Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754832AbaBDUZh (ORCPT ); Tue, 4 Feb 2014 15:25:37 -0500 Received: from mail.eperm.de ([89.247.134.16]:37565 "EHLO mail.eperm.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753440AbaBDUZf (ORCPT ); Tue, 4 Feb 2014 15:25:35 -0500 From: Stephan Mueller To: "Theodore Ts'o" Cc: =?ISO-8859-1?Q?J=F6rn?= Engel , "H. Peter Anvin" , Linux Kernel Developers List , macro@linux-mips.org, ralf@linux-mips.org, dave.taht@gmail.com, blogic@openwrt.org, andrewmcgr@gmail.com, geert@linux-m68k.org, tg@mirbsd.de, sandyinchina@gmail.com Subject: Re: [RFC PATCH 0/5] CPU Jitter RNG Date: Tue, 04 Feb 2014 21:25:19 +0100 Message-ID: <2913164.1FI4GNAxTm@tauon> User-Agent: KMail/4.11.5 (Linux/3.12.7-300.fc20.x86_64; KDE/4.11.5; x86_64; ; ) In-Reply-To: <20140204170823.GF12768@thunk.org> References: <2039634.jSmQAS6tdi@myon.chronox.de> <20140204170823.GF12768@thunk.org> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am Dienstag, 4. Februar 2014, 12:08:23 schrieb Theodore Ts'o: Hi Theodore, > >> [2] http://www.chronox.de/jent/doc/CPU-Jitter-NPTRNG.html > >which don't really add much to the discussion, but instead just simply >make an expert question how deep the analysis has gone. Measuring the >statistical tests of the entropy pool is a complete waste of time --- >and in general, using things like "dieharder" don't do anything to >increase one's confidence (and could decrease one's confidence if it >makes it appear too much like a snake oil sales document). Sure, >passing dieharder is necessary, but it isn't even vaguely close to >sufficient. > I am a bit surprised by this statement because I use statistical test only as a necessary baseline. After that, the hard work started on the actual noise source by measuring the actual noise coming out of the noise sources. All of these tests have nothing to do with the statistical tests of dieharder & Co. That is the sole reason why I looked into testing the timing variations on bare metal, independently for each noise source. Also, measuring the basic noise on a large array of different CPUs which then show similar behaviors are used to help my case. So, when only looking at the statistical tests, the majority of the work is not considered. Ciao Stephan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/