|ARC4RANDOM(3)||Library Functions Manual||ARC4RANDOM(3)|
arc4random_addrandom — arc4
random number generator
function provides a high quality 32-bit pseudo-random number very quickly.
arc4random() seeds itself on a regular basis from
the kernel strong random number subsystem described in
random(4). On each call, an
ARC4 generator is used to generate a new result. The
arc4random() function uses the ARC4 cipher key
stream generator, which uses 8*8 8-bit S-Boxes. The S-Boxes can be in about
fits into a middle ground not covered by other subsystems such as the
strong, slow, and resource expensive random devices described in
random(4) versus the fast but
poor quality interfaces described in
fills the region buf of length
nbytes with ARC4-derived random data.
will return a uniformly distributed random number less than
arc4random_uniform() is recommended over
constructions like “
upper_bound” as it avoids "modulo bias" when the
upper bound is not a power of two.
There is no need to call
arc4random() automatically initializes itself.
These functions are always successful, and no return value is reserved to indicate an error.
An algorithm called RC4 was designed by
RSA Data Security, Inc. It was considered a trade secret. Because it was a
trade secret, it obviously could not be patented. A clone of this was posted
anonymously to USENET and confirmed to be equivalent by several sources who
had access to the original cipher. Because of the trade secret situation,
RSA Data Security, Inc. could do nothing about the release of the
Alleged RC4’ algorithm. Since
RC4 was trademarked, the cipher is now referred to
These functions first appeared in OpenBSD 2.1.
|December 23, 2008||OpenBSD-5.1|