From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754962Ab3KEPAf (ORCPT ); Tue, 5 Nov 2013 10:00:35 -0500 Received: from mail.eperm.de ([89.247.134.16]:47411 "EHLO mail.eperm.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754518Ab3KEPAe (ORCPT ); Tue, 5 Nov 2013 10:00:34 -0500 From: Stephan Mueller To: Pavel Machek Cc: "Theodore Ts'o" , sandy harris , linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org Subject: Re: [PATCH] CPU Jitter RNG: inclusion into kernel crypto API and /dev/random Date: Tue, 05 Nov 2013 14:45:58 +0100 Message-ID: <7447932.fADKoNoZRI@tauon> User-Agent: KMail/4.11.2 (Linux/3.11.6-200.fc19.x86_64; KDE/4.11.2; x86_64; ; ) In-Reply-To: <4763730.CsXSbevC1J@tauon> References: <2579337.FPgJGgHYdz@tauon> <20131103233207.GA5105@amd.pavel.ucw.cz> <4763730.CsXSbevC1J@tauon> 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, 5. November 2013, 13:25:40 schrieb Stephan Mueller: Hi Pavel, >Am Montag, 4. November 2013, 00:32:07 schrieb Pavel Machek: >>But they usually _do_ have RTC or other clock, not driven by CPU >>oscilator. Good. >> >>What about just >> >>while (!enough_entropy) { >> >> cur_time = read_rtc(); >> simulated_tsc = 0; >> while (cur_time == read_rtc()) >> >> simulated_tsc++; >> >> gain_entropy_from(simulated_tsc) >> >>} > >That is an interesting piece of code -- what would you do in the >gain_entropy_from function? Please disregard my question. I plugged that idea into my current Jitter RNG processing and disabled the other jitter measurements to get a clear, isolated picture. The result is also a white noise! And it is even quite fast. That means with this approach, even another noise source is available that I could combine with the jitter measurements. I will have to perform more tests on that noise source. But the smoke test is already quite interesting. Ciao Stephan