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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. | |
0f113f3e | 8 | * |
d02b48c6 RE |
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). | |
0f113f3e | 15 | * |
d02b48c6 RE |
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. | |
0f113f3e | 22 | * |
d02b48c6 RE |
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 :-). | |
0f113f3e | 37 | * 4. If you include any Windows specific code (or a derivative thereof) from |
d02b48c6 RE |
38 | * the apps directory (application code) you must include an acknowledgement: |
39 | * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)" | |
0f113f3e | 40 | * |
d02b48c6 RE |
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. | |
0f113f3e | 52 | * |
d02b48c6 RE |
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 | ||
b39fc560 | 59 | #include "internal/cryptlib.h" |
d02b48c6 RE |
60 | #include "bn_lcl.h" |
61 | ||
6b691a5c | 62 | void BN_RECP_CTX_init(BN_RECP_CTX *recp) |
0f113f3e MC |
63 | { |
64 | BN_init(&(recp->N)); | |
65 | BN_init(&(recp->Nr)); | |
66 | recp->num_bits = 0; | |
67 | recp->flags = 0; | |
68 | } | |
dfeab068 | 69 | |
6b691a5c | 70 | BN_RECP_CTX *BN_RECP_CTX_new(void) |
0f113f3e MC |
71 | { |
72 | BN_RECP_CTX *ret; | |
dfeab068 | 73 | |
b4faea50 | 74 | if ((ret = OPENSSL_malloc(sizeof(*ret))) == NULL) |
0f113f3e | 75 | return (NULL); |
dfeab068 | 76 | |
0f113f3e MC |
77 | BN_RECP_CTX_init(ret); |
78 | ret->flags = BN_FLG_MALLOCED; | |
79 | return (ret); | |
80 | } | |
dfeab068 | 81 | |
6b691a5c | 82 | void BN_RECP_CTX_free(BN_RECP_CTX *recp) |
0f113f3e MC |
83 | { |
84 | if (recp == NULL) | |
85 | return; | |
e03ddfae | 86 | |
0f113f3e MC |
87 | BN_free(&(recp->N)); |
88 | BN_free(&(recp->Nr)); | |
89 | if (recp->flags & BN_FLG_MALLOCED) | |
90 | OPENSSL_free(recp); | |
91 | } | |
dfeab068 | 92 | |
84c15db5 | 93 | int BN_RECP_CTX_set(BN_RECP_CTX *recp, const BIGNUM *d, BN_CTX *ctx) |
0f113f3e MC |
94 | { |
95 | if (!BN_copy(&(recp->N), d)) | |
96 | return 0; | |
97 | BN_zero(&(recp->Nr)); | |
98 | recp->num_bits = BN_num_bits(d); | |
99 | recp->shift = 0; | |
100 | return (1); | |
101 | } | |
dfeab068 | 102 | |
020fc820 | 103 | int BN_mod_mul_reciprocal(BIGNUM *r, const BIGNUM *x, const BIGNUM *y, |
0f113f3e MC |
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) | |
112 | goto err; | |
113 | if (y != NULL) { | |
114 | if (x == y) { | |
115 | if (!BN_sqr(a, x, ctx)) | |
116 | goto err; | |
117 | } else { | |
118 | if (!BN_mul(a, x, y, ctx)) | |
119 | goto err; | |
120 | } | |
121 | ca = a; | |
122 | } else | |
123 | ca = x; /* Just do the mod */ | |
124 | ||
125 | ret = BN_div_recp(NULL, r, ca, recp, ctx); | |
126 | err: | |
127 | BN_CTX_end(ctx); | |
128 | bn_check_top(r); | |
129 | return (ret); | |
130 | } | |
dfeab068 | 131 | |
020fc820 | 132 | int BN_div_recp(BIGNUM *dv, BIGNUM *rem, const BIGNUM *m, |
0f113f3e MC |
133 | BN_RECP_CTX *recp, BN_CTX *ctx) |
134 | { | |
135 | int i, j, ret = 0; | |
136 | BIGNUM *a, *b, *d, *r; | |
137 | ||
138 | BN_CTX_start(ctx); | |
139 | a = BN_CTX_get(ctx); | |
140 | b = BN_CTX_get(ctx); | |
141 | if (dv != NULL) | |
142 | d = dv; | |
143 | else | |
144 | d = BN_CTX_get(ctx); | |
145 | if (rem != NULL) | |
146 | r = rem; | |
147 | else | |
148 | r = BN_CTX_get(ctx); | |
149 | if (a == NULL || b == NULL || d == NULL || r == NULL) | |
150 | goto err; | |
151 | ||
152 | if (BN_ucmp(m, &(recp->N)) < 0) { | |
153 | BN_zero(d); | |
154 | if (!BN_copy(r, m)) | |
155 | return 0; | |
156 | BN_CTX_end(ctx); | |
157 | return (1); | |
158 | } | |
159 | ||
160 | /* | |
161 | * We want the remainder Given input of ABCDEF / ab we need multiply | |
162 | * ABCDEF by 3 digests of the reciprocal of ab | |
163 | */ | |
164 | ||
165 | /* i := max(BN_num_bits(m), 2*BN_num_bits(N)) */ | |
166 | i = BN_num_bits(m); | |
167 | j = recp->num_bits << 1; | |
168 | if (j > i) | |
169 | i = j; | |
170 | ||
171 | /* Nr := round(2^i / N) */ | |
172 | if (i != recp->shift) | |
173 | recp->shift = BN_reciprocal(&(recp->Nr), &(recp->N), i, ctx); | |
174 | /* BN_reciprocal could have returned -1 for an error */ | |
175 | if (recp->shift == -1) | |
176 | goto err; | |
dfeab068 | 177 | |
e95bbc3c AP |
178 | /*- |
179 | * d := |round(round(m / 2^BN_num_bits(N)) * recp->Nr / 2^(i - BN_num_bits(N)))| | |
180 | * = |round(round(m / 2^BN_num_bits(N)) * round(2^i / N) / 2^(i - BN_num_bits(N)))| | |
181 | * <= |(m / 2^BN_num_bits(N)) * (2^i / N) * (2^BN_num_bits(N) / 2^i)| | |
182 | * = |m/N| | |
183 | */ | |
0f113f3e MC |
184 | if (!BN_rshift(a, m, recp->num_bits)) |
185 | goto err; | |
186 | if (!BN_mul(b, a, &(recp->Nr), ctx)) | |
187 | goto err; | |
188 | if (!BN_rshift(d, b, i - recp->num_bits)) | |
189 | goto err; | |
190 | d->neg = 0; | |
191 | ||
192 | if (!BN_mul(b, &(recp->N), d, ctx)) | |
193 | goto err; | |
194 | if (!BN_usub(r, m, b)) | |
195 | goto err; | |
196 | r->neg = 0; | |
dfeab068 | 197 | |
0f113f3e MC |
198 | j = 0; |
199 | while (BN_ucmp(r, &(recp->N)) >= 0) { | |
200 | if (j++ > 2) { | |
201 | BNerr(BN_F_BN_DIV_RECP, BN_R_BAD_RECIPROCAL); | |
202 | goto err; | |
203 | } | |
204 | if (!BN_usub(r, r, &(recp->N))) | |
205 | goto err; | |
206 | if (!BN_add_word(d, 1)) | |
207 | goto err; | |
208 | } | |
d02b48c6 | 209 | |
0f113f3e MC |
210 | r->neg = BN_is_zero(r) ? 0 : m->neg; |
211 | d->neg = m->neg ^ recp->N.neg; | |
212 | ret = 1; | |
213 | err: | |
214 | BN_CTX_end(ctx); | |
215 | bn_check_top(dv); | |
216 | bn_check_top(rem); | |
217 | return (ret); | |
218 | } | |
219 | ||
220 | /* | |
221 | * len is the expected size of the result We actually calculate with an extra | |
222 | * word of precision, so we can do faster division if the remainder is not | |
223 | * required. | |
dfeab068 | 224 | */ |
78a0c1f1 | 225 | /* r := 2^len / m */ |
6343829a | 226 | int BN_reciprocal(BIGNUM *r, const BIGNUM *m, int len, BN_CTX *ctx) |
0f113f3e MC |
227 | { |
228 | int ret = -1; | |
229 | BIGNUM *t; | |
230 | ||
231 | BN_CTX_start(ctx); | |
232 | if ((t = BN_CTX_get(ctx)) == NULL) | |
233 | goto err; | |
234 | ||
235 | if (!BN_set_bit(t, len)) | |
236 | goto err; | |
237 | ||
238 | if (!BN_div(r, NULL, t, m, ctx)) | |
239 | goto err; | |
240 | ||
241 | ret = len; | |
242 | err: | |
243 | bn_check_top(r); | |
244 | BN_CTX_end(ctx); | |
245 | return (ret); | |
246 | } |