bn_sqr.c revision 312826
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/* 65 * I've just gone over this and it is now %20 faster on x86 - eay - 27 Jun 96 66 */ 67int BN_sqr(BIGNUM *r, const BIGNUM *a, BN_CTX *ctx) 68{ 69 int max, al; 70 int ret = 0; 71 BIGNUM *tmp, *rr; 72 73#ifdef BN_COUNT 74 fprintf(stderr, "BN_sqr %d * %d\n", a->top, a->top); 75#endif 76 bn_check_top(a); 77 78 al = a->top; 79 if (al <= 0) { 80 r->top = 0; 81 r->neg = 0; 82 return 1; 83 } 84 85 BN_CTX_start(ctx); 86 rr = (a != r) ? r : BN_CTX_get(ctx); 87 tmp = BN_CTX_get(ctx); 88 if (!rr || !tmp) 89 goto err; 90 91 max = 2 * al; /* Non-zero (from above) */ 92 if (bn_wexpand(rr, max) == NULL) 93 goto err; 94 95 if (al == 4) { 96#ifndef BN_SQR_COMBA 97 BN_ULONG t[8]; 98 bn_sqr_normal(rr->d, a->d, 4, t); 99#else 100 bn_sqr_comba4(rr->d, a->d); 101#endif 102 } else if (al == 8) { 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 } else { 110#if defined(BN_RECURSION) 111 if (al < BN_SQR_RECURSIVE_SIZE_NORMAL) { 112 BN_ULONG t[BN_SQR_RECURSIVE_SIZE_NORMAL * 2]; 113 bn_sqr_normal(rr->d, a->d, al, t); 114 } else { 115 int j, k; 116 117 j = BN_num_bits_word((BN_ULONG)al); 118 j = 1 << (j - 1); 119 k = j + j; 120 if (al == j) { 121 if (bn_wexpand(tmp, k * 2) == NULL) 122 goto err; 123 bn_sqr_recursive(rr->d, a->d, al, tmp->d); 124 } else { 125 if (bn_wexpand(tmp, max) == NULL) 126 goto err; 127 bn_sqr_normal(rr->d, a->d, al, tmp->d); 128 } 129 } 130#else 131 if (bn_wexpand(tmp, max) == NULL) 132 goto err; 133 bn_sqr_normal(rr->d, a->d, al, tmp->d); 134#endif 135 } 136 137 rr->neg = 0; 138 /* 139 * If the most-significant half of the top word of 'a' is zero, then the 140 * square of 'a' will max-1 words. 141 */ 142 if (a->d[al - 1] == (a->d[al - 1] & BN_MASK2l)) 143 rr->top = max - 1; 144 else 145 rr->top = max; 146 if (r != rr && BN_copy(r, rr) == NULL) 147 goto err; 148 149 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 */ 158void 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 ap++; 173 rp[j] = bn_mul_words(rp, ap, j, ap[-1]); 174 rp += 2; 175 } 176 177 for (i = n - 2; i > 0; i--) { 178 j--; 179 ap++; 180 rp[j] = bn_mul_add_words(rp, ap, j, ap[-1]); 181 rp += 2; 182 } 183 184 bn_add_words(r, r, r, max); 185 186 /* There will not be a carry */ 187 188 bn_sqr_words(tmp, a, n); 189 190 bn_add_words(r, r, tmp, max); 191} 192 193#ifdef BN_RECURSION 194/*- 195 * r is 2*n words in size, 196 * a and b are both n words in size. (There's not actually a 'b' here ...) 197 * n must be a power of 2. 198 * We multiply and return the result. 199 * t must be 2*n words in size 200 * We calculate 201 * a[0]*b[0] 202 * a[0]*b[0]+a[1]*b[1]+(a[0]-a[1])*(b[1]-b[0]) 203 * a[1]*b[1] 204 */ 205void bn_sqr_recursive(BN_ULONG *r, const BN_ULONG *a, int n2, BN_ULONG *t) 206{ 207 int n = n2 / 2; 208 int zero, c1; 209 BN_ULONG ln, lo, *p; 210 211# ifdef BN_COUNT 212 fprintf(stderr, " bn_sqr_recursive %d * %d\n", n2, n2); 213# endif 214 if (n2 == 4) { 215# ifndef BN_SQR_COMBA 216 bn_sqr_normal(r, a, 4, t); 217# else 218 bn_sqr_comba4(r, a); 219# endif 220 return; 221 } else if (n2 == 8) { 222# ifndef BN_SQR_COMBA 223 bn_sqr_normal(r, a, 8, t); 224# else 225 bn_sqr_comba8(r, a); 226# endif 227 return; 228 } 229 if (n2 < BN_SQR_RECURSIVE_SIZE_NORMAL) { 230 bn_sqr_normal(r, a, n2, t); 231 return; 232 } 233 /* r=(a[0]-a[1])*(a[1]-a[0]) */ 234 c1 = bn_cmp_words(a, &(a[n]), n); 235 zero = 0; 236 if (c1 > 0) 237 bn_sub_words(t, a, &(a[n]), n); 238 else if (c1 < 0) 239 bn_sub_words(t, &(a[n]), a, n); 240 else 241 zero = 1; 242 243 /* The result will always be negative unless it is zero */ 244 p = &(t[n2 * 2]); 245 246 if (!zero) 247 bn_sqr_recursive(&(t[n2]), t, n, p); 248 else 249 memset(&(t[n2]), 0, n2 * sizeof(BN_ULONG)); 250 bn_sqr_recursive(r, a, n, p); 251 bn_sqr_recursive(&(r[n2]), &(a[n]), n, p); 252 253 /*- 254 * t[32] holds (a[0]-a[1])*(a[1]-a[0]), it is negative or zero 255 * r[10] holds (a[0]*b[0]) 256 * r[32] holds (b[1]*b[1]) 257 */ 258 259 c1 = (int)(bn_add_words(t, r, &(r[n2]), n2)); 260 261 /* t[32] is negative */ 262 c1 -= (int)(bn_sub_words(&(t[n2]), t, &(t[n2]), n2)); 263 264 /*- 265 * t[32] holds (a[0]-a[1])*(a[1]-a[0])+(a[0]*a[0])+(a[1]*a[1]) 266 * r[10] holds (a[0]*a[0]) 267 * r[32] holds (a[1]*a[1]) 268 * c1 holds the carry bits 269 */ 270 c1 += (int)(bn_add_words(&(r[n]), &(r[n]), &(t[n2]), n2)); 271 if (c1) { 272 p = &(r[n + n2]); 273 lo = *p; 274 ln = (lo + c1) & BN_MASK2; 275 *p = ln; 276 277 /* 278 * The overflow will stop before we over write words we should not 279 * overwrite 280 */ 281 if (ln < (BN_ULONG)c1) { 282 do { 283 p++; 284 lo = *p; 285 ln = (lo + 1) & BN_MASK2; 286 *p = ln; 287 } while (ln == 0); 288 } 289 } 290} 291#endif 292