| 1 | /* crypto/bn/bn_add.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 "bn_lcl.h" |
| 61 | |
| 62 | /* r can == a or b */ |
| 63 | int BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) |
| 64 | { |
| 65 | const BIGNUM *tmp; |
| 66 | |
| 67 | bn_check_top(a); |
| 68 | bn_check_top(b); |
| 69 | |
| 70 | /* a + b a+b |
| 71 | * a + -b a-b |
| 72 | * -a + b b-a |
| 73 | * -a + -b -(a+b) |
| 74 | */ |
| 75 | if (a->neg ^ b->neg) |
| 76 | { |
| 77 | /* only one is negative */ |
| 78 | if (a->neg) |
| 79 | { tmp=a; a=b; b=tmp; } |
| 80 | |
| 81 | /* we are now a - b */ |
| 82 | |
| 83 | if (BN_ucmp(a,b) < 0) |
| 84 | { |
| 85 | if (!BN_usub(r,b,a)) return(0); |
| 86 | r->neg=1; |
| 87 | } |
| 88 | else |
| 89 | { |
| 90 | if (!BN_usub(r,a,b)) return(0); |
| 91 | r->neg=0; |
| 92 | } |
| 93 | return(1); |
| 94 | } |
| 95 | |
| 96 | if (a->neg) /* both are neg */ |
| 97 | r->neg=1; |
| 98 | else |
| 99 | r->neg=0; |
| 100 | |
| 101 | if (!BN_uadd(r,a,b)) return(0); |
| 102 | return(1); |
| 103 | } |
| 104 | |
| 105 | /* unsigned add of b to a, r must be large enough */ |
| 106 | int BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) |
| 107 | { |
| 108 | register int i; |
| 109 | int max,min; |
| 110 | BN_ULONG *ap,*bp,*rp,carry,t1; |
| 111 | const BIGNUM *tmp; |
| 112 | |
| 113 | bn_check_top(a); |
| 114 | bn_check_top(b); |
| 115 | |
| 116 | if (a->top < b->top) |
| 117 | { tmp=a; a=b; b=tmp; } |
| 118 | max=a->top; |
| 119 | min=b->top; |
| 120 | |
| 121 | if (bn_wexpand(r,max+1) == NULL) |
| 122 | return(0); |
| 123 | |
| 124 | r->top=max; |
| 125 | |
| 126 | |
| 127 | ap=a->d; |
| 128 | bp=b->d; |
| 129 | rp=r->d; |
| 130 | carry=0; |
| 131 | |
| 132 | carry=bn_add_words(rp,ap,bp,min); |
| 133 | rp+=min; |
| 134 | ap+=min; |
| 135 | bp+=min; |
| 136 | i=min; |
| 137 | |
| 138 | if (carry) |
| 139 | { |
| 140 | while (i < max) |
| 141 | { |
| 142 | i++; |
| 143 | t1= *(ap++); |
| 144 | if ((*(rp++)=(t1+1)&BN_MASK2) >= t1) |
| 145 | { |
| 146 | carry=0; |
| 147 | break; |
| 148 | } |
| 149 | } |
| 150 | if ((i >= max) && carry) |
| 151 | { |
| 152 | *(rp++)=1; |
| 153 | r->top++; |
| 154 | } |
| 155 | } |
| 156 | if (rp != ap) |
| 157 | { |
| 158 | for (; i<max; i++) |
| 159 | *(rp++)= *(ap++); |
| 160 | } |
| 161 | /* memcpy(rp,ap,sizeof(*ap)*(max-i));*/ |
| 162 | return(1); |
| 163 | } |
| 164 | |
| 165 | /* unsigned subtraction of b from a, a must be larger than b. */ |
| 166 | int BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) |
| 167 | { |
| 168 | int max,min; |
| 169 | register BN_ULONG t1,t2,*ap,*bp,*rp; |
| 170 | int i,carry; |
| 171 | #if defined(IRIX_CC_BUG) && !defined(LINT) |
| 172 | int dummy; |
| 173 | #endif |
| 174 | |
| 175 | bn_check_top(a); |
| 176 | bn_check_top(b); |
| 177 | |
| 178 | if (a->top < b->top) /* hmm... should not be happening */ |
| 179 | { |
| 180 | return(0); |
| 181 | } |
| 182 | |
| 183 | max=a->top; |
| 184 | min=b->top; |
| 185 | if (bn_wexpand(r,max) == NULL) return(0); |
| 186 | |
| 187 | ap=a->d; |
| 188 | bp=b->d; |
| 189 | rp=r->d; |
| 190 | |
| 191 | #if 1 |
| 192 | carry=0; |
| 193 | for (i=0; i<min; i++) |
| 194 | { |
| 195 | t1= *(ap++); |
| 196 | t2= *(bp++); |
| 197 | if (carry) |
| 198 | { |
| 199 | carry=(t1 <= t2); |
| 200 | t1=(t1-t2-1)&BN_MASK2; |
| 201 | } |
| 202 | else |
| 203 | { |
| 204 | carry=(t1 < t2); |
| 205 | t1=(t1-t2)&BN_MASK2; |
| 206 | } |
| 207 | #if defined(IRIX_CC_BUG) && !defined(LINT) |
| 208 | dummy=t1; |
| 209 | #endif |
| 210 | *(rp++)=t1&BN_MASK2; |
| 211 | } |
| 212 | #else |
| 213 | carry=bn_sub_words(rp,ap,bp,min); |
| 214 | ap+=min; |
| 215 | bp+=min; |
| 216 | rp+=min; |
| 217 | i=min; |
| 218 | #endif |
| 219 | if (carry) /* subtracted */ |
| 220 | { |
| 221 | while (i < max) |
| 222 | { |
| 223 | i++; |
| 224 | t1= *(ap++); |
| 225 | t2=(t1-1)&BN_MASK2; |
| 226 | *(rp++)=t2; |
| 227 | if (t1 > t2) break; |
| 228 | } |
| 229 | } |
| 230 | #if 0 |
| 231 | memcpy(rp,ap,sizeof(*rp)*(max-i)); |
| 232 | #else |
| 233 | if (rp != ap) |
| 234 | { |
| 235 | for (;;) |
| 236 | { |
| 237 | if (i++ >= max) break; |
| 238 | rp[0]=ap[0]; |
| 239 | if (i++ >= max) break; |
| 240 | rp[1]=ap[1]; |
| 241 | if (i++ >= max) break; |
| 242 | rp[2]=ap[2]; |
| 243 | if (i++ >= max) break; |
| 244 | rp[3]=ap[3]; |
| 245 | rp+=4; |
| 246 | ap+=4; |
| 247 | } |
| 248 | } |
| 249 | #endif |
| 250 | |
| 251 | r->top=max; |
| 252 | bn_fix_top(r); |
| 253 | return(1); |
| 254 | } |
| 255 | |
| 256 | int BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) |
| 257 | { |
| 258 | int max; |
| 259 | int add=0,neg=0; |
| 260 | const BIGNUM *tmp; |
| 261 | |
| 262 | bn_check_top(a); |
| 263 | bn_check_top(b); |
| 264 | |
| 265 | /* a - b a-b |
| 266 | * a - -b a+b |
| 267 | * -a - b -(a+b) |
| 268 | * -a - -b b-a |
| 269 | */ |
| 270 | if (a->neg) |
| 271 | { |
| 272 | if (b->neg) |
| 273 | { tmp=a; a=b; b=tmp; } |
| 274 | else |
| 275 | { add=1; neg=1; } |
| 276 | } |
| 277 | else |
| 278 | { |
| 279 | if (b->neg) { add=1; neg=0; } |
| 280 | } |
| 281 | |
| 282 | if (add) |
| 283 | { |
| 284 | if (!BN_uadd(r,a,b)) return(0); |
| 285 | r->neg=neg; |
| 286 | return(1); |
| 287 | } |
| 288 | |
| 289 | /* We are actually doing a - b :-) */ |
| 290 | |
| 291 | max=(a->top > b->top)?a->top:b->top; |
| 292 | if (bn_wexpand(r,max) == NULL) return(0); |
| 293 | if (BN_ucmp(a,b) < 0) |
| 294 | { |
| 295 | if (!BN_usub(r,b,a)) return(0); |
| 296 | r->neg=1; |
| 297 | } |
| 298 | else |
| 299 | { |
| 300 | if (!BN_usub(r,a,b)) return(0); |
| 301 | r->neg=0; |
| 302 | } |
| 303 | return(1); |
| 304 | } |
| 305 | |
| 306 | |
