NAME
arc4random —
kernel random subsystem
SYNOPSIS
#include
<dev/rndvar.h>
void
add_true_randomness(int);
void
add_timer_randomness(int);
void
add_mouse_randomness(int);
void
add_tty_randomness(int);
void
add_net_randomness(int);
void
add_disk_randomness(int);
void
add_audio_randomness(int);
u_int32_t
arc4random(void);
void
arc4random_buf(void
*buf, size_t
nbytes);
u_int32_t
arc4random_uniform(u_int32_t
upper_bound);
DESCRIPTION
The
add_mouse_randomness(),
add_tty_randomness(),
add_net_randomness(),
add_disk_randomness()
and
add_audio_randomness()
routines are used to supply data for the random data source device for
further processing. The processing involves calculating inter-event
timedelta and measuring entropy contained in the resulting delta-T; the
argument data supplied is just mixed into the pool and does not increase the
entropy counter.
add_true_randomness()
does not involve the usual timing calculations, and causes the supplied data
argument to be added to the entropy pool, increasing the entropy counter by
32 bits.
add_timer_randomness()
will not cause the entropy counter to rise. It is used to change the state
of the pool periodically, mostly by means of timing the random driver's
operations.
arc4random()
and
arc4random_buf()
provide random numbers. They may be called safely in any kernel context.
arc4random_uniform()
will return a uniformly distributed random number less than
upper_bound, avoiding "modulo bias" when the
upper bound is not a power of two.