diff options
| author | Andrey A. Chernov <ache@FreeBSD.org> | 2003-02-04 11:24:08 +0000 |
|---|---|---|
| committer | Andrey A. Chernov <ache@FreeBSD.org> | 2003-02-04 11:24:08 +0000 |
| commit | ddd972a9bd5f8a73cd9eb33181072d07ea99aa73 (patch) | |
| tree | b794978ed6263b8a5298e3cbb4e07dc4fce01682 /lib/libc/stdlib/rand.c | |
| parent | 3967e18ad6a675e4fe0ec1cfe1754be37274b893 (diff) | |
For rand(3) and random(3) TYPE_0 drop NSHUFF values right after srand{om}()
to remove part of seed -> 1st value correlation. Correlation still remains
because of algorithm limits. Note that old algorithm have even stronger
correlation, especially in the lower bits area, but not eye-visible, as
current one.
Notes
svn path=/head/; revision=110321
Diffstat (limited to 'lib/libc/stdlib/rand.c')
| -rw-r--r-- | lib/libc/stdlib/rand.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/lib/libc/stdlib/rand.c b/lib/libc/stdlib/rand.c index 47bb36dcad9b..dcc445f13ebd 100644 --- a/lib/libc/stdlib/rand.c +++ b/lib/libc/stdlib/rand.c @@ -51,6 +51,8 @@ __FBSDID("$FreeBSD$"); #include <stdio.h> #endif /* TEST */ +#define NSHUFF 100 /* to drop part of seed -> 1st value correlation */ + static int do_rand(unsigned long *ctx) { @@ -108,7 +110,11 @@ void srand(seed) u_int seed; { + int i; + next = seed; + for (i = 0; i < NSHUFF; i++) + (void)do_rand(&next); } @@ -137,7 +143,7 @@ sranddev() unsigned long junk; gettimeofday(&tv, NULL); - next = (getpid() << 16) ^ tv.tv_sec ^ tv.tv_usec ^ junk; + srand((getpid() << 16) ^ tv.tv_sec ^ tv.tv_usec ^ junk); } } |