HP-UX Reference (11i v1 05/09) - 7 Device (Special) Files, 9 General Information, Index (vol 10)

random(7) random(7)

Speciﬁc Information About /dev/urandom

To address the limited random data collection rate problem, the

/dev/urandom device is strictly non-

blocking. The

/dev/urandom holding buffer is regularly updated with random data, yet a high number of

reads can decrease the entropy in its holding buffer. Under this conditions, the entropy of the data from

/dev/urandom will be slightly lower that the one from

/dev/random , yet /dev/urandom can still

be considered a good source of random numbers.

There are no

open() ﬂags that result in device-speciﬁc actions with

/dev/urandom read().

ERRORS

[EAGAIN]

For

/dev/random read(), O_NONBLOCK was set when

/dev/random was opened, and there

is insufﬁcient content in the holding buffer to complete the request.

[EACCES]

For the

/dev/random RNG_GETRAW ioctl(), the requesting thread did not have superuser

authority.

AUTHORS

The random number generator was developed by HP.

For bias removal, the generator uses an algorithm by Dr. Yuval Perez, University of California.

The secure hashing uses an AES implementation provided by Dr. Brian Gladman, UK.

The NIST statistical tests are available at http://csrc.nist.gov/rng

FILES

/dev/random

/dev/urandom