IETF Logo Mail Archive

Re: [TLS] Constraining ECH to HKDF-based HPKE ciphersuites

Christopher Patton <cpatton@cloudflare.com> Mon, 17 August 2020 23:57 UTC

Return-Path: <cpatton@cloudflare.com>
X-Original-To: tls@ietfa.amsl.com
Delivered-To: tls@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 7BB2C3A1489 for <tls@ietfa.amsl.com>; Mon, 17 Aug 2020 16:57:49 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.099
X-Spam-Level:
X-Spam-Status: No, score=-2.099 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, HTML_MESSAGE=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (1024-bit key) header.d=cloudflare.com
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 4wSAkQui2E3G for <tls@ietfa.amsl.com>; Mon, 17 Aug 2020 16:57:48 -0700 (PDT)
Received: from mail-qv1-xf2f.google.com (mail-qv1-xf2f.google.com [IPv6:2607:f8b0:4864:20::f2f]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 5B9DA3A146E for <tls@ietf.org>; Mon, 17 Aug 2020 16:57:48 -0700 (PDT)
Received: by mail-qv1-xf2f.google.com with SMTP id l13so8686863qvt.10 for <tls@ietf.org>; Mon, 17 Aug 2020 16:57:48 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cloudflare.com; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=9GAKIyYY9HGPlDPeZJZfr7pF1Nr20zItpFueSKXb/CA=; b=f20FBCpzsQMs/s91AdBmUPsAMfxi9SgoKN2qrJ24M74dnKvLTpIOq3puNo40j6sMsX RaFkWEPjIz/21cwdDzoBN8JQwa200SrVX9Nl4DQXh/Al+vUklRowARpRf+ei5EZDNGw5 pH73gCQoiE6Rep52DpsiVxZ77ww965UIidEgU=
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=9GAKIyYY9HGPlDPeZJZfr7pF1Nr20zItpFueSKXb/CA=; b=kEOwnjwbgbp+qTU+Xazzx4wU69jG2z+hFBH0C6XQ/w6YYRFp6Stey9tfqYRVnVjaur TGkfQ4HOiQE050FBp5jPmX0xs/wyLVnj2hazdC7kdPyIfigAB2kfH9z3LWfRfC/HTluO Na0XrvykD1D1Ui85qm0KHZAbu7/8pVgytS+FdvueOBO40RPG3JBxS4Q8r1EcocH/rlCA n+8wvz09WeAyu2FHg7nY+4kru8X0c+fJlVmZjJ0hZiE2/aGtz34u2kGaJHLccbs5BSyn WBH8CijhoyI42tCIZc19R+RN6wTuiFM/r3p63UZ7kf8EkaF3O8X6Ou2LqHD94fyUQk+u pB6w==
X-Gm-Message-State: AOAM5324od7o4Zy9QwLhMUL9ePJiks1e2vz1PdU0tXiPeO//49zzJh3V W6dmcwCVgCzlFg3tqTr3qTh1T/an0IXeJ5Qs+Vm+ChsgWEH7IoLl
X-Google-Smtp-Source: ABdhPJwQoyQuHpQR1Cl6+fTPf5Fx1qsadwvBGY+XKwVFMpdXkwEzwvvTYGgW5+THqGoXKZBzhCfVPSi6xd1z50UUf1Y=
X-Received: by 2002:ad4:564d:: with SMTP id bl13mr16075088qvb.60.1597708667233; Mon, 17 Aug 2020 16:57:47 -0700 (PDT)
MIME-Version: 1.0
References: <ee8c4bb1-554a-4f45-a1d5-17e49b320562@www.fastmail.com> <170e077f-2ad1-4794-9227-b7e9fcf74b0c@www.fastmail.com> <CAG2Zi22BdP_EYGrCiDMqKrkQN4ZwE-igBjQypMbUJrSiaXER=A@mail.gmail.com> <dae86080-2818-4ea8-8c2d-ae8cf55ab149@www.fastmail.com> <CAG2Zi203YumwAiLPUVw8G731Lp+ByrYK+uFf_5Z2wvPb4QvC0A@mail.gmail.com> <d2a84a14-cac7-46b4-a9f8-f1c9bee7b2ff@www.fastmail.com>
In-Reply-To: <d2a84a14-cac7-46b4-a9f8-f1c9bee7b2ff@www.fastmail.com>
From: Christopher Patton <cpatton@cloudflare.com>
Date: Mon, 17 Aug 2020 16:57:36 -0700
Message-ID: <CAG2Zi21iiJS5Df1BB8VP=ZypS5rQDeps3iupkPKS7koUv-Hqyw@mail.gmail.com>
To: Martin Thomson <mt@lowentropy.net>
Cc: "<tls@ietf.org>" <tls@ietf.org>
Content-Type: multipart/alternative; boundary="00000000000090d4af05ad1b89df"
Archived-At: <https://mailarchive.ietf.org/arch/msg/tls/RdbaLallikVAxsIilr1I9HLVm5k>
Subject: Re: [TLS] Constraining ECH to HKDF-based HPKE ciphersuites
X-BeenThere: tls@ietf.org
X-Mailman-Version: 2.1.29
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: <https://mailarchive.ietf.org/arch/browse/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: Mon, 17 Aug 2020 23:57:50 -0000

I worked out this suggestion into a PR:
https://github.com/tlswg/draft-ietf-tls-esni/pull/276

Please have a look!
Chris P.

On Mon, Aug 17, 2020 at 4:28 PM Martin Thomson <mt@lowentropy.net> wrote:

>
>
> On Tue, Aug 18, 2020, at 09:04, Christopher Patton wrote:
> > Just to be clear, you're proposing something like this? Referring to
> > the KDF API called for in draft-irtf-cfrg-hpke-05:
> >
> > config_digest = Expand(PRK=Extract("some_salt", "some_label",
> > IKM=config), "some_info", 16)
> > It's maybe more hashing than necessary, but I'd be good with this.
>
> Something like that yeah.  And yes, that's a lot of hashing.  But that's a
> lower-order concern.  Maybe if we try to find a KDF that doesn't cost so
> much to operate we won't feel so bad about this.
>

v2.23.0 | Report a Bug | By Email