1*e7776783SApple OSS Distributions.Dd September 6, 2001 2*e7776783SApple OSS Distributions.Dt RANDOM 4 3*e7776783SApple OSS Distributions.Os Darwin 4*e7776783SApple OSS Distributions.Sh NAME 5*e7776783SApple OSS Distributions.Nm random 6*e7776783SApple OSS Distributions, 7*e7776783SApple OSS Distributions.Nm urandom 8*e7776783SApple OSS Distributions.Nd random data source devices. 9*e7776783SApple OSS Distributions.Sh SYNOPSIS 10*e7776783SApple OSS Distributions.Cd "pseudo-device random" 11*e7776783SApple OSS Distributions.Sh DESCRIPTION 12*e7776783SApple OSS DistributionsThe 13*e7776783SApple OSS Distributions.Nm 14*e7776783SApple OSS Distributionsdevice produces uniformly distributed random byte values 15*e7776783SApple OSS Distributionsof potentially high quality. 16*e7776783SApple OSS Distributions.Pp 17*e7776783SApple OSS DistributionsTo obtain random bytes, open 18*e7776783SApple OSS Distributions.Nm /dev/random 19*e7776783SApple OSS Distributionsfor reading and read from it. 20*e7776783SApple OSS Distributions.Pp 21*e7776783SApple OSS DistributionsThe same random data is also available from 22*e7776783SApple OSS Distributions.Xr getentropy 2 . 23*e7776783SApple OSS DistributionsUsing the 24*e7776783SApple OSS Distributions.Xr getentropy 2 25*e7776783SApple OSS Distributionssystem call interface will provide resiliency to file descriptor exhaustion, chroot, or sandboxing which can make 26*e7776783SApple OSS Distributions.Nm /dev/random 27*e7776783SApple OSS Distributionsunavailable. Additionally, the 28*e7776783SApple OSS Distributions.Xr arc4random 3 29*e7776783SApple OSS DistributionsAPI provides a fast userspace random number generator built on the 30*e7776783SApple OSS Distributions.Nm 31*e7776783SApple OSS Distributionsdata source and is preferred over directly accessing the system's random device. 32*e7776783SApple OSS Distributions.Pp 33*e7776783SApple OSS Distributions.Nm /dev/urandom 34*e7776783SApple OSS Distributionsis a compatibility nod to Linux. On Linux, 35*e7776783SApple OSS Distributions.Nm /dev/urandom 36*e7776783SApple OSS Distributionswill produce lower quality output if the entropy pool drains, while 37*e7776783SApple OSS Distributions.Nm /dev/random 38*e7776783SApple OSS Distributionswill prefer to block and wait for additional entropy to be collected. 39*e7776783SApple OSS DistributionsWith Fortuna, this choice and distinction is not necessary, and 40*e7776783SApple OSS Distributionsthe two devices behave identically. You may use either. 41*e7776783SApple OSS Distributions.Pp 42*e7776783SApple OSS DistributionsThe 43*e7776783SApple OSS Distributions.Nm 44*e7776783SApple OSS Distributionsdevice implements the 45*e7776783SApple OSS Distributions.Nm Fortuna 46*e7776783SApple OSS Distributionspseudo random number generator algorithm and maintains its entropy pool. 47*e7776783SApple OSS DistributionsThe kernel automatically seeds the algorithm with additional entropy during normal execution. 48*e7776783SApple OSS Distributions.Sh FILES 49*e7776783SApple OSS Distributions.Bl -tag -width /dev/urandom -compact 50*e7776783SApple OSS Distributions.It Pa /dev/random 51*e7776783SApple OSS Distributions.It Pa /dev/urandom 52*e7776783SApple OSS Distributions.El 53*e7776783SApple OSS Distributions.Sh HISTORY 54*e7776783SApple OSS DistributionsA 55*e7776783SApple OSS Distributions.Nm 56*e7776783SApple OSS Distributionsdevice appeared in the Linux operating system. 57