1 /* crypto/bn/bn_mod.c */
2 /* Includes code written by Lenka Fibikova <fibikova@exp-math.uni-essen.de>
3 * for the OpenSSL project. */
4 /* ====================================================================
5 * Copyright (c) 1998-2000 The OpenSSL Project. All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 *
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 *
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in
16 * the documentation and/or other materials provided with the
17 * distribution.
18 *
19 * 3. All advertising materials mentioning features or use of this
20 * software must display the following acknowledgment:
21 * "This product includes software developed by the OpenSSL Project
22 * for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
23 *
24 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
25 * endorse or promote products derived from this software without
26 * prior written permission. For written permission, please contact
27 * openssl-core@openssl.org.
28 *
29 * 5. Products derived from this software may not be called "OpenSSL"
30 * nor may "OpenSSL" appear in their names without prior written
31 * permission of the OpenSSL Project.
32 *
33 * 6. Redistributions of any form whatsoever must retain the following
34 * acknowledgment:
35 * "This product includes software developed by the OpenSSL Project
36 * for use in the OpenSSL Toolkit (http://www.openssl.org/)"
37 *
38 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
39 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
40 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
41 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
42 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
43 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
44 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
45 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
46 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
47 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
48 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
49 * OF THE POSSIBILITY OF SUCH DAMAGE.
50 * ====================================================================
51 *
52 * This product includes cryptographic software written by Eric Young
53 * (eay@cryptsoft.com). This product includes software written by Tim
54 * Hudson (tjh@cryptsoft.com).
55 *
56 */
57 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
58 * All rights reserved.
59 *
60 * This package is an SSL implementation written
61 * by Eric Young (eay@cryptsoft.com).
62 * The implementation was written so as to conform with Netscapes SSL.
63 *
64 * This library is free for commercial and non-commercial use as long as
65 * the following conditions are aheared to. The following conditions
66 * apply to all code found in this distribution, be it the RC4, RSA,
67 * lhash, DES, etc., code; not just the SSL code. The SSL documentation
68 * included with this distribution is covered by the same copyright terms
69 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
70 *
71 * Copyright remains Eric Young's, and as such any Copyright notices in
72 * the code are not to be removed.
73 * If this package is used in a product, Eric Young should be given attribution
74 * as the author of the parts of the library used.
75 * This can be in the form of a textual message at program startup or
76 * in documentation (online or textual) provided with the package.
77 *
78 * Redistribution and use in source and binary forms, with or without
79 * modification, are permitted provided that the following conditions
80 * are met:
81 * 1. Redistributions of source code must retain the copyright
82 * notice, this list of conditions and the following disclaimer.
83 * 2. Redistributions in binary form must reproduce the above copyright
84 * notice, this list of conditions and the following disclaimer in the
85 * documentation and/or other materials provided with the distribution.
86 * 3. All advertising materials mentioning features or use of this software
87 * must display the following acknowledgement:
88 * "This product includes cryptographic software written by
89 * Eric Young (eay@cryptsoft.com)"
90 * The word 'cryptographic' can be left out if the rouines from the library
91 * being used are not cryptographic related :-).
92 * 4. If you include any Windows specific code (or a derivative thereof) from
93 * the apps directory (application code) you must include an acknowledgement:
94 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
95 *
96 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
97 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
98 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
99 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
100 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
101 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
102 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
103 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
104 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
105 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
106 * SUCH DAMAGE.
107 *
108 * The licence and distribution terms for any publically available version or
109 * derivative of this code cannot be changed. i.e. this code cannot simply be
110 * copied and put under another distribution licence
111 * [including the GNU Public Licence.]
112 */
113
114 #include "cryptlib.h"
115 #include "bn_lcl.h"
116
117
118 #if 0 /* now just a #define */
119 int BN_mod(BIGNUM *rem, const BIGNUM *m, const BIGNUM *d, BN_CTX *ctx)
120 {
121 return(BN_div(NULL,rem,m,d,ctx));
122 /* note that rem->neg == m->neg (unless the remainder is zero) */
123 }
124 #endif
125
126
127 int BN_nnmod(BIGNUM *r, const BIGNUM *m, const BIGNUM *d, BN_CTX *ctx)
128 {
129 /* like BN_mod, but returns non-negative remainder
130 * (i.e., 0 <= r < |d| always holds) */
131
132 if (!(BN_mod(r,m,d,ctx)))
133 return 0;
134 if (!r->neg)
135 return 1;
136 /* now -|d| < r < 0, so we have to set r := r + |d| */
137 return (d->neg ? BN_sub : BN_add)(r, r, d);
138 }
139
140
141 int BN_mod_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m, BN_CTX *ctx)
142 {
143 if (!BN_add(r, a, b)) return 0;
144 return BN_nnmod(r, r, m, ctx);
145 }
146
147
148 /* BN_mod_add variant that may be used if both a and b are non-negative
149 * and less than m */
150 int BN_mod_add_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m)
151 {
152 if (!BN_uadd(r, a, b)) return 0;
153 if (BN_ucmp(r, m) >= 0)
154 return BN_usub(r, r, m);
155 return 1;
156 }
157
158
159 int BN_mod_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m, BN_CTX *ctx)
160 {
161 if (!BN_sub(r, a, b)) return 0;
162 return BN_nnmod(r, r, m, ctx);
163 }
164
165
166 /* BN_mod_sub variant that may be used if both a and b are non-negative
167 * and less than m */
168 int BN_mod_sub_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m)
169 {
170 if (!BN_sub(r, a, b)) return 0;
171 if (r->neg)
172 return BN_add(r, r, m);
173 return 1;
174 }
175
176
177 /* slow but works */
178 int BN_mod_mul(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m,
179 BN_CTX *ctx)
180 {
181 BIGNUM *t;
182 int ret=0;
183
184 bn_check_top(a);
185 bn_check_top(b);
186 bn_check_top(m);
187
188 BN_CTX_start(ctx);
189 if ((t = BN_CTX_get(ctx)) == NULL) goto err;
190 if (a == b)
191 { if (!BN_sqr(t,a,ctx)) goto err; }
192 else
193 { if (!BN_mul(t,a,b,ctx)) goto err; }
194 if (!BN_nnmod(r,t,m,ctx)) goto err;
195 bn_check_top(r);
196 ret=1;
197 err:
198 BN_CTX_end(ctx);
199 return(ret);
200 }
201
202
203 int BN_mod_sqr(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx)
204 {
205 if (!BN_sqr(r, a, ctx)) return 0;
206 /* r->neg == 0, thus we don't need BN_nnmod */
207 return BN_mod(r, r, m, ctx);
208 }
209
210
211 int BN_mod_lshift1(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx)
212 {
213 if (!BN_lshift1(r, a)) return 0;
214 bn_check_top(r);
215 return BN_nnmod(r, r, m, ctx);
216 }
217
218
219 /* BN_mod_lshift1 variant that may be used if a is non-negative
220 * and less than m */
221 int BN_mod_lshift1_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *m)
222 {
223 if (!BN_lshift1(r, a)) return 0;
224 bn_check_top(r);
225 if (BN_cmp(r, m) >= 0)
226 return BN_sub(r, r, m);
227 return 1;
228 }
229
230
231 int BN_mod_lshift(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m, BN_CTX *ctx)
232 {
233 BIGNUM *abs_m = NULL;
234 int ret;
235
236 if (!BN_nnmod(r, a, m, ctx)) return 0;
237
238 if (m->neg)
239 {
240 abs_m = BN_dup(m);
241 if (abs_m == NULL) return 0;
242 abs_m->neg = 0;
243 }
244
245 ret = BN_mod_lshift_quick(r, r, n, (abs_m ? abs_m : m));
246 bn_check_top(r);
247
248 if (abs_m)
249 BN_free(abs_m);
250 return ret;
251 }
252
253
254 /* BN_mod_lshift variant that may be used if a is non-negative
255 * and less than m */
256 int BN_mod_lshift_quick(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m)
257 {
258 if (r != a)
259 {
260 if (BN_copy(r, a) == NULL) return 0;
261 }
262
263 while (n > 0)
264 {
265 int max_shift;
266
267 /* 0 < r < m */
268 max_shift = BN_num_bits(m) - BN_num_bits(r);
269 /* max_shift >= 0 */
270
271 if (max_shift < 0)
272 {
273 BNerr(BN_F_BN_MOD_LSHIFT_QUICK, BN_R_INPUT_NOT_REDUCED);
274 return 0;
275 }
276
277 if (max_shift > n)
278 max_shift = n;
279
280 if (max_shift)
281 {
282 if (!BN_lshift(r, r, max_shift)) return 0;
283 n -= max_shift;
284 }
285 else
286 {
287 if (!BN_lshift1(r, r)) return 0;
288 --n;
289 }
290
291 /* BN_num_bits(r) <= BN_num_bits(m) */
292
293 if (BN_cmp(r, m) >= 0)
294 {
295 if (!BN_sub(r, r, m)) return 0;
296 }
297 }
298 bn_check_top(r);
299
300 return 1;
301 }