alternative random device

Matthew Byng-Maddick gnupg at
Sun Feb 9 20:20:01 CET 2003

On Sun, Feb 09, 2003 at 07:58:38PM +0100, Janusz A . Urbanowicz wrote:
> Jacob Perkins napisa?[a]/wrote/schrieb:
> > I'm not sure how common this is, but I am using gentoo, which provides a
> > /dev/urandom device, which seems to have much better performance than
> > /dev/random. I actually had to restart earlier because /dev/random
> > stopped working, and gnupg couldn't generate any keys, though
> > /dev/urandom worked fine.  Is it possible to configure gnupg to use
> > /dev/urandom instead of /dev/random?  How? --enable-static-rnd doesn't
> > seem to allow specifying the device.  If it current isn't possible, I
> > think a configure time option should be added, maybe --random-device=.
> > This is all with gnupg-1.2.1
> This is a feature. 
> /dev/random is assumed to be a source of cryptographically safe random bits
> source, while /dev/urandom is not. No one should use /dev/urandom for crypto.

This depends on the type of crypto, in fact. Something like the secret
number in a (session) DH key is perfectly adequately generated by
/dev/urandom, because you're very unlikely to be able to recover the state,
however something like a long-lived private key is a bad thing to be
generating in that way, because you would rather have real randomness than
any sort of (possibly recoverable later with some attack on the random
device) pseudo-randomness.


Matthew Byng-Maddick         <mbm at> 

More information about the Gnupg-devel mailing list