Re: [Cbor] [COSE] CBOR magic number, file format and tags

Michael Richardson <mcr+ietf@sandelman.ca> Sat, 23 January 2021 20:01 UTC

Return-Path: <mcr+ietf@sandelman.ca>
X-Original-To: cbor@ietfa.amsl.com
Delivered-To: cbor@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id C76B03A0D52 for <cbor@ietfa.amsl.com>; Sat, 23 Jan 2021 12:01:54 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.899
X-Spam-Level:
X-Spam-Status: No, score=-1.899 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
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 o7VrMTh3xi0o for <cbor@ietfa.amsl.com>; Sat, 23 Jan 2021 12:01:52 -0800 (PST)
Received: from tuna.sandelman.ca (tuna.sandelman.ca [209.87.249.19]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 3E8763A0EEF for <cbor@ietf.org>; Sat, 23 Jan 2021 12:01:23 -0800 (PST)
Received: from localhost (localhost [127.0.0.1]) by tuna.sandelman.ca (Postfix) with ESMTP id 5892F3898C; Sat, 23 Jan 2021 15:03:34 -0500 (EST)
Received: from tuna.sandelman.ca ([127.0.0.1]) by localhost (localhost [127.0.0.1]) (amavisd-new, port 10024) with LMTP id C-wxJzh-psJM; Sat, 23 Jan 2021 15:03:33 -0500 (EST)
Received: from sandelman.ca (obiwan.sandelman.ca [209.87.249.21]) by tuna.sandelman.ca (Postfix) with ESMTP id 8E0A33899F; Sat, 23 Jan 2021 15:03:33 -0500 (EST)
Received: from localhost (localhost [IPv6:::1]) by sandelman.ca (Postfix) with ESMTP id 719D2493; Sat, 23 Jan 2021 15:01:22 -0500 (EST)
From: Michael Richardson <mcr+ietf@sandelman.ca>
To: Carsten Bormann <cabo@tzi.org>, "Dale R. Worley" <worley@ariadne.com>, cbor@ietf.org, doug@ewellic.org
In-Reply-To: <3DD6CB17-103F-48BF-A4EF-B2AEF1573C93@tzi.org>
References: <87wnw49wez.fsf@hobgoblin.ariadne.com> <3DD6CB17-103F-48BF-A4EF-B2AEF1573C93@tzi.org>
X-Mailer: MH-E 8.6+git; nmh 1.7+dev; GNU Emacs 26.1
X-Face: $\n1pF)h^`}$H>Hk{L"x@)JS7<%Az}5RyS@k9X%29-lHB$Ti.V>2bi.~ehC0; <'$9xN5Ub# z!G,p`nR&p7Fz@^UXIn156S8.~^@MJ*mMsD7=QFeq%AL4m<nPbLgmtKK-5dC@#:k
MIME-Version: 1.0
Content-Type: multipart/signed; boundary="=-=-="; micalg=pgp-sha512; protocol="application/pgp-signature"
Date: Sat, 23 Jan 2021 15:01:22 -0500
Message-ID: <30869.1611432082@localhost>
Archived-At: <https://mailarchive.ietf.org/arch/msg/cbor/v_GJ0ylnCpX1a4PSBAL2lXoaix8>
Subject: Re: [Cbor] [COSE] CBOR magic number, file format and tags
X-BeenThere: cbor@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: "Concise Binary Object Representation \(CBOR\)" <cbor.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/cbor>, <mailto:cbor-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/cbor/>
List-Post: <mailto:cbor@ietf.org>
List-Help: <mailto:cbor-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/cbor>, <mailto:cbor-request@ietf.org?subject=subscribe>
X-List-Received-Date: Sat, 23 Jan 2021 20:01:55 -0000

Carsten Bormann <cabo@tzi.org> wrote:
    > Right.  Something like this would probably make sense as an alternative
    > to the primary approach proposed, which is based on CBOR sequences.  If
    > you want to keep the magic-numbered file a single data item, this is
    > the way to go.

I am personally agnostic about CBOR Sequence vs something else.

I believe that:
  a) the magic number needs to be at least 4 bytes
  b) we shouldn't mandate that it be transmitted on the wire.

Being able to split off the magic part easily make sense to me.
That's why I proposed either:
  1) CBOR Sequence
  2) Two-element array.

--
Michael Richardson <mcr+IETF@sandelman.ca>   . o O ( IPv6 IøT consulting )
           Sandelman Software Works Inc, Ottawa and Worldwide