Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754016Ab3IMD5M (ORCPT ); Thu, 12 Sep 2013 23:57:12 -0400 Received: from longford.logfs.org ([213.229.74.203]:60291 "EHLO longford.logfs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752300Ab3IMD5K (ORCPT ); Thu, 12 Sep 2013 23:57:10 -0400 Date: Thu, 12 Sep 2013 22:22:08 -0400 From: =?utf-8?B?SsO2cm4=?= Engel To: "Theodore Ts'o" Cc: Andy Lutomirski , Jeff Garzik , David Safford , "H. Peter Anvin" , Leonidas Da Silva Barbosa , Ashley Lai , Rajiv Andrade , Marcel Selhorst , Sirrix AG , Linux Kernel Mailing List , Kent Yoder , David Safford , Mimi Zohar , "Johnston, DJ" Subject: Re: TPMs and random numbers Message-ID: <20130913022207.GA8825@logfs.org> References: <1378920168.26698.64.camel@localhost> <1378925224.26698.90.camel@localhost> <20130912215718.GF3809@logfs.org> <20130912221340.GG3809@logfs.org> <20130912222309.GH3809@logfs.org> <20130913021349.GB9445@thunk.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20130913021349.GB9445@thunk.org> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1407 Lines: 38 On Thu, 12 September 2013 22:13:49 -0400, Theodore Ts'o wrote: > On Thu, Sep 12, 2013 at 06:23:09PM -0400, Jörn Engel wrote: > > It is worse in three ways: > > - it costs performance, > > - it may create a false sense of safety and > > - it actively does harm if we credit it as entropy. > > > > How much weight you assign to each of those is up to you. So long as > > we don't credit any of it as entropy, I am not too adverse to mixing > > it in. But I can equally see benefit in burning the bridges. > > Well, mixing it in and using /dev/[u]random is certainly better than > blindly using the output from the RNG from the TPM directly as a > key. Absolutely! > I'm not sure what you mean by "burning the bridges"; what is the > alternative that you are suggesting? Not using hardware RNGs at all, see three messages back. We know those things can be compromised, we know a compromise cannot be detected and we know of people/groups that have both a strong motivation and likely the ability to pull it off. I am not taking sides, but I can see good arguments for both approaches. Jörn -- ...one more straw can't possibly matter... -- Kirby Bakken -- 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/