bn_mod.c revision 296341
1/* crypto/bn/bn_mod.c */ 2/* 3 * Includes code written by Lenka Fibikova <fibikova@exp-math.uni-essen.de> 4 * for the OpenSSL project. 5 */ 6/* ==================================================================== 7 * Copyright (c) 1998-2000 The OpenSSL Project. All rights reserved. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in 18 * the documentation and/or other materials provided with the 19 * distribution. 20 * 21 * 3. All advertising materials mentioning features or use of this 22 * software must display the following acknowledgment: 23 * "This product includes software developed by the OpenSSL Project 24 * for use in the OpenSSL Toolkit. (http://www.openssl.org/)" 25 * 26 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to 27 * endorse or promote products derived from this software without 28 * prior written permission. For written permission, please contact 29 * openssl-core@openssl.org. 30 * 31 * 5. Products derived from this software may not be called "OpenSSL" 32 * nor may "OpenSSL" appear in their names without prior written 33 * permission of the OpenSSL Project. 34 * 35 * 6. Redistributions of any form whatsoever must retain the following 36 * acknowledgment: 37 * "This product includes software developed by the OpenSSL Project 38 * for use in the OpenSSL Toolkit (http://www.openssl.org/)" 39 * 40 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY 41 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 42 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 43 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR 44 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 45 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 46 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 47 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 48 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 49 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 50 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 51 * OF THE POSSIBILITY OF SUCH DAMAGE. 52 * ==================================================================== 53 * 54 * This product includes cryptographic software written by Eric Young 55 * (eay@cryptsoft.com). This product includes software written by Tim 56 * Hudson (tjh@cryptsoft.com). 57 * 58 */ 59/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) 60 * All rights reserved. 61 * 62 * This package is an SSL implementation written 63 * by Eric Young (eay@cryptsoft.com). 64 * The implementation was written so as to conform with Netscapes SSL. 65 * 66 * This library is free for commercial and non-commercial use as long as 67 * the following conditions are aheared to. The following conditions 68 * apply to all code found in this distribution, be it the RC4, RSA, 69 * lhash, DES, etc., code; not just the SSL code. The SSL documentation 70 * included with this distribution is covered by the same copyright terms 71 * except that the holder is Tim Hudson (tjh@cryptsoft.com). 72 * 73 * Copyright remains Eric Young's, and as such any Copyright notices in 74 * the code are not to be removed. 75 * If this package is used in a product, Eric Young should be given attribution 76 * as the author of the parts of the library used. 77 * This can be in the form of a textual message at program startup or 78 * in documentation (online or textual) provided with the package. 79 * 80 * Redistribution and use in source and binary forms, with or without 81 * modification, are permitted provided that the following conditions 82 * are met: 83 * 1. Redistributions of source code must retain the copyright 84 * notice, this list of conditions and the following disclaimer. 85 * 2. Redistributions in binary form must reproduce the above copyright 86 * notice, this list of conditions and the following disclaimer in the 87 * documentation and/or other materials provided with the distribution. 88 * 3. All advertising materials mentioning features or use of this software 89 * must display the following acknowledgement: 90 * "This product includes cryptographic software written by 91 * Eric Young (eay@cryptsoft.com)" 92 * The word 'cryptographic' can be left out if the rouines from the library 93 * being used are not cryptographic related :-). 94 * 4. If you include any Windows specific code (or a derivative thereof) from 95 * the apps directory (application code) you must include an acknowledgement: 96 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)" 97 * 98 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND 99 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 100 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 101 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 102 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 103 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 104 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 105 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 106 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 107 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 108 * SUCH DAMAGE. 109 * 110 * The licence and distribution terms for any publically available version or 111 * derivative of this code cannot be changed. i.e. this code cannot simply be 112 * copied and put under another distribution licence 113 * [including the GNU Public Licence.] 114 */ 115 116#include "cryptlib.h" 117#include "bn_lcl.h" 118 119#if 0 /* now just a #define */ 120int BN_mod(BIGNUM *rem, const BIGNUM *m, const BIGNUM *d, BN_CTX *ctx) 121{ 122 return (BN_div(NULL, rem, m, d, ctx)); 123 /* note that rem->neg == m->neg (unless the remainder is zero) */ 124} 125#endif 126 127int BN_nnmod(BIGNUM *r, const BIGNUM *m, const BIGNUM *d, BN_CTX *ctx) 128{ 129 /* 130 * like BN_mod, but returns non-negative remainder (i.e., 0 <= r < |d| 131 * always holds) 132 */ 133 134 if (!(BN_mod(r, m, d, ctx))) 135 return 0; 136 if (!r->neg) 137 return 1; 138 /* now -|d| < r < 0, so we have to set r := r + |d| */ 139 return (d->neg ? BN_sub : BN_add) (r, r, d); 140} 141 142int BN_mod_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m, 143 BN_CTX *ctx) 144{ 145 if (!BN_add(r, a, b)) 146 return 0; 147 return BN_nnmod(r, r, m, ctx); 148} 149 150/* 151 * BN_mod_add variant that may be used if both a and b are non-negative and 152 * less than m 153 */ 154int BN_mod_add_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, 155 const BIGNUM *m) 156{ 157 if (!BN_uadd(r, a, b)) 158 return 0; 159 if (BN_ucmp(r, m) >= 0) 160 return BN_usub(r, r, m); 161 return 1; 162} 163 164int BN_mod_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m, 165 BN_CTX *ctx) 166{ 167 if (!BN_sub(r, a, b)) 168 return 0; 169 return BN_nnmod(r, r, m, ctx); 170} 171 172/* 173 * BN_mod_sub variant that may be used if both a and b are non-negative and 174 * less than m 175 */ 176int BN_mod_sub_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, 177 const BIGNUM *m) 178{ 179 if (!BN_sub(r, a, b)) 180 return 0; 181 if (r->neg) 182 return BN_add(r, r, m); 183 return 1; 184} 185 186/* slow but works */ 187int BN_mod_mul(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m, 188 BN_CTX *ctx) 189{ 190 BIGNUM *t; 191 int ret = 0; 192 193 bn_check_top(a); 194 bn_check_top(b); 195 bn_check_top(m); 196 197 BN_CTX_start(ctx); 198 if ((t = BN_CTX_get(ctx)) == NULL) 199 goto err; 200 if (a == b) { 201 if (!BN_sqr(t, a, ctx)) 202 goto err; 203 } else { 204 if (!BN_mul(t, a, b, ctx)) 205 goto err; 206 } 207 if (!BN_nnmod(r, t, m, ctx)) 208 goto err; 209 bn_check_top(r); 210 ret = 1; 211 err: 212 BN_CTX_end(ctx); 213 return (ret); 214} 215 216int BN_mod_sqr(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx) 217{ 218 if (!BN_sqr(r, a, ctx)) 219 return 0; 220 /* r->neg == 0, thus we don't need BN_nnmod */ 221 return BN_mod(r, r, m, ctx); 222} 223 224int BN_mod_lshift1(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx) 225{ 226 if (!BN_lshift1(r, a)) 227 return 0; 228 bn_check_top(r); 229 return BN_nnmod(r, r, m, ctx); 230} 231 232/* 233 * BN_mod_lshift1 variant that may be used if a is non-negative and less than 234 * m 235 */ 236int BN_mod_lshift1_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *m) 237{ 238 if (!BN_lshift1(r, a)) 239 return 0; 240 bn_check_top(r); 241 if (BN_cmp(r, m) >= 0) 242 return BN_sub(r, r, m); 243 return 1; 244} 245 246int BN_mod_lshift(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m, 247 BN_CTX *ctx) 248{ 249 BIGNUM *abs_m = NULL; 250 int ret; 251 252 if (!BN_nnmod(r, a, m, ctx)) 253 return 0; 254 255 if (m->neg) { 256 abs_m = BN_dup(m); 257 if (abs_m == NULL) 258 return 0; 259 abs_m->neg = 0; 260 } 261 262 ret = BN_mod_lshift_quick(r, r, n, (abs_m ? abs_m : m)); 263 bn_check_top(r); 264 265 if (abs_m) 266 BN_free(abs_m); 267 return ret; 268} 269 270/* 271 * BN_mod_lshift variant that may be used if a is non-negative and less than 272 * m 273 */ 274int BN_mod_lshift_quick(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m) 275{ 276 if (r != a) { 277 if (BN_copy(r, a) == NULL) 278 return 0; 279 } 280 281 while (n > 0) { 282 int max_shift; 283 284 /* 0 < r < m */ 285 max_shift = BN_num_bits(m) - BN_num_bits(r); 286 /* max_shift >= 0 */ 287 288 if (max_shift < 0) { 289 BNerr(BN_F_BN_MOD_LSHIFT_QUICK, BN_R_INPUT_NOT_REDUCED); 290 return 0; 291 } 292 293 if (max_shift > n) 294 max_shift = n; 295 296 if (max_shift) { 297 if (!BN_lshift(r, r, max_shift)) 298 return 0; 299 n -= max_shift; 300 } else { 301 if (!BN_lshift1(r, r)) 302 return 0; 303 --n; 304 } 305 306 /* BN_num_bits(r) <= BN_num_bits(m) */ 307 308 if (BN_cmp(r, m) >= 0) { 309 if (!BN_sub(r, r, m)) 310 return 0; 311 } 312 } 313 bn_check_top(r); 314 315 return 1; 316} 317