Re: [Cbor] Packed CBOR review

Christian Amsüss <christian@amsuess.com> Fri, 18 June 2021 08:05 UTC

Return-Path: <christian@amsuess.com>
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 AC3B73A4180 for <cbor@ietfa.amsl.com>; Fri, 18 Jun 2021 01:05:53 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.9
X-Spam-Level:
X-Spam-Status: No, score=-1.9 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, SPF_HELO_NONE=0.001, SPF_PASS=-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 l59y1sNu17bA for <cbor@ietfa.amsl.com>; Fri, 18 Jun 2021 01:05:51 -0700 (PDT)
Received: from prometheus.amsuess.com (prometheus.amsuess.com [5.9.147.112]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 0660E3A417C for <cbor@ietf.org>; Fri, 18 Jun 2021 01:05:50 -0700 (PDT)
Received: from poseidon-mailhub.amsuess.com (unknown [IPv6:2a02:b18:c13b:8010:a800:ff:fede:b1bd]) by prometheus.amsuess.com (Postfix) with ESMTPS id 575FD408B8; Fri, 18 Jun 2021 10:05:48 +0200 (CEST)
Received: from poseidon-mailbox.amsuess.com (hermes.amsuess.com [10.13.13.254]) by poseidon-mailhub.amsuess.com (Postfix) with ESMTP id CED99D7; Fri, 18 Jun 2021 10:05:47 +0200 (CEST)
Received: from hephaistos.amsuess.com (unknown [IPv6:2a02:b18:c13b:8010:14:5625:3c22:75e]) by poseidon-mailbox.amsuess.com (Postfix) with ESMTPSA id 96DB5CD; Fri, 18 Jun 2021 10:05:47 +0200 (CEST)
Received: (nullmailer pid 685442 invoked by uid 1000); Fri, 18 Jun 2021 08:05:47 -0000
Date: Fri, 18 Jun 2021 10:05:47 +0200
From: Christian =?iso-8859-1?Q?Ams=FCss?= <christian@amsuess.com>
To: Brendan Moran <Brendan.Moran@arm.com>
Cc: Carsten Bormann <cabo@tzi.org>, "cbor@ietf.org" <cbor@ietf.org>
Message-ID: <YMxT2+zFIJ1McNTb@hephaistos.amsuess.com>
References: <8713C3AB-71C0-4EC0-8977-15F80EC11309@arm.com> <212CE7EA-73BC-47BF-B192-D2D523F4A376@tzi.org> <33C84949-0F9C-432C-9C94-DE2C9EE17976@arm.com> <3F367A6D-5CAD-474F-AFEE-DF1AC9A34135@tzi.org> <146F670A-48EA-4A90-B77C-4CCC535F1DB1@arm.com>
MIME-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="qshtEZIr/E6HbRTL"
Content-Disposition: inline
In-Reply-To: <146F670A-48EA-4A90-B77C-4CCC535F1DB1@arm.com>
Archived-At: <https://mailarchive.ietf.org/arch/msg/cbor/ny0rIcy0rKXc7lAH0pdKt2i-BSg>
Subject: Re: [Cbor] Packed CBOR review
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: Fri, 18 Jun 2021 08:05:54 -0000

On Thu, Jun 17, 2021 at 11:17:34AM +0000, Brendan Moran wrote:
> > How would the hash reference specify the algorithm?
> > (I think CFRG would tell us that collision resistance between algorithms isn’t a well-defined property.)
> 
> We could possibly reuse SUIT digest definitions for this:
> suit-digest = [algorithm-id : uint, digest: bstr]

When we already cater for URIs, we could just use RFC6920 URIs that do
express the used hash -- example:
ni:///sha-256;UyaQV-Ev4rdLoHyJJWCi11OHfrYv9E1aGQAlMO2X_-Q

That's annoying encoding and verbose, but CRIs could maybe (ok, it's a
big maybe) provide a compact serialization for them if [#5] happens.

BR
c

[#5]: https://github.com/core-wg/coral/issues/5

-- 
To use raw power is to make yourself infinitely vulnerable to greater powers.
  -- Bene Gesserit axiom