random.4 revision 1.15
$OpenBSD: random.4,v 1.15 2002/10/26 15:34:52 jakob Exp $
Copyright (c) 1996, 1997 Michael Shalayeff
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
3. All advertising materials mentioning features or use of this software
must display the following acknowledgement:
This product includes software developed by Michael Shalayeff.
4. Neither the name of the University nor the names of its contributors
may be used to endorse or promote products derived from this software
without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.
.Dd March 25, 1996 .Dt RANDOM 4 .Os .Sh NAME .Nm random , .Nm srandom , .Nm urandom , .Nm prandom , .Nm arandom .Nd random data source devices .Sh SYNOPSIS .Fd #include <sys/types.h> .Fd #include <dev/rndvar.h> .Fd #include <dev/rndioctl.h> .Sh DESCRIPTION The various .Nm 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. l -hang -width /dev/srandomX t /dev/random This device is reserved for future support of hardware random generators. t /dev/srandom 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. t /dev/urandom 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. t /dev/prandom Simple pseudo-random generator. t /dev/arandom As required, entropy pool data re-seeds an ARC4 generator, which then generates high-quality pseudo-random output data.
Copyright (c) 1996, 1997 Michael Shalayeff
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
3. All advertising materials mentioning features or use of this software
must display the following acknowledgement:
This product includes software developed by Michael Shalayeff.
4. Neither the name of the University nor the names of its contributors
may be used to endorse or promote products derived from this software
without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.
.Dd March 25, 1996 .Dt RANDOM 4 .Os .Sh NAME .Nm random , .Nm srandom , .Nm urandom , .Nm prandom , .Nm arandom .Nd random data source devices .Sh SYNOPSIS .Fd #include <sys/types.h> .Fd #include <dev/rndvar.h> .Fd #include <dev/rndioctl.h> .Sh DESCRIPTION The various .Nm 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. l -hang -width /dev/srandomX t /dev/random This device is reserved for future support of hardware random generators. t /dev/srandom 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. t /dev/urandom 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. t /dev/prandom Simple pseudo-random generator. t /dev/arandom As required, entropy pool data re-seeds an ARC4 generator, which then generates high-quality pseudo-random output data.
p The .Xr arc4random 3 function in userland libraries seeds itself from this device, providing a second level of ARC4 hashed data. .El .Sh SEE ALSO .Xr arc4random 3 , .Xr md5 3 , .Xr random 3 , .Xr amdpm 4 , .Xr pchb 4 , .Xr md5 9 , .Xr random 9 .Sh FILES l -tag -width /dev/srandom -compact t Pa /dev/random t Pa /dev/srandom t Pa /dev/urandom t Pa /dev/prandom t Pa /dev/arandom .El .Sh BUGS No randomness testing suite provided. .Sh HISTORY A .Nm device first appeared in Linux operating system. This is a cloned interface.
p ARC4 routines added by David Mazieres.