Subject: Re: cgd randomkey at start
To: Christian Weniger <>
From: Roland Dowdeswell <>
List: tech-security
Date: 03/01/2005 11:42:20
On 1109694258 seconds since the Beginning of the UNIX epoch
"Christian Weniger" wrote:

>i just want to encrypt (using cgd) my swap partition and the /tmp
>partion with a randomkey at startup. My problem is that /dev/random is
>empty at startup and so cgd hangs and can't generate a randomkey until
>i help and generate random data by typing on the keyboard. That's not a
>solution because i'm going to use the computer without a keyboard.
>So how can i genrate random data without sitting in fornt of the pc?
>Or can i use /dev/urandom for the randomkey? (i found a 2 year old mail
>with the same
>  - but it seems that there is no option "urandomkey" today).

A urandom option was added after the 2.0 branch.

So, you have a few options:

	1.  rebuild cgdconfig with current sources (which is not
	    too difficult),
	2.  wait for the next release major release,
	3.  ask us to pull the changes back to the 2.0 branch and
	    wait for the next minor release, or
	4.  write a program that causes lots of disk access before
	    cgdconfig(1) is called in the boot sequence.

Most modern computers have an entropy device, so I didn't see this
problem when I was developing cgd(4).

I'd feel a tad uncomfortable about using /dev/urandom for this,
but it is certainly better than hanging.  :)

    Roland Dowdeswell                      http://www.Imrryr.ORG/~elric/