Re: [dsfjdssdfsd] what not to do... Wed, 02 April 2014 18:32 UTC

Return-Path: <>
Received: from localhost ( []) by (Postfix) with ESMTP id CB4BB1A0368 for <>; Wed, 2 Apr 2014 11:32:23 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -0.81
X-Spam-Status: No, score=-0.81 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, FROM_LOCAL_NOVOWEL=0.5, J_CHICKENPOX_21=0.6, T_RP_MATCHES_RCVD=-0.01] autolearn=no
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id bHGT4y0wyGax for <>; Wed, 2 Apr 2014 11:32:19 -0700 (PDT)
Received: from ( []) by (Postfix) with ESMTP id C73811A0374 for <>; Wed, 2 Apr 2014 11:32:19 -0700 (PDT)
Received: by (Postfix, from userid 1001) id 1878C3F756; Wed, 2 Apr 2014 11:32:16 -0700 (PDT)
Date: Wed, 2 Apr 2014 11:32:16 -0700
To: Theodore Ts'o <>
Message-ID: <>
Mail-Followup-To: Theodore Ts'o <>, Paul Hoffman <>, "" <>
References: <> <> <> <> <> <>
MIME-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="kHRd/tpU31Zn62xO"
Content-Disposition: inline
In-Reply-To: <>
User-Agent: Mutt/1.5.21 (2010-09-15)
Cc: "" <>, Paul Hoffman <>
Subject: Re: [dsfjdssdfsd] what not to do...
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: "The dsfjdssdfsd list provides a venue for discussion of randomness in IETF protocols, for example related to updating RFC 4086." <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Wed, 02 Apr 2014 18:32:24 -0000

On Wed, Apr 02, 2014 at 01:34:26PM -0400, Theodore Ts'o wrote:
> One of the problems is that there is a lot of nuance which is
> required.  For example, if you can't change the hardware, on a mobile
> device, one of the few sources of unpredictability might be the radio
> strength --- if you grab this in early boot and if you know that the
> values aren't being fed via centralized logging scheme.  It's not
> really _entropy_ per se, but if you are assuming that someone sitting
> in Fort Meade won't know whether your cell phone is in your knapsack
> under the steel desk, or on top of the desk, it probably does add a
> certain amount of protection.
> Ditto grabbing touch screen information; sure, if someone has a camera
> surveilling you, it might not have much unpredictabiliy, but it's
> still probably a good thing to mix into your entropy pool.
> And if we try to tell people that if you can't do anything at all
> which is True Entropy (tm), you might as well go home, then people
> might just do that.

In the movie "The Sting", horse race results are delayed to allow
betting-after-the-fact; this demonstrates that with the knowledge you
have after its disclosure, unpredictability no longer exists.

So philosophically, all unpredictability is measured relative to some
knowledge set.

As a pragmatic exercise we can measure an upper bound on entropy
(using min-entropy) based on what we assume are standard assumptions,
but we don't know what we don't know.

Which is an interesting parallel to computational security assurances.

BTW, hello Paul, nice list :-)
Remediating... LIKE A BOSS