[GNUnet-SVN] r11645 - gnunet/src/util

[gnunet]

Author: grothoff
Date: 2010-06-09 13:06:50 +0200 (Wed, 09 Jun 2010)
New Revision: 11645

Modified:
   gnunet/src/util/crypto_random.c
Log:
fixing bias

Modified: gnunet/src/util/crypto_random.c
===================================================================
--- gnunet/src/util/crypto_random.c     2010-06-09 09:18:45 UTC (rev 11644)
+++ gnunet/src/util/crypto_random.c     2010-06-09 11:06:50 UTC (rev 11645)
@@ -55,6 +55,7 @@
   static unsigned int invokeCount;
 #endif
   uint32_t ret;
+  uint32_t ul;
 
   GNUNET_assert (i > 0);
 
@@ -65,8 +66,13 @@
       if ((invokeCount++ % 256) == 0)
         gcry_fast_random_poll ();
 #endif
-      gcry_randomize ((unsigned char *) &ret,
-                      sizeof (uint32_t), GCRY_STRONG_RANDOM);
+      ul = ((uint32_t)-1) - (((uint32_t)-1) % i);
+      do
+       {
+         gcry_randomize ((unsigned char *) &ret,
+                         sizeof (uint32_t), GCRY_STRONG_RANDOM);
+       }
+      while (ret >= ul);
       return ret % i;
     }
   else
@@ -121,12 +127,18 @@
 GNUNET_CRYPTO_random_u64 (enum GNUNET_CRYPTO_Quality mode, uint64_t max)
 {
   uint64_t ret;
+  uint64_t ul;
 
   GNUNET_assert (max > 0);
   if (mode == GNUNET_CRYPTO_QUALITY_STRONG)
     {
-      gcry_randomize ((unsigned char *) &ret,
-                      sizeof (uint64_t), GCRY_STRONG_RANDOM);
+      ul = ((uint64_t)-1LL) - (((uint64_t)-1LL) % max);
+      do
+       {
+         gcry_randomize ((unsigned char *) &ret,
+                         sizeof (uint64_t), GCRY_STRONG_RANDOM);
+       }
+      while (ret >= ul);
       return ret % max;
     }
   else