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3 (C) 2001, 2002, 2003, 2004, 2005, 2006 Christian Grothoff (and other contributing authors)
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6 it under the terms of the GNU General Public License as published
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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;
59 GNUNET_assert (i > 0);
61 if (mode == GNUNET_CRYPTO_QUALITY_STRONG)
63 /* see http://lists.gnupg.org/pipermail/gcrypt-devel/2004-May/000613.html */
64 #ifdef gcry_fast_random_poll
65 if ((invokeCount++ % 256) == 0)
66 gcry_fast_random_poll ();
68 gcry_randomize ((unsigned char *) &ret,
69 sizeof (uint32_t), GCRY_STRONG_RANDOM);
74 ret = i * weak_random ();
83 * Get an array with a random permutation of the
85 * @param mode GNUNET_RANDOM_QUALITY_STRONG if the strong (but expensive)
86 * PRNG should be used, GNUNET_RANDOM_QUALITY_WEAK otherwise
87 * @param n the size of the array
88 * @return the permutation array (allocated from heap)
91 GNUNET_CRYPTO_random_permute (enum GNUNET_CRYPTO_Quality mode, unsigned int n)
98 GNUNET_assert (n > 0);
99 ret = GNUNET_malloc (n * sizeof (unsigned int));
100 for (i = 0; i < n; i++)
102 for (i = n - 1; i > 0; i--)
104 x = GNUNET_CRYPTO_random_u32 (mode, i+1);
113 * Random on unsigned 64-bit values.
116 * @param mode desired quality of the random number
117 * @param max value returned will be in range [0,max) (exclusive)
118 * @return random 64-bit number
121 GNUNET_CRYPTO_random_u64 (enum GNUNET_CRYPTO_Quality mode, uint64_t max)
125 GNUNET_assert (max > 0);
126 if (mode == GNUNET_CRYPTO_QUALITY_STRONG)
128 gcry_randomize ((unsigned char *) &ret,
129 sizeof (uint64_t), GCRY_STRONG_RANDOM);
134 ret = max * weak_random ();
142 * This function should only be called in testcases
143 * where strong entropy gathering is not desired
144 * (for example, for hostkey generation).
147 GNUNET_CRYPTO_random_disable_entropy_gathering ()
149 gcry_control (GCRYCTL_ENABLE_QUICK_RANDOM, 0);
155 void __attribute__ ((constructor)) GNUNET_util_random_init ()
157 SRANDOM (time (NULL));
160 /* end of crypto_random.c */