[TriLUG] need help, netcat as a traffic generator?

[Aaron S. Joyner]

Brian Henning wrote:

>I was about to reply along this line earlier today, before I googled
>"urandom"...  Assuming it works similarly on all *nix systems (which, I
>realize, could be a big assumption), both urandom and random pull from the
>entropy pool; the only difference being that random blocks when it runs out,
>whereas urandom forges ahead with a pseudo-random generator.  At least,
>that's how I interpreted what I read.
>  
>
That's essentially the meat of it.  Both random and urandom use entropy 
when they have it, but random will block until it gets more, once it 
runs out, urandom will continue with the last bit of random it had as a 
seed, which works reasonably well, but isn't as secure.  The real 
problem comes when something else that wants to be secure decides to 
read from /dev/random, it will block until it gets sufficient entropy to 
continue.  I haven't tested for sure, but at the least it's going to 
cause some unnecessary delay for that process if you've run the system 
out of random data (until more can be acquired).  At the worst, it may 
continually deplete the random pool via urandom so fast that random 
never gets a sufficiently large chunk to return it to the blocked 
process (not likely, but possible).

Aaron S. Joyner