1*699cd480SApple OSS Distributions.Dd September 6, 2001 2*699cd480SApple OSS Distributions.Dt RANDOM 4 3*699cd480SApple OSS Distributions.Os Darwin 4*699cd480SApple OSS Distributions.Sh NAME 5*699cd480SApple OSS Distributions.Nm random 6*699cd480SApple OSS Distributions, 7*699cd480SApple OSS Distributions.Nm urandom 8*699cd480SApple OSS Distributions.Nd random data source devices. 9*699cd480SApple OSS Distributions.Sh SYNOPSIS 10*699cd480SApple OSS Distributions.Cd "pseudo-device random" 11*699cd480SApple OSS Distributions.Sh DESCRIPTION 12*699cd480SApple OSS DistributionsThe 13*699cd480SApple OSS Distributions.Nm 14*699cd480SApple OSS Distributionsdevice produces uniformly distributed random byte values 15*699cd480SApple OSS Distributionsof potentially high quality. 16*699cd480SApple OSS Distributions.Pp 17*699cd480SApple OSS DistributionsTo obtain random bytes, open 18*699cd480SApple OSS Distributions.Nm /dev/random 19*699cd480SApple OSS Distributionsfor reading and read from it. 20*699cd480SApple OSS Distributions.Pp 21*699cd480SApple OSS DistributionsThe same random data is also available from 22*699cd480SApple OSS Distributions.Xr getentropy 2 . 23*699cd480SApple OSS DistributionsUsing the 24*699cd480SApple OSS Distributions.Xr getentropy 2 25*699cd480SApple OSS Distributionssystem call interface will provide resiliency to file descriptor exhaustion, chroot, or sandboxing which can make 26*699cd480SApple OSS Distributions.Nm /dev/random 27*699cd480SApple OSS Distributionsunavailable. Additionally, the 28*699cd480SApple OSS Distributions.Xr arc4random 3 29*699cd480SApple OSS DistributionsAPI provides a fast userspace random number generator built on the 30*699cd480SApple OSS Distributions.Nm 31*699cd480SApple OSS Distributionsdata source and is preferred over directly accessing the system's random device. 32*699cd480SApple OSS Distributions.Pp 33*699cd480SApple OSS Distributions.Nm /dev/urandom 34*699cd480SApple OSS Distributionsis a compatibility nod to Linux. On Linux, 35*699cd480SApple OSS Distributions.Nm /dev/urandom 36*699cd480SApple OSS Distributionswill produce lower quality output if the entropy pool drains, while 37*699cd480SApple OSS Distributions.Nm /dev/random 38*699cd480SApple OSS Distributionswill prefer to block and wait for additional entropy to be collected. 39*699cd480SApple OSS DistributionsWith Fortuna, this choice and distinction is not necessary, and 40*699cd480SApple OSS Distributionsthe two devices behave identically. You may use either. 41*699cd480SApple OSS Distributions.Pp 42*699cd480SApple OSS DistributionsThe 43*699cd480SApple OSS Distributions.Nm 44*699cd480SApple OSS Distributionsdevice implements the 45*699cd480SApple OSS Distributions.Nm Fortuna 46*699cd480SApple OSS Distributionspseudo random number generator algorithm and maintains its entropy pool. 47*699cd480SApple OSS DistributionsThe kernel automatically seeds the algorithm with additional entropy during normal execution. 48*699cd480SApple OSS Distributions.Sh FILES 49*699cd480SApple OSS Distributions.Bl -tag -width /dev/urandom -compact 50*699cd480SApple OSS Distributions.It Pa /dev/random 51*699cd480SApple OSS Distributions.It Pa /dev/urandom 52*699cd480SApple OSS Distributions.El 53*699cd480SApple OSS Distributions.Sh HISTORY 54*699cd480SApple OSS DistributionsA 55*699cd480SApple OSS Distributions.Nm 56*699cd480SApple OSS Distributionsdevice appeared in the Linux operating system. 57