg=0; 88 if (al == 4) 89 { 90#ifndef BN_SQR_COMBA 91 BN_ULONG t[8]; 92 bn_sqr_normal(rr->d,a->d,4,t); 93#else 94 bn_sqr_comba4(rr->d,a->d); 95#endif 96 } 97 else if (al == 8) 98 { 99#ifndef BN_SQR_COMBA 100 BN_ULONG t[16]; 101 bn_sqr_normal(rr->d,a->d,8,t); 102#else 103 bn_sqr_comba8(rr->d,a->d); 104#endif 105 } 106 else 107 { 108#if defined(BN_RECURSION) 109 if (al < BN_SQR_RECURSIVE_SIZE_NORMAL) 110 { 111 BN_ULONG t[BN_SQR_RECURSIVE_SIZE_NORMAL*2]; 112 bn_sqr_normal(rr->d,a->d,al,t); 113 } 114 else 115 { 116 int j,k; 117 118 j=BN_num_bits_word((BN_ULONG)al); 119 j=1<<(j-1); 120 k=j+j; 121 if (al == j) 122 { 123 if (bn_wexpand(a,k*2) == NULL) return(0); 124 if (bn_wexpand(tmp,k*2) == NULL) return(0); 125 bn_sqr_recursive(rr->d,a->d,al,tmp->d); 126 } 127 else 128 { 129 if (bn_wexpand(tmp,max) == NULL) return(0); 130 bn_sqr_normal(rr->d,a->d,al,tmp->d); 131 } 132 } 133#else 134 if (bn_wexpand(tmp,max) == NULL) return(0); 135 bn_sqr_normal(rr->d,a->d,al,tmp->d); 136#endif 137 } 138 139 rr->top=max; 140 if ((max > 0) && (rr->d[max-1] == 0)) rr->top--; 141 if (rr != r) BN_copy(r,rr); 142 return(1); 143 } 144 145/* tmp must have 2*n words */ 146void bn_sqr_normal(BN_ULONG *r, BN_ULONG *a, int n, BN_ULONG *tmp) 147 { 148 int i,j,max; 149 BN_ULONG *ap,*rp; 150 151 max=n*2; 152 ap=a; 153 rp=r; 154 rp[0]=rp[max-1]=0; 155 rp++; 156 j=n; 157 158 if (--j > 0) 159 { 160 ap++; 161 rp[j]=bn_mul_words(rp,ap,j,ap[-1]); 162 rp+=2; 163 } 164 165 for (i=n-2; i>0; i--) 166 { 167 j--; 168 ap++; 169 rp[j]=bn_mul_add_words(rp,ap,j,ap[-1]); 170 rp+=2; 171 } 172 173 bn_add_words(r,r,r,max); 174 175 /* There will not be a carry */ 176 177 bn_sqr_words(tmp,a,n); 178 179 bn_add_words(r,r,tmp,max); 180 } 181 182#ifdef BN_RECURSION 183/* r is 2*n words in size, 184 * a and b are both n words in size. 185 * n must be a power of 2. 186 * We multiply and return the result. 187 * t must be 2*n words in size 188 * We calulate 189 * a[0]*b[0] 190 * a[0]*b[0]+a[1]*b[1]+(a[0]-a[1])*(b[1]-b[0]) 191 * a[1]*b[1] 192 */ 193void bn_sqr_recursive(BN_ULONG *r, BN_ULONG *a, int n2, BN_ULONG *t) 194 { 195 int n=n2/2; 196 int zero,c1; 197 BN_ULONG ln,lo,*p; 198 199#ifdef BN_COUNT 200printf(" bn_sqr_recursive %d * %d\n",n2,n2); 201#endif 202 if (n2 == 4) 203 { 204#ifndef BN_SQR_COMBA 205 bn_sqr_normal(r,a,4,t); 206#else 207 bn_sqr_comba4(r,a); 208#endif 209 return; 210 } 211 else if (n2 == 8) 212 { 213#ifndef BN_SQR_COMBA 214 bn_sqr_normal(r,a,8,t); 215#else 216 bn_sqr_comba8(r,a); 217#endif 218 return; 219 } 220 if (n2 < BN_SQR_RECURSIVE_SIZE_NORMAL) 221 { 222 bn_sqr_normal(r,a,n2,t); 223 return; 224 } 225 /* r=(a[0]-a[1])*(a[1]-a[0]) */ 226 c1=bn_cmp_words(a,&(a[n]),n); 227 zero=0; 228 if (c1 > 0) 229 bn_sub_words(t,a,&(a[n]),n); 230 else if (c1 < 0) 231 bn_sub_words(t,&(a[n]),a,n); 232 else 233 zero=1; 234 235 /* The result will always be negative unless it is zero */ 236 p= &(t[n2*2]); 237 238 if (!zero) 239 bn_sqr_recursive(&(t[n2]),t,n,p); 240 else 241 memset(&(t[n2]),0,n*sizeof(BN_ULONG)); 242 bn_sqr_recursive(r,a,n,p); 243 bn_sqr_recursive(&(r[n2]),&(a[n]),n,p); 244 245 /* t[32] holds (a[0]-a[1])*(a[1]-a[0]), it is negative or zero 246 * r[10] holds (a[0]*b[0]) 247 * r[32] holds (b[1]*b[1]) 248 */ 249 250 c1=(int)(bn_add_words(t,r,&(r[n2]),n2)); 251 252 /* t[32] is negative */ 253 c1-=(int)(bn_sub_words(&(t[n2]),t,&(t[n2]),n2)); 254 255 /* t[32] holds (a[0]-a[1])*(a[1]-a[0])+(a[0]*a[0])+(a[1]*a[1]) 256 * r[10] holds (a[0]*a[0]) 257 * r[32] holds (a[1]*a[1]) 258 * c1 holds the carry bits 259 */ 260 c1+=(int)(bn_add_words(&(r[n]),&(r[n]),&(t[n2]),n2)); 261 if (c1) 262 { 263 p= &(r[n+n2]); 264 lo= *p; 265 ln=(lo+c1)&BN_MASK2; 266 *p=ln; 267 268 /* The overflow will stop before we over write 269 * words we should not overwrite */ 270 if (ln < (BN_ULONG)c1) 271 { 272 do { 273 p++; 274 lo= *p; 275 ln=(lo+1)&BN_MASK2; 276 *p=ln; 277 } while (ln == 0); 278 } 279 } 280 } 281#endif 282