2 This file is part of GNUnet.
3 (C) 2001, 2002, 2003, 2004, 2005, 2006 Christian Grothoff (and other contributing authors)
5 GNUnet is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published
7 by the Free Software Foundation; either version 2, or (at your
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11 WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 General Public License for more details.
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23 * @file util/crypto_random.c
24 * @brief functions to gather random numbers
25 * @author Christian Grothoff
28 #include "gnunet_common.h"
29 #include "gnunet_crypto_lib.h"
33 * Create a cryptographically weak pseudo-random number in the interval of 0 to 1.
35 * @return number between 0 and 1.
40 return ((double) RANDOM () / RAND_MAX);
45 * Produce a random value.
47 * @param mode desired quality of the random number
48 * @param i the upper limit (exclusive) for the random number
49 * @return a random value in the interval [0,i[.
52 GNUNET_CRYPTO_random_u32 (enum GNUNET_CRYPTO_Quality mode, uint32_t i)
54 #ifdef gcry_fast_random_poll
55 static unsigned int invokeCount;
60 GNUNET_assert (i > 0);
62 if (mode == GNUNET_CRYPTO_QUALITY_STRONG)
64 /* see http://lists.gnupg.org/pipermail/gcrypt-devel/2004-May/000613.html */
65 #ifdef gcry_fast_random_poll
66 if ((invokeCount++ % 256) == 0)
67 gcry_fast_random_poll ();
69 ul = UINT32_MAX - (UINT32_MAX % i);
72 gcry_randomize ((unsigned char *) &ret,
73 sizeof (uint32_t), GCRY_STRONG_RANDOM);
80 ret = i * weak_random ();
89 * Get an array with a random permutation of the
91 * @param mode GNUNET_RANDOM_QUALITY_STRONG if the strong (but expensive)
92 * PRNG should be used, GNUNET_RANDOM_QUALITY_WEAK otherwise
93 * @param n the size of the array
94 * @return the permutation array (allocated from heap)
97 GNUNET_CRYPTO_random_permute (enum GNUNET_CRYPTO_Quality mode, unsigned int n)
104 GNUNET_assert (n > 0);
105 ret = GNUNET_malloc (n * sizeof (unsigned int));
106 for (i = 0; i < n; i++)
108 for (i = n - 1; i > 0; i--)
110 x = GNUNET_CRYPTO_random_u32 (mode, i+1);
119 * Random on unsigned 64-bit values.
122 * @param mode desired quality of the random number
123 * @param max value returned will be in range [0,max) (exclusive)
124 * @return random 64-bit number
127 GNUNET_CRYPTO_random_u64 (enum GNUNET_CRYPTO_Quality mode, uint64_t max)
132 GNUNET_assert (max > 0);
133 if (mode == GNUNET_CRYPTO_QUALITY_STRONG)
135 ul = UINT64_MAX - (UINT64_MAX % max);
138 gcry_randomize ((unsigned char *) &ret,
139 sizeof (uint64_t), GCRY_STRONG_RANDOM);
146 ret = max * weak_random ();
154 * This function should only be called in testcases
155 * where strong entropy gathering is not desired
156 * (for example, for hostkey generation).
159 GNUNET_CRYPTO_random_disable_entropy_gathering ()
161 gcry_control (GCRYCTL_ENABLE_QUICK_RANDOM, 0);
167 void __attribute__ ((constructor)) GNUNET_util_random_init ()
169 SRANDOM (time (NULL));
172 /* end of crypto_random.c */