Re: [TLS] Reducing record expansion overhead allowance

"StJohns, Michael" <msj@nthpermutation.com> Sun, 20 July 2014 16:09 UTC

Return-Path: <msj@nthpermutation.com>
X-Original-To: tls@ietfa.amsl.com
Delivered-To: tls@ietfa.amsl.com
Received: from localhost (ietfa.amsl.com [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id F2C8E1B2C78 for <tls@ietfa.amsl.com>; Sun, 20 Jul 2014 09:09:08 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.977
X-Spam-Level:
X-Spam-Status: No, score=-1.977 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, FM_FORGED_GMAIL=0.622, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_LOW=-0.7] autolearn=ham
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id jgciFY_FBfrc for <tls@ietfa.amsl.com>; Sun, 20 Jul 2014 09:08:58 -0700 (PDT)
Received: from mail-qg0-f51.google.com (mail-qg0-f51.google.com [209.85.192.51]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id ABF561B2C74 for <tls@ietf.org>; Sun, 20 Jul 2014 09:08:58 -0700 (PDT)
Received: by mail-qg0-f51.google.com with SMTP id a108so4629651qge.24 for <tls@ietf.org>; Sun, 20 Jul 2014 09:08:57 -0700 (PDT)
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-type; bh=jjl4iEMDn1WzGyiGXqDryUHBkA4M9VZOE247LwQIkCg=; b=Ysbom2Et2TFATgZrN0F+IbnQqn9GnHHmEytdsRFbfYcP7g7SB3/pgG8pDbk95isJdo //0GkeEbFIuCK7CwP8LN4vRJ24CI+21su3PuDViKfIS66iy7Dovm2EH2MTNiRSmbPzNr 3UlkGJUTA7gDROyL8ZrV6jFDnjR6sC9YBiqzqt1m8fEX/LtiWDKEUWefvjMTSNm/XZPR 0gtB8FnSdVSAHN7HAfSV3N+uTHsvXo0znvaUh/ue6J9vhHw2sgt9dCPZ/rz5Qs/woFvF UIRb3ubQIpEIvU5g2pm+0CzWg4byB1k7XU0H9/KVNX5aYO4hcPsKE13Vl2QW4sz3wgu/ Rpuw==
X-Gm-Message-State: ALoCoQn32rahWnMRYfCo9kXn/SIXnkBqb5wOg4b+181ZxWi5RlGr4p+hWXE4PsmDQFRKvsQETaby
MIME-Version: 1.0
X-Received: by 10.224.92.83 with SMTP id q19mr30960343qam.29.1405872537468; Sun, 20 Jul 2014 09:08:57 -0700 (PDT)
Received: by 10.140.108.75 with HTTP; Sun, 20 Jul 2014 09:08:57 -0700 (PDT)
X-Originating-IP: [172.56.29.108]
In-Reply-To: <CABcZeBMt++Oc4-UNiXuHX=mY0CEw_DorNLCdRLBsKdj5gu=oBg@mail.gmail.com>
References: <CABcZeBODbabpOUgb431X3Xz_fB1KK8wn8-SMJgYZVE2V3oCLow@mail.gmail.com> <CANeU+ZCX4wGOPytP3qO80Q+6yq=TFCM0Xi9SMmxdMrveDv8ZCA@mail.gmail.com> <CABcZeBMt++Oc4-UNiXuHX=mY0CEw_DorNLCdRLBsKdj5gu=oBg@mail.gmail.com>
Date: Sun, 20 Jul 2014 12:08:57 -0400
Message-ID: <CANeU+ZA8zgU2FK5KOK2i9G0eVGPb5XVVq2PRUNVdMDA0BH285A@mail.gmail.com>
From: "StJohns, Michael" <msj@nthpermutation.com>
To: Eric Rescorla <ekr@rtfm.com>
Content-Type: multipart/alternative; boundary=089e0149cf94321db504fea235a1
Archived-At: http://mailarchive.ietf.org/arch/msg/tls/ipGxRyfCr6Wbhjdbiwgf5E3JHI0
Cc: "tls@ietf.org" <tls@ietf.org>
Subject: Re: [TLS] Reducing record expansion overhead allowance
X-BeenThere: tls@ietf.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: "This is the mailing list for the Transport Layer Security working group of the IETF." <tls.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/tls>, <mailto:tls-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/tls/>
List-Post: <mailto:tls@ietf.org>
List-Help: <mailto:tls-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/tls>, <mailto:tls-request@ietf.org?subject=subscribe>
X-List-Received-Date: Sun, 20 Jul 2014 16:09:09 -0000

You mean as part of the plain text?

On Sunday, July 20, 2014, Eric Rescorla <ekr@rtfm.com> wrote:

> On Sun, Jul 20, 2014 at 7:52 AM, StJohns, Michael <msj@nthpermutation.com
> <javascript:_e(%7B%7D,'cvml','msj@nthpermutation.com');>> wrote:
>
>> The only other thing that hasn't been mentioned that was discussed at the
>> interim in Denver is padding for traffic analysis resistance. That could
>> hit 1k in size.  But since there's no proposal that's just a guess on size.
>>
>
>
> I believe the consensus here was to have padding be done separately.
>
> -Ekr
>
>
>>
>> On Saturday, July 19, 2014, Eric Rescorla <ekr@rtfm.com
>> <javascript:_e(%7B%7D,'cvml','ekr@rtfm.com');>> wrote:
>>
>>>  https://github.com/tlswg/tls13-spec/issues/55
>>>
>>> In TLS 1.2, we had the following maximum values:
>>>
>>> TLSPlaintext: 2^{14}
>>> TLSCompressed: 2^{14} + 1024
>>> TLSCiphertext: 2^{14} + 2048
>>>
>>> These overhead values allow for expansion in these transforms
>>> due to potential bad compression overhead or padding, etc.
>>>
>>> Wan-Teh Chang points out that we no longer have compression
>>> so there's no need to allow for 1024 bytes of expansion there.
>>>
>>> Minimally we should reduce the TLSCiphertext overhead to
>>> 2^{14} + 1024. Do people believe that we will have AEAD
>>> ciphers with 1024 bytes of expansion or should we reduce
>>> it further? I'm inclined to not re-judge that and just leave it
>>> at 2^{14} + 1024.
>>>
>>> Thoughts?
>>> -Ekr
>>>
>>>
>