From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754156AbXLEM3V (ORCPT ); Wed, 5 Dec 2007 07:29:21 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751668AbXLEM3O (ORCPT ); Wed, 5 Dec 2007 07:29:14 -0500 Received: from torres.zugschlus.de ([85.214.68.41]:39905 "EHLO torres.zugschlus.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751461AbXLEM3N (ORCPT ); Wed, 5 Dec 2007 07:29:13 -0500 Date: Wed, 5 Dec 2007 13:29:12 +0100 From: Marc Haber To: linux-kernel@vger.kernel.org Subject: Re: Why does reading from /dev/urandom deplete entropy so much? Message-ID: <20071205122912.GC24685@torres.zugschlus.de> References: <20071204114125.GA17310@torres.zugschlus.de> <20071204161811.GB15974@stusta.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20071204161811.GB15974@stusta.de> User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 04, 2007 at 05:18:11PM +0100, Adrian Bunk wrote: > On Tue, Dec 04, 2007 at 12:41:25PM +0100, Marc Haber wrote: > > While debugging Exim4's GnuTLS interface, I recently found out that > > reading from /dev/urandom depletes entropy as much as reading from > > /dev/random would. This has somehow surprised me since I have always > > believed that /dev/urandom has lower quality entropy than /dev/random, > > but lots of it. > > man 4 random Thanks for this pointer, I was not aware of the documentation. After reading this thread and the docs, I am now convinced that GnuTLS should seed a PRNG from /dev/(u)random instead of using the entropy directly. I will go filing a bug against GnuTLS. Greetings Marc -- ----------------------------------------------------------------------------- Marc Haber | "I don't trust Computers. They | Mailadresse im Header Mannheim, Germany | lose things." Winona Ryder | Fon: *49 621 72739834 Nordisch by Nature | How to make an American Quilt | Fax: *49 3221 2323190