random —
srandom,
urandom,
prandom,
arandom
random data source devices
SYNOPSIS
#include <sys/types.h> #include <dev/rndvar.h>
DESCRIPTION
The various
random
devices produce random output data with different random qualities.
Entropy data is collected from system activity (like disk and
network device interrupts and such), and then run through various
hash or message digest functions to generate the output.
This device is reserved for future support of hardware
random generators.
Strong random data.
This device returns reliable random data.
If sufficient entropy is not currently available (i.e., the entropy
pool quality starts to run low), the driver pauses while more of
such data is collected.
The entropy pool data is converted into output data using MD5.
Same as above, but does not guarantee the data to be strong.
The entropy pool data is converted into output data using MD5.
When the entropy pool quality runs low, the driver will continue
to output data.
Simple pseudo-random generator.
As required, entropy pool data re-seeds an ARC4 generator,
which then generates high-quality pseudo-random output data.
The
arc4random(3)
function in userland libraries seeds itself from this device,
providing a second level of ARC4 hashed data.