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Re: [Suit] self-describing format vs fixed/binary manifest structure

Michael Richardson <mcr+ietf@sandelman.ca> Fri, 14 December 2018 20:03 UTC

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From: Michael Richardson <mcr+ietf@sandelman.ca>
To: Martin Pagel <Martin.Pagel@microsoft.com>
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Subject: Re: [Suit] self-describing format vs fixed/binary manifest structure
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Martin Pagel <Martin.Pagel@microsoft.com> wrote:
> I think the greatest value of the SUIT draft is the Architecture and
> Information Model documents as they define the rationale for a specific set
> of manifest fields. How you encode these fields is secondary and I believe
> it is more important that these fields can get easily loaded by the MCU
> rather than coming up with a portable/standard format. I only specified
> 64-bytes as an example, yes, 32-byte are enough for ECDSA. Same applies to
> thumbprint. Each manufacturer (or whoever develops the boot and
> installation software) would need to define the details of the manifest
> structure format it expects including byte alignment, crypto algorithms,
> keys etc.

If each manufacturer (of a chip? board? subsystem?) defines their own format,
then we effectively have no standard.

The value of a standard is that the rest of the infrastructure required can
be amortized over many kinds of devices.  Being able to audit all of the
images+manifests in a central point is of extreme value.

> I will address your notes on Security Considerations with my next revision.

Thank you.


--
Michael Richardson <mcr+IETF@sandelman.ca>, Sandelman Software Works
 -= IPv6 IoT consulting =-

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