From owner-freebsd-security@FreeBSD.ORG  Thu Sep 20 22:01:38 2012
Return-Path: <owner-freebsd-security@FreeBSD.ORG>
Delivered-To: freebsd-security@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52])
	by hub.freebsd.org (Postfix) with ESMTP id BFA57106564A
	for <freebsd-security@freebsd.org>;
	Thu, 20 Sep 2012 22:01:38 +0000 (UTC)
	(envelope-from rwmaillists@googlemail.com)
Received: from mail-we0-f182.google.com (mail-we0-f182.google.com
	[74.125.82.182])
	by mx1.freebsd.org (Postfix) with ESMTP id 49E628FC16
	for <freebsd-security@freebsd.org>;
	Thu, 20 Sep 2012 22:01:37 +0000 (UTC)
Received: by weyx56 with SMTP id x56so1853615wey.13
	for <freebsd-security@freebsd.org>;
	Thu, 20 Sep 2012 15:01:36 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
	d=googlemail.com; s=20120113;
	h=date:from:to:cc:subject:message-id:in-reply-to:references:x-mailer
	:mime-version:content-type:content-transfer-encoding;
	bh=NlIGL+KYr1Q//DyENcrBok93xSTl9fQSv71PePnkfmA=;
	b=rk2++JUU49XpwTOdWo0Xz+ZOHaU9wunK8tj69z++QXIczXQtf8VWW+Y7VAkA4qQWRV
	3F2/yR6iG8Os9mBJXqI7v2RS7KMkYhX37mPST3dpG7RxGsOasi0SSEkZQUEEz3mao/KP
	jOSkWKDhPYS6R8sW0EpNS57Sdy6yAEy/D/qCybz0OXZ6xQ9wLhCeSOJnyi/EPulH8B4c
	MOo7pS+p7geGFWVC1BjH7eWkse39IOQnt3LdR916/RF29eho3/mNO5q1mOWlkdm0AIgs
	ZigKWH19sftRSau/JQuo8ymQsRefoGKS40Sr5lSfiyPX3nwf/S5YmNAn+xK/5pfYELSC
	7F4w==
Received: by 10.180.80.134 with SMTP id r6mr42673wix.1.1348178496844;
	Thu, 20 Sep 2012 15:01:36 -0700 (PDT)
Received: from gumby.homeunix.com (87-194-105-247.bethere.co.uk.
	[87.194.105.247])
	by mx.google.com with ESMTPS id eu4sm34628010wib.2.2012.09.20.15.01.35
	(version=SSLv3 cipher=OTHER); Thu, 20 Sep 2012 15:01:35 -0700 (PDT)
Date: Thu, 20 Sep 2012 23:01:33 +0100
From: RW <rwmaillists@googlemail.com>
To: Dag-Erling =?ISO-8859-1?Q?Sm=F8rgrav?= <des@des.no>
Message-ID: <20120920230133.55b63dea@gumby.homeunix.com>
In-Reply-To: <86sjadt677.fsf@ds4.des.no>
References: <20120918211422.GA1400@garage.freebsd.pl>
	<867grqm3pt.fsf@ds4.des.no>
	<20120919184758.28589516@gumby.homeunix.com>
	<86sjadt677.fsf@ds4.des.no>
X-Mailer: Claws Mail 3.8.1 (GTK+ 2.24.6; amd64-portbld-freebsd8.3)
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
Cc: freebsd-security@freebsd.org
Subject: Re: Collecting entropy from device_attach() times.
X-BeenThere: freebsd-security@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: "Security issues \[members-only posting\]"
	<freebsd-security.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-security>, 
	<mailto:freebsd-security-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-security>
List-Post: <mailto:freebsd-security@freebsd.org>
List-Help: <mailto:freebsd-security-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-security>, 
	<mailto:freebsd-security-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Thu, 20 Sep 2012 22:01:38 -0000

On Thu, 20 Sep 2012 11:05:32 +0200
Dag-Erling Sm=F8rgrav wrote:

> RW <rwmaillists@googlemail.com> writes:
> > Dag-Erling Sm=F8rgrav <des@des.no> writes:
> > > I would also suggest modifying yarrow to block reseeding as long
> > > as possible, ideally right up until the first time something asks
> > > for a random number, since reseeding throws away all accumulated
> > > entropy.
> > reseeding doesn't throw away entropy
>=20
> Yes, it does.

Would you elaborate? I don't see what you mean by that?

When yarrow reseeds, the previous generator key is hashed with the
pool[s], into the new key. They key will therefore *accumulate* entropy
across multiple reseeds.