Re: [MLS] Unpredictable epochs?

Jon Callas <jon@callas.org> Fri, 26 April 2019 19:26 UTC

Return-Path: <jon@callas.org>
X-Original-To: mls@ietfa.amsl.com
Delivered-To: mls@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 5A2CE12011D for <mls@ietfa.amsl.com>; Fri, 26 Apr 2019 12:26:59 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2
X-Spam-Level:
X-Spam-Status: No, score=-2 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (2048-bit key) header.d=callas.org
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 ayMyPsIH1XJv for <mls@ietfa.amsl.com>; Fri, 26 Apr 2019 12:26:57 -0700 (PDT)
Received: from mail-qk1-x736.google.com (mail-qk1-x736.google.com [IPv6:2607:f8b0:4864:20::736]) (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 9ADEC12012E for <mls@ietf.org>; Fri, 26 Apr 2019 12:26:57 -0700 (PDT)
Received: by mail-qk1-x736.google.com with SMTP id w20so2562454qka.7 for <mls@ietf.org>; Fri, 26 Apr 2019 12:26:57 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=callas.org; s=google; h=mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=vkfZhidVX4o4X5Z4Zz8OB11kfXJizeIVKREP4gQo7ms=; b=bXpiC1sa7/tQKnyVfSNo+Gn7djCduh10UlDmEsgdFRvnntsWBLsoiZUmnlyNPUCvmT 4NtObktuKe+gR1+m7hnZHY+cwQoP45VBNi51GCJd7V4oOjDC8Eo0xHWrpRaZeqiyLhj3 sI2dtqNmHDJTnx4ye21xL6s4Ggc+G7hCYxUUcmWTR9pmJOACzqDv3X6/v5vnCg59TajG T5Y8IDzWzdImvV38He0TVSKehlGN+zK9KmCZyAQobq4fHX/CKbZCZ6FtTnD++Sp/tHGE 9hBF9llbBLXCgFIcC9pDeERdlOeknhHxtDCrQck6QW2fNF0K1fRiZx9qaS6xBua16QDg pLqA==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=vkfZhidVX4o4X5Z4Zz8OB11kfXJizeIVKREP4gQo7ms=; b=eDvAW5HlnjWF8nuvdteY+kj5ksbzIsGiR08WPc5ULaF8sD58WV8sZ1e2CgAyjr0IHd efv74PgzaZn1g9vq/lWtEC0h4Se5vXr2ETIidgqoXazedAL97QxmDdsFZmQAaVNu7xLL a3TKalbrwko+zDVzXLf2oiG8e00ct4bjtbftsan5QqmZ4a6Wg5oTSPe4pTFIdzZnHWkP vU4pHhtN+Q+hN3cdq+qzSyYsprA1pPiipzOtpThu6Kcf+Iq31DoAzKRoPtXcA0puz6Gj Cwjm9/KsXmrEfqmqCt/feOpGUBsINA/pAlWfOewuWtr+bIFtwhK1fK/AKLWwsjRMEsME Yzfg==
X-Gm-Message-State: APjAAAWblSK5+TXKy6DEGOji4EaH4iW5RxuShZQMV5NnLQi0x1xecYDo Z3cJ3SN/CkgplRqcG1U/om3Y6Q==
X-Google-Smtp-Source: APXvYqx6gUWxG1o+NBQaruzrjpdr5AOdEeFMrH0vbrFbZeALOLnxKcK6NgVsgHiFaUs9IJJkb/7sEA==
X-Received: by 2002:a37:4896:: with SMTP id v144mr35191012qka.194.1556306816709; Fri, 26 Apr 2019 12:26:56 -0700 (PDT)
Received: from [10.137.13.58] ([45.56.171.31]) by smtp.gmail.com with ESMTPSA id i123sm9006218qkf.9.2019.04.26.12.26.55 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 26 Apr 2019 12:26:55 -0700 (PDT)
Content-Type: text/plain; charset=utf-8
Mime-Version: 1.0 (Mac OS X Mail 12.2 \(3445.102.3\))
From: Jon Callas <jon@callas.org>
In-Reply-To: <AC74CACD-541B-49CD-9CC9-63343307A53D@fastmail.com>
Date: Fri, 26 Apr 2019 15:26:54 -0400
Cc: Jon Callas <jon@callas.org>, Richard Barnes <rlb@ipv.sx>, Messaging Layer Security WG <mls@ietf.org>
Content-Transfer-Encoding: quoted-printable
Message-Id: <CEAEFC1B-7581-4263-A45D-44E7348D7DB7@callas.org>
References: <CAL02cgSE1xTF2Wsq-u=BCu2Z_4UzMzqMPi=D_H7_7hbRpUMVVA@mail.gmail.com> <2D195D14-9F9A-4D64-92EF-35C601C52C01@inria.fr> <CAL02cgR8gQ6cH_QXd_9v46aJ5aeo=b=1GiYu9YxCNYzJb0tOFQ@mail.gmail.com> <B36BF8F5-EAE9-4C96-A867-82CDFBF830C0@inria.fr> <CAL02cgQ7-JMQsG6sq6YBB3G-5tmCVQoo07nvW63tzBzHPQ0ZWw@mail.gmail.com> <AC74CACD-541B-49CD-9CC9-63343307A53D@fastmail.com>
To: Michael Rosenberg <micro@fastmail.com>
X-Mailer: Apple Mail (2.3445.102.3)
Archived-At: <https://mailarchive.ietf.org/arch/msg/mls/cTA3LuU5tusHIVeUSnxaxOpBCvM>
Subject: Re: [MLS] Unpredictable epochs?
X-BeenThere: mls@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Messaging Layer Security <mls.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/mls>, <mailto:mls-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/mls/>
List-Post: <mailto:mls@ietf.org>
List-Help: <mailto:mls-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/mls>, <mailto:mls-request@ietf.org?subject=subscribe>
X-List-Received-Date: Fri, 26 Apr 2019 19:26:59 -0000


> On Apr 26, 2019, at 2:22 AM, Michael Rosenberg <micro@fastmail.com>; wrote:
> 
> So why not remove epoch entirely?

An epoch lets you deal with things happening neither too often nor not often enough. Presume there is a client that is either malicious or just stupid. You want to keep it from forcing a rekey every 100┬Ás. You want to force a rekey every so often. Hence epochs. Yeah, picking the right epoch size is an exercise left to the reader.

	Jon