[ale] what's the difference between

[Mike Fletcher]

Jim Kinney wrote:
> /dev/random and /dev/urandom?
>
> /dev/random is very slow and on a newly installed machine `cat 
> /dev/random` does little. Same machine `cat /dev/urandom` fills the 
> screen quickly.
>
Quoth http://en.wikipedia.org/wiki/Urandom

A counterpart to /dev/random is /dev/urandom ("unlocked" random source) 
which reuses the internal pool to produce more pseudo-random bits. This 
means that the call will not block, but the output may contain less 
entropy than the corresponding read from /dev/random. The intent is to 
serve as a cryptographically secure pseudorandom number generator. This 
may be used for less secure applications.


> Is there a way to "add entropy" to get /dev/random to fill quicker?
Ibid says that priviledged users can write to it and call an ioctl to 
change the entropy estimate, but if you're going to do that you probably 
might as well be using urandom (unless you're reading from your webcam 
watching your lava lamp collection, of course . . .)