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 "cryptlib.h" 61 #include "bn_lcl.h" 62 63 /* r can == a or b */ 64 int BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) 65 { 66 const BIGNUM *tmp; 67 int a_neg = a->neg, ret; 68 69 bn_check_top(a); 70 bn_check_top(b); 71 72 /* a + b a+b 73 * a + -b a-b 74 * -a + b b-a 75 * -a + -b -(a+b) 76 */ 77 if (a_neg ^ b->neg) 78 { 79 /* only one is negative */ 80 if (a_neg) 81 { tmp=a; a=b; b=tmp; } 82 83 /* we are now a - b */ 84 85 if (BN_ucmp(a,b) < 0) 86 { 87 if (!BN_usub(r,b,a)) return(0); 88 r->neg=1; 89 } 90 else 91 { 92 if (!BN_usub(r,a,b)) return(0); 93 r->neg=0; 94 } 95 return(1); 96 } 97 98 ret = BN_uadd(r,a,b); 99 r->neg = a_neg; 100 bn_check_top(r); 101 return ret; 102 } 103 104 /* unsigned add of b to a */ 105 int BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) 106 { 107 int max,min,dif; 108 BN_ULONG *ap,*bp,*rp,carry,t1,t2; 109 const BIGNUM *tmp; 110 111 bn_check_top(a); 112 bn_check_top(b); 113 114 if (a->top < b->top) 115 { tmp=a; a=b; b=tmp; } 116 max = a->top; 117 min = b->top; 118 dif = max - min; 119 120 if (bn_wexpand(r,max+1) == NULL) 121 return 0; 122 123 r->top=max; 124 125 126 ap=a->d; 127 bp=b->d; 128 rp=r->d; 129 130 carry=bn_add_words(rp,ap,bp,min); 131 rp+=min; 132 ap+=min; 133 bp+=min; 134 135 if (carry) 136 { 137 while (dif) 138 { 139 dif--; 140 t1 = *(ap++); 141 t2 = (t1+1) & BN_MASK2; 142 *(rp++) = t2; 143 if (t2) 144 { 145 carry=0; 146 break; 147 } 148 } 149 if (carry) 150 { 151 /* carry != 0 => dif == 0 */ 152 *rp = 1; 153 r->top++; 154 } 155 } 156 if (dif && rp != ap) 157 while (dif--) 158 /* copy remaining words if ap != rp */ 159 *(rp++) = *(ap++); 160 r->neg = 0; 161 bn_check_top(r); 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,dif; 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 max = a->top; 179 min = b->top; 180 dif = max - min; 181 182 if (dif < 0) /* hmm... should not be happening */ 183 { 184 BNerr(BN_F_BN_USUB,BN_R_ARG2_LT_ARG3); 185 return(0); 186 } 187 188 if (bn_wexpand(r,max) == NULL) return(0); 189 190 ap=a->d; 191 bp=b->d; 192 rp=r->d; 193 194 #if 1 195 carry=0; 196 for (i = min; i != 0; i--) 197 { 198 t1= *(ap++); 199 t2= *(bp++); 200 if (carry) 201 { 202 carry=(t1 <= t2); 203 t1=(t1-t2-1)&BN_MASK2; 204 } 205 else 206 { 207 carry=(t1 < t2); 208 t1=(t1-t2)&BN_MASK2; 209 } 210 #if defined(IRIX_CC_BUG) && !defined(LINT) 211 dummy=t1; 212 #endif 213 *(rp++)=t1&BN_MASK2; 214 } 215 #else 216 carry=bn_sub_words(rp,ap,bp,min); 217 ap+=min; 218 bp+=min; 219 rp+=min; 220 #endif 221 if (carry) /* subtracted */ 222 { 223 if (!dif) 224 /* error: a < b */ 225 return 0; 226 while (dif) 227 { 228 dif--; 229 t1 = *(ap++); 230 t2 = (t1-1)&BN_MASK2; 231 *(rp++) = t2; 232 if (t1) 233 break; 234 } 235 } 236 #if 0 237 memcpy(rp,ap,sizeof(*rp)*(max-i)); 238 #else 239 if (rp != ap) 240 { 241 for (;;) 242 { 243 if (!dif--) break; 244 rp[0]=ap[0]; 245 if (!dif--) break; 246 rp[1]=ap[1]; 247 if (!dif--) break; 248 rp[2]=ap[2]; 249 if (!dif--) break; 250 rp[3]=ap[3]; 251 rp+=4; 252 ap+=4; 253 } 254 } 255 #endif 256 257 r->top=max; 258 r->neg=0; 259 bn_correct_top(r); 260 return(1); 261 } 262 263 int BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) 264 { 265 int max; 266 int add=0,neg=0; 267 const BIGNUM *tmp; 268 269 bn_check_top(a); 270 bn_check_top(b); 271 272 /* a - b a-b 273 * a - -b a+b 274 * -a - b -(a+b) 275 * -a - -b b-a 276 */ 277 if (a->neg) 278 { 279 if (b->neg) 280 { tmp=a; a=b; b=tmp; } 281 else 282 { add=1; neg=1; } 283 } 284 else 285 { 286 if (b->neg) { add=1; neg=0; } 287 } 288 289 if (add) 290 { 291 if (!BN_uadd(r,a,b)) return(0); 292 r->neg=neg; 293 return(1); 294 } 295 296 /* We are actually doing a - b :-) */ 297 298 max=(a->top > b->top)?a->top:b->top; 299 if (bn_wexpand(r,max) == NULL) return(0); 300 if (BN_ucmp(a,b) < 0) 301 { 302 if (!BN_usub(r,b,a)) return(0); 303 r->neg=1; 304 } 305 else 306 { 307 if (!BN_usub(r,a,b)) return(0); 308 r->neg=0; 309 } 310 bn_check_top(r); 311 return(1); 312 } 313 314