bn_recp.c revision 59191
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 *)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 Free(recp); 92 } 93 94int BN_RECP_CTX_set(BN_RECP_CTX *recp, const BIGNUM *d, BN_CTX *ctx) 95 { 96 BN_copy(&(recp->N),d); 97 BN_zero(&(recp->Nr)); 98 recp->num_bits=BN_num_bits(d); 99 recp->shift=0; 100 return(1); 101 } 102 103int BN_mod_mul_reciprocal(BIGNUM *r, BIGNUM *x, BIGNUM *y, BN_RECP_CTX *recp, 104 BN_CTX *ctx) 105 { 106 int ret=0; 107 BIGNUM *a; 108 109 BN_CTX_start(ctx); 110 if ((a = BN_CTX_get(ctx)) == NULL) goto err; 111 if (y != NULL) 112 { 113 if (x == y) 114 { if (!BN_sqr(a,x,ctx)) goto err; } 115 else 116 { if (!BN_mul(a,x,y,ctx)) goto err; } 117 } 118 else 119 a=x; /* Just do the mod */ 120 121 BN_div_recp(NULL,r,a,recp,ctx); 122 ret=1; 123err: 124 BN_CTX_end(ctx); 125 return(ret); 126 } 127 128int BN_div_recp(BIGNUM *dv, BIGNUM *rem, BIGNUM *m, BN_RECP_CTX *recp, 129 BN_CTX *ctx) 130 { 131 int i,j,ret=0; 132 BIGNUM *a,*b,*d,*r; 133 134 BN_CTX_start(ctx); 135 a=BN_CTX_get(ctx); 136 b=BN_CTX_get(ctx); 137 if (dv != NULL) 138 d=dv; 139 else 140 d=BN_CTX_get(ctx); 141 if (rem != NULL) 142 r=rem; 143 else 144 r=BN_CTX_get(ctx); 145 if (a == NULL || b == NULL || d == NULL || r == NULL) goto err; 146 147 if (BN_ucmp(m,&(recp->N)) < 0) 148 { 149 BN_zero(d); 150 BN_copy(r,m); 151 BN_CTX_end(ctx); 152 return(1); 153 } 154 155 /* We want the remainder 156 * Given input of ABCDEF / ab 157 * we need multiply ABCDEF by 3 digests of the reciprocal of ab 158 * 159 */ 160 i=BN_num_bits(m); 161 162 j=recp->num_bits<<1; 163 if (j>i) i=j; 164 j>>=1; 165 166 if (i != recp->shift) 167 recp->shift=BN_reciprocal(&(recp->Nr),&(recp->N), 168 i,ctx); 169 170 if (!BN_rshift(a,m,j)) goto err; 171 if (!BN_mul(b,a,&(recp->Nr),ctx)) goto err; 172 if (!BN_rshift(d,b,i-j)) goto err; 173 d->neg=0; 174 if (!BN_mul(b,&(recp->N),d,ctx)) goto err; 175 if (!BN_usub(r,m,b)) goto err; 176 r->neg=0; 177 178#if 1 179 j=0; 180 while (BN_ucmp(r,&(recp->N)) >= 0) 181 { 182 if (j++ > 2) 183 { 184 BNerr(BN_F_BN_MOD_MUL_RECIPROCAL,BN_R_BAD_RECIPROCAL); 185 goto err; 186 } 187 if (!BN_usub(r,r,&(recp->N))) goto err; 188 if (!BN_add_word(d,1)) goto err; 189 } 190#endif 191 192 r->neg=BN_is_zero(r)?0:m->neg; 193 d->neg=m->neg^recp->N.neg; 194 ret=1; 195err: 196 BN_CTX_end(ctx); 197 return(ret); 198 } 199 200/* len is the expected size of the result 201 * We actually calculate with an extra word of precision, so 202 * we can do faster division if the remainder is not required. 203 */ 204int BN_reciprocal(BIGNUM *r, BIGNUM *m, int len, BN_CTX *ctx) 205 { 206 int ret= -1; 207 BIGNUM t; 208 209 BN_init(&t); 210 211 BN_zero(&t); 212 if (!BN_set_bit(&t,len)) goto err; 213 214 if (!BN_div(r,NULL,&t,m,ctx)) goto err; 215 ret=len; 216err: 217 BN_free(&t); 218 return(ret); 219 } 220 221