Re: Why does reading from /dev/urandom deplete entropy so much?

Ismail Dönmez
2007-12-09T06:20:25Z

Sunday 09 December 2007 01:46:12 tarihinde Theodore Tso şunları yazmıştı:
> On Sun, Dec 09, 2007 at 12:10:10AM +0200, Ismail Dönmez wrote:
> > > As long as /dev/random is readable for all users there's no reason to
> > > use /dev/urandom for a local DoS...
> >
> > Draining entropy in /dev/urandom means that insecure and possibly not
> > random data will be used and well thats a security bug if not a DoS bug.
>
> Actually in modern 2.6 kernels there are two separate output entropy
> pools for /dev/random and /dev/urandom. So assuming that the
> adversary doesn't know the contents of the current state of the
> entropy pool (i.e., the RNG is well seeded with entropy), you can read
> all you want from /dev/urandom and that won't give an adversary
> successful information to attack /dev/random.

My understanding was if you can drain entropy from /dev/urandom any futher
reads from /dev/urandom will result in data which is not random at all. Is
that wrong?

Regards,
ismail

--
Never learn by your mistakes, if you do you may never dare to try again.