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Re: [Danish] [EXT] Re: IoT Device Identification with TLSA via Danish

Michael Richardson <mcr+ietf@sandelman.ca> Tue, 15 June 2021 19:57 UTC

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From: Michael Richardson <mcr+ietf@sandelman.ca>
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Date: Tue, 15 Jun 2021 15:57:00 -0400
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Subject: Re: [Danish] [EXT] Re: IoT Device Identification with TLSA via Danish
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Viktor Dukhovni <ietf-dane@dukhovni.org> wrote:
    >> {I personally think that this is a negative of DANISH.  Maybe it's not
    >> a core aspect of it, but it seems like it to me.}

    > If the key is immutable for the lifetime of the device, and not
    > strongly protected against extraction by its previous owner, then
    > change of ownership potentially leaves the new owner unsure whether
    > the device is still "trustworthy" (assuming it was ever trustworthy
    > to begin with, ...walks away muttering something about supply chain
    > security under his breath...)

Yes, that's the point.
The immutability for the lifetime of the device is a source of great power,
but also a problem.

We should consider if we can use either subcerts/delegated certificates here
in a useful way.
  https://datatracker.ietf.org/doc/draft-ietf-acme-star-delegation/
  https://datatracker.ietf.org/doc/draft-ietf-tls-subcerts/

I have considered that using them would be appropriate when the IDevID is
stored at the far side of a really slow I2C/SPI bus into a TPM.  You don't want
to use it for "day to day" operations in that case.

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

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