bn_recp.c revision 296317
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->shift = 0; 69 recp->flags = 0; 70} 71 72BN_RECP_CTX *BN_RECP_CTX_new(void) 73{ 74 BN_RECP_CTX *ret; 75 76 if ((ret = (BN_RECP_CTX *)OPENSSL_malloc(sizeof(BN_RECP_CTX))) == NULL) 77 return (NULL); 78 79 BN_RECP_CTX_init(ret); 80 ret->flags = BN_FLG_MALLOCED; 81 return (ret); 82} 83 84void BN_RECP_CTX_free(BN_RECP_CTX *recp) 85{ 86 if (recp == NULL) 87 return; 88 89 BN_free(&(recp->N)); 90 BN_free(&(recp->Nr)); 91 if (recp->flags & BN_FLG_MALLOCED) 92 OPENSSL_free(recp); 93} 94 95int BN_RECP_CTX_set(BN_RECP_CTX *recp, const BIGNUM *d, BN_CTX *ctx) 96{ 97 if (!BN_copy(&(recp->N), d)) 98 return 0; 99 BN_zero(&(recp->Nr)); 100 recp->num_bits = BN_num_bits(d); 101 recp->shift = 0; 102 return (1); 103} 104 105int BN_mod_mul_reciprocal(BIGNUM *r, const BIGNUM *x, const BIGNUM *y, 106 BN_RECP_CTX *recp, BN_CTX *ctx) 107{ 108 int ret = 0; 109 BIGNUM *a; 110 const BIGNUM *ca; 111 112 BN_CTX_start(ctx); 113 if ((a = BN_CTX_get(ctx)) == NULL) 114 goto err; 115 if (y != NULL) { 116 if (x == y) { 117 if (!BN_sqr(a, x, ctx)) 118 goto err; 119 } else { 120 if (!BN_mul(a, x, y, ctx)) 121 goto err; 122 } 123 ca = a; 124 } else 125 ca = x; /* Just do the mod */ 126 127 ret = BN_div_recp(NULL, r, ca, recp, ctx); 128 err: 129 BN_CTX_end(ctx); 130 bn_check_top(r); 131 return (ret); 132} 133 134int BN_div_recp(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m, 135 BN_RECP_CTX *recp, BN_CTX *ctx) 136{ 137 int i, j, ret = 0; 138 BIGNUM *a, *b, *d, *r; 139 140 BN_CTX_start(ctx); 141 a = BN_CTX_get(ctx); 142 b = BN_CTX_get(ctx); 143 if (dv != NULL) 144 d = dv; 145 else 146 d = BN_CTX_get(ctx); 147 if (rem != NULL) 148 r = rem; 149 else 150 r = BN_CTX_get(ctx); 151 if (a == NULL || b == NULL || d == NULL || r == NULL) 152 goto err; 153 154 if (BN_ucmp(m, &(recp->N)) < 0) { 155 BN_zero(d); 156 if (!BN_copy(r, m)) { 157 BN_CTX_end(ctx); 158 return 0; 159 } 160 BN_CTX_end(ctx); 161 return (1); 162 } 163 164 /* 165 * We want the remainder Given input of ABCDEF / ab we need multiply 166 * ABCDEF by 3 digests of the reciprocal of ab 167 */ 168 169 /* i := max(BN_num_bits(m), 2*BN_num_bits(N)) */ 170 i = BN_num_bits(m); 171 j = recp->num_bits << 1; 172 if (j > i) 173 i = j; 174 175 /* Nr := round(2^i / N) */ 176 if (i != recp->shift) 177 recp->shift = BN_reciprocal(&(recp->Nr), &(recp->N), i, ctx); 178 /* BN_reciprocal could have returned -1 for an error */ 179 if (recp->shift == -1) 180 goto err; 181 182 /*- 183 * d := |round(round(m / 2^BN_num_bits(N)) * recp->Nr / 2^(i - BN_num_bits(N)))| 184 * = |round(round(m / 2^BN_num_bits(N)) * round(2^i / N) / 2^(i - BN_num_bits(N)))| 185 * <= |(m / 2^BN_num_bits(N)) * (2^i / N) * (2^BN_num_bits(N) / 2^i)| 186 * = |m/N| 187 */ 188 if (!BN_rshift(a, m, recp->num_bits)) 189 goto err; 190 if (!BN_mul(b, a, &(recp->Nr), ctx)) 191 goto err; 192 if (!BN_rshift(d, b, i - recp->num_bits)) 193 goto err; 194 d->neg = 0; 195 196 if (!BN_mul(b, &(recp->N), d, ctx)) 197 goto err; 198 if (!BN_usub(r, m, b)) 199 goto err; 200 r->neg = 0; 201 202#if 1 203 j = 0; 204 while (BN_ucmp(r, &(recp->N)) >= 0) { 205 if (j++ > 2) { 206 BNerr(BN_F_BN_DIV_RECP, BN_R_BAD_RECIPROCAL); 207 goto err; 208 } 209 if (!BN_usub(r, r, &(recp->N))) 210 goto err; 211 if (!BN_add_word(d, 1)) 212 goto err; 213 } 214#endif 215 216 r->neg = BN_is_zero(r) ? 0 : m->neg; 217 d->neg = m->neg ^ recp->N.neg; 218 ret = 1; 219 err: 220 BN_CTX_end(ctx); 221 bn_check_top(dv); 222 bn_check_top(rem); 223 return (ret); 224} 225 226/* 227 * len is the expected size of the result We actually calculate with an extra 228 * word of precision, so we can do faster division if the remainder is not 229 * required. 230 */ 231/* r := 2^len / m */ 232int BN_reciprocal(BIGNUM *r, const BIGNUM *m, int len, BN_CTX *ctx) 233{ 234 int ret = -1; 235 BIGNUM *t; 236 237 BN_CTX_start(ctx); 238 if ((t = BN_CTX_get(ctx)) == NULL) 239 goto err; 240 241 if (!BN_set_bit(t, len)) 242 goto err; 243 244 if (!BN_div(r, NULL, t, m, ctx)) 245 goto err; 246 247 ret = len; 248 err: 249 bn_check_top(r); 250 BN_CTX_end(ctx); 251 return (ret); 252} 253