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Re: [COSE] The one-byte saving from use of a sequence

Laurence Lundblade <lgl@island-resort.com> Fri, 14 May 2021 18:03 UTC

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From: Laurence Lundblade <lgl@island-resort.com>
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Date: Fri, 14 May 2021 11:03:22 -0700
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To: John Mattsson <john.mattsson=40ericsson.com@dmarc.ietf.org>
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Subject: Re: [COSE] The one-byte saving from use of a sequence
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> On May 14, 2021, at 1:22 AM, John Mattsson <john.mattsson=40ericsson.com@dmarc.ietf.org> wrote:
> 
> > I'm I'm pretty sure it is incorrect CDDL
> I don't know why you think this was incorrect CDDL. RFC 8610 even has the following example [+(left: uint, right: uint)] (but this does not matter as I think we have already taken the decision to use arrays).
> 
> > It would not be possible to decode correctly.
>  
> I don’t think that was true. That would only be true if you cannot determine the number of elements from c509CertificateType (but this does not matter as I think we have already taken the decision to use arrays).
>  

Yes, you are right, as long as the number of items is fixed, you can count and successfully decode (didn’t think of counting like that).

You’d have to be aware of this every time you designed a CBOR protocol that uses CBORCertificate

For example, you couldn’t count for this protocol, but it works fine if CBORCertificate is an array.

   [ 
       * cert : CBORCertificate
       * vector : int
   ]

I still think everyone’s life will be easier if CBORCertificate defined as an array so it works as expected for CBOR-based protocols and you unwrap the array to save the byte in non-CBOR protocols.

LL

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