From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1765545AbXE2UGS (ORCPT ); Tue, 29 May 2007 16:06:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757797AbXE2UGL (ORCPT ); Tue, 29 May 2007 16:06:11 -0400 Received: from keetweej.vanheusden.com ([213.84.46.114]:56095 "EHLO keetweej.vanheusden.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758101AbXE2UGJ (ORCPT ); Tue, 29 May 2007 16:06:09 -0400 Date: Tue, 29 May 2007 22:06:08 +0200 From: Folkert van Heusden To: Pavel Machek , Theodore Tso , M Macnair , linux-kernel@vger.kernel.org Subject: Re: Seeding /dev/random not working Message-ID: <20070529200608.GF19229@vanheusden.com> References: <20070529131501.GA9899@thunk.org> <20070529141456.GC5840@ucw.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070529141456.GC5840@ucw.cz> Organization: www.unixexpert.nl X-Chameleon-Return-To: folkert@vanheusden.com X-Xfmail-Return-To: folkert@vanheusden.com X-Phonenumber: +31-6-41278122 X-URL: http://www.vanheusden.com/ X-PGP-KeyID: 1F28D8AE X-GPG-fingerprint: AC89 09CE 41F2 00B4 FCF2 B174 3019 0E8C 1F28 D8AE X-Key: http://pgp.surfnet.nl:11371/pks/lookup?op=get&search=0x1F28D8AE Read-Receipt-To: Reply-By: Tue May 29 21:31:50 CEST 2007 X-Message-Flag: PGP key-id: 0x1f28d8ae - consider encrypting your e-mail to me with PGP! User-Agent: Mutt/1.5.15+20070515 (2007-05-02) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > > > I have two embedded boards (one ARM, one PowerPC), running two > > > different versions of 2.6. They have no hard drives, keyboards or > > > mice. They each have a NIC, but I understand these make no > > > contribution to the entropy pool. > > > if [ -f $random_seed ]; then > > > cat $random_seed >/dev/urandom # should seed the pool > > > fi > > > dd if=/dev/urandom of=$random_seed count=1 2>/dev/null # save some > > > data from urandom for next boot > > > I have rebooted my boards many times, and after each boot I read the > > > contents of $random_seed. Whilst it does not happen every time, the > > > contents of $random_seed are /often the same/. To give you a feel: > > > rebooted 11 times, got a total of 3 different outputs. > > > > Ok, so this is telling me a couple of things. First of all, if you're > > only getting three outputs, it means that you don't have any > > peripherals feeding entropy into the system from the boot sequence. > > Without any hard drives, keyboards or mice, and a NIC whose device > > driver hasn't been configured to feed entropy, you're definitely > > hosed. > > Can we get at least time-of-boot from rtc clock to the pool? We really > should not be getting identical outputs... And add readings from lm-sensors as well? I guess harddisk and cpu temperatures (lower bits) and such are pretty random? Folkert van Heusden -- MultiTail est un flexible tool pour suivre de logfiles et execution de commandements. Filtrer, pourvoir de couleur, merge, 'diff-view', etc. http://www.vanheusden.com/multitail/ ---------------------------------------------------------------------- Phone: +31-6-41278122, PGP-key: 1F28D8AE, www.vanheusden.com