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d02b48c6 | 1 | /* crypto/bn/bn_recp.c */ |
58964a49 | 2 | /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) |
d02b48c6 RE |
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 | ||
dfeab068 RE |
63 | void BN_RECP_CTX_init(recp) |
64 | BN_RECP_CTX *recp; | |
65 | { | |
66 | BN_init(&(recp->N)); | |
67 | BN_init(&(recp->Nr)); | |
68 | recp->num_bits=0; | |
69 | recp->flags=0; | |
70 | } | |
71 | ||
72 | BN_RECP_CTX *BN_RECP_CTX_new() | |
73 | { | |
74 | BN_RECP_CTX *ret; | |
75 | ||
76 | if ((ret=(BN_RECP_CTX *)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 | ||
84 | void BN_RECP_CTX_free(recp) | |
85 | BN_RECP_CTX *recp; | |
86 | { | |
e03ddfae BL |
87 | if(recp == NULL) |
88 | return; | |
89 | ||
dfeab068 RE |
90 | BN_free(&(recp->N)); |
91 | BN_free(&(recp->Nr)); | |
92 | if (recp->flags & BN_FLG_MALLOCED) | |
93 | Free(recp); | |
94 | } | |
95 | ||
96 | int BN_RECP_CTX_set(recp,d,ctx) | |
97 | BN_RECP_CTX *recp; | |
98 | BIGNUM *d; | |
99 | BN_CTX *ctx; | |
100 | { | |
101 | BN_copy(&(recp->N),d); | |
102 | BN_zero(&(recp->Nr)); | |
103 | recp->num_bits=BN_num_bits(d); | |
104 | recp->shift=0; | |
105 | return(1); | |
106 | } | |
107 | ||
108 | int BN_mod_mul_reciprocal(r, x, y, recp, ctx) | |
d02b48c6 RE |
109 | BIGNUM *r; |
110 | BIGNUM *x; | |
111 | BIGNUM *y; | |
dfeab068 RE |
112 | BN_RECP_CTX *recp; |
113 | BN_CTX *ctx; | |
114 | { | |
115 | int ret=0; | |
116 | BIGNUM *a; | |
117 | ||
118 | a= &(ctx->bn[ctx->tos++]); | |
119 | if (y != NULL) | |
120 | { | |
121 | if (x == y) | |
122 | { if (!BN_sqr(a,x,ctx)) goto err; } | |
123 | else | |
124 | { if (!BN_mul(a,x,y,ctx)) goto err; } | |
125 | } | |
126 | else | |
127 | a=x; /* Just do the mod */ | |
128 | ||
129 | BN_div_recp(NULL,r,a,recp,ctx); | |
130 | ret=1; | |
131 | err: | |
132 | ctx->tos--; | |
133 | return(ret); | |
134 | } | |
135 | ||
136 | int BN_div_recp(dv,rem,m,recp,ctx) | |
137 | BIGNUM *dv; | |
138 | BIGNUM *rem; | |
d02b48c6 | 139 | BIGNUM *m; |
dfeab068 | 140 | BN_RECP_CTX *recp; |
d02b48c6 RE |
141 | BN_CTX *ctx; |
142 | { | |
dfeab068 RE |
143 | int i,j,tos,ret=0,ex; |
144 | BIGNUM *a,*b,*d,*r; | |
145 | ||
146 | tos=ctx->tos; | |
147 | a= &(ctx->bn[ctx->tos++]); | |
148 | b= &(ctx->bn[ctx->tos++]); | |
149 | if (dv != NULL) | |
150 | d=dv; | |
151 | else | |
152 | d= &(ctx->bn[ctx->tos++]); | |
153 | if (rem != NULL) | |
154 | r=rem; | |
155 | else | |
156 | r= &(ctx->bn[ctx->tos++]); | |
157 | ||
158 | if (BN_ucmp(m,&(recp->N)) < 0) | |
159 | { | |
160 | BN_zero(d); | |
161 | BN_copy(r,m); | |
162 | ctx->tos=tos; | |
163 | return(1); | |
164 | } | |
d02b48c6 | 165 | |
dfeab068 RE |
166 | /* We want the remainder |
167 | * Given input of ABCDEF / ab | |
168 | * we need multiply ABCDEF by 3 digests of the reciprocal of ab | |
169 | * | |
170 | */ | |
171 | i=BN_num_bits(m); | |
d02b48c6 | 172 | |
dfeab068 RE |
173 | j=recp->num_bits*2; |
174 | if (j > i) | |
175 | { | |
176 | i=j; | |
177 | ex=0; | |
178 | } | |
d02b48c6 | 179 | else |
dfeab068 RE |
180 | { |
181 | ex=(i-j)/2; | |
182 | } | |
183 | ||
184 | j=i/2; | |
185 | ||
186 | if (i != recp->shift) | |
187 | recp->shift=BN_reciprocal(&(recp->Nr),&(recp->N), | |
188 | i,ctx); | |
189 | ||
190 | if (!BN_rshift(a,m,j-ex)) goto err; | |
191 | if (!BN_mul(b,a,&(recp->Nr),ctx)) goto err; | |
192 | if (!BN_rshift(d,b,j+ex)) goto err; | |
193 | d->neg=0; | |
194 | if (!BN_mul(b,&(recp->N),d,ctx)) goto err; | |
195 | if (!BN_usub(r,m,b)) goto err; | |
196 | r->neg=0; | |
197 | ||
d02b48c6 | 198 | j=0; |
dfeab068 RE |
199 | #if 1 |
200 | while (BN_ucmp(r,&(recp->N)) >= 0) | |
d02b48c6 RE |
201 | { |
202 | if (j++ > 2) | |
203 | { | |
204 | BNerr(BN_F_BN_MOD_MUL_RECIPROCAL,BN_R_BAD_RECIPROCAL); | |
205 | goto err; | |
206 | } | |
dfeab068 RE |
207 | if (!BN_usub(r,r,&(recp->N))) goto err; |
208 | if (!BN_add_word(d,1)) goto err; | |
d02b48c6 | 209 | } |
dfeab068 | 210 | #endif |
d02b48c6 | 211 | |
dfeab068 RE |
212 | r->neg=BN_is_zero(r)?0:m->neg; |
213 | d->neg=m->neg^recp->N.neg; | |
d02b48c6 RE |
214 | ret=1; |
215 | err: | |
dfeab068 | 216 | ctx->tos=tos; |
d02b48c6 | 217 | return(ret); |
dfeab068 | 218 | } |
d02b48c6 | 219 | |
dfeab068 RE |
220 | /* len is the expected size of the result |
221 | * We actually calculate with an extra word of precision, so | |
222 | * we can do faster division if the remainder is not required. | |
223 | */ | |
224 | int BN_reciprocal(r,m,len,ctx) | |
d02b48c6 RE |
225 | BIGNUM *r; |
226 | BIGNUM *m; | |
dfeab068 | 227 | int len; |
d02b48c6 RE |
228 | BN_CTX *ctx; |
229 | { | |
dfeab068 RE |
230 | int ret= -1; |
231 | BIGNUM t; | |
d02b48c6 | 232 | |
dfeab068 | 233 | BN_init(&t); |
d02b48c6 | 234 | |
dfeab068 RE |
235 | BN_zero(&t); |
236 | if (!BN_set_bit(&t,len)) goto err; | |
d02b48c6 | 237 | |
dfeab068 RE |
238 | if (!BN_div(r,NULL,&t,m,ctx)) goto err; |
239 | ret=len; | |
d02b48c6 | 240 | err: |
dfeab068 | 241 | BN_free(&t); |
d02b48c6 RE |
242 | return(ret); |
243 | } | |
244 |