1 /* crypto/bn/bn_rand.c */
2 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
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.
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).
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.
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
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)"
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
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.]
63 #include <openssl/rand.h>
65 static int bnrand(int pseudorand, BIGNUM *rnd, int bits, int top, int bottom)
67 unsigned char *buf=NULL;
68 int ret=0,bit,bytes,mask;
81 buf=(unsigned char *)OPENSSL_malloc(bytes);
84 BNerr(BN_F_BN_RAND,ERR_R_MALLOC_FAILURE);
88 /* make a random number and set the top and bottom bits */
90 RAND_add(&tim,sizeof(tim),0);
94 if (RAND_pseudo_bytes(buf, bytes) == -1)
99 if (RAND_bytes(buf, bytes) <= 0)
106 /* generate patterns that are more likely to trigger BN
111 for (i = 0; i < bytes; i++)
113 RAND_pseudo_bytes(&c, 1);
114 if (c >= 128 && i > 0)
135 buf[0]|=(3<<(bit-1));
144 if (bottom) /* set bottom bit if requested */
146 if (!BN_bin2bn(buf,bytes,rnd)) goto err;
157 int BN_rand(BIGNUM *rnd, int bits, int top, int bottom)
159 return bnrand(0, rnd, bits, top, bottom);
162 int BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom)
164 return bnrand(1, rnd, bits, top, bottom);
168 int BN_bntest_rand(BIGNUM *rnd, int bits, int top, int bottom)
170 return bnrand(2, rnd, bits, top, bottom);
174 /* random number r: 0 <= r < range */
175 int BN_rand_range(BIGNUM *r, BIGNUM *range)
179 if (range->neg || BN_is_zero(range))
181 BNerr(BN_F_BN_RAND_RANGE, BN_R_INVALID_RANGE);
185 n = BN_num_bits(range); /* n > 0 */
189 if (!BN_zero(r)) return 0;
191 else if (BN_is_bit_set(range, n - 2))
195 /* range = 11..._2, so each iteration succeeds with probability >= .75 */
196 if (!BN_rand(r, n, -1, 0)) return 0;
198 while (BN_cmp(r, range) >= 0);
203 * so 3*range (= 11..._2) is exactly one bit longer than range */
206 if (!BN_rand(r, n + 1, -1, 0)) return 0;
207 /* If r < 3*range, use r := r MOD range
208 * (which is either r, r - range, or r - 2*range).
209 * Otherwise, iterate once more.
210 * Since 3*range = 11..._2, each iteration succeeds with
211 * probability >= .75. */
212 if (BN_cmp(r ,range) >= 0)
214 if (!BN_sub(r, r, range)) return 0;
215 if (BN_cmp(r, range) >= 0)
216 if (!BN_sub(r, r, range)) return 0;
219 while (BN_cmp(r, range) >= 0);