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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 *)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 | Free(recp); | |
92 | } | |
93 | ||
94 | int BN_RECP_CTX_set(BN_RECP_CTX *recp, 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 | ||
103 | int 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 | a= &(ctx->bn[ctx->tos++]); | |
110 | if (y != NULL) | |
111 | { | |
112 | if (x == y) | |
113 | { if (!BN_sqr(a,x,ctx)) goto err; } | |
114 | else | |
115 | { if (!BN_mul(a,x,y,ctx)) goto err; } | |
116 | } | |
117 | else | |
118 | a=x; /* Just do the mod */ | |
119 | ||
120 | BN_div_recp(NULL,r,a,recp,ctx); | |
121 | ret=1; | |
122 | err: | |
123 | ctx->tos--; | |
124 | return(ret); | |
125 | } | |
126 | ||
127 | int BN_div_recp(BIGNUM *dv, BIGNUM *rem, BIGNUM *m, BN_RECP_CTX *recp, | |
128 | BN_CTX *ctx) | |
129 | { | |
130 | int i,j,tos,ret=0,ex; | |
131 | BIGNUM *a,*b,*d,*r; | |
132 | ||
133 | tos=ctx->tos; | |
134 | a= &(ctx->bn[ctx->tos++]); | |
135 | b= &(ctx->bn[ctx->tos++]); | |
136 | if (dv != NULL) | |
137 | d=dv; | |
138 | else | |
139 | d= &(ctx->bn[ctx->tos++]); | |
140 | if (rem != NULL) | |
141 | r=rem; | |
142 | else | |
143 | r= &(ctx->bn[ctx->tos++]); | |
144 | ||
145 | if (BN_ucmp(m,&(recp->N)) < 0) | |
146 | { | |
147 | BN_zero(d); | |
148 | BN_copy(r,m); | |
149 | ctx->tos=tos; | |
150 | return(1); | |
151 | } | |
152 | ||
153 | /* We want the remainder | |
154 | * Given input of ABCDEF / ab | |
155 | * we need multiply ABCDEF by 3 digests of the reciprocal of ab | |
156 | * | |
157 | */ | |
158 | i=BN_num_bits(m); | |
159 | ||
160 | j=recp->num_bits*2; | |
161 | if (j > i) | |
162 | { | |
163 | i=j; | |
164 | ex=0; | |
165 | } | |
166 | else | |
167 | { | |
168 | ex=(i-j)/2; | |
169 | } | |
170 | ||
171 | j=i/2; | |
172 | ||
173 | if (i != recp->shift) | |
174 | recp->shift=BN_reciprocal(&(recp->Nr),&(recp->N), | |
175 | i,ctx); | |
176 | ||
177 | if (!BN_rshift(a,m,j-ex)) goto err; | |
178 | if (!BN_mul(b,a,&(recp->Nr),ctx)) goto err; | |
179 | if (!BN_rshift(d,b,j+ex)) goto err; | |
180 | d->neg=0; | |
181 | if (!BN_mul(b,&(recp->N),d,ctx)) goto err; | |
182 | if (!BN_usub(r,m,b)) goto err; | |
183 | r->neg=0; | |
184 | ||
185 | j=0; | |
186 | #if 1 | |
187 | while (BN_ucmp(r,&(recp->N)) >= 0) | |
188 | { | |
189 | if (j++ > 2) | |
190 | { | |
191 | BNerr(BN_F_BN_MOD_MUL_RECIPROCAL,BN_R_BAD_RECIPROCAL); | |
192 | goto err; | |
193 | } | |
194 | if (!BN_usub(r,r,&(recp->N))) goto err; | |
195 | if (!BN_add_word(d,1)) goto err; | |
196 | } | |
197 | #endif | |
198 | ||
199 | r->neg=BN_is_zero(r)?0:m->neg; | |
200 | d->neg=m->neg^recp->N.neg; | |
201 | ret=1; | |
202 | err: | |
203 | ctx->tos=tos; | |
204 | return(ret); | |
205 | } | |
206 | ||
207 | /* len is the expected size of the result | |
208 | * We actually calculate with an extra word of precision, so | |
209 | * we can do faster division if the remainder is not required. | |
210 | */ | |
211 | int BN_reciprocal(BIGNUM *r, BIGNUM *m, int len, BN_CTX *ctx) | |
212 | { | |
213 | int ret= -1; | |
214 | BIGNUM t; | |
215 | ||
216 | BN_init(&t); | |
217 | ||
218 | BN_zero(&t); | |
219 | if (!BN_set_bit(&t,len)) goto err; | |
220 | ||
221 | if (!BN_div(r,NULL,&t,m,ctx)) goto err; | |
222 | ret=len; | |
223 | err: | |
224 | BN_free(&t); | |
225 | return(ret); | |
226 | } | |
227 |