Re: Secdir last call review of draft-ietf-httpbis-encryption-encoding-08

Martin Thomson <martin.thomson@gmail.com> Wed, 05 April 2017 22:32 UTC

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From: Martin Thomson <martin.thomson@gmail.com>
Date: Thu, 6 Apr 2017 08:32:42 +1000
Message-ID: <CABkgnnU7qXVeCDxoRbG8i6GbxJTA6gRpyHH0Yf+h0eRAJ+WLxw@mail.gmail.com>
Subject: Re: Secdir last call review of draft-ietf-httpbis-encryption-encoding-08
To: Robert Sparks <rjsparks@nostrum.com>
Cc: "secdir@ietf.org" <secdir@ietf.org>, draft-ietf-httpbis-encryption-encoding.all@ietf.org, "ietf@ietf.org" <ietf@ietf.org>, HTTP Working Group <ietf-http-wg@w3.org>
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On 6 April 2017 at 06:47, Robert Sparks <rjsparks@nostrum.com>; wrote:
>
> My only concern is that the document suggests it would be ok to use a
> counter to provide a unique salt value
> for each message. I suspect that provides the kind of information leak
> the draft discusses avoiding.

Hi Robert, can you explain what sort of leakage you are concerned
about?  I mean, I can understand how you could construct the sequence
of resources that were encrypted using a counter for the salt, but I
don't know what that might imply.

That said, I think that the counter thing can be removed.  We require
128 bits of salt, which is a space that is large enough to select
randomly from in perpetuity.