Re: [Anima] I-D Action: draft-richardson-anima-masa-considerations-02.txt

Michael Richardson <mcr+ietf@sandelman.ca> Tue, 21 January 2020 00:51 UTC

From: Michael Richardson <mcr+ietf@sandelman.ca>
To: Brian E Carpenter <brian.e.carpenter@gmail.com>
cc: Anima WG <anima@ietf.org>
In-Reply-To: <27700b3a-8ef8-d716-e894-23ef785ce313@gmail.com>
References: <157558079151.16429.14274182498632037900@ietfa.amsl.com> <27700b3a-8ef8-d716-e894-23ef785ce313@gmail.com>
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Date: Mon, 20 Jan 2020 19:51:53 -0500
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Archived-At: <https://mailarchive.ietf.org/arch/msg/anima/Zo40-a0SOkWvadsECt1T-doOXas>
Subject: Re: [Anima] I-D Action: draft-richardson-anima-masa-considerations-02.txt
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Brian E Carpenter <brian.e.carpenter@gmail.com> wrote:
    >> There are a number of options of how to get the public key securely
    >> from the device to the certification authority.  This transmission
    >> must be done in an integral manner, and must be securely associated
    >> with the assigned serial number.  The serial number goes into the
    >> certificate, and the resulting certificate needs to be loaded into
    >> the manufacturer's asset database.  This asset database needs to be
    >> shared with the MASA.

    > The first sentence made me stop and think. Normally, a "public" key
    > can and must be revealed in public, so doesn't need to be moved
    > securely. I *think* you are saying that the association of a given
    > public key with a given serial number must be kept secret. If so,
    > please say that explicitly.

The association between the public key and the serial number must integral.
This isn't about privacy, but about integrity.
I'm not saying that the association with a serial number must be secret, but
that it must be very difficult to be interferred with.

    >> One way to do the transmission is during a manufacturing during a Bed
    >> of Nails (see [BedOfNails]) or Boundary Scan.

    > I think that needs a bit more description.

okay.
I will ask a few friends in the electronics business what kind of reference
they would make.
Was  https://en.wikipedia.org/wiki/In-circuit_test#Bed_of_nails_tester
insufficient, or do you want something inline?

    >> There are other ways
    >> that could be used where a certificate signing request is sent over a
    >> special network channel after the system has been started the first
    >> time.

    > What's special? Couldn't it just be a TLS session?

It depends a lot about the environment.
It neededn't be TLS at all: it could be just a special network cable that is
plugged in.  What matters is that the system be secure against interloppers.

    >> There are risks with these methods, as an attacker with
    >> physical access may be able to put device back into this mode
    >> afterwards.

    > You could recommend that the device sets a hard flag that
    > makes this impossible. Maybe it should simply *delete* its
    > public key after uploading it once.

Yes. I mean to read some of the documentation for TPM chips.
I believe that they blow a fuse.

--
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]   Michael Richardson, Sandelman Software Works        |    IoT architect   [
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Re: [Anima] I-D Action: draft-richardson-anima-ma… Brian E Carpenter
Re: [Anima] I-D Action: draft-richardson-anima-ma… Michael Richardson

Re: [Anima] I-D Action: draft-richardson-anima-masa-considerations-02.txt

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