Re: [tcpinc] Eric Rescorla's Discuss on draft-ietf-tcpinc-tcpeno-13: (with DISCUSS and COMMENT)

Eric Rescorla <ekr@rtfm.com> Sun, 12 November 2017 07:22 UTC

Return-Path: <ekr@rtfm.com>
X-Original-To: tcpinc@ietfa.amsl.com
Delivered-To: tcpinc@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id EBBFF128891 for <tcpinc@ietfa.amsl.com>; Sat, 11 Nov 2017 23:22:25 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.599
X-Spam-Level:
X-Spam-Status: No, score=-2.599 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_LOW=-0.7] autolearn=unavailable autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (2048-bit key) header.d=rtfm-com.20150623.gappssmtp.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 4zniGuz2UEjT for <tcpinc@ietfa.amsl.com>; Sat, 11 Nov 2017 23:22:25 -0800 (PST)
Received: from mail-yw0-x232.google.com (mail-yw0-x232.google.com [IPv6:2607:f8b0:4002:c05::232]) (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 0968B12711D for <tcpinc@ietf.org>; Sat, 11 Nov 2017 23:22:24 -0800 (PST)
Received: by mail-yw0-x232.google.com with SMTP id i198so11194802ywe.7 for <tcpinc@ietf.org>; Sat, 11 Nov 2017 23:22:24 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rtfm-com.20150623.gappssmtp.com; s=20150623; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=Wgh3uqvzpCb/qIUC6+w9A2GL49IaJRxuYFzKk2qlqww=; b=PXpzrJRja7AheMHV09PtKyzqILjF1qz6PTabJplpebtbhDUMXWPiksyEXC/r6u8ckF aEi35by0nk9oK5qGANUUGPS4+iXPx+OMNd+z8QDutocNtRNnqtCOVXOE7gs0LZknMLTY mTqrXRXhd3xv2ZGpNgVF9Kva+/aHzRAYSeqcsNANIvDBCJfeRFQpJt8XwkpC2Rzj6ChG xNAly/hiLlzXd1VYZ52pRuUA70Mu+WC91KHB17zNdtmcsmaALYimtQlUU5YA2674zmGp h9xSImAY6PdmiVhMVVEolXxcmcThQ132GcR8JNPzrOm60j6s6GEcdQ0LHxobSAUXUtCp UEnQ==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=Wgh3uqvzpCb/qIUC6+w9A2GL49IaJRxuYFzKk2qlqww=; b=IVd1VNIyETKpRPCrzHCtk6/zquKLtXJhQIiIp1lgvZcBDiVgGAIJdXRamyzra8PGUc 4IxufwZQymMDYrMg7RUATj+9eGpR7yQ/QTT8RaWPqPYAAZzVrC7Q9sVn1+YI4XTgvBYC ixzk45ZJXx+P+2tlY1QBuwtda4MTm+O37c/uMcBsD+FkFf2O8VLSNCoYkFoERv2VrDek U9esIh8En7CwhMADlPL7eNlSbI/GborYnHV8V7eXtpCWcydD8RMjab8sko/OABCC+stH CqvrQdCRDXwl0MLVcisFQxvG2UQuxYgOh+FmFhbwEWI2crLAXaMtrPjkvBCMehQ+c4zC P5Zg==
X-Gm-Message-State: AJaThX6PwtqNZFxfSANpVXfjT2cytMIp+FySQgO0dvPcfwkyDAdmckM9 pS9ts7H3tK1/WKFF73U+i7fjL1xn076lAkc2MDWJYQ==
X-Google-Smtp-Source: AGs4zMYfG2H1HpmdMPitIDjCgbtora5J/eVLCE9WcG3UNfZUjUjFERDqzs4mkYbnta8eHel+k4q5MRTt/gRr72WkB1Y=
X-Received: by 10.37.195.65 with SMTP id t62mr3432158ybf.71.1510471343270; Sat, 11 Nov 2017 23:22:23 -0800 (PST)
MIME-Version: 1.0
Received: by 10.129.61.12 with HTTP; Sat, 11 Nov 2017 23:21:42 -0800 (PST)
In-Reply-To: <CAJU8_nWpVhm4oTT+SLyG-nk=ww7nBU-DaVe86rUU-LGGqJvHvQ@mail.gmail.com>
References: <151036581280.449.10740505473540594433.idtracker@ietfa.amsl.com> <CE03DB3D7B45C245BCA0D243277949362FD495EF@MX307CL04.corp.emc.com> <CABcZeBPfk6Pi=_UPvTBaS9jQBYjExUdqkdX5Q--iUuyCv_qZtw@mail.gmail.com> <CAJU8_nWpVhm4oTT+SLyG-nk=ww7nBU-DaVe86rUU-LGGqJvHvQ@mail.gmail.com>
From: Eric Rescorla <ekr@rtfm.com>
Date: Sun, 12 Nov 2017 07:21:42 +0000
Message-ID: <CABcZeBO0TD0KnpTfe6CbHUoiS=FmGiGW6r_mFMH_9bYFWKqKLA@mail.gmail.com>
To: Kyle Rose <krose@krose.org>
Cc: "Black, David" <David.Black@dell.com>, The IESG <iesg@ietf.org>, "draft-ietf-tcpinc-tcpeno@ietf.org" <draft-ietf-tcpinc-tcpeno@ietf.org>, "tcpinc-chairs@ietf.org" <tcpinc-chairs@ietf.org>, "tcpinc@ietf.org" <tcpinc@ietf.org>
Content-Type: multipart/alternative; boundary="001a114d7db2dc0514055dc403f3"
Archived-At: <https://mailarchive.ietf.org/arch/msg/tcpinc/MaSFUm6eHd71yO2TRzPhroqNZvQ>
Subject: Re: [tcpinc] Eric Rescorla's Discuss on draft-ietf-tcpinc-tcpeno-13: (with DISCUSS and COMMENT)
X-BeenThere: tcpinc@ietf.org
X-Mailman-Version: 2.1.22
Precedence: list
List-Id: "Working group mailing list for TCP Increased Security \(tcpinc\)" <tcpinc.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/tcpinc>, <mailto:tcpinc-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/tcpinc/>
List-Post: <mailto:tcpinc@ietf.org>
List-Help: <mailto:tcpinc-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/tcpinc>, <mailto:tcpinc-request@ietf.org?subject=subscribe>
X-List-Received-Date: Sun, 12 Nov 2017 07:22:26 -0000

On Sun, Nov 12, 2017 at 7:19 AM, Kyle Rose <krose@krose.org> wrote:

> On Sun, Nov 12, 2017 at 1:13 PM, Eric Rescorla <ekr@rtfm.com> wrote:
> > On Sun, Nov 12, 2017 at 5:08 AM, Black, David <David.Black@dell.com>
> wrote:
> >> - Encryption: The intent is - don't use anything weaker than AES-128,
> >> e.g., don't even think about using 3DES.  The concern is how to write
> that
> >> requirement in a way that would survive hypothetical discovery of a
> >> catastrophic cryptanalytic attack on AES-128.
> >
> >
> > Or even a small one. I mean, what does this say about Curve25519 or 4Q.
>
> I think this is actually the issue driving the vagueness of the
> requirement: e.g., if some hypothetical attack against AES-128 reduced
> security by a few bits. The intent, as David suggests, is to prohibit
> the use of something like DES, not to prohibit a 128-bit cipher with
> only (say) 125 bits of security.
>

That's not a reasonable desire, but this is an RFC 2119 requirement, so it
really does need to be unambiguous.

-Ekr