Alexandre Savard | 1b09e31 | 2012-08-07 20:33:29 -0400 | [diff] [blame] | 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 | |
| 63 | void 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 | |
| 71 | BN_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 | |
| 83 | void 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 | |
| 94 | int BN_RECP_CTX_set(BN_RECP_CTX *recp, const BIGNUM *d, BN_CTX *ctx) |
| 95 | { |
| 96 | if (!BN_copy(&(recp->N),d)) return 0; |
| 97 | BN_zero(&(recp->Nr)); |
| 98 | recp->num_bits=BN_num_bits(d); |
| 99 | recp->shift=0; |
| 100 | return(1); |
| 101 | } |
| 102 | |
| 103 | int BN_mod_mul_reciprocal(BIGNUM *r, const BIGNUM *x, const BIGNUM *y, |
| 104 | BN_RECP_CTX *recp, BN_CTX *ctx) |
| 105 | { |
| 106 | int ret=0; |
| 107 | BIGNUM *a; |
| 108 | const BIGNUM *ca; |
| 109 | |
| 110 | BN_CTX_start(ctx); |
| 111 | if ((a = BN_CTX_get(ctx)) == NULL) goto err; |
| 112 | if (y != NULL) |
| 113 | { |
| 114 | if (x == y) |
| 115 | { if (!BN_sqr(a,x,ctx)) goto err; } |
| 116 | else |
| 117 | { if (!BN_mul(a,x,y,ctx)) goto err; } |
| 118 | ca = a; |
| 119 | } |
| 120 | else |
| 121 | ca=x; /* Just do the mod */ |
| 122 | |
| 123 | ret = BN_div_recp(NULL,r,ca,recp,ctx); |
| 124 | err: |
| 125 | BN_CTX_end(ctx); |
| 126 | bn_check_top(r); |
| 127 | return(ret); |
| 128 | } |
| 129 | |
| 130 | int BN_div_recp(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m, |
| 131 | BN_RECP_CTX *recp, BN_CTX *ctx) |
| 132 | { |
| 133 | int i,j,ret=0; |
| 134 | BIGNUM *a,*b,*d,*r; |
| 135 | |
| 136 | BN_CTX_start(ctx); |
| 137 | a=BN_CTX_get(ctx); |
| 138 | b=BN_CTX_get(ctx); |
| 139 | if (dv != NULL) |
| 140 | d=dv; |
| 141 | else |
| 142 | d=BN_CTX_get(ctx); |
| 143 | if (rem != NULL) |
| 144 | r=rem; |
| 145 | else |
| 146 | r=BN_CTX_get(ctx); |
| 147 | if (a == NULL || b == NULL || d == NULL || r == NULL) goto err; |
| 148 | |
| 149 | if (BN_ucmp(m,&(recp->N)) < 0) |
| 150 | { |
| 151 | BN_zero(d); |
| 152 | if (!BN_copy(r,m)) return 0; |
| 153 | BN_CTX_end(ctx); |
| 154 | return(1); |
| 155 | } |
| 156 | |
| 157 | /* We want the remainder |
| 158 | * Given input of ABCDEF / ab |
| 159 | * we need multiply ABCDEF by 3 digests of the reciprocal of ab |
| 160 | * |
| 161 | */ |
| 162 | |
| 163 | /* i := max(BN_num_bits(m), 2*BN_num_bits(N)) */ |
| 164 | i=BN_num_bits(m); |
| 165 | j=recp->num_bits<<1; |
| 166 | if (j>i) i=j; |
| 167 | |
| 168 | /* Nr := round(2^i / N) */ |
| 169 | if (i != recp->shift) |
| 170 | recp->shift=BN_reciprocal(&(recp->Nr),&(recp->N), |
| 171 | i,ctx); /* BN_reciprocal returns i, or -1 for an error */ |
| 172 | if (recp->shift == -1) goto err; |
| 173 | |
| 174 | /* d := |round(round(m / 2^BN_num_bits(N)) * recp->Nr / 2^(i - BN_num_bits(N)))| |
| 175 | * = |round(round(m / 2^BN_num_bits(N)) * round(2^i / N) / 2^(i - BN_num_bits(N)))| |
| 176 | * <= |(m / 2^BN_num_bits(N)) * (2^i / N) * (2^BN_num_bits(N) / 2^i)| |
| 177 | * = |m/N| |
| 178 | */ |
| 179 | if (!BN_rshift(a,m,recp->num_bits)) goto err; |
| 180 | if (!BN_mul(b,a,&(recp->Nr),ctx)) goto err; |
| 181 | if (!BN_rshift(d,b,i-recp->num_bits)) goto err; |
| 182 | d->neg=0; |
| 183 | |
| 184 | if (!BN_mul(b,&(recp->N),d,ctx)) goto err; |
| 185 | if (!BN_usub(r,m,b)) goto err; |
| 186 | r->neg=0; |
| 187 | |
| 188 | #if 1 |
| 189 | j=0; |
| 190 | while (BN_ucmp(r,&(recp->N)) >= 0) |
| 191 | { |
| 192 | if (j++ > 2) |
| 193 | { |
| 194 | BNerr(BN_F_BN_DIV_RECP,BN_R_BAD_RECIPROCAL); |
| 195 | goto err; |
| 196 | } |
| 197 | if (!BN_usub(r,r,&(recp->N))) goto err; |
| 198 | if (!BN_add_word(d,1)) goto err; |
| 199 | } |
| 200 | #endif |
| 201 | |
| 202 | r->neg=BN_is_zero(r)?0:m->neg; |
| 203 | d->neg=m->neg^recp->N.neg; |
| 204 | ret=1; |
| 205 | err: |
| 206 | BN_CTX_end(ctx); |
| 207 | bn_check_top(dv); |
| 208 | bn_check_top(rem); |
| 209 | return(ret); |
| 210 | } |
| 211 | |
| 212 | /* len is the expected size of the result |
| 213 | * We actually calculate with an extra word of precision, so |
| 214 | * we can do faster division if the remainder is not required. |
| 215 | */ |
| 216 | /* r := 2^len / m */ |
| 217 | int BN_reciprocal(BIGNUM *r, const BIGNUM *m, int len, BN_CTX *ctx) |
| 218 | { |
| 219 | int ret= -1; |
| 220 | BIGNUM *t; |
| 221 | |
| 222 | BN_CTX_start(ctx); |
| 223 | if((t = BN_CTX_get(ctx)) == NULL) goto err; |
| 224 | |
| 225 | if (!BN_set_bit(t,len)) goto err; |
| 226 | |
| 227 | if (!BN_div(r,NULL,t,m,ctx)) goto err; |
| 228 | |
| 229 | ret=len; |
| 230 | err: |
| 231 | bn_check_top(r); |
| 232 | BN_CTX_end(ctx); |
| 233 | return(ret); |
| 234 | } |