Alexandre Savard | 1b09e31 | 2012-08-07 20:33:29 -0400 | [diff] [blame] | 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 |