ARC4RANDOM(9) Kernel Developer's Manual ARC4RANDOM(9)

arc4random, arc4random_buf, arc4random_uniform, enqueue_randomnesskernel random subsystem

#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);

void
enqueue_randomness(int);

() and () provide random numbers and are intended to be called in any circumstance where random numbers are required.

() 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.

() causes the supplied data argument to be added to the entropy pool.

arc4random(3), random(4)

OpenBSD 7.8 May 29, 2020 ARC4RANDOM(9)