NAME
arc4random,
arc4random_buf,
arc4random_uniform,
enqueue_randomness —
kernel random subsystem
SYNOPSIS
#include
<sys/systm.h>
u_int32_t
arc4random(void);
void
arc4random_buf(void
*buf, size_t
nbytes);
u_int32_t
arc4random_uniform(u_int32_t
upper_bound);
#include
<dev/rndvar.h>
void
enqueue_randomness(int);
DESCRIPTION
The
add_random()
functions below mix input into the system entropy pool, which is then used
to create a key for the ChaCha stream cipher used in the
arc4random() series of functions.
enqueue_randomness()
causes the supplied data argument to be added to the entropy pool,
increasing the entropy counter by 32 bits.
arc4random()
and
arc4random_buf()
provide random numbers and are intended to be called in any circumstance
where random numbers are required.
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. In the worst case, this function may
consume multiple iterations to ensure uniformity; see the source code to
understand the problem and solution.
arc4random(),
arc4random_buf(),
and arc4random_uniform() may be called in nearly any
kernel context.