bn_recp.c revision 291721
1/* crypto/bn/bn_recp.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 63void BN_RECP_CTX_init(BN_RECP_CTX *recp) 64{ 65 BN_init(&(recp->N)); 66 BN_init(&(recp->Nr)); 67 recp->num_bits = 0; 68 recp->flags = 0; 69} 70 71BN_RECP_CTX *BN_RECP_CTX_new(void) 72{ 73 BN_RECP_CTX *ret; 74 75 if ((ret = (BN_RECP_CTX *)OPENSSL_malloc(sizeof(BN_RECP_CTX))) == NULL) 76 return (NULL); 77 78 BN_RECP_CTX_init(ret); 79 ret->flags = BN_FLG_MALLOCED; 80 return (ret); 81} 82 83void BN_RECP_CTX_free(BN_RECP_CTX *recp) 84{ 85 if (recp == NULL) 86 return; 87 88 BN_free(&(recp->N)); 89 BN_free(&(recp->Nr)); 90 if (recp->flags & BN_FLG_MALLOCED) 91 OPENSSL_free(recp); 92} 93 94int BN_RECP_CTX_set(BN_RECP_CTX *recp, const BIGNUM *d, BN_CTX *ctx) 95{ 96 if (!BN_copy(&(recp->N), d)) 97 return 0; 98 BN_zero(&(recp->Nr)); 99 recp->num_bits = BN_num_bits(d); 100 recp->shift = 0; 101 return (1); 102} 103 104int BN_mod_mul_reciprocal(BIGNUM *r, const BIGNUM *x, const BIGNUM *y, 105 BN_RECP_CTX *recp, BN_CTX *ctx) 106{ 107 int ret = 0; 108 BIGNUM *a; 109 const BIGNUM *ca; 110 111 BN_CTX_start(ctx); 112 if ((a = BN_CTX_get(ctx)) == NULL) 113 goto err; 114 if (y != NULL) { 115 if (x == y) { 116 if (!BN_sqr(a, x, ctx)) 117 goto err; 118 } else { 119 if (!BN_mul(a, x, y, ctx)) 120 goto err; 121 } 122 ca = a; 123 } else 124 ca = x; /* Just do the mod */ 125 126 ret = BN_div_recp(NULL, r, ca, recp, ctx); 127 err: 128 BN_CTX_end(ctx); 129 bn_check_top(r); 130 return (ret); 131} 132 133int BN_div_recp(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m, 134 BN_RECP_CTX *recp, BN_CTX *ctx) 135{ 136 int i, j, ret = 0; 137 BIGNUM *a, *b, *d, *r; 138 139 BN_CTX_start(ctx); 140 a = BN_CTX_get(ctx); 141 b = BN_CTX_get(ctx); 142 if (dv != NULL) 143 d = dv; 144 else 145 d = BN_CTX_get(ctx); 146 if (rem != NULL) 147 r = rem; 148 else 149 r = BN_CTX_get(ctx); 150 if (a == NULL || b == NULL || d == NULL || r == NULL) 151 goto err; 152 153 if (BN_ucmp(m, &(recp->N)) < 0) { 154 BN_zero(d); 155 if (!BN_copy(r, m)) { 156 BN_CTX_end(ctx); 157 return 0; 158 } 159 BN_CTX_end(ctx); 160 return (1); 161 } 162 163 /* 164 * We want the remainder Given input of ABCDEF / ab we need multiply 165 * ABCDEF by 3 digests of the reciprocal of ab 166 */ 167 168 /* i := max(BN_num_bits(m), 2*BN_num_bits(N)) */ 169 i = BN_num_bits(m); 170 j = recp->num_bits << 1; 171 if (j > i) 172 i = j; 173 174 /* Nr := round(2^i / N) */ 175 if (i != recp->shift) 176 recp->shift = BN_reciprocal(&(recp->Nr), &(recp->N), i, ctx); 177 /* BN_reciprocal could have returned -1 for an error */ 178 if (recp->shift == -1) 179 goto err; 180 181 /*- 182 * d := |round(round(m / 2^BN_num_bits(N)) * recp->Nr / 2^(i - BN_num_bits(N)))| 183 * = |round(round(m / 2^BN_num_bits(N)) * round(2^i / N) / 2^(i - BN_num_bits(N)))| 184 * <= |(m / 2^BN_num_bits(N)) * (2^i / N) * (2^BN_num_bits(N) / 2^i)| 185 * = |m/N| 186 */ 187 if (!BN_rshift(a, m, recp->num_bits)) 188 goto err; 189 if (!BN_mul(b, a, &(recp->Nr), ctx)) 190 goto err; 191 if (!BN_rshift(d, b, i - recp->num_bits)) 192 goto err; 193 d->neg = 0; 194 195 if (!BN_mul(b, &(recp->N), d, ctx)) 196 goto err; 197 if (!BN_usub(r, m, b)) 198 goto err; 199 r->neg = 0; 200 201#if 1 202 j = 0; 203 while (BN_ucmp(r, &(recp->N)) >= 0) { 204 if (j++ > 2) { 205 BNerr(BN_F_BN_DIV_RECP, BN_R_BAD_RECIPROCAL); 206 goto err; 207 } 208 if (!BN_usub(r, r, &(recp->N))) 209 goto err; 210 if (!BN_add_word(d, 1)) 211 goto err; 212 } 213#endif 214 215 r->neg = BN_is_zero(r) ? 0 : m->neg; 216 d->neg = m->neg ^ recp->N.neg; 217 ret = 1; 218 err: 219 BN_CTX_end(ctx); 220 bn_check_top(dv); 221 bn_check_top(rem); 222 return (ret); 223} 224 225/* 226 * len is the expected size of the result We actually calculate with an extra 227 * word of precision, so we can do faster division if the remainder is not 228 * required. 229 */ 230/* r := 2^len / m */ 231int BN_reciprocal(BIGNUM *r, const BIGNUM *m, int len, BN_CTX *ctx) 232{ 233 int ret = -1; 234 BIGNUM *t; 235 236 BN_CTX_start(ctx); 237 if ((t = BN_CTX_get(ctx)) == NULL) 238 goto err; 239 240 if (!BN_set_bit(t, len)) 241 goto err; 242 243 if (!BN_div(r, NULL, t, m, ctx)) 244 goto err; 245 246 ret = len; 247 err: 248 bn_check_top(r); 249 BN_CTX_end(ctx); 250 return (ret); 251} 252