Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 1 Feb 2002 21:08:01 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 1 Feb 2002 21:07:51 -0500 Received: from abraham.CS.Berkeley.EDU ([128.32.247.199]:13829 "EHLO paip.net") by vger.kernel.org with ESMTP id ; Fri, 1 Feb 2002 21:07:48 -0500 To: linux-kernel@vger.kernel.org Path: not-for-mail From: daw@mozart.cs.berkeley.edu (David Wagner) Newsgroups: isaac.lists.linux-kernel Subject: Re: Continuing /dev/random problems with 2.4 Date: 2 Feb 2002 02:05:29 GMT Organization: University of California, Berkeley Lines: 23 Distribution: isaac Message-ID: In-Reply-To: <20020201031744.A32127@asooo.flowerfire.com> <1012582401.813.1.camel@phantasy> <20020201202334.72F921C5@www.pmonta.com> NNTP-Posting-Host: mozart.cs.berkeley.edu X-Trace: abraham.cs.berkeley.edu 1012615529 30983 128.32.45.153 (2 Feb 2002 02:05:29 GMT) X-Complaints-To: news@abraham.cs.berkeley.edu NNTP-Posting-Date: 2 Feb 2002 02:05:29 GMT X-Newsreader: trn 4.0-test74 (May 26, 2000) Originator: daw@mozart.cs.berkeley.edu (David Wagner) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Peter Monta wrote: >Many motherboards have on-board sound. Why not turn the mic >gain all the way up and use the noise---surely there will be >a few bits' worth? That may be reasonable, but beware: there are some potential pitfalls. For instance, is there a risk that the audio data you read is strongly correlated to 60Hz mains noise in some scenarios? Also, my understanding is that the quality of randomness you get can depend on which sound card you have, and moreover that the left and right channels can be strongly correlated (audio-entropyd takes the difference between the two). I think there are some things you can do, but it seems that one might want to be a bit careful here. In general, I am warmly supportive of using as diverse a set of entropy sources as possible to provide robustness in case one source unexpectedly fails, but I also recommend care in analyzing how much entropy each source really gives you (it seems prudent to be a bit conservative in one's entropy estimates, due to the variety of subtle effects that can compromise the quality of your randomness sources). Also, you may be interested in audio-entropyd, rexx, and Nautilus, all of which use something like this as part of their entropy collection. - 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/